Effect of Macronutrients and of Anaerobic Digestrate on The Heterotrophic Cultivation of Chlorella Vulgaris Grown With Biodiesel By-Products
Abstract The aim of this work was to investigate the kinetics of the heterotrophic growth of Chlorella vulgaris as a means of producing bio-oil for biodiesel production. Glycerol was used as the sole organic carbon substrate. Anaerobic digestrate from a local plant was used to examine its effect on the kinetics and the protein and lipid content of the biomass. The effect of the initial carbon and nitrogen concentrations on the carbon uptake rate was studied independently. In one set of five experiments the organic carbon in the form of glycerol, varied from 0.27 g L-1 to 5.36 g L-1 while the concentration of atomic nitrogen was held constant and equal to 45.4 mg L-1. The Co/No ratio varied from 6 to 118.1. In a second set, also of five experiments, the organic carbon was held constant and equal to 3.3 g L-1 and atomic nitrogen varied from 22.7 mg L-1 to 450 mg L-1. The Co/No ratio varied from 7.3 to 145.4. In a third set of experiments anaerobic digestrate was added in increasing amounts into the culture media from 4% to 16%. It was found that the carbon uptake rate as well as the lipid and protein content depended on the Co/No ratio. Increasing ratios of Co/No lead to higher carbon uptake rates, higher lipid content and lower protein content. The initial nitrogen concentration was also found to affect the growth rate of C. vulgaris. The addition of anaerobic digestrate did not affect appreciably the protein and lipid content of the biomass while, addition of anaerobic digestrate up to 16% in the culture medium increased the carbon uptake rate up to about 24%.
