Knut Olav Strætkvern

• Augustine, M.; Strætkvern, Knut Olav; Nguyen, M.; Johnston, M. & Blümich, B. (2026). Relaxation in water from different sources in Rome: Field testing a portable, center-field relaxometer. Journal of magnetic resonance (San Diego, Calif. 1997 : Print). ISSN 1090-7807. 391. doi: 10.1016/j.jmr.2026.108131. Full text in Research Archive
• Miranda, Diego A.; Fernández, Lucía; Strætkvern, Knut Olav; Carrasco, Cristhian; Martín, Carlos & Soto, Luis Alejandro Romero (2025). Production of exopolysaccharides by halotolerant bacteria cultivated in hydrolysates of spent mushroom substrate and hydrothermally pretreated Jerusalem artichoke stalks. Industrial crops and products (Print). ISSN 0926-6690. 236. doi: 10.1016/j.indcrop.2025.121961. Full text in Research Archive Show summary

  Global issues over the unsustainable use of resources demand novel bio-based processes. The production of edible mushrooms from forest and agricultural residues offers efficient bio-based solutions. Spent mushroom substrate (SMS), a by-product from mushroom cultivation, can be valorized as a source of fermentable sugars. Similarly, the stalks of Jerusalem artichoke (Helianthus tuberosus), a crop of increased interest, represent under-investigated bioresources to be considered for biorefinery applications. In this study, SMS and Jerusalem artichoke stalks (JAS) were used for the first time as substrates to produce exopolysaccharides (EPS) by cultivating halotolerant bacteria (coded SU4M and SU3A) isolated from a hypersaline environment. Cultivations were performed using either cellulosic hydrolysates obtained by enzymatic saccharification or synthetic media. Acid-catalyzed hydrothermal pretreatment was applied to enhance the enzymatic saccharification of JAS, while no pretreatment was needed to saccharify SMS. The use of a SMS hydrolysate-based medium resulted in the highest biomass concentration (3.8 g L−1) and EPS production (852.1 mg L−1) among the media used in shake-flask fermentations. The fermentations in SMS hydrolysates resulted in comparable EPS volumetric productivity (17.8 ± 0.7 mg L−1 h−1) to that of synthetic medium (16.8 ± 0.8 mg L−1 h−1), but higher than that of the JAS hydrolysates (13.3 ± 0.6 mg L−1 h−1). Cultivation in SMS hydrolysates was particularly advantageous, as it did not require either pretreatment or external nutrient supplementation. The highest volumetric productivity of EPS production was achieved in a bioreactor when SMS hydrolysate was used, reaching 100 mg L⁻¹ h⁻¹ . This study demonstrates the potential of spent mushroom substrate and Jerusalem artichoke stalks, two underexploited agroresidues, as sustainable substrates for EPS production, thereby contributing to the strengthening of the regional bioeconomy in rural areas.

• Akter, Afrina; Klausen, Sarah Jasmin; Soto, Luis Alejandro Romero; Díaz, Francisco; Domínguez, Herminia & Xiong, Shaojun [Show all 8 contributors for this article] (2025). Comparative extraction of bioactive compounds from spent mushroom substrates of Lentinula edodes and Pleurotus ostreatus using subcritical water and pressurized ethanol. Industrial crops and products (Print). ISSN 0926-6690. 235. doi: 10.1016/j.indcrop.2025.121750. Full text in Research Archive Show summary

  This study aimed to assess subcritical water extraction (SWE) and pressurized ethanol extraction (PEE) for recovering bioactive compounds from spent mushroom substrate (SMS) derived from shiitake and oyster mushrooms. The extraction of bioactive compounds can facilitate the valorisation of SMS, an increasingly important waste stream whose management and disposal pose challenges for both mushroom producers and the environment. A 32 experimental design, using three temperatures (125, 150, and 175 °C) and three holding times (0, 15, and 30 min) was used in SWE. PEE was run at a single temperature (175 °C) and two holding times (0 and 15 min). The experimental results revealed that the highest extraction yield was achieved in shiitake SMS using SWE at 175 °C and 15 min. In most SWE conditions, shiitake SMS yielded higher concentrations of total phenolic compounds, total carbohydrates, and β-glucans compared to oyster mushroom SMS. Ascorbic acid, vanillic acid, protocatechuic acid, and gallic acid were the most abundant phenolic acids identified in both extracts. The SWE extracts of shiitake SMS exhibited higher DPPH and FRAP antioxidant activity than those of oyster mushroom SMS, and this activity increased with increasing temperature and time. PEE extracts exhibited higher DPPH and TEAC antioxidant activity for oyster mushroom SMS compared to shiitake SMS and showed a negative trend with increasing extraction time at 175 °C for both SMS. Our results show that SWE and PEE are viable methods for extracting bioactive compounds from SMS.

• Klausen, Sarah Jasmin; Soto, Luis Alejandro Romero; Liaqat, Ayesha; Dehghanmanshadi, Zahra; Strætkvern, Knut Olav & Xiong, Shaojun [Show all 7 contributors for this article] (2025). Biorefining spent substrates of shiitake (Lentinula edodes) and oyster mushroom (Pleurotus ostreatus): enzymatic saccharification of cellulose and xylan, with lignin recovery from residues. Bioengineered. ISSN 2165-5979. 16(1). doi: 10.1080/21655979.2025.2536443. Full text in Research Archive Show summary

  Spent mushroom substrate (SMS), the main by-product of mushroom cultivation, is a source of sugars that can be released by saccharification. This work aimed at investigating the enzymatic saccharification of the polysaccharides of the SMS of shiitake (Lentinula edodes) and oyster mushroom (Pleurotus ostreatus) and exploring the lignin extraction from the saccharification residues. First, analytical enzymatic saccharification (AES) with a cellulase cocktail and an experimental hemicellulase-rich preparation was applied. AES revealed higher digestibility of both polysaccharides for shiitake SMS than for oyster mushroom SMS. Using the cellulase cocktail, shiitake SMS resulted in a digestibility above 80% and 70% (w/w) for cellulose and xylan, respectively, while the maximum values for oyster mushroom SMS were 52% and 32% (w/w). The experimental enzyme preparation resulted in lower cellulose digestibility and higher xylan digestibility. Still, the saccharification trend between the two SMS types remained unchanged. To enhance the enzymatic saccharification of oyster mushroom SMS, hydrothermal treatment was applied. The treatment improved the enzymatic digestibility of cellulose by up to 84%. A validation experiment at larger scale showed that hydrothermally treated oyster mushroom SMS had a comparable overall conversion with non-treated shiitake SMS. Following a biorefinery strategy, lignin was extracted from the residues of the preparative enzymatic saccharification using the green solvent γ-valerolactone under different temperatures and holding times. The extracted product contained 98.8% lignin and did not contain cellulose or xylan. The results of this study provide the grounds for biorefinery processes enabling recovery of bioactive compounds, fermentable sugars, and high-quality lignin from SMS

• Klausen, Sarah Jasmin; Falck-Ytter, Anne Bergljot; Strætkvern, Knut Olav & Martín, Carlos (2023). Evaluation of the Extraction of Bioactive Compounds and the Saccharification of Cellulose as a Route for the Valorization of Spent Mushroom Substrate. Molecules. ISSN 1431-5157. 28(13). doi: 10.3390/molecules28135140. Full text in Research Archive Show summary

  The extraction of bioactive compounds and cellulose saccharification are potential directions for the valorization of spent mushroom substrate (SMS). Therefore, investigating the suitability of different extraction methods for recovering bioactive compounds from SMS and how the extractionmaffects the enzymatic saccharification is of uppermost relevance. In this work, bioactive compounds were extracted from Pleurotus spp. SMS using four extraction methods. For Soxhlet extraction (SoE), a 40:60 ethanol/water mixture gave the highest extraction efficiency (EE) (69.9–71.1%) among the seven solvent systems assayed. Reflux extraction with 40:60 ethanol/water increased the extraction yield and EE compared to SoE. A shorter reflux time yielded a higher extraction of carbohydrates than SoE, while a longer time was more effective for extracting phenolics. The extracts from 240 min of reflux had comparable antioxidant activity (0.3–0.5 mM GAE) with that achieved for SoE. Ultrasound-assisted extraction (UAE) at 65 ◦C for 60 min allowed an EE (~82%) higher than that achieved by either reflux for up to 150 min or SoE. Subcritical water extraction (SWE) at 150 ◦C resulted in the best extraction parameters among all the tested methods. Vanillic acid and chlorogenic acid were the primary phenolic acids identified in the extracts. A good correlation between the concentration of caffeic acid and the antioxidant activity of the extracts was found. Saccharification tests revealed an enhancement of the enzymatic digestibility of SMS cellulose after the extraction of bioactive compounds. The findings of this initial study provide indications on new research directions for maximizing the recovery of bioactive compounds and fermentable sugars from SMS.

