Co-production of fucoxanthin, docosahexaenoic acid (DHA) and bioethanol from the marine microalga Tisochrysis lutea

Abstract

The marine microalga Tisochrysis lutea is renowned for its ability to synthesize fucoxanthin and docosahexaenoic acid (DHA), which are nutritionally valuable high-value compounds. Although numerous studies in literature have assessed fucoxanthin and DHA production by T. lutea, very few studies have evaluated the feasibility of comprehensively utilizing biomass for co-production of these metabolites within the framework of biorefineries. To this end, the current study focused on the synthesis of fucoxanthin and DHA by cultivation of T. lutea under two different initial nitrate concentrations (1x: 882 µM, 3x: 2,646 µM) and three different light intensities (LL: 50 µmol/m2/s; ML: 100 µmol/m2/s; HL: 150 µmol/m2/s). The maximum fucoxanthin yield of 8.80 ± 0.30 mg/L (14.43 ± 0.52 mg/g) and DHA yield of 7.08 ± 0.02 mg/L (11.90 ± 0.14 mg/g) were achieved in the 3x HL culture at the end of 16 days of cultivation. Thereafter, a novel process of biphasic solvent extraction using ethanol/n-hexane/water (10:9:1 v/v/v) was utilized for co-extraction 97.96 ± 0.54% fucoxanthin and 74.11 ± 1.49% DHA from 3x HL biomass, and products were separated into two fractions. Fermentation of the residual biomass obtained from co-extraction resulted in a bioethanol yield of 48.49 ± 0.58 mg/g. Accordingly, the current study demonstrated the potential of T. lutea as a feedstock for biorefineries.