A strategy for stimulating astaxanthin and lipid production in Haematococcus pluvialis by exogenous glycerol application under low light

In large-scale outdoor cultivation, Haematococcus pluvialis cultures are frequently exposed to low light caused by continuous rain conditions. Low light significantly restricts biomass and astaxanthin accumulation, thereby decreasing astaxanthin productivity. In this study, the effects of exogenous glycerol on the growth, photosynthesis, and astaxanthin and lipid accumulation in H. pluvialis under low light were investigated. A strategy was developed for promoting astaxanthin and lipid production in H. pluvialis under low light by the application of exogenous glycerol. Under low light, exogenous glycerol did not change the biomass and photosynthetic capacity of H. pluvialis. The addition of 1 mL L-1 glycerol increased total lipid content by 36.8% by increasing the formation of fatty acids during an 11-day growth period. Furthermore, exogenous glycerol could directly accelerate astaxanthin production under low light by increasing the formation of substrates (e.g. pyruvate). Meanwhile, the elevated fatty acid level due to the addition of glycerol facilitated the esterification of astaxanthin, thereby accelerating the biosynthesis of astaxanthin indirectly, which is indicated by the fact that exogenous glycerol enhanced astaxanthin esters content significantly under low light. All these results suggest that H. pluvialis has the ability to utilize glycerol for astaxanthin and lipid production under low light.