• Ali, Jawad; Joshi, Mukund; Ahmadi, Asal; Strætkvern, Knut Olav & Ahmad, Rafi (2023). Increased growth temperature and vitamin B12 supplementation reduces the lag time for rapid pathogen identification in BHI agar and blood cultures. F1000 Research. 12(131). doi: 10.12688/f1000research.129668.2. Full text in Research Archive Show summary

  Background: The rapid diagnostics of pathogens is essential to prescribe appropriate and early antibiotic therapy. The current methods for pathogen detection require the bacteria to grow in a culture medium, which is time-consuming. This increases the mortality rate and the global burden of antimicrobial resistance. Culture-free detection methods are still under development and are not used in the clinical routine. Therefore decreasing the culture time for accurate detection of infection and resistance is vital for diagnosis. Methods: In this study, we wanted to investigate easy-to-implement factors (in a minimal laboratory set-up), including inoculum size, incubation temperature, and additional supplementation (e.g., vitamin B12 and trace metals), that can significantly reduce the lag time (tlag). These factors were arranged in simple two-level factorial designs using Gram-positive (Escherichia coli and Pseudomonas aeruginosa) and Gram-negative (Staphylococcus aureus and Bacillus subtilis) bacteria, including clinical isolates with known antimicrobial resistance profiles. Blood samples spiked with a clinical isolate of E. coli CCUG17620 were also tested to see the effect of elevated incubation temperature on bacterial growth in blood cultures. Results: We observed that increased incubation temperature (42°C) along with vitamin B12 supplementation significantly reduced the tlag (10 – 115 minutes or 4% - 49%) in pure clinical isolates and blood samples spiked with E. coli CCUG17620. In the case of the blood sample, PCR results also detected bacterial DNA after only 3h of incubation and at three times the CFU/mL. Conclusions: Enrichment of bacterial culture media with growth supplements such as vitamin B12 and increased incubation temperature can be a cheap and rapid method for the early detection of pathogens. This is a proof-of-concept study restricted to a few bacterial strains and growth conditions. In the future, the effect of other growth conditions and difficult-to-culture bacteria should be explored to shorten the lag phase.

• Martín, Carlos; Xiong, Shaojun; Passoth, Volkmar; Põldmaa, Kadri; Solberg, Svein Øivind & Hultberg, M [Show all 13 contributors for this article] (2023). Mushrooms for enhanced agriculture sustainability the MUSA concept. C3-Bioeconomy Circular and Sustainable Bioeconomy. p. 131–146. Full text in Research Archive Show summary

  The project MUSA – MUshrooms for Sustainable Agriculture is an effort to use mushroom-based processes to enhance agriculture sustainability in Nordic and Baltic countries. The project covers both the production of fruitbodies of edible fungi and the upgrading of the exhausted substrate from mushroom cultivation. The suitability of residues generated locally for producing edible mushrooms is investigated. Residues from Nordic agriculture and sub-utilized streams from forestry management, as well as wood processing by-products, are evaluated as the substrate base for producing shiitake (Lentinula edodes) and oyster (Pleurotus spp.) mushrooms. The project explores the potential of spent mushroom substrate (SMS) to support food production. SMS prospective as source of bioactive compounds and sugars is evaluated. MUSA investigates the suitability of SMS hydrolysates as carbon sources for cultivating oleaginous yeast to produce microbial oil suitable for human consumption. Using SMS for substituting mineral fertilizers and providing wastewater bioremediation solutions is also assessed

• Castro, Eulogio; Strætkvern, Knut Olav; Romero-García, J.M. & Martín, Carlos (2023). Pretreatment and Bioconversion for Valorization of Residues of Non-Edible Oilseeds. Agronomy. 13(9). doi: 10.3390/agronomy13092196. Full text in Research Archive Show summary

  Biodiesel production currently follows a first-generation model using edible oils as raw materials. Such a production model is unsustainable, considering that it is limited by the high cost of edible oils, competes with the food sector, and is linked to deforestation and other environmental threats. Changing the raw material base to non-edible oils provides an opportunity to increase the sustainability of the biodiesel industry and to avoid conflicts with food production. Processing non-edible oilseeds for extracting the oil to be used for producing biodiesel generates large amounts of residues, such as de-oiled cakes, seed husks, and fruit shells and pods as well as plant stems and leaves resulting from pruning and other agronomy practices. Most of those residues are currently disposed of by burning or used in a suboptimal way. Bioconversion following the sugar platform route, anaerobic digestion, or enzyme production provides means for upgrading them to advanced biofuels and high-added value products. Bioconversion of plant biomass, including oilseed residues, requires pretreatment to enhance their susceptibility to enzymes and microorganisms. This review provides an outlook on bioconversion approaches applicable to different residues of oilseed-bearing plant species. Recent reports on the pretreatment of non-edible oilseed residues for enhancing their bioconversion through either the sugar platform route or anaerobic digestion are critically discussed. This review is based on an exhaustive Web of Science search performed in January–May 2023.

• Martín, Carlos; Zervakis, Georgios I.; Xiong, Shaojun; Koutrotsios, Georgios & Strætkvern, Knut Olav (2023). Spent substrate from mushroom cultivation: exploitation potential toward various applications and value-added products. Bioengineered. ISSN 2165-5979. 14(1), p. 2252138–2252138. doi: 10.1080/21655979.2023.2252138. Full text in Research Archive Show summary

  Spent mushroom substrate (SMS) is the residual biomass generated after harvesting the fruitbodies of edible/medicinal fungi. Disposal of SMS, the main by-product of the mushroom cultivation process, often leads to serious environmental problems and is financially demanding. Efficient recycling and valorization of SMS are crucial for the sustainable development of the mushroom industry in the frame of the circular economy principles. The physical properties and chemical composition of SMS are a solid fundament for developing several applications, and recent literature shows an increasing research interest in exploiting that inherent potential. This review provides a thorough outlook on SMS exploitation possibilities and discusses critically recent findings related to specific applications in plant and mushroom cultivation, animal husbandry, and recovery of enzymes and bioactive compounds.

• Johansen, Wenche; Grove, Søren; Anonsen, Jan Haug; Moen, Anders; Agusti-Ridaura, Celia & Azar, Amir Sefidmouy [Show all 7 contributors for this article] (2019). Complement factor C5 in Atlantic salmon (Salmo salar): Characterization of cDNA, protein and glycosylation. Developmental and Comparative Immunology. ISSN 0145-305X. 100. doi: 10.1016/j.dci.2019.103424. Full text in Research Archive Show summary

  Complement component 5 (C5) is an essential factor of the defensive complement system in all vertebrates. We report the characterization of C5 cDNA and protein from Atlantic salmon (Salmo salar), a teleost fish species of high importance in aquaculture. The C5 cDNA cloned from liver is 5079 nucleotides long, whose translation product has a molecular weight of 190 kDa, with the classical β-α orientation and motifs/sites for β-α cleavage (678RPKR681) and cleavage by C5 convertases (R758). Mass spectrometric analysis show a single N-linked, biantennary, complex glycan at N1125. Moreover, the N-linked glycan displays an unusual modification in the form of acetylated sialic acid residues. Three anti-C5 antisera produced in mice using purified C5 worked in immunohistochemical analyses of formalin fixed liver tissue. The purification method, whereby inactive and activated (C5b) forms were isolated, opens for interesting studies on the complement function in fish, including possible connection to stress, disease and glycosylation.

• Strætkvern, Knut Olav & Stana, Astrid (2019). Linselusa: Geithamsen (Vespa crabro), vår største veps... Insektnytt. ISSN 0800-1804. 44(4), p. 4–4. Full text in Research Archive Show summary

  Geithamsen (Vespa crabro), vår største veps, sikret seg maksimal eksponering for sin ‘penthouse-leilighet’, da dronningen sist vår etablerte bolet sitt sentralt på denne hytteveggen utenfor Sandefjord (Engeveien, EIS 19). Et modent bol som dette kan romme mellom 650 og 700 individer (wikipedia). Det var imidlertid lav aktivitet ved bolet og ingen tegn til aggresjon da det ble fotografert 1.september; et par geithams kan skimtes ved noen av de mange inngangene (sentralt og oppe til høyre). Veldig ulikt i struktur og farge fra de vanlige gråaktige stikkvepsebolene, framstår dette vakre byggverket med en slags Trump-isk karakter og tilsvarende ‘hair-do’. Foto: Astrid Stana. Tekst: Knut Olav Strætkvern

• Showkat, Muhammad Mir; Falck-Ytter, Anne Bergljot & Strætkvern, Knut Olav (2019). Phenolic acids in Jerusalem artichoke (Helianthus tuberosus L.): Plant organ dependent antioxidant activity and optimized extraction from leaves. Molecules. ISSN 1431-5157. 24(18). doi: 10.3390/molecules24183296. Full text in Research Archive
• Strætkvern, Knut Olav & Strætkvern, Sunniva Briså (2018). Linselusa: Hodelusa- Når språkforvirring går til hodet... Insektnytt. ISSN 0800-1804. 43(3/4), p. 4–4. Full text in Research Archive Show summary

  Når språkforvirringen går til hodet … Sensommeren betyr oppstart og ny aktivitet i skoler og i barnehager, ikke bare gjelder det barna men også Pediculus humanus capitis – hodelusa, som nå finner seg nye formeringsmuligheter. Følgelig skjedde det nylig i en skoleklasse ‘et sted i Norge med sidestilte målformer’, at det kom et brev med til hjemmet fra en bekymret kontaktlærer, om at «hovedlusa» nå var observert. Og om at man måtte ta de nødvendige forholdsregler. For en stakkars lærer med mange tanker og oppgaver i hodet - eller hovudet, var det nok ikke lett å skille «hovud» fra «hoved». Da det lille kreket nå med ett var titulert som ‘capo de tutti capi(tis) - boss of the bosses’ - eller ‘bawse’ som internett-generasjonen gjerne staver det, MÅTTE det bare avstedkomme følgende illustrative kommentar fra min småkryp-interesserte datter.

