Study on the optimal growing conditions of Chlorella vulgaris in a bubble column photobioreactor

An in-dept investigation on productivity and lipid yield of Chlorella vulgaris, a freshwater unicellular alga belonging to the Chlorophyceae class, in a wide range of growing conditions is presented. Various combinations of starvation are designed to turn the metabolism into an anabolic lipid accumulating phase, with the aim of defining the most suitable growing conditions for large scale biodiesel production. The assays in regimen of mixotrophy, heterotrophy and autotrophy, conducted in the same conditions of irradiance, algal concentration and culture medium, show that C. vulgaris is able to increase its lipid content from similar to 6% (balanced-, autotrophically-grown biomass) to similar to 40% and highlighted the difference between the type (i.e., polar or nonpolar) of the lipids accumulated upon nitrogen and phosphorus starvation.