Optimization of Batch Cultivation of Chlorella sp. Using Response Surface Methodology

Optimal biomass production from microalgae using the NPK 20:20:20 medium; a relatively cheaper and locally available medium has been identified as an important factor in the large-scale algal biomass production. In this study, various concentrations (0.3-0.7 g/l) of NPK 20:20:20 were considered as the source of nitrogen in the growth medium for Chlorella sp. Four independent parameters in algae culture (nitrogen concentration, pH, inoculum size and duration of the experiment at varying ranges were studied for maximum biomass and chlorophyll production. Response Surface Methodology (RSM) procedure result that nitrogen concentration and pH level are the dominant factors affecting biomass and chlorophyll production. Maximum biomass was achieved at 0.5 g/l N and 8.5 pH value. Higher N (0.8 g/l) and lower N (0.3 g/l) had minimal effect on biomass and chlorophyll production. There was a linear relationship between chlorophyll and biomass production while the residual nitrogen had an inverse relationship with biomass production. Nitrogen concentration and pH were shown to be limiting factors under the conditions of the study. The inoculum size and duration of the experiment had a minimal effect on biomass production.