Mr. Thanh Nguyen Van

Microalgae are intensively investigated and used commercially as food and feed ingredients, including protein, carbohydrates, antioxidants and omega-3 long-chain polyunsaturated fatty acid (LC-PUFA). Microalgal biotechnology for omega-3 LC-PUFA production holds promise to reduce human dependence on fish oils. This research was conducted to investigate a novel thermotolerant indigenous microalga isolated in Israel (tentative name: BZ). This eustigmatophyte microalga is a promising producer of the omega-3 LC-PUFA eicosapentaenoic acid (EPA). Molecular phylogenetic analysis revealed BZ to be a new species. BZ was grown in nitrogen replete and deprivation conditions; total lipids were extracted and fractionated into polar and neutral lipids to elucidate the distribution of EPA in different lipid classes. Under nutrient replete conditions, EPA accounted for over 35% of total fatty acids (TFA) and ~ 3% of dry weight. Saturated fatty acids, dominated by myristic acid (14:0), accounted for 23 – 26% of TFA. Under N starvation, TFA content increased to 30% of dry weight. Under nutrient-repleted conditions, the major chloroplast lipid monogalactosyldiacylglycerol (MGDG) (42% of total polar lipids) and the betaine lipid 1,2 diacylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (DGTS) (6.1 % of total polar lipids) contained over 60% EPA, indicating their major role in the biosynthesis of EPA. Triacylglycerol accounted for 13 % of total lipids and comprised ~ 15% of EPA. Nitrogen starvation triggered storage lipid accumulation and changes in cell morphology. Storage lipid triacylglycerol increased under N starvation conditions along with modification in the fatty acid profile. During N starvation, the main fatty acid EPA decreased from 38% of TFA to 14.5% but accounted for 4% of the dry biomass by day 12 of N starvation conditions.