Supplementation of alanine improves biomass accumulation and lipid production of Chlorella pyrenoidosa by increasing the respiratory and metabolic processes

The function of exogenous alanine (Ala) in regulating biomass accumulation, lipid production, photosynthesis, and respiration in Chlorella pyrenoidosa was studied. Result shows that the supplementation of Ala increased C. pyrenoidosa biomass and lipid production in an 8-d batch culture. The concentration of 10 mmol/L of Ala was optimum and increased the microalgal cell biomass and lipid content by 39.3% and 21.4%, respectively, compared with that in the control (0-mmol/L Ala). Ala supplementation reduced photosynthetic activity while boosting respiratory activity and pyruvate levels, indicating that C. pyrenoidosa used exogenous Ala for biomass accumulation through the respiratory metabolic process. The accelerated respiratory metabolism due to Ala supplementation elevated the substrate pool and improved the lipogenic gene expression, promoting lipid production at last. This study provided a novel method for increasing biomass accumulation and lipid production and elucidated the role of Ala in regulating lipid production.