Jette Jakobsen

Nannochloropsis oceanica is cultivated, at industrial scale, mainly for aquaculture feed and is known to contain different bioactive compounds, such as fat-soluble vitamins and long-chain polyunsaturated fatty acids. However, data on the variability and availability of these compounds over year-long outdoor cultivation conditions are absent. We conducted a longitudinal observational assessment of vitamin D₃ and fatty acid content and composition of N. oceanica cultivated in an outdoor pilot scale pond in southern Israel (29.6° N). Cultivation cycles of 30 days were monitored across eight months between January and October. We further determined the vitamin K content during January and March. In freeze-dried biomass the vitamin D₃ content ranged from 3 to 253 ng/gram and was positively associated with mean UV-index and pond pH. Menaquinone-4 was the only vitamin K vitamer detected (14–37 µg/gram) and was primarily associated with pond temperature. Total fatty acid in freeze-dried biomass was relatively constant at 7.6 ± 1.7% of which 1–3.5% was eicosapentaenoic acid (EPA). The fatty acid profile shifted during the 30-day cultivation period, with increasing relative proportions of EPA and decreasing proportion of saturated fatty acids. The results highlight substantial temporal and cultivation-related variability under real production conditions and provide a basis for controlled optimization studies.

The marine microalga Nannochloropsis oceanica is a promising organism for sustainable production of lipids, omega-3 fatty acids, and biomass with a high nutritional value. We demonstrate UV mutagenesis combined with visual screening to generate novel non-GMO strains with improved industrial traits. Four mutants displayed altered pigmentation and/or enhanced growth after UV treatment, of which mutants M34 and M181 were selected for detailed characterization. Mutant M34 displayed enhanced biomass productivity under high light conditions (400 µmol m⁻² s⁻¹) in small-scale photobioreactor cultivations, indicating improved tolerance to elevated irradiance. Pigment analyses revealed reduced levels of several xanthophyll carotenoids, suggesting altered light adaptation and photoprotective responses. However, the improved growth phenotype was not consistently maintained at medium and pilot scale, highlighting the strong influence of cultivation conditions on measured strain performance. Mutant M181 exhibited strongly reduced chlorophyll content, accompanied by impaired growth at elevated light intensities. Pilot-scale cultivation demonstrated significantly increased lipid accumulation, reaching up to 25% of dry matter compared to 17% in the wild type. While M181 showed an unaltered composition of amino acids, total fatty acids, and eicosapentaenoic acid, we found elevated vitamin D3 accumulation after UVB exposure and significantly higher menaquinone-4 (MK-4) bioaccessibility, potentially improving the nutritional functionality. The results demonstrate that UV mutagenesis combined with simple visual screening is an effective strategy to generate N. oceanica strains with altered biomass composition and growth performance. Our study shows the importance of evaluating mutants under industrially relevant conditions, as phenotypes observed at laboratory scale may not translate well to pilot-scale systems.

The marine microalga Nannochloropsis oceanica is a promising organism for sustainable production of lipids, omega-3 fatty acids, and biomass with a high nutritional value. We demonstrate UV mutagenesis combined with visual screening to generate novel non-GMO strains with improved industrial traits. Four mutants displayed altered pigmentation and/or enhanced growth after UV treatment, of which mutants M34 and M181 were selected for detailed characterization. Mutant M34 displayed enhanced biomass productivity under high light conditions (500 µmol m⁻² s⁻¹) in small-scale photobioreactor cultivations, indicating improved tolerance to elevated irradiance. Pigment analyses revealed reduced levels of several xanthophyll carotenoids, suggesting altered light adaptation and photoprotective responses. However, the improved growth phenotype was not consistently maintained at medium and pilot scale, highlighting the strong influence of cultivation conditions on measured strain performance. Mutant M181 exhibited strongly reduced chlorophyll content, accompanied by impaired growth at elevated light intensities. Pilot-scale cultivation demonstrated significantly increased lipid accumulation, reaching up to 25% of dry matter compared to 17% in the wild type. While M181 showed unaltered composition of amino acids, total fatty acids and eicosapentanoic acid, we found elevated vitamin D3 accumulation after UVB exposure and significantly higher menaquinone-4 (MK-4) bioaccessibility, indicating improved nutritional functionality. The results demonstrate that UV mutagenesis combined with simple visual screening is an effective strategy to generate N. oceanica strains with altered biomass composition and growth performance. Our study shows the importance of evaluating mutants under industrially relevant conditions, as phenotypes observed at laboratory scale may not translate well to pilot-scale systems.

