The difference in light intensities during culture affects the production of health-beneficial metabolites in a diatom used in producing aquaculture feed.

Microalgae are increasingly being utilized as sustainable materials for aquaculture feed production. As microalgae-derived compounds, including those with health benefits to humans, can accumulate in the bodies of fish and shellfish, enhancing the production of these compounds will further add value to the utilization of microalgae as aquaculture feed. Although light intensity has been known to affect the composition of intracellular compounds, the relationship between light intensity and the production of health-beneficial metabolites in microalgae remains unclear. Hence, in this study, the changes in the production of water- and lipid-soluble compounds in Chaetoceros gracilis, a diatom species used as aquaculture feed, under high and normal light conditions were quantified by performing metabolome analyses. While there was no significant difference in the growth of C. gracilis between the light conditions, the overall composition of compounds differed between the light intensities, and several health-beneficial metabolites were specifically produced under each light condition. Interestingly, these included compounds such as nobiletin and carnosine, which are not commonly reported to be produced by microalgae. Our results suggest the potential that by varying light intensity, we selectively modulate the types and amounts of health-beneficial metabolites in microalgal cells without altering the overall yield of the feed.