Two-stage cultivation of two Chlorella sp. strains by simultaneous treatment of brewery wastewater and maximizing lipid productivity

[Display omitted] ► Utilization of wastewater before and after anaerobic digestion as nutrient sources. ► A hybrid system to improve algal biofuel economy with wastewater treatment. ► A new two-stage microalgae cultivation mode to increase lipid productivity. ► Better control on bacterial contamination without any pretreatment. A cultivation system in the two-stage photoautotrophic–photoheterotrophic/mixotrophic mode was adapted to maximize lipid productivity of two freshwater strains of Chlorella sp. grown in brewery wastewater (BWW). The endogenous Chlorella sp. isolated from BWW had a higher growth rate than wild-type Chlorella vulgaris (UTEX-265) while C. vulgaris (UTEX-265) had a higher maximal biomass and lipid contents than that of endogenous Chlorella sp., resulting in more than 90% of the inorganic nutrients in both total nitrogen (TN) and phosphorus (TP) was removed during the first stage in the two-stage photoautotrophic–photoheterotrophic mode in each Chlorella sp. The maximal biomass and lipid contents of C. vulgaris (UTEX-265) for single stage photoautotrophic cultivation were 1.5g/L and 18%, respectively. Importantly, during two-stage photoautotrophic–photoheterotrophic cultivation for C. vulgaris (UTEX-265), the biomass was increased to 3.5g/L, and the lipid productivity was increased from 31.1 to 108.0mg/Lday.