A novel two-stage culture strategy used to cultivate Chlorella vulgaris for increasing the lipid productivity

A novel two-stage culture strategy was used to cultivate Chlorella vulgaris (ESP-6) for increasing the lipid productivity. In the first stage, ESP-6 was grown in the cathode chamber of Air-lift-type microbial carbon capture cell (ALMCC) to obtain maximum biomass productivity (nutrient-sufficient condition). In the second stage, the culture was transferred into the air-lift-type photobioreactor (ALP) to cultivate continuously for increasing the lipid content of ESP-6 (nutrient-starvation condition). The maximum CO2 fixation rate (887.49 mg L-1 d(-1)) was achieved on day 7, and the maximum lipid content (54.23%) was achieved on day 12, while the maximum lipid productivity was 190.45 mg L-1 d(-1) on day 11, which was 1.7 folds than that cultivated in nutrient-sufficient condition. In this study, the lipid productivity was improved by the two-stage culture strategy. Moreover, the microalgae suspension could be directly transferred to the second stage without the traditional pre-centrifugation treatment, which could thereby reduce the energy consumption and greenhouse gas emissions.