• Ahmad, Rafi; Borowiec, Paulina; Falck-Ytter, Anne Bergljot & Strætkvern, Knut Olav (2017). Extraction, Solubility and Antimicrobial Activity of (-) Usnic Acid in Ethanol, a Pharmaceutically Relevant Solvent. Natural Product Communications. ISSN 1934-578X. 12(7), p. 1101–1104. doi: 10.1177/1934578x1701200725. Full text in Research Archive Show summary

  Usnic acid (UA) is the most studied bioactive secondary metabolite from lichens. Recently, UA research has focused on its antibacterial activity. However, increased application in healthcare products of UA is hampered by low solubility in aqueous solutions. Here, we report ethanol both as an alternative extraction solvent to acetone and as a pharmaceutically relevant solvent for future formulations. Dried samples of the abundant reindeer lichen (Cladonia stellaris) were extracted in a 23 factorial design using either ethanol or acetone, varying both time and solvent-to-dry mass ratio. In both extracts, UA was the predominant compound as shown by two-dimensional thin-layer chromatography (TLC). In a disc diffusion assay, both extracts demonstrated similar antibacterial susceptibility towards Gram-positive (Bacillus subtilis and Staphylococcus aureus), while showing little to no activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Among a range of pharmaceutically relevant solvents tested, UA was only soluble in ethanol (at concentrations up to 1-2 mg mL-1).

• Rahman, Mahfizur; Falck-Ytter, Anne Bergljot; Antonsen, Øyvind Gunnar & Strætkvern, Knut Olav (2015). Reindeer lichen (Cladonia stellaris) from a Norwegian mountain region as a sustainable source of usnic acid. International Journal of Applied Research in Natural Products. 8(3), p. 17–23. Full text in Research Archive
• Bril'kov, Maxim; Falck-Ytter, Anne Bergljot & Strætkvern, Knut Olav (2015). Evaluation of methods for reducing the ash content of waste frying oil processed to biofuel oil. Fuel processing technology. ISSN 0378-3820. 134, p. 487–493. doi: 10.1016/j.fuproc.2015.03.008. Full text in Research Archive
• Strætkvern, Knut Olav & Schwarz, Jurgen G. (2012). Recovery of Native Potato Protein Comparing Expanded Bed Adsorption and Ultrafiltration. Food and Bioprocess Technology. ISSN 1935-5130. 5(5), p. 1939–1949. doi: 10.1007/s11947-010-0494-2. Full text in Research Archive Show summary

  Obtaining native protein from potato fruit water (PFW) acceptable for food consumption was attempted by comparing expanded bed adsorption (EBA) and ultrafiltration (UF).The methods were assessed on their process performance and the product quality. Extractable tuber proteins were recovered from lab-prepared PFW either by adsorption to an EBA column using a mixed mode resin (0.31 L) or by batch concentration in an UF (10 kDa MWCO, 0.093 m2) unit and then freeze dried. The yields on protein and esterase activity were higher (p < 0.05 and p < 0.01; Mann–Whitney U-test) in UF (3.2 g l−1 PFW and 3.17 kU l−1 PFW) than in EBA (1.8 and 1.21). The performance difference was also reflected in process productivity for esterase activity which was fivefold better (p < 0.01) in UF (4.30 kU h−1) than with EBA (0.84) due to the higher enzyme retention; protein productivities were the same. The content of solanidine glycoalkaloids was depleted to moderate levels but came out unaffected by the processing method: EBA 286 ppm, UF 213 ppm. The low levels of chlorogenic acid in all EBA preparations were negatively correlated to high brightness score (L* = 73.8%), a favorable attribute in food-quality proteins. Both methodologies produced native preparations of comparable protein content (75%). EBA processing, however, increased the fraction of the patatin protein which may offer advantages in food applications.

• Rudi, Knut & Strætkvern, Knut Olav (2012). Correlations between Lumbricus terrestris survival and gut microbiota. Microbial Ecology in Health and Disease. ISSN 0891-060X. 23, p. 1–5. doi: 10.3402/mehd.v23i0.17316. Full text in Research Archive Show summary

  Background: The interplay between diet, gut bacteria and health still remain enigmatic. Here, we addressed this issue through the investigation of the effect of crystalline cellulose on the earthworm Lumbricus terrestris gut microbiota composition and survival. Methods: Earthworm gut contents were analyzed after 14 days of feeding using a mixed 16S rRNA gene sequencing approach, in addition to direct measurements of cellulase activity. The survival of earthworms was followed each week for 17 weeks. Results: We found a tendency that the crystalline cellulose fed earthworms survived better than the high energy fed earthworms (p=0.08). Independent of feeding we found that the bacterial group related to Ferrimonadaceae was correlated to an increased lifespan (p=0.01). We also found a positive correlation between Ruminococcaceae related bacteria and cellulase activity in the earthworm gut (p=0.05). Surprisingly, however, the cellulase activity was not correlated to the feeding regime. Conclusion: Taken together, the interactions between diet, gut microbiota and lifespan seem complex.

• Trosvik, Pål; Rudi, Knut; Strætkvern, Knut Olav; Jakobsen, Kjetill Sigurd; Næs, Tormod & Stenseth, Nils Christian (2010). Web of ecological interactions in an experimental gut microbiota. Environmental Microbiology. ISSN 1462-2912. 12(10), p. 2677–2687. doi: 10.1111/j.1462-2920.2010.02236.x. Full text in Research Archive
• Løkra, Sissel; Schüller, Reidar Barfod; Egelandsdal, Bjørg; Egelandsdal, Bjørg; Engebretsen, Bjørn & Strætkvern, Knut Olav (2009). Comparison of composition, enzyme activity and selected functional properties of potato proteins isolated from potato juice with two different expanded bed resins. Lebensmittel-Wissenschaft + Technologie. ISSN 0023-6438. 42(4), p. 906–913. doi: 10.1016/j.lwt.2008.11.011. Full text in Research Archive Show summary

  Protein concentrates prepared by expanded bed adsorption (EBA) chromatography from industrial potato juice (PJ) were analysed for chemical composition, color, enzyme activities, thermal properties and selected functional properties (solubility and emulsifying stability). Two EBA multi-modal resins, MIMO 1-45 and MIMO 1300 (UpFront Chromatography), were employed under various pH conditions resulting in four potato protein concentrates, A-D. Concentrate B contained an electrophoretically pure protease inhibitor fraction (20-21 kDa), whereas concentrate A, C and D contained both patatin (41 kDa) and protease inhibitors. The potato protein concentrates were explored for the presence of transitions from native to denatured states using differential scanning calorimetry (DSC). Concentrate C had lower heat of transition (Delta H) and T-onset than the other concentrates. The concentrate containing protease inhibitors exhibited the highest denaturation temperature and enthalpy. All concentrates differed significantly (P < 0.05) in color brightness, with concentrate B and D emerging as the brightest. The solubility of the concentrates was evaluated at pH 6 and pH 4.5. All concentrates had lower solubility at pH 4.5 than at pH 6 (70-80%). The stability of emulsions (1% protein, 20% oil, 0.08% xanthan gum) against creaming was analysed with a new method based on the Single electrode Capacitance Probe (SeCaP) technology. Small differences among concentrates were observed by the new SeCaP method. (C) 2008 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.

• Løkra, Sissel & Strætkvern, Knut Olav (2009). Industrial proteins from potato juice. A review. Food. ISSN 1749-7140. 3(Special Issue 1), p. 88–95. Full text in Research Archive Show summary

  Industrial proteins constitute proteins of nutritious and functional values obtained from animal and plant sources, and recovered commercially on a large scale. Among the plant crop proteins, potato has up to recently been regarded only as a nutritious supplement to feeds, unsuitable in human foods due to low technical quality. Major potato proteins characterized by molecular size, are the 40-42 kDa patatin group (35-40%) and the protease inhibitor group of 7-21 kDa (25-50%). Although well-balanced in amino acid composition, and possessing valuable protein functionality, food utilization has been limited due to high levels of total glycoalkaloids (TGA) and phenolic compounds. Potato juice (PJ) from starch manufacturing is the major source of protein extraction. The voluminous and dilute protein solution (1-2%) has a complex composition and is high in organic matter; hence, the rigorous demands on the effluent require efficient recovery of protein and peptide fractions. The recovery methods from PJ that are reviewed here include precipitation with various acids, membrane separation and chromatographic adsorption. Precipitation with various acids, often in combination with heat coagulation, gives high recoveries but destroys functionality. Membrane separation (reverse osmosis, ultrafiltration) is better, but ultrafiltration is often difficult to perform and uneconomical due to filter fouling. As a gentle processing alternative, expanded bed adsorption (EBA) has been demonstrated as a scalable chromatographic method with the ability to separate the major protein groups from phenolic compounds and TGA, resulting in highly functional protein preparations. EBA, as well as other improvements in established technologies are now gradually moving potato proteins into a better position as an industrial protein.

