Heterotrophic cultivation of Chlorella vulgaris using broken rice hydrolysate as carbon source for biomass and pigment production.

• Broken rice hydrolysate was used as carbon source. • The pH decreased sharply leading to failure of microalgal growth. • Ammonium led to a decrease in the pH of the medium. • Batch pH adjustment could increase biomass production of Chlorella vulgaris. • The cost of the culture medium decreased by 89.58%. The high cost of carbon source limits the heterotrophic culture of Chlorella. In this study, broken rice was hydrolyzed into glucose. Then, the broken rice hydrolysate (BRH) was utilized for heterotrophic cultivation of C. vulgaris instead of glucose. Results showed that algal cells released H+ when they consumed NH 4 +, leading to a sharp decrease in pH. Growth inhibition by acid could be avoided by using a pH buffer. Adding alkaline reagents intermittently during culture could not only reduce the amount of pH stabilizer but also obtain increased biomass production. When using Tris as pH stabilizer, the biomass productivity of C. vulgaris in BRH was the largest (1.01 g/L/d), followed by NaOH (1.00 g/L/d), and Na 2 CO 3 (0.95 g/L/d). Using BRH instead of glucose for heterotrophic cultivation of C. vulgaris could save 89.58% of the cost of culture medium. This study developed a novel strategy for cultivating C. vulgaris heterotrophically using BRH. [ABSTRACT FROM AUTHOR]