Spent yeast as an efficient medium supplement for fucoxanthin and eicosapentaenoic acid (EPA) production by Phaeodactylum tricornutum

Fucoxanthin and eicosapentaenoic acid (EPA) are high-value compounds that can be found in the marine diatom Phaeodactylum tricornutum. Yet, the growth rate of this microalga is relatively low under photoautotrophic conditions. The purpose of this study was to evaluate the feasibility of using spent yeast, the second-major by-product of the brewing industry, as a useful substrate for P. tricornutum cultivation. Different pretreatments, concentrations of spent yeast, and initial cell densities of P. tricornutum were investigated. After 12 days of cultivation in f/2 medium, P. tricornutum supplemented with 1.33 g L-1 preautoclaved spent yeast yielded 3.28 times more fucoxanthin (5.97 mg L-1) and 3.55 times more EPA (16.82 mg L-1) than P. tricornutum grown without the yeast (fucoxanthin 1.82 mg L-1, EPA 4.64 mg L-1). Nutrient analysis showed that the nitrogen and phosphorus released by the spent yeast were consumed over time. Overall, spent yeast effectively promoted the fucoxanthin and EPA yields of P. tricornutum.