EMPLOYMENT OF ORGANIC ACIDS TO ENHANCE ASTAXANTHIN FORMATION IN HETEROTROPHIC CHLORELLA ZOFINGIENSIS

The green alga Chlorella zofingiensis produces significant amounts of the valuable ketocarotenoid astaxanthin under heterotrophic growth conditions. In this study, pyruvate, citrate and malic acid were investigated, for the first time, to promote the formation of secondary carotenoids including astaxanthin in C. zofingiensis in the dark. The addition of pyruvate, citrate and malic acid into the culture medium at a concentration above 10 mM stimulated biosynthesis of astaxanthin and other secondary carotenoids. The addition of 100 mM pyruvate enhanced the yield of astaxanthin from 8.36 to 10.72 mg/L, representing an increase of 28.2%. Citrate and malic acid also had stimulatory effects on the formation of astaxanthin. The results showed that organic acid supplementation was potentially useful for commercial production of astaxanthin by C. zofingiensis in dark heterotrophic culture.