Strategies to enhance cell growth and achieve high-level oil production of a Chlorella vulgaris isolate.

ABSTRACT

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 NaHCO(3) concentration of 1,500 mg/L as carbon source, the v(oil) and E(c) 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 (KNO(3)) 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.