Assessment of the feasibility of co-production of fucoxanthin, omega-3 fatty acids and bioethanol from marine microalgae

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 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 illuminance levels (LL: 3,750 lux; ML: 7,500 lux; HL: 11,250 lux). 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 biphasic solvent extraction procedure using ethanol/n-hexane/water (10:9:1 v/v/v) was utilized for co-extraction of 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. Thus, results showcase the efficacy of the developed co-extraction procedure and the biorefinery potential of T. lutea.