Vitamin D has been shown to influence growth in both fetuses and piglets. Pigs housed indoors rely solely on their feed as a source of vitamin D since they are never exposed to natural sunlight. UVB light is effective in improving the vitamin D status in sows and piglets housed indoors. This study aimed to investigate an innovative method for UVB lighting to enhance the vitamin D status of gestating sows to a level that could positively impact the growth of both fetuses and suckling piglets. A total of 386 sows were included at the time of insemination. Of these, 197 were exposed to a daily dose of UVB light, and 189 sows served as a control group. Both sows and piglets in the UVB group had significantly higher vitamin D levels in serum samples at the time of farrowing than sows and piglets from the control group. No statistically significant differences in litter weight or the number of liveborn or stillborn piglets were observed between groups. UVB light installed in an electronic sow feeder was successful, but, unfortunately, the lamp used in the study was unable to induce the production of vitamin D to the desired level in the sows. Further studies are needed to investigate the effect of higher doses of UVB light.

Vitamin C could be a potential candidate for antioxidant therapy in ulcerative colitis (UC) patients, but efficient small intestinal absorption of vitamin C prevents it from reaching the colon, limiting the direct antioxidative effect on inflamed colonic tissue. We applied a colitis mouse model to compare three oral delivery strategies for high-dose vitamin C: dissolved in drinking water, mixed into peanut butter, and in colon-targeted microcontainers administered with peanut butter. Mice were administered dextran sulfate sodium (DSS) to induce UC symptoms. Healthy control and DSS control groups were included. Alleviation of disease symptoms and microbial dysbiosis were assessed to elucidate the effects of encapsulation and stabilization of vitamin C during intestinal transit. Vitamin C in peanut butter, independent of microcontainers, alleviated UC symptoms. Administration in drinking water surprisingly exacerbated symptoms compared to the DSS control group. DSS-treatment caused an increased level of facultative anaerobes in the fecal microbial community that was not affected by vitamin C administration. Vitamin C partially reduces disease activity index in DSS-treated mice, when delivered in peanut butter, likely promoting vitamin C stability. Drinking water delivery did not support vitamin C-related alleviating effects. None of the evaluated delivery strategies affected the DSS-induced changes of the microbial community.

Microalga Nannochloropsis oceanica presents a promising source of high-value food ingredients such as protein, omega-3 fatty acids, and vitamins. To fully unlock its potential, a thorough understanding of how cultivation conditions affect both growth and the nutritional composition is required. Hence, this study aimed to test and model the effects of temperature, light intensity, and salinity on biomass productivity and the final contents of protein, eicosapentaenoic acid (EPA), and vitamin K₂ using response surface methodology (RSM). The RSM experiment revealed that the highest temperature and light intensity tested favored biomass productivity and protein content. According to the generated models, the two responses peaked with 0.135 g DM·L⁻¹·day⁻¹ and 0.559 g·g⁻¹ DM, respectively, at 27 °C and 300–350 µmol·m⁻²·s⁻¹. In contrast, the contents of both EPA and menaquinone-4 (MK-4), the only detected K vitamer, were stimulated at the lowest tested temperature. Based on the generated models, the two responses peaked with 0.037 g·g⁻¹ DM and 89.3 µg·g⁻¹ DM, respectively, at 19 °C combined with 3.0% salinity (EPA) or 120 µmol·m⁻²·s⁻¹ (MK-4). Although additional optima may exist beyond the tested conditions, these findings provide valuable information on N. oceanica’s cellular response to changes in key cultivation conditions. Furthermore, it shows that two-stage cultivation may be needed to fully unlock the potential of this microalga as a future source of valuable lipid ingredients.

With the aim to upcycle fish side-streams, enzymatic hydrolysis is often applied to produce protein hydrolysates with bioactive properties or just as a protein source for food and feed. However, the production of hydrolysates generates a side-stream. For underutilized fish and fish backbone this side-stream will contain fish bones and make it rich in minerals. The aim of this study was to assess the relative bioaccessibility (using the standardized in vitro model INFOGEST 2.0) of minerals in a dietary supplement compared to bone powder generated after enzymatic hydrolysis of three different fish side-streams: undersized whole hake, cod and salmon backbones consisting of insoluble protein and bones. Differences in the bioaccessibility of protein between the powders were also investigated. The enzyme hydrolysis was carried out using different enzymes and hydrolysis conditions for the different fish side-streams. The content and bioaccessibility of protein and the minerals phosphorus (P), calcium (Ca), potassium (K) and magnesium (Mg) were measured to evaluate the potential of the powder as an ingredient in, e.g., dietary supplements. The bone powders contained bioaccessible proteins and minerals. Thus, new side-streams generated from enzymatic hydrolysis can have possible applications in the food sector due to bioaccessible proteins and minerals.