Functional expression of RuBisCO reduces CO2 emission during fermentation by engineered Saccharomyces cerevisiae

Industrial biotechnology based on yeast fermentation is a promising strategy that can alleviate global warming and climate change. However, Saccharomyces cerevisiae, widely used in bioprocesses, releases a large amount of carbon dioxide (CO2) during fermentation. This study developed a mixotrophic CO2-fixing S. cerevisiae to achieve carbon neutrality and sustainability in bioprocess. A CO2-fixation pathway was constructed in a xylose-utilizing S. cerevisiae by heterologous expression of ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO) and phosphoribulokinase (PRK). Furthermore, a delta-integration strategy was utilized, and the RuBisCO gene copy number was increased to 10 copies to improve the efficiency of CO2-fixation. An additional Cas9-based genome editing was performed to overexpress other CO2-fixation related genes. The resulting CO2-fixing yeast, SJ03, exhibited the highest RuBisCO activity. During anaerobic xylose fermentation, ethanol concentration was increased by 17% and ethanol yield was increased by 16% compared to the control strain. In addition, CO2 emissions decreased by 7%. These results suggest that overexpression of the CO2-fixation pathway coupled with xylose utilization in S. cerevisiae might reduce CO2 emission in bioprocesses.