• Løkra, Sissel; Helland, Merete Hagen; Helland, Merete Hagen; Claussen, Ingrid Camilla; Strætkvern, Knut Olav & Egelandsdal, Bjørg [Show all 7 contributors for this article] (2008). Chemical characterization and functional properties of a potato protein concentrate prepared by large-scale expanded bed adsorption chromatography. Lebensmittel-Wissenschaft + Technologie. ISSN 0023-6438. 41(6), p. 1089–1099. Full text in Research Archive Show summary

  Native potato proteins consisting mainly of patatin and protease inhibitors were isolated from industrial potato fruit water by expanded bed adsorption (EBA) chromatography. The EBA-refined proteins were dried by different methods and the effect of drying-conditions on solubility, extent of denaturation, rheology and emulsifying properties was investigated. Drying methods include spray drying at varying outlet temperatures, vacuum freeze drying, fluid-bed and atmospherical freeze drying. Solubilities measured in the range pH 4-6 showed that the higher solubility was at pH 6 of around 65%, except for spray drying using an outlet temperature of 165 degrees C, which showed low solubility for all pH values. Spray drying at 90 degrees C and atmospheric freeze-drying emerged as the least deleterious methods with respect to retaining esterase and protease inhibitor activities, comparable to the vacuum freeze drying. The values obtained for the complex modulus suggest that potato protein is not a good gel former even when the protein was vacuum freeze dried. Emulsions prepared with xanthan as stabilizer were more stable at pH 6 compared to pH 4 judged from oil particle sizes. This study showed that potato proteins obtained under gentle isolation and drying conditions will provide interesting functional properties for potential application in food systems. (c) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.

• Claussen, Ingrid Camilla; Strømmen, Ingvald; Egelandsdal, Bjørg & Strætkvern, Knut Olav (2007). Effects of drying methods on functionality of a native potato protein concentrate. Drying Technology. ISSN 0737-3937. 25(04.jun), p. 1091–1098. doi: 10.1080/07373930701396444. Full text in Research Archive
• Claussen, Ingrid Camilla; Strømmen, Ingvald; Egelandsdal, B. & Strætkvern, K. O. (2007). Effects of Drying Methods on Functionality of a Native Potato Protein Concentrate. Drying Technology. ISSN 0737-3937. 25, p. 1091–1098. doi: 10.1080/07373930701396444. Full text in Research Archive
• Claussen, Ingrid Camilla; Strømmen, Ingvald; Egelandsdal, B. & Strætkvern, K. O. (2005). Functional Properties of Dried Potato Protein. Comparison of Drying Technologies Intended to Preserve Functional Properties of Potato Protein Concentrate Isolated by Large Scale Expanded Bed Chromatography. Drying Technology. ISSN 0737-3937. Full text in Research Archive
• Strætkvern, Knut Olav; Schwarz, Jurgen G.; Wiesenborn, Dennis P.; Zafirakos, Elias & Lihme, Allan (1999). Expanded bed adsorption for recovery of patatin from crude potato juice. Bioseparation (Dordrecht). ISSN 0923-179X. 7(6), p. 333–345. Full text in Research Archive
• Strætkvern, Knut Olav; Husøy, A.-M.; Maaseide, Nils Petter Devold; Olsen, S. O. & Goksøyr, A. (1996). Polyclonal and monoclonal antibodies against immunoaffinity-purified Atlantic cod (Gadus morhua L) CYP1A. Molecular Marine Biology and Biotechnology. ISSN 1053-6426. 5(nr 1), p. 84–92. Full text in Research Archive Show summary

  Polyclonal and monoclonal antibodies against immunoaffinity-purified cod liver cytochrome P450 1A (CYP1A) have been developed. The monoclo nal antib (denoted MAb-NP7) and polyclonal antibody (PAb-Dy) recogniz ed inducible CYP1A orthologues (55-58 kDa) in hepatic microsomes and 12,000 X g supernatants from several fish species exposed to P-naphth oflavone and aromatic hydrocarbon in Western blots, with some differe nces in cross-reactivity. The antibodies worked in enzyme-linked immu nosorbent assay (ELISA) and immunohistochemical analyses, but were no ninhibitory in analytical assays. The results indicate that anti-cod CYP1A PAb-Dy and MAb-NP7 recognize different epitopes on the CYP1A pr otein, and that the crossreacting deter minants are only partially co nserved over the wide range of fish phylogeny.

• Strætkvern, Knut Olav; Raae, Arnt Johan & Walther, Bernt T. (1992). Characterization of a pancreatic DNase from polyric caeca of Atlantic cod. Fish Physiology & Biochemistry. ISSN 0920-1742. 9, p. 439–452. Full text in Research Archive
• Strætkvern, Knut Olav; Raae, Arnt Johan & Walther, Bernt T. (1992). Characterization of a pancreatic DNase from pyloric caeca of Atlantic cod (Gadus morhua). Fish Physiology & Biochemistry. ISSN 0920-1742. 9(5-6), p. 439–452. Full text in Research Archive

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• Klausen, Sarah Jasmin; Akter, Afrina; Soto, Luis Alejandro Romero; Martín, Carlos; F., Díaz, & H., Domínguez, [Show all 8 contributors for this article] (2025). Turning trash into treasure: Pressurized liquid extraction as a method for extracting bioactive compounds from spent mushroom substrate. Full text in Research Archive
• Soto, Luis Alejandro Romero; Klausen, Sarah Jasmin; Strætkvern, Knut Olav; Martín, Carlos; Shaojun, Xiong, & A., Liaqat, [Show all 7 contributors for this article] (2025). Deciphering biorefinery valorization routes for spent mushroom substrates: enzymatic saccharification and lignin recovery. Full text in Research Archive
• Martín, Carlos; J., Jönsson, Leif; P., Dixit,; F., Momayez,; Z., Dehghanmanshadi, & V., Benavente, [Show all 12 contributors for this article] (2025). Biorefining Norway spruce-based bioresources with the green solvent γ-valerolactone. Full text in Research Archive
• Strætkvern, Knut Olav (2025). Hydrodynamic cavitation - a low-energy weapon of biomass destruction. Lessons from disrupting recalcitrant biomasses in an orifice-plate system. Full text in Research Archive
• Martín, Carlos; Xiong, Shaojun; Passoth, Volkmar; Strætkvern, Knut Olav; Klausen, Sarah J. & Romero-Soto, Luis Alejandro (2024). Spent substrate from mushroom cultivation – potential feedstock for biorefinery exploitation. Full text in Research Archive
• Romero-Soto, Luis Alejandro; Fernández, Lucía; Miranda, Diego A.; Strætkvern, Knut Olav & Martín, Carlos (2024). Exopolysaccharide production from underexplored agrowastes through microbial fermentation using bacterial isolates from a hypersaline environment. Full text in Research Archive
• Akter, Afrina; Klausen, Sarah Jasmin; Romero-Soto, Luis Alejandro; Diaz, F; Dominguez, Herminia & Strætkvern, Knut Olav [Show all 7 contributors for this article] (2024). Pressurized liquid extraction of bioactive compounds from spent mushroom substrate of Lentinula edodes and Pleurotus ostreatus. Full text in Research Archive
• Klausen, Sarah J.; Falck-Ytter, Anne Bergljot; Strætkvern, Knut Olav & Martín, Carlos (2023). Extraction of bioactive compounds and saccharification of polysaccharides for valorization of spent mushroom substrate following a biorefinery approach. Full text in Research Archive
• Chhetri, Jyoti; Falck-Ytter, Anne Bergljot & Strætkvern, Knut Olav (2023). Phenolic acids from the leaves of Jerusalem artichoke (Helianthus tuberosus L.): Effect of drying, intensification, and solvent system on yield and antioxidant activity. Full text in Research Archive Show summary

  The perennial and tuberous Jerusalem artichoke (JA) is a hardy vegetable growing under almost any condition. Besides its inulin-rich underground tubers, the sunflower-like plant’s aerial parts (leaf, flower, stem) are a rich yet unexploited source of bioactive phytochemicals. The leaves are abundant in various phenolic acids having antioxidant activity. In this study, leaves of JA were harvested from full-grown plants (> 2 m) and subjected to conventional and non-conventional solvent extraction techniques to maximize the yield of phenolic acids. Harvested leaves were either dried or used as fresh. The two solvent systems were aqueous ethanol (55 %) and choline chloride/glucose/water (1:3:30), a natural deep eutectic solvent (NADES) acting through multiple hydrogen bond formation. The techniques compared were maceration at room temperature (ME) and ultrasound-assisted extraction (UAE). For each solvent system, the effect on total phenolics yield (TPC, mg gallic acid eqv./ g dry substance) was tested with both fresh and dried leaves in a two-level full factorial design (n=14) through a combination of varying extraction time (20-60 min) and liquid-to-solids ratio (20-50:1). The extraction output was also assayed as the ferric reducing antioxidant power (FRAP, mM Fe2+ eqv. /g DS). The main findings are: (1) The drying of JA leaves compared to fresh material improved the TPC yield (3-fold) and FRAP activity (10-20 fold) in aqueous ethanol irrespective of ME and UAE; (2) NADES was a better solvent for extraction giving 5-8 fold higher TPC yields and FRAP activities than with ethanol; (3) the additive effect of UAE was significant (approx. 40 %) only for fresh leaves in NADES, with maximum study values of TPC (15.7) and FRAP (17.7). Overall, drying of the biomass helps the extraction output, likely due to the destabilization and rupture of the leaf cell matrix, improving the mass transfer of phenolic compounds. On the other hand, extraction in NADES – a green solvent, is less dependent on the state of the leaves, probably due to the swelling of cells from water uptake and the subsequent improved mobilization and mass transfer of solutes.

