Dual-mode cultivation of Chlorella protothecoides applying inter-reactors gas transfer improves microalgae biodiesel production

Chlorella protothecoides, a lipid-producing microalga, was grown heterotrophically and autotrophicallyin separate reactors, the off-gases exiting the former being used to aerate the latter. Autotrophic biomass productivity with the two-reactor association, 0.0249 g L-1h-1, was 2.2-fold thevalue obtained in a control autotrophic culture, aerated with ambient air. Fatty acid productivity was1.7-fold the control value. C. protothecoides heterotrophic biomass productivity was 0.229 g L-1h-1. This biomass’ fatty acid con-tent was 34.5% (w/w) with a profile suitable for biodiesel production, according to European Standards.The carbon dioxide fixed by the autotrophic biomass was 45 mg CO2L-1h-1in the symbiotic arrange-ment, 2.1 times the control reactor value.The avoided CO2 atmospheric emission represented 30% of the CO2 produced in the heterotrophic stage, while the released O2 represented 49% of the oxygen demand in that stage.Thus, an increased efficiency in the glucose carbon source use and a higher environmental sustainability were achieved in microalgal biodiesel production using the proposed assembly