Effects of sodium acetate and ammonium acetate on the growth and production of cellular components by Chlorella vulgaris 31

Mixotrophic cultivation using organic carbon sources has become increasingly important for large-scale production and application of microalgae, as it can overcome the current commercial bottleneck of low yield and high cost associated with photoautotrophic and heterotrophic cultivation. In this study, we investigated the effects of adding two acetates, sodium acetate (NaAc) and ammonium acetate (NH 4 Ac), at different concentrations (2, 4, 6, 8, 10 and 12 g L -1 ) on the biomass, biochemical components content (pigments, proteins, soluble sugars and lipids) and fatty acid composition of Chlorella vulgaris 31 ( Cv -31) under mixotrophic cultures. Our results showed that the addition of NaAc significantly increased the biomass and lipid content of microalgae compared with NH 4 Ac, with 10 g L -1 NaAc having the best effect on the growth and lipid synthesis. Furthermore, only 2 and 4 g L -1 NaAc promoted the synthesis of pigments in algal cells, while all different concentrations of NH 4 Ac were inhibitory. In contrast to pigments, the effect of two acetates on protein synthesis was opposite, which was promoted by low concentrations of NH 4 Ac. Both acetates had a "low concentration promotion, high concentration inhibition" effect on the synthesis of soluble sugars. Moreover, the percentage of saturated fatty acids in the fatty acid profile increased with the amount of NaAc supplementation, while stearic acid and oleic acid appeared. Our findings suggest that regulating the type and concentration of acetate can improve the biomass and lipid yield of Cv -31 to promote the microalgal biomass production.