Interactive effects of light and temperature on pigments and n-3 LC-PUFA-enriched oil accumulation in batch-cultivated Pavlova lutheri using high-bicarbonate supply

We investigated the simultaneous effects of light and temperature on pigments, lipid remodeling, and omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) partitioning into lipid classes of P. lutheri. Biomass was produced in batch cultivation using high bicarbonate supply, and hence, any potential accumulation of lipid and triacylglycerols (TAG) containing n-3 LC-PUFA was triggered by nitrogen (N) limitation. The maximum productivities of both eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were obtained after nitrate-depletion when P. lutheri was cultivated at optimal growth conditions; these occurred at an intermediate temperature of 18 °C and low light intensity (40 μmol photons·m− 2·s− 1) for EPA, but there was no impact of light (40 or 200 μmol photons·m− 2·s− 1) for DHA production. Under these respective optimum conditions, TAG accounted for 82-84% of TFA on day 15 of cultivation, which contained up to 76-84% of the total cellular EPA and 67-81% of total cellular DHA. Our results clearly demonstrate the process of lipid remodeling in P. lutheri and, for the first time, a potential membrane lipid turnover with transfer of n-3 LC-PUFA (EPA and DHA) from membranes (polar lipids, PL) to storage lipids (TAG), highlighting the accumulation of n-3 LC-PUFA-rich oil during N-starvation (i.e., TAG containing: EPA ~ 12-13% and DHA ~ 5-6% of TFA). When cultivated under low light conditions, P. lutheri additionally accumulated substantial quantities of antioxidant pigments (i.e., fucoxanthin, diadinoxanthin and β-carotene), which add value to extracted bioactive oil for functional food applications. Omega-3 rich oil accumulation and pigment levels in P. lutheri appear to be simultaneously regulated by both light and temperature, in addition to N-limitation during batch-cultivation.