Effect of Ph on Biomass Production and Carbohydrate Accumulation of Chlorella Vulgaris Jsc-6 Under Autotrophic, Mixotrophic, and Photoheterotrophic Cultivation

Microalgal carbohydrates are a sustainable carbon-rich feedstock for microbial conversion into biofuels. In this investigation, Chlorella vulgaris JSC-6 was used for carbohydrates production from CO2 and fatty acids under different cultivation strategies to meet the requirements of a CO2-neutral and non-polluting fermentation system for biofuel production. Autotrophic cultivation resulted in better carbon assimilation and carbohydrate accumulation; about 1.4 g CO2 could be converted to 1 g biomass, of which 50% are carbohydrates. Under photoheterotrophy, a maximum biomass yield of 3.62 g biomass/ g carbon assimilated was obtained at pH 7.0. JSC-6 could also utilize dual-carbon sources (CO2 and organic acid) completely under mixotrophic cultivation, with 3.86 g/L cell-mass, and 0.53 g/L/day cell growth rate at pH 7.5. The maximum carbohydrate content was 49.86%, and the ratio of the simple sugars glucose-xylose-arabinose was 1:0.11:0.02. The higher glucose content makes the microalgal biomass a suitable feedstock for sugar-based fermentations