Oil accumulation via Chlorella species using carbon sources from waste

One of the global issues acquiring significant attention these days is related to energy supply and demand. The irreversible decrease of fossil fuels left to supply energy and the greenhouse gases increase in the atmosphere have led to the utilization of alternate sources of energy, such as oil from microalgae. Oil from microalgae is an economically attractive source of energy because of their high capacity to accumulate lipid. The aim of this study is to optimize the lipid accumulation of Chlorella protothecoides and Chlorella vulgaris by using carbon sources other than glucose as the organic carbon source in heterotrophic and mixotrophic cultures. Carbon source, carbon and nitrogen concentrations, pH level, salinity, and rotational speed are some of the factors controlling the accumulation of oil that are considered in the present study.;The heterotrophic and mixotrophic cultures of Chlorella protothecoides grow faster and produce higher biomass concentrations and lipid contents than their autotrophic cultures, without a significant difference between heterotrophic and mixotrophic modes. Mixotrophic Chlorella vulgaris produce higher biomass concentrations than in its autotrophic and heterotrophic cultures, without significant differences between their lipid contents. In addition to the biomass and lipid content advantages of heterotrophic and mixotrophic cultures, the utilization of glycerol and acetate as carbon sources for microalgae fermentation has the potential to reduce the overall costs of biofuels production since these substrates can be obtained from waste, glycerol from biodiesel industry and acetate from biohydrogen production. Chlorella protothecoides grow well on glycerol and sodium acetate and Chlorella vulgaris on sodium acetate, both with high biomass concentrations and high lipid contents.