• Strætkvern, Knut Olav (2022). '...til mest verdige personer av Arbeiderklassen...' -Om Severin Olsen Dælin sin bokpremie, Gammalt frå Stange og Romedal 2022. Stange historielag. ISSN 9788291366463. p. 39–49. Full text in Research Archive
• Strætkvern, Knut Olav (2022). En lysende forretning, Glimt fra Hamars historie - Årbok 2022. Hamar Historielag. ISSN 9788293109105. p. 67–84. Full text in Research Archive Show summary

  En beretning om firmaet Ingeniør Strætkvern i Storhamargaten 21, og dets grunnlegger Olav Strætkvern (1879-1947) og hustru Marit f.Pedersen (1884-1971). Firmaet, etablert 1921-22, var en av pionerbedriften på Innlandet innenfor elektrobransjen, med et stort virkeområde fra Akershus til Møre. Artikkelen omfatter glimt fra bygnings-, personal-, og firmahistorien gjennom 100 år. Episoder fra krigsårene er også beskrevet.

• Wetterhus, Elin Merete; Kiran, Nosheen; Falk-Ytter, Anne B.; Nilsson, Astrid & Strætkvern, Knut Olav (2022). Concentrated ethanol extracts from potato peel reduce the oxidation of omega-3 and omega-6 fatty acids. Full text in Research Archive
• Strætkvern, Knut Olav (2021). Bli med på en reise gjennom vaksinenes historie. [Journal]. Østlendingen og Ringsaker Blad. Full text in Research Archive Show summary

  Puss fra sårskorpene ble ført inn under huden på småbarn i alderen ett til fire år, som da ble immune mot kopper. Det var ganske rå vaksinasjonsmetoder den gangen, og mye kunne gå galt, sier professor Knut Olav Strætkvern ved Høgskolen i Innlandet.

• Strætkvern, Knut Olav (2020). Stripetegen er vakker, men sier klart ifra - ‘hold avstand’! Insektnytt. ISSN 0800-1804. 45(3/4), p. 19–21. Full text in Research Archive
• Strætkvern, Knut Olav; Nielsen, Nis Valentin & Eide, Stein S (2020). Potetskrell skal gi mer holdbar mat. [Internet]. nrk.no/innlandet. Full text in Research Archive
• Strætkvern, Knut Olav (2020). Pilfinkpar med tre ungekull. Fuglevennen. ISSN 1504-0623. 17(1), p. 28–28. Full text in Research Archive
• Christensen, Ekaterina & Strætkvern, Knut Olav (2018). Boosting biogas with hydrolytic enzymes – effect of cellulase pretreatment of wheat straw on sugar release, onset and ultimate gas production. Full text in Research Archive Show summary

  In biogas reactors, hydrolysis of fibrous substrate can be improved by supplementing hydrolytic enzymes, however, reports are not conclusive on this claim. In this study, two commercial preparations consisting of cellulases and hemicellulases, were characterized and tested for their effect on biogas yield. Milled wheat straw was incubated with enzymes in a pretreatment step, prior to mixing with cow’s manure. Following anaerobic digestion (AD), improved gas yield and increased volatile fatty acids VFA) was demonstrated in small scale syringe reactors (100 ml) under various conditions. As a further verification, enzyme pretreatment and AD was scaled up (1.5 L) with optimized conditions. Monitored for extended time, both enzyme-treated reactors performed 16-23% better on gas yield compared to control. Although the increased release of fermentable sugar shortens lag time and lowered volatile solids (VS), enzyme hydrolysis can also cause microbial imbalance compromising reactor pH due to rapid acid accumulation.

• Strætkvern, Knut Olav; Davenne, Tamara; Falck-Ytter, Anne Bergljot & Thøgersen, Jesper (2015). Screening by DoE of critical chromatographic variables in the capture of anionic and cationic proteins from industrial potato fruit juice. Full text in Research Archive Show summary

  Ion exchange chromatography is usually predictable in its outcome when setting the system pH at an appropriate distance from the target protein pI. But how predictable is that with a complex feed like potato fruit juice (PFJ)? A voluminous by-product from starch processing, rich in minerals and phytochemicals, PFJ contains proteins (about 1.5%) of both anionic (patatin) and cationic (potato protease inhibitors, PPI) types. In studies to determine optimum capture of both, we examined the influence of critical adsorption factors (pH, ionic strength, flow rate, sample load). Design of Experiments (DoE) was used with two or three factor levels to screen for main effects and possible factor interactions on the protein yield. The patatin group (pI 4.5-5.2) and the PPI group (pI ca. 6.5-9) were captured from PFJ on bioprocess ion exchange resins, anionic and cationic respectively, using lab scale columns (1, 5 and 25ml). Lab scale-up of the chromatography to validate the capture process was facilitated with a 250 ml radial flow chromatography (RFC) column. For the PPI capture, the process was transferred to a 10 liter pilot scale RFC column in a starch processing plant. Analysis of patatin capture showed that ionic strength was a more determinative factor than pH, where optimum binding was favored around pH 7-7.5 and 6-7 mS/cm. Screening of PPI capture revealed that acidic pH 3.5-4 was advantageous, as expected from the overall pI-values. However, ionic strength above 7 mS/cm significantly improved the protein yield, which may indicate favorable ionic shielding effects. In both types of chromatography, the loading flow rate, instead of impairing the mass transfer, showed a positive correlation with protein yield over the range 250-650 cm/h and 450-900 cm/h, respectively. This observation made use of RFC even more desirable, since the column geometry provides low back pressures at high flow rates. However, in the RFC scale-up of patatin capture on anion exchanger, significant interaction effects between sample load (negative) and flow rate (positive) was observed. In the RFC scale-up of PPI capture on cation exchanger, although binding kinetics is rapid, extended column residence time (0.4 vs 0.8 min) showed to be a more important factor than keeping a high flow rate during loading. This was confirmed when transferring from lab to pilot scale RFC columns, both with 12 cm bed depth. Overall, optimum conditions for capture of potato proteins were efficiently obtained through the screening process, resulting in consistent protein yields. KEY WORDS: Potato proteins - Design of experiments - Ion exchange chromatography - Radial flow column HIGHLIGHTS: * Potato fruit juice is an interesting system to for capture of high abundance proteins. * With DoE unexpected interaction effects were observed for ionic strength and flow rate * Radial flow columns enhanced capture probably due to better sample-resin interaction.

• Iarovitcyna, Ekaterina & Strætkvern, Knut Olav (2015). Practical use of cellulase enzymes to improve the frementative conversion of biogas substrate. Full text in Research Archive
• Strætkvern, Knut Olav (2015). Hva spiser vi framtiden? Insekter på menyen? Full text in Research Archive
• Chernakova, Elena & Strætkvern, Knut Olav (2013). Potato proteins captured on a mixed mode resin: an optimization and scale up study using predictions. Full text in Research Archive Show summary

  Background: The increased interest in the use of plant proteins in food products as an alternative functional ingredients to animal proteins, has called for efficient methods to isolate valuable fractions. Potato proteins represent a source of valuable industrial proteins, especially when harvested from the fruit juice of starch processing. Mixed mode chromatographic resins offer multiple adsorption sites even at increased ionic content, and thus have proven successful in capturing proteins from industrial by-streams. Aim: To successfully employ chromatographic capture in production of functional industrial proteins, conditions should be sought where most of the soluble proteins are recovered in a single passage. In this study we used modeling tools of protein surface determinants to optimize the capture of major potato proteins on the Capto Mixed Mode Cation resin (GE Healthcare). Methods: Theoretical prediction of binding behavior of patatin (80 kDa) and a selection of the various protease inhibitors (18-22 kDa) was carried out using bioinformatic web tools (PROPKA, Kyte-Doolitte scale plot, APBS and PyMol). Alignment of pH-dependent surface electrostatic and hydropathicity densities of the major protein fractions was used to set ranges of pH values to be tested. Results: Binding experiments on Capto MMC miniature columns and SDS-PAGE analysis confirmed that maximum binding occurred in the overlapping pH-range where proteins were dominantly positively charged. Further testing verified that the binding of patatin was less sensitive to changes in ionic strength as predicted from its hydrophobicity. This indicates patatin binding to MMC preferentially through the ligand’s hydrophobic domain. Design of Experiments (DoE) methodology was applied to find optimum flow rate (600 cm h-1) and column load (8XCV) in packed bed columns. A transfer from 1 to 30 and finally to 125 ml column (radial flow) verified the scalability of the capture process; dynamic binding capacity remained at 12 mg protein ml-1 resin. In addition radial flow columns reduced column cycle by 20%. Conclusion: Predictive modeling was successful in finding best protein capture conditions. A model for potato protein adsorption onto the resin is proposed where the relatively smaller protease inhibitor proteins bind strongly through their higher charge density, less sensitive to overload and flow rate. The larger patatins show random charge distribution, binding preferentially to the resin surface, and thus are more sensitive to displacement in secondary layers.

• Strætkvern, Knut Olav (2009). Slik lages influensavaksinen. p. 5–5. Full text in Research Archive Show summary

  Slik lages influensvaksinen Å lage vaksiner har kommet langt siden Edward Jenner (1749-1823) gjorde sine forsøk med sårpuss for å immunisere mot kopper for 200 år siden. Louis Pasteur (1822-95) laget en vaksine mot rabies med svekkede virus som var dyrket i ryggmargen hos kaniner. Dagens influensavaksine består av inaktiverte viruspartikler som skal gi oss immunitet, men vaksinen har overraskende nok blitt laget på samme måte i over 50 år, nemlig i hønseegg. Ikke de vanlige eggene vi spiser til frokost, men i befruktede egg der kyllingfosteret utsettes for et massivt virusangrep. Virus kan ikke formere seg på egenhånd, de har arbeidstegningene men mangler verktøy og materialer. De må innta levende celler og særlig celler som reagerer på dem. Et kyllingfoster er derfor et godt voksested. Den tekniske prosessen fram til influensavaksinen er klar på hetteglass eller i sprøyte er både langvarig og omstendelig. De tekniske stegene i framstillingen går i etapper. Ofte er den første pandemibølgen på retur innen en virksom vaksine er klar.

