Effects of organic carbon sources on growth and oil accumulation by Desmodesmus subspicatus LC172266 under mixotrophic condition

Energy crisis and environmental sustainability have attracted global attention to microalgal biofuels. The present study investigated the impact of organic carbon sources on growth and bio-oil accumulation by an oleaginous microalga Desmodesmus subspicatus LC172266 under mixotrophic culture condition. Glucose and glycerol supported higher growth rates and lipid productivities than sucrose, fructose, mannitol and acetate. Each of the organic carbon source tested supported significantly (P < 0.05) higher growth rates and lipid productivities than the photoautotrophic culture (without organic carbon source). The lipid productivity obtained with a mixture of optima concentrations of glucose and glycerol (5.0 gL(-1) glycerol + 10.0 gL(-1)glucose) (0.14875 +/- 0.002 g/L/day) was about 25% and 66% higher than the values obtained with only 10.0 gL(-1)glucose and 5.0 gL(-1)glycerol, respectively. When a batch culture with 5gL(-1)glycerol was fed with 0.5 gL(-1)glucose daily the cell growth and lipid productivity were lower than the values obtained in a batch culture with a mixture of glucose and glycerol. The lipid productivity obtained in a 4-L photobioreactor was 94% (0.217 gL(-1) day(-1)), higher than the value obtained in a flask culture with 10.0 g/Lglucose (0.112 gL(-1) day(-1)) and 46% higher than the value obtained in a flask culture with 5.0 gL(-1)glycerol (0.086 gL(-1) day(-1)).

Automated summary

This study investigated the impact of different organic carbon sources on the growth and bio-oil accumulation of an oleaginous microalga. Glucose and glycerol supported higher growth rates and lipid productivities compared to other carbon sources. The mixture of glucose and glycerol at optimal concentrations resulted in the highest lipid productivity.