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

Abstract

The influence of initial glucose concentrations on the production of biomass and lutein by Chlorella protothecoides CS-41 was investigated in batch cultures using both shake flasks and fermentors. The maximum biomass concentration 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 initial glucose concentration (100 g litre-1) resulted in a lower biomass concentration, a lower specific growth rate, a lower growth yield coefficient and a considerably longer lag phase, which might be due to substrate inhibition. The initial glucose level also had a significant effect on the production of lutein. In a 3.7-litre fermentor an increase in lutein production from 19.39 to 76.56 mg litre-1 was obtained with an increase in initial glucose concentration from 10 to 40 g litre-1, within which range, lutein yield coefficient was constant (Y(ltn) = 1.90 ± 0.02 mg g-1). A simple substrate 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 fermentors were also constructed, which were in good agreement with the experimental results and could be employed to predict the production of biomass and lutein, and the consumption of glucose in fermentor cultures.