Enhanced Biomass and Lipid Production Capacity of Chlamydomonas reinhardtii under Mixotrophic Cultivation using Sewage Effluent and Waste Molasses

Abstract

 Microalgae are recognized as a renewable feedstock for biofuel production. However, low lipid productivity and high cultivation costs are the major bottlenecks for the practical application of microalgal biofuel production. This study aimed to investigate the benefits of a mixotrophic cultivation of Chlamydomonas reinhardtii using organic wastes and wastewater effluent for enhanced biomass and lipid production and reducing cultivation cost. C. reinhardtii was cultured under mixotrophic conditions in a synthetic C medium or sewage effluent supplemented with a commercial organic carbon source (glucose, fructose, sucrose, or acetate) or organic wastes (molasses or corn steep liquor). C. reinhardtii grew and accumulated lipids in the all cultivation conditions using C medium or sewage effluent. Sewage effluent could be an alternative culture medium for C. reinhardtii. Supplementing a commercial organic carbon or organic wastes enhanced C. reinhardtii’s biomass production. The highest biomass (86 mg–dry cell/L/d) and lipid (34 mg/L/d) production by C. reinhardtii was observed in the C medium with 1 g/L molasses. Cultivation using sewage effluent with 1 g/L of molasses also provided a relatively high biomass (73 mg–dry cell/L/d) and lipid (27 mg/L/d) production; these rates were significantly higher than those under photoautotrophic cultivation and mixotrophic cultivation in C medium supplemented with other commercial carbon sources except for acetate. Molasses was thus found to enhance growth and lipid synthesis of C. reinhardtii. These results indicate that mixotrophic cultivation using sewage effluent and molasses can be a promising strategy for a cost-effective and highly efficient biofuel production by C. reinhardtii.