Purple LED light and crude glycerol synergistically enhance astaxanthin production in Aurantiochytrium limacinum

Aurantiochytrium limacinum is a heterotrophic marine protist known for its ability to co-produce docosahexaenoic acid (DHA) and carotenoids such as astaxanthin. Despite its biotechnological potential, industrial application is hindered by high production costs. In this study, we investigated the effects of different light wavelengths and carbon sources on the production of carotenoids and neutral lipids in A. limacinum. Purple LED light (410–420 nm) significantly enhanced the biosynthesis of β-carotene, canthaxanthin, and astaxanthin compared to white light or darkness. Additionally, the use of glycerol or crude glycerol, a byproduct of biodiesel production, affected carotenoid profiles. β-Carotene and canthaxanthin were more abundant in cultures supplemented with glycerol or crude glycerol, whereas astaxanthin was predominantly produced in cultures supplemented with glucose. Notably, crude glycerol treated via acidification and activated carbon enabled cell growth and metabolite production comparable to that observed with glucose. These findings suggest that light quality and carbon source synergistically influence carotenoid biosynthesis in A. limacinum. The use of industrial byproducts combined with light optimization represents a sustainable and cost-effective strategy for enhancing microbial production of high-value compounds.