Production of biomass and lutein by Chlorella protothecoides at various glucose concentrations in heterotrophic cultures

The influence of initial glucose concentrations on the production of biomas s and lutein by Chlorella protothecoides CS-41 was investigated in batch cu ltures using both shake flasks and fermenters. The maximum biomass concentr ation increased from 4.9 to 31.2 g litre(-1) dry cells with an increase in initial glucose concentration from 10 to 80 g litre(-1). An even higher ini tial glucose concentration (100 g litre(-1)) resulted in a lower biomass co ncentration, a lower specific growth rate, a lower growth yield coefficient and a considerably longer lag phase, which might be due to substrate inhib ition. The initial glucose level also had a significant effect on the produ ction of lutein. In a 3.7-litre fermenter an increase in lutein production from 19.39 to 76.56 mg litre(-1) was obtained with an increase in initial g lucose concentration from 10 to 40 g litre(-1), within which range, lutein yield coefficient was constant (Y-Itn = 1.90 +/- 0.02 mg g(-1)). A simple s ubstrate inhibition model was developed, which fitted the experimental data better than the classical Haldane model. A group of time-dependent kinetic models for algal cultivation in fermenters were also constructed, which we re in good agreement with the experimental results and could be employed to predict the production of biomass and lutein, and the consumption of gluco se in fermenter cultures. (C) 1999 Elsevier Science Ltd. All rights reserve d.