Optimization of the Induction Conditions and Fermentation Processes for High-yield Production of Astaxanthin by Chromochloris zofingiensis
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Abstract:
In this study, the effects of different induction conditions and tank photo-fermentation processes on mixotrophic Chromochloris zofingiensis were investigated, and the algal cell biomass and astaxanthin accumulation were increased through parameter optimization. Different induction conditions including the effects of different mixed carbon sources and hydrogen peroxide concentrations in the shake-flask system on the growth and astaxanthin accumulation of Chromochloris zofingiensis were first systematically compared. In the photo-fermentation tanks, the effects of three different fermentation process conditions, i.e., constant high light intensity, lowlight intensity-high light intensity, and lowlight intensity-high light intensity combined with hydrogen peroxide addition, on the accumulation of astaxanthin in Chromochloris zofingiensis were examined. The results demonstrated that the highest biomass (6.50 g/L) was obtained in C. zofingiensis cultivation using the mixed carbon source (a mixture of glucose (20 g/L) and sodium acetate (2.50 g/L)) instead of the sole carbon source. The supplementation of hydrogen peroxide at 107.50 mg/L further increased the astaxanthin content to 3.23 mg/g with the highest astaxanthin yield as 72.47 mg/L (which was 1.80 times that of the control), resulting in effective promotion of cellular growth of algal biomass and accumulation of astaxanthin. In a 5-L photo-fermenter, 20 g/L glucose and 2.50 g/L sodium acetate were used as a mixed carbon source to cultivate C. zofingiensis via the combination of low light intensity-high light intensity-hydrogen peroxide supplementation, leading to a relatively high astaxanthin content (3.82 mg/g) and yield (41.41 mg/L), which were 36.92% and 92.96%, respectively, higher than those obtained under the constant high light intensity conditions. This work improved effectively the biomass and astaxanthin production of Chromochloris zofingiensis through the optimization of induction conditions and fermentation processes, which provides a basis for astaxanthin production by C. zofingiensis in photo-fermenters.
