Optimizing fucoxanthin production from Phaeodactylum tricornutum: Impact of harvesting methods on culture medium reusability.

The growing demand for naturally-synthesized fucoxanthin has driven increased focus on microalgae-based production methods. However, the high costs associated with microalgae harvesting and processing remain a significant challenge. To overcome this obstacle and promote the development of the microalgae-based fucoxanthin industry, this study aimed to develop an efficient and cost-effective methods for harvesting Phaeodactylum tricornutum , a promising microalgal strain for fucoxanthin production, while maximizing the reuse of the culture medium. This study investigated the feasibility of reusing the FeCl 3 -based flocculation medium for P. tricornutum cultivation, and explored the optimal proportion of recycled supernatant and fresh medium for maximizing biomass and fucoxanthin yield of P. tricornutum. It also examined the effect of residual iron on harvested biomass and pigment and proposed a simple washing method for its removal. The results showed that FeCl 3 -based flocculation was highly effective (>93 %) in harvesting P. tricornutum , and a 50/50 proportion of recycled medium and fresh medium can be used without significant negative effects on biomass and fucoxanthin productivity, allowing a reduction of approximately 43 % water consumption. Although a negative effect on algal fucoxanthin content was observed, the productivity of fucoxanthin per unit volume (mg/L) did not decrease compared to centrifugation-based algae cells. Furthermore, simple washing with water can effectively remove the residual iron from the harvested biomass or pigment, resulting in a reduction of approximately 42 % and 64 %, respectively. These findings suggest that the reuse of FeCl 3 -based flocculation medium for P. tricornutum cultivation is feasible and holds promise for cost-effective fucoxanthin production. This study contributes to develop a sustainable approach for microalgae-based fucoxanthin production at a lower cost and higher production capacity, benefiting both society and industry. [Display omitted] • FeCl 3 was highly effective (>93 %) in harvesting P. tricornutum. • FeCl 3 flocculation slightly decreased fucoxanthin content but not biomass yield. • Recycling 50 % of flocculated medium affected biomass and fucoxanthin yield little. • Reusing flocculated medium is feasible for P. tricornutum fucoxanthin production. [ABSTRACT FROM AUTHOR]