Strategies to Enhance Cell Growth and Achieve High-Level Oil Production of a Chlorella vulgaris Isolate

The autotrophic growth of an oil-rich indigenous microalgal isolate, identified as Chlorella vulgaris C-C, was promoted by using engineering strategies to obtain the microalgal oil for biodiesel synthesis. Illumination with a light/dark cycle of 14/10 (i.e., 14 h light-on and 10 h light-off) resulted in a high overall oil production rate (v(oil)) of 9.78 mg/L/day and a high electricity conversion efficiency (E-c) of 23.7 mg cell/kw h. When using a NaHCO3 concentration of 1,500 mg/L as carbon source, the v(oil) and Ec were maximal at 100 mg/L/day and 128 mg/kw h, respectively. A Monod type model was used to describe the microalgal growth kinetics with an estimated maximum specific growth rate (mu(max)) of 0.605 day(-1) and a half saturation coefficient (K-s) of 124.9 mg/L. An optimal nitrogen source (KNO3) concentration of 625 mg/L could further enhance the microalgal biomass and oil production, leading to a nearly 6.19 fold increase in v(oil) value. (C) 2010 American Institute of Chemical Engineers Biotechnol. Prog., 26: 679-686, 2010