Kinetic models for heterotrophic growth of Chlamydomonas reinhardtii in batch and fed-batch cultures

Abstract

Heterotrophic growth of Chlamydomonas reinhardtii using acetate as a carbon source and nitrate, ammonium and urea as nitrogen sources in batch cultures was investigated. These nitrogen sources supported good growth of C. reinhardtii, the resulting cell concentrations for nitrate, ammonium chloride and urea were 0.48, 0.44 and 0.61 g l-1, respectively. The specific growth rate μ(x) of the urea culture was the highest (0.071 h-1), followed by that of the nitrate culture (0.062 h-1), and the specific growth rate μ(x) of the ammonium culture was the lowest (0.058 h-1). Urea is therefore considered to be the best nitrogen source for the growth of the alga. Based on these results fed-batch cultures were performed to reach the maximum cell concentration of 1.1482 g l-1, about 1.9-fold that obtained in batch culture. Finally, a group of kinetic models for describing cell growth, pH variation and acetate consumption were proposed and a satisfactory fit between the experimental results and predicted values was demonstrated. The effects of dilution rate and acetate feed concentration on cell growth were analyzed with those with these models.