Evaluation of the Carbon to Nitrogen and Carbon to Phosphorus ratios for improving the production of biomass and fatty acids in Chlorela sorokiniana

Background. Microalgae are being studied as a source of fatty acids to produce food with high added value. The content of oils can increase or decrease due to changes in abiotic factors such as nitrogen and phosphorus concentration in the culture medium. Goals. To determine the carbon/nitrogen and carbon/phosphorus ratio that favor biomass and fatty acid production in the native microalgae Chlorella sorokiniana. Methods. Microalgae isolated from the Parque Norte Lake in the city of Medellin, Antioquia, Colombia, was cultured in a heterotrophic way using glucose as carbon source at different carbon to nitrogen (C/N) (10/1, 25/1 y 50/1) and carbon to phosphorus (C/P) (200/1, 300/1 y 400/1) ratios. Results. The highest concentration of biomass was 9.70 gL(-1) and 9.17 gL(-1) at C/N 10/1 and C/P 200/1. The yields were 1.08 gL(-1)d(-1) and 1.02 gL(-1)d(-1). The biomass yield from glucose (were 0.43gg(-1) and 0.44gg(-1). Total fatty acids are favored by the C/N and C/P ratios of 50/1 and 400/1, yielding 24.27% and 20.48% total fatty acids measured over dried cell weight alongside higher fatty acid yield from biomass of 26.97m gL(-1)d(-1) and 22.76m gL(-1)d(-1), respectively. Conclusions. Lower C/N and C/P ratios favor the production of biomass while lowering the production of total fatty acids; conversely, higher C/N and C/P rations favor the production of total fatty acids and the lipid yield from biomass. Therefore, it is necessary to reach the highest production of biomass with low C/N ratio for enabling the elongation of the polyunsaturated fatty acid chain during the nutrient depletion stage in the culture medium as a response to the stress conditions.