• Løkra, Sissel & Strætkvern, Knut Olav (2008). Potato protein isolation by expanded bed adsorption and ultrafiltration. Full text in Research Archive Show summary

  The economically viable recovery of waste protein from processing streams for use in developing valuable food products has focused interest on the use of gentle bioprocessing techniques. The objective of this study was to explore how expanded bed adsorption (EBA) and ultrafiltration (UF) can be used to upgrade protein from industrial potato juice (PJ), a by-product otherwise used as feed supplement. EBA-processing on mixed-mode ligands (3.5 gcm-1) in combination with gentle drying was used to obtain potato protein isolates that displayed improved technical functionality [Claussen et al. (2007), Drying Technology, 25:1101-1108; Løkra et al. (2008), LWT/Food Science & Technology, 41: in press]. In pilot scale EBA experiments (17 L resin, 20x200 cm, 400-800 cmh-1), variations in adsorption characteristics were observed for total protein capture from PJ. From breakthrough curves, analysis of the two major components, patatin (42/80 kDa) and the 20-22 kDa protease inhibitors (PI), showed significantly different binding. While a fraction of patatin tends to form homo-oligomeric aggregates escaping adsorption, the native dimeric patatin competes with the PI fraction for binding. Patatin aggregates were studied (HP-SEC) under both native and denaturing conditions, and as covalent aggregates, in order to explain the overall protein adsorption on the mixed-modal ligand. The influence of phenolic compounds, which add to the complexity of PJ, was also investigated in controlled experiments. However, steric hindrance from aggregates appears to be the major mechanism determining differentiated protein capture between native and aggregated patatin, and the PIs. Membrane separation of proteins is a well-established method in bioprocessing. A bench-scale comparison of UF (10 kDa PES, 0.19 m2) and EBA (300 ml resin, 5x65 cm, 400-700 cmh-1) on the same PJ material was carried out. UF operated in batch concentration/diafiltration mode gave a protein composition comparable to EBA. However, the EBA processing was superior to UF in separating phenolic pigments from the concentrated protein, and also concerning protein solubility. Although bioprocessing by UF or EBA is optional in the high-volume recovery of industrial protein, separation on mixed-mode ligands can produce defined fractions with improved qualities relevant to functionality in foods.

• Strætkvern, Knut Olav (2008). Bioteknologi på Hedemarken - hvorfor? Min Y-manns slekt, farskap hos storfe og nyttige potetproteiner. Full text in Research Archive
• Strætkvern, Knut Olav (2008). Hvordan tenke forskning: bruk av modellsystemer og forsøksdesign Faktorielt forsøksdesign på to nivåer. Full text in Research Archive Show summary

  I naturvitenskaplig forskning søker vi svar på spørsmål gjennom eksperimentell metode. Forutsetningen for å finne klare svar på spørsmålene vi stiller er at vi først lager oss et godt modellsystem, så finneut hvilke faktorer som kan påvirke systemet, og deretter spørre "hva skjer hvis...?". Gjennom eksperimenter forandrer vi størrelsen eller nivået av de ulike faktorene på en systematisk måte. Et begrenset antall forsøk kan utføres ved å bruke faktorielt forsøksdesign. Antall forsøk er 2^n, der n = antall faktorer som testet på to nivåer. Tre faktoere eller variabler gir 2^3 = 8 forsøk. Prinisippet belyses med å vise et konkret demonstrasjonsforsøk; immobilisert gjær i alginat for å lage etanol fra glukose. I en omrørt flaske med kontinuerlig gjennomløp er sukkerkonsentrasjon, kulestørrelse og oppholdstid i flasken viktige faktorer for produktiviteten av etanol. Et forsøksdesign krever altså nøye planlegging og bruk av pålitelige målemetoder for å registrere endringer.

• Eggset, Guri & Strætkvern, Knut Olav (2008). Bioteknologi på Hamar - med eller uten CSI. p. 5–5. Full text in Research Archive
• Strætkvern, Knut Olav (2007). Bioprosessteknologi. Full text in Research Archive Show summary

  Gjesteforelesning om fagområdet bioprosessteknologi, med hovedvekt på renseprosesser for industriell proteiner (eks. potetprotein). Bidrag var del av EVU-kurs i bioteknologi for lærere i VGS (kursnr. 2MOBITE19).

• Strætkvern, Knut Olav (2007). Bruk av mikroorganismer til industriformål. Full text in Research Archive Show summary

  Presentasjon av aktiviteter innen bioprosessteknologi ved Høgskolen i Hedmark, avd. LUNA. presentasjon for gruppe fra Elverum vgs (3.kl biologi).

• Strætkvern, Knut Olav (2006). Fusk og fanteri i forskningen Om overtramp som svekker forskningens omdømme. Full text in Research Archive Show summary

  Definisjoner: Scientific misconduct - unnlate å gi kredit til viktige bidragsytere til en oppdagelse. Scientific fraud - utgi forfalskede, manipulerte, plagierte eller fabrikkerte forskningsresultater. Historisk: Darwin, Pasteur, Mendel, Freud. Eksempler fra moderne tid: 1946 Otto Hahn- Lise Meitner; 1953 Watson & Crick, Wilkins- Rosalind Franklin; 1969/93Kjell Kleppe- Kary Mullis; 2005 Hwang Woo-suk; 2006 Jon Sudbø; 1998 " Varsleren" Arpad Pusztai.

• Strætkvern, Knut Olav; Løkra, Sissel; Stenseth, Else-Berit & Frydenlund, Kirsten (2005). Expanded bed adsorption (EBA) for producing food protein from potato processing waste Adsorbsjon med ekspansjonskromatografi (EBA) til å produsere matprotein fra potetavfall. Full text in Research Archive Show summary

  Potato proteins are very nutritious and possess interesting functionality for food formulations. Obtained from dilute fruit water (1-2%) from potato starch processing, this voluminous protein source has been difficult to upgrade from animal feed quality due to an undesirable content of polyphenolic substances, fiber, cell residue and minerals. Chlorogenic acid, the main polyphenolic substance in potato, causes enzymatic browning and off-taste. Plant phenols are also known to react with protein. In this project, applying an industrial processing effluent to novel and robust adsorption resins in expanded bed columns (EBA) has been developed as a possible large scale method for bulk protein recovery. Major protein fractions adsorbed to a heterofunctional ligand attached to a density-controlled resin, followed by a wash step. Change of pH facilitated desorption of refined protein. On the expanded column, chlorogenic acid separated from the proteins, as well as other crude components. The refined protein product has been analyzed for amino acid composition and esterase activity. In pilot scale trials with 50-150 liter of processing effluent, we have demonstrated that expanded bed adsorption is a scaleable method. However, the complexity of the feedstock offers several challenges for optimizing process productivity and thus cost effectiveness. Whether chlorogenic acid or other constituents of the crude extract interact with proteins to change adsorption characteristics is hypothesized. Assessing the effect of interacting components can assist in predicting chromatographic behavior in EBA-processing.

• Strætkvern, Knut Olav; Løkra, Sissel; Olander, Morten Aae & Lihme, Allan (2005). Food-grade protein from industrial potato starch effluent recovered by an expanded bed adsorption process. Journal of Biotechnology. ISSN 0168-1656. p. 33–33. Full text in Research Archive Show summary

  Potato tuber proteins are nutritious and show potential as functional ingredient in food systems. However, the present bulk processing technology can only recover byproduct protein for animal feed use. An expanded bed adsorption (EBA) process for isolating functional food-grade protein from crude potato starch effluent was previously developed. Moderate capture efficiency (20-25%) of the total crude protein was most likely caused by diffusion limitations and aggregated protein, inaccessible for adsorption. We employed the same adsorption ligand attached to agarose-tungsten carbide beads to create stable beds of 2.0-2.7X expansion using flow rates at 400-750 cm h-1. A pilot scale EBA process was run in a commercial processing plant over a three month campaign of starch production from potatoes of mixed variety. Fresh crude effluent (150-300 liter/cycle) was applied to a column (20 cm x 2 m) containing 20 liter of resin. Protein capture by EBA was reliable in operation, producing a refined proteinmaterial, which after dewatering and gentle drying, showed improved functionality over heat-coagulated protein produced at the same plant. Overall productivity increased. However, finding a robust operating window of predictable productivity is challenging since the potato fruit water is complex and deteriorates easily. From breakthrough curves, it is observed that the major bulk protein, patatin, displays non-Langmuir adsorption behavior. This may indicate a range of interactions for different species of the same protein. Chlorogenic acid (CQA), the main polyphenolic substance in potato tuber, causes enzymatic browning and undesirable flavor changes, but polyphenols can also react with protein. Assessing the effects of interacting cell components therfore applies to the bioprocessing of plant material.

