Enhanced carbon capture and utilization in transgenic Chlorella sorokiniana harboring pyridoxal kinase under dynamic carbon dioxide levels

Abstract

Microalgae are crucial in carbon capture, utilization, and storage due to the efficient CO₂ assimilation through photosynthesis and potential for high-value biochemical production. However, limited research has explored genetic strain to enhance carbon capture under dynamic CO₂ conditions. This research aimed to optimize carbon capture in Chlorella sorokiniana by introducing pyridoxal kinase (pdxY) and cultivation in fluctuating CO₂ concentrations. The sequential optimization successfully led to 34% increase in growth with improved carbon capture efficiency to 88.5%. Transgenic strains 2023PY and BSLPY demonstrated superior performance under high (2%) and low (0.04%) CO₂, respectively. Addition of Tris base to the medium stabilized pH at favorable level, which is crucial for optimum growth. Scale-up cultivation in 2-L photobioreactor achieved net-zero carbon emissions across all strains. These findings highlight the potential of genetic engineering and process optimization in advancing microalgal carbon capture, along with the production of protein, starch, and lipid for sustainable applications.

Keywords: Carbon neutrality; Direct air capture; Microalgal carbon fixation; PdxY; Photobioreactor.