Enhanced carbon dioxide bio-fixation and protein production of Chlorella pyrenoidosa through a highly efficient sequential heterotrophic and photoautotrophic culture strategy

Abstract

Chlorella pyrenoidosa is one of the most promising microalgae for protein production with carbon dioxide (CO2) bio-fixation. However, the high production cost and low production capability under traditional photoautotrophic culture mode had severely limited its application. Here, a highly efficient sequential heterotrophic and photoautotrophic cultivation strategy was established. Firstly, the heterotrophic seeds culture conditions were optimized with glucose as the carbon source and 1 g L−1 of yeast extract was selected as a useful stimulus to boost cell growth. Then, the heterotrophic cells were transferred to photoautotrophic conditions directly and cultured under varied concentrations of CO2. Moreover, 8 % (v/v) of CO2, high light and high initial cell density were found to be beneficial for cell growth and CO2 sequestration. Finally, different initial nitrogen concentrations and nitrogen feeding strategies were evaluated to increase the protein content to 62.69 % of dry biomass. These results provide feasible strategies for efficient CO2 sequestration and protein production jointly in C. pyrenoidosa.