• Løkra, Sissel; Egelandsdal, Bjørg; Egelandsdal, Bjørg; Vegarud, Gerd; Vegarud, Gerd & Strætkvern, Knut Olav (2005). Polyphenolic interactions with potato proteins durig expandedn bed adsorption processing. Full text in Research Archive
• Løkra, Sissel; Vegarud, Gerd; Vegarud, Gerd; Strætkvern, Knut Olav; Egelandsdal, Bjørg & Egelandsdal, Bjørg (2005). Polyphenolic interactions with potato proteins during industrial expanded bed adsorption processing. Journal of Biotechnology. ISSN 0168-1656. p. 58–58. Full text in Research Archive Show summary

  In plant extracts it has been shown that polyphenols have a tendency to react with proteins, either by covalent or non-covalent interactions. These reactions can induce changes in the surface properties of the proteins, and e.g. cause proteins to be insoluble and precipitate at pH-values below their isoelectric point. Potato proteins have a high nutritional quality and show interesting functional properties in food systems. Moreover, chlorogenic acid (CA) and caffeic acid constitute about 90% of the total polyphenol content of potato tuber. We have experienced expanded bed adsorption (EBA) chromatography to be a method well suited for recovering industrial proteins from potato starch effluent. The process separates proteins from polyphenolic pigments, fiber and minerals. During the adsorption step, patatin, the major potato tuber protein shows complex binding kinetics demonstrated by breakthrough curves. In addition to diffusion limitations in the EBA resin, changes in protein structure and surface properties probably are likely to affect this adsorption behavior. Reactions between CA and patatin might result in a range of interactions for different species of the same protein. This project therefore aims to assess the interactions between CA, patatin and other major tuber protein fractions and how these changes affect the protein capture in EBA. Changes in size and charge are screened in 2-D electrophoresis and analyzed further. Samples of different protein fractions are taken from breakthrough curves and dynamic binding capacity experiments in model systems with real feedstock.

• Strætkvern, Knut Olav (2004). Eddik er tingen. Full text in Research Archive
• Strætkvern, Knut Olav; Olander, Morten Aae & Lihme, Allan (2002). EBA processing of potato fruit water on mixed mode adsorbent for functional protein recovery: A difficult separation task made possible. Full text in Research Archive Show summary

  Potato starch processing produces large volumes of fruit water (PFW), a crude, protein-rich effluent, that causes costly treatment steps before disposal. Potato proteins are both nutritious, low allergenic and offer a range of interesting functionalities in food systems, provided they can be recovered without denaturation. However, no economical process is yet available to extract palatable and native potato proteins for human consumption. The soluble protein fraction has to be separated from coarse particulate matter, plant fibers, phenolic pigments and salts that make up the complexity of crude PFW. In this study we evaluate Expanded Bed Adsorption as a potential industrial-scale processing method for this demanding separation task. We developed a recovery process and tested it in an all-expanded pilot-scale EBA system using a real industrial feedstock. The major protein fractions were captured on a mixed mode (heterofunctional) ligand on glass-agarose beads. Crude PFW was collected fresh several times during the milling campaign from a local potato starch mill, adjusted to a suitable pH, and extracted for protein on the column. The process cycle was optimized in a 5-cm column (700 ml adsorbent, H0 33 cm), and transferred to the pilot-scale column (20 cm Æ, 17 liter, H0 60 cm). The column cycle was run in expanded mode (H/H0 = 1.6) in all steps, keeping a constant bed height. Varying feed loads (30-135 liter) of crude PFW were tested, and the column runs analyzed for protein capture efficiency. Protein was desorbed with an alkaline pH step and collected in 1.5 column volumes in expanded mode. Tap water proved sufficient for column re-equilibration and wash steps. As a marker for structural integrity of the captured proteins, the fattyacid esterase activity of patatin was monitored 1. Protein and enzyme data were applied to mass balance and recovery calculations. Of the crude protein content of potato processing effluent (8-15 g/l), about two-thirds are soluble, while the aggregated protein fraction is yet inaccessible to adsorption. Although the protein capture efficiency was moderate (20-25 %), binding characteristics of the mixed mode adsorbent suggest that feed loads of 8-10 times the gel volume are possible. A saturated EBA-column is able to concentrate the patatin activity 3-fold. Over the range of feed volumes and batch variability we experienced with the industrial feedstock, the process proved robust and reliable. In repeated runs, a milky white, native protein concentrate (2%) resulted, effectively separated from dark-colored phenols and aggregates. Gentle dewatering in subsequent steps gives a protein preparation that can be used as a food ingredient and for novel food applications. 1 Strætkvern KO, Schwarz JG, Wiesenborn DP, Zafirakos E, & Lihme A (1999). Expanded bed adsorption for recovery of patatin from crude potato juice. Bioseparation 7: 333-345.

• Strætkvern, Knut Olav; Olander, Morten Aae & Lihme, Allan (2002). Expanded bed adsorption of total soluble proteins from crude feedstock: A pilot-scale study with potato fruit juice. Full text in Research Archive Show summary

  (Abstr. no. P75)Stabilized fluidized chromatography beds, or expanded bed adsorption (EBA), is now established in the biotech industry as a first step unit operation in downstream processing of proteins. In the bioprocessing of waste streams in the food industry, EBA is a potentially cost-effective method to utilize diluted proteins of functional or biological value. We have studied an EBA process at pilot scale to capture potato tuber proteins from the processing effluent of starch milling at Hoff Norske Potetindustrier BA. Of the crude protein content of potato processing effluent (10-15 g/l), about two-thirds are soluble, while the aggregated protein fraction is inaccessible to adsorption. Using a mixed mode (heterofunctional) adsorption ligand on density-controlled agarose beads, total soluble proteins were retained as the crude feed passed upward in the expanded column bed. The process was optimized in a 5-cm column (700 ml gel), and transferred to a pilot scale column (20cm Æ, 17 liter). The column cycle was run in expanded mode (H/H0 = 1.6) in all steps, keeping a constant bed height (95-100cm). Different feed loads (30-135 liters) of crude effluents were tested, and the column runs analyzed for protein capture efficiency. As a marker of structural integrity of the captured protein, the fatty acid esterase activity of patatin was employed. The EBA process captured 80-85% of the total soluble protein, while patatin recovery in the product pool was 70-75%, collected in 1.5 column volumes. In repeated runs, a milky white, native protein product resulted, separated from dark-colored phenolic components and aggregates.

• Kommisrud, Elisabeth; Fuglestveit, Ragnhild; Mathisen, Lene; Skinstad, Ingvild J K & Strætkvern, Knut Olav (2002). Microbiological examination of bovine semen during processing and effect of different duration of antibiotic exposure. Full text in Research Archive Show summary

  Semen may contain bacteria from the prepuce, the environment, equipment or from human handling. Semen processing should, however, guarantee frozen semen from AI-bulls to be free from both specific and non-specific opportunistic bacteria. Important measures to achieve this objective are strict hygiene during collection and processing, together with addition of antibiotics (AB) to the semen. The aim of the present study was to determine the total number of bacteria in neat bull semen, extended/cooled and frozen/thawed semen. Semen extenders were examined with regard to microbiological contamination and for the effect of duration of AB* exposure. Two pooled ejaculates from 20 Norwegian Cattle AI-bulls were included in the study. Samples for microbiological examination were collected from neat semen, extended/cooled semen and frozen/thawed semen. Prior to inoculation on agar spreadplates, samples were diluted to a titre according to preliminary studies. Total bacterial counts (TC), coliforms (CF) and termostable coliforms (TCF) from neat and frozen/thawed semen were estimated on Luria-Bertani (LB) medium and Brilliant Green Bile (BGB). In addition, the frozen/thawed semen was inoculated on LB supplemented with AB to examine the presence of AB resistant bacteria. Extended/cooled semen was examined for TC only. Semen extenders with and without AB stored for one or three days were investigated for microbiological contamination, including TC, AB-resistant bacteria, CF, TCF and fungi. Fungiform growth was examined on Sabouraud Agar. The effect of AB at 35°C was examined by inoculating the extender with E. coli, P. aeruginosa and S. aureus at a titre corresponding to the median TC in neat semen, in addition to lower titres. Samples were spread on LB-medium after 0, 10, 15, 20, 30 and 45 min incubation. Bacteria were found in neat semen from 19 of the bulls, coliforms from 4 and thermostable coliforms in only one (Table 1). No bacterial growth was observed in extended/cooled, frozen/thawed semenor from extender containing AB. In extender without AB, significant bacterial growth was observed, but no growth of AB-resistant or coliform bacteria was detected. In AB-containing extender inoculated with bacteria, bacterial growth was found on samples collected 0, 10, 15 and 20 min after inoculation, but not after 30 and 45 min incubation. The bacterial growth persisted for a longer period when the contaminating dose was increased. Table 1. Bacterial count in neat semen from 20 Norwegian Cattlebulls. Number of bacteria per ml Examination No of bulls pos. Range Average ± SD Median Total bacteria count (TC) 19 0-2.5*105 3.5*104±5.3*104 7.2*103 Coliforms (CF) 4 0-6.6*102 1.0*102±2.2*102 0 Thermostable col. (TCF) 1 0-2.8*103 - 0 Key words: bull semen, bacteria, quality control, antibiotics * Antibiotics used in the study: penicillin/ streptomycin

• Strætkvern, Knut Olav; Zafirakos, Elias & Oleander, Morten Aae (2001). Capture of functional proteins from potato processing effluents : a model system for plant protein recovery using expanded bed adsorption. Full text in Research Archive
• Strætkvern, Knut Olav; Wiesenborn, Dennis P; Zafirakos, Elias & Lihme, Allan (2001). Capture of patatin from potato fruit juice using mixed mode EBA matric es. Full text in Research Archive Show summary

