Enzymatic conversion of fatty acids (FAs) by fatty acid hydratases (FAHs) presents a green and efficient route for high‐value hydroxy fatty acid (HFA) production. However, limited diversity was achieved among HFAs, to date, with respect to chain length and hydroxy position. In this study, two highly similar FAHs from Lactobacillus acidophilus were compared: FA‐HY2 has a narrow substrate scope and strict regioselectivity, whereas FA‐HY1 utilizes longer chain substrates and hydrates various double‐bond positions. It is revealed that three active‐site residues play a remarkable role in directing substrate specificity and regioselectivity of hydration. If these residues on FA‐HY2 are mutated to the corresponding ones in FA‐HY1, a significant expansion of substrate scope and a distinct enhancement in hydration of double bonds towards the ω‐end of FAs is observed. A three‐residue mutant of FA‐HY2 (TM‐FA‐HY2) displayed an impressive reversal of regioselectivity towards linoleic acid, shifting the ratio of the HFA regioisomers (10‐OH/13‐OH) from 99:1 to 12:88. Notable changes in regioselectivity were also observed for arachidonic acid and for C18 polyunsaturated fatty acid substrates. In addition, TM‐FA‐HY2 converted eicosapentaenoic acid into its 12‐hydroxy product with high conversion at the preparative scale. Furthermore, it is demonstrated that microalgae are a source of diverse FAs for HFA production. This study paves the way for tailor‐made FAH design to enable the production of diverse HFAs for various applications from the polymer industry to medical fields.

Chlorella pyrenoidosa and Chlorella vulgaris were cultivated in pre-gasified industrial process water with high concentration of ammonia representing effluent from a local biogas plant. The study aimed to investigate the effects of growth media and cultivation duration on the nutritional composition of biomass. Variations in proteins, lipid, fatty acid composition, amino acids, tocopherols, and pigments were studied. Both species grew well in industrial process water. The contents of proteins were affected significantly by the growth media and cultivation duration. Microalga Chlorella pyrenoidosa produced the highest concentrations of protein (65.2% ± 1.30% DW) while Chlorella vulgaris accumulated extremely high concentrations of lutein and chlorophylls (7.14 ± 0.66 mg/g DW and 32.4 ± 1.77 mg/g DW, respectively). Cultivation of Chlorella species in industrial process water is an environmentally friendly, sustainable bioremediation method with added value biomass production and resource valorization, since the resulting biomass also presented a good source of proteins, amino acids, and carotenoids for potential use in aquaculture feed industry.

For the last two decades there has been a rise in awareness about the general low dietary intake of vitamin D3. Fish have the highest natural content of vitamin D3, which is suggested to originate from zooplankton and microalgae. However there are no studies reporting which microalgal species may be the source of vitamin D3. In this study, four selected microalgal species were cultivated during exposure of artificial UVB. The effect of UVB dose on the growth and biochemical composition of the cells (vitamin D3, PUFAs and carotenoids) was evaluated. Of the four species, exclusively Nannochloropsis oceanica was able to produce vitamin D3 (up to 1±0.3 µg/g DM), and production was significantly enhanced by increasing the dose of the UVB. These findings suggest that N. oceanica exposed to artificial UVB could be used as a new natural source of vitamin D3, either as direct source or through animal feed.

No abstract

No abstract