  We have employed crude potato fruit juice (PFJ) as a model feedstock to isolate patatin as the target protein using an expanded bed adsorp tion (E process to investigate bioprocessing of proteins from plant b iomass. Patatin is the major storage protein of potato tubers, and is released in ample amounts (20-40% of soluble protein) in the fruit j uice during starch milling. The protein possesses lipid acyl esterase activity, which facilitates easy enrichment monitoring during purifi cation. The patatins, heterogeneous by charge, are glycoproteins (44 kDa), and dimerize to obtain the active enzyme form. Crude PFJ is a p rocess waste effluent rich in proteins, minerals, and organic acids, however, the juice is unstable due to the oxidation of plant phenolic s which rapidly discolor the juice. To avoid dilution of the high-con ductivity

• Strætkvern, Knut Olav (2000). Hva er genmodifisering ? Hva gjør det med maten vår ? Full text in Research Archive
• Strætkvern, Knut Olav (2000). Bioteknologi - nye muligheter for Hedmark ? Horisont 21: scenarier ved et nytt årstusen. Konferanse i regi av Hedmark Fylkeskommune og Sparebanken Hedmark. Full text in Research Archive
• Strætkvern, Knut Olav; Zafirakos, Elias & Olander, Morten Aae (2000). Direct recovery of target and total protein from crude feedstock with mixed mode adsorbents in expanded beds. Full text in Research Archive Show summary

  Expanded bed adsorption (EBA) bioprocessing of potato processing effluents, opposite to traditional harsh bulk precipitation methods retain the structural integrity of the tuber proteins. Whole or fractionated potato tuber protein, with improved functional qualities could prove useful in food systems and other biological applications. Employing high-density agarose-glass adsorbent particles in a fluidized bed configuration, expanded beds allow the crude feedstock to be fed directly to the column in a uniform upward flow. The adsorbent particles are coupled with a heterofunctional (mixed mode) ligand developed by UpFront Chromatography AS. The ligands consist of small organic molecules containing both hydrophobic and ionic substituents, customized to capture the target proteins. Protein binding is strongly pH dependent, but insensitive to high ionic strength. We describe a scaleable approach for native protein recovery on customized mixed mode adsorbents. Following a pH adjustment, the crude effluent (15-20 gl-1 protein) from potato starch milling was applied to a 5-cm expanded

• Strætkvern, Knut Olav (2000). Bioteknologi ved Høgskolen i Hedmark. Debattinnlegg. "Perspektiver i moderne bioteknologi- nye muligheter for Innlandet.". Full text in Research Archive
• Strætkvern, Knut Olav (1998). Bioteknologi og poteten : ny teknologi under skallet. Full text in Research Archive
• Strætkvern, Knut Olav; Lund, Tina & Rønning, Rolf S. (1998). Patatin - the plentiful potato protein : Some molecular characteristics and enzymology of the lipid acyl hydrolase. Full text in Research Archive Show summary

  We have purified patatin, the lipid acyl hydrolase of potato tubers ( cv. Laila), to homogeneity. Patatin is an fatty acid esterase hydroly sing a va of mono- and diacyl lipids. Besides its function as storage protein, patatin has potency as an insecticide, possibly due to its release of cytotoxic fatty acids. We have studied patatin in relation to its large scale recovery from potato processing waste and potenti al technological applications. Our report adresses some enzymological aspects as well as its protein chemistry. N-terminal analysis of the first 22 residues confirmed its identity as it almost have complete homolgy to other known patatin sequences. Isoelectric focusing of the homogenous 44 kDa protein revealed 6-10 isozymes in the range 4,5-5, 1, as judged by paralell zymogram analysis. Charge heterogenity of pa tains is thought of different gene products. The native enzyme protei n was also analysed by gelfiltration, appearing as a possible multime ric aggregate form. The temperature stability at pH 8,2 showed rapid inactivation at 60ºC (t=1,7 min), whereas prolonged stability was obs erved at 50ºC (192 min) and 40ºC (>48 h). Rapid deactivation is consi stent with the collapse of

• Strætkvern, Knut Olav; Blystad, Frøydis D. & Bøhler, Randi A. (1998). Deproteinised potato fruit juice as a complete medium for growth of Lactobacillus plantarum NCDO 1752. Full text in Research Archive Show summary

  Potato starch mills generate waste effluents rich in minerals, free a mino acids and proteins, and non-protein N-substances, essential for microbial growth. From a potato processing plant, two aseptic juice f ractions were obtained after deproteinisation; potato protein liquo r (PPL) and potato ultrafiltration permeate (PUP). Both media were te st ed as complete growth media for Lactobacillus plantarum, strain NC DO 1752, and were compared to the standard Man-Rogosa-Sharp media for la ctobacilli. Optimal growth conditions on PPL and PUP were establi shed in a microtiter screening assay (300 ml), verified in shaking b ottle s (100 ml), and finally transferred to 2 liter CSTR-fermentatio ns und er pH-stat conditions. On pure PPL and PUP, with 2% dextrose a nd at 3 7oC, pH 6.5, the growth rate, lactic acid production and the total ce ll mass yield, were comparable on all levels of cultivation. However, fermentable sugars present in the potato juices, alone pro vided enou gh energy for growth and lactate production, typically 20- 40 % of the control. Growth yields on 2 % dextrose in PPL and PUP fer mentations, were 30-40 % higher than the MRS-control, but the specifi c growth rat es were 80% an

• Strætkvern, Knut Olav; Lund, Tina; Mathisen, Tone & Rønning, Rolf S. (1998). Recovery by adsorbtion of esterase active patatins from potato processing waste. Full text in Research Archive Show summary

  We have designed an ion exchange adsorbtion process which concentrate s and fractionates the major soluble proteins from potato waste, the patatins. patatins are anionic isoenzymes (44 kDa), having a lipid ac yl hydrolase (LAH) activity, which is useful for monitoring protein e nrichment. The raw potato juice (36 g protein l-1) collected from a c onventional starch manufacturing process, was conditioned with respec t to the protein concentration, pH and conductivity prior to capture on Q Sepharose Big Beads in an axial flow, 40 ml lab scale column. Pa tatin was selectively concentrated with a factor of five, at 80-98 % recovery, and after freeze drying, 81% of the initial LAH-activity re mained. Analysis of the contaminating protease inhibitors, currently a major hindrance for food applications of the raw protein fraction, demonstrated a 43-57% reduction compared to the raw feed. The column cycle was succesfully scaled up employing a 250 ml radial flow column . The dynamic binding capacity of the adsorption process was sensitiv e to the linear flow rate, possibly due to diffusion limitations. How ever, doubling the total protein load to 150 mg ml-1 gel, the enrichm ent factor increased from 2

• Strætkvern, Knut Olav & Føllesdal, Liv Marthe Stigen (1998). Fractionation of potato proteins by ultrafiltration. Full text in Research Archive Show summary

  Potato starch processing generates large volumes of process juice (5% dry weight) with a high content (50%) of water soluble proteins. Pot ato prote consist of 3-4 distinct molecular weight fractions of 5-100 kDa, the major fractions beeing Kunitz-type protease inhibitor compo nents (22kDa) and the glycoprotein patatin (44 kDa). Mainly considere d a waste stream of low economical value, potato juice concentrates a re now seeking new applications. Based on gel permeation profiles of crude process juice, we have performed preliminary fractionation and concentration experiments by ultrafiltration in an open channel filte r unit (Bioengineering). Selective retenetion of all proteins above 1 5 kDa was attained with membrane of 30kDa MWCO, whereas a membrane of 100kDa MWCO leaked the major protein fractions to the permeate. Char acteristics of batch processes are presented.

• Joshi, Mukund; Ahmad, Rafi & Strætkvern, Knut Olav (2021). Testing of different conditions to accelerate culturing and potentially reduce the time of detection of pathogens and antimicrobial resistance. HINN. Full text in Research Archive
• Strætkvern, Knut Olav (1997). Laboratorium for bioanalyser - Delprosjekt "Analyse av aminosyrer i fôrvarer". Sluttrapport for prosjektperioden 1995-96. Høgskolen i Innlandet. Full text in Research Archive Show summary

  Kvantitativ bestemmelse av essensielle aminosyrer i fôrvarer står sen tralt i dokumentasjonen av fôrets ernæringsverdi. Rask og sikker best emmelse er viktig for å sikre tilfredstillende produkter. Delprosjekt et ble startet som et utviklingsprosjekt for å etablere nødvendig kun nskap og metodikk for å kunne utføre aminosyreanalyser her i regionen , med utgangspunkt i laboratoriemiljøet ved Blæstad, i samarbeid med HIAS. Utvikling av metoder for aminosyrebestemmelse av essensielle am inosyrer i fast og flytende fôr ble utført. Det foreligger standard o perasjonsprosedyrer (SOP) for de fleste prosedyretrinnene som grunnla g for senere akkreditering. Prosjektet har dokumentert anvendelsen av en ny og raskere metode med bruk av mikrobølgeovn for prøveopparbeid ing som vil kunne gi en mer rasjonell analysedrift. Mikrobølgeovn-hyd rolyse ga også overraskende gode data for enkelte sårbare aminosyrer. Prosjektet oppnådde ikke å nå tilfredsstillende analysebetingelser f or alle aminosyrer, slik at det fortsatt er nødvendig med en instrume ntbetinget optimalisering av HPLC-analysene. Prosjektet har vist at d et er teknisk mulig å etablere et analyseopplegg for aminosyrer i fôr varer med de ressurser som

• Strætkvern, Knut Olav (1991). Cod panereatic deoxyribonuclease. Studies on an alkaline DNase from pyloric caeca of Atlantic cod (Gadus morhua L.). Universitetet i Bergen. ISSN 9788275580045. Full text in Research Archive

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