Metabolic engineering of threonine catabolism enables <i>Saccharomyces cerevisiae</i> to produce propionate under aerobic conditions
Wentao Ding, Qiongyu Meng, Genlai Dong, Nailing Qi, Huimin Zhao, Shuobo Shi
Abstract
Abstract Background Propionate is widely used as a preservative in the food and animal feed industries. Propionate is currently produced by petrochemical processes, and fermentative production of propionate remains challenging. Methods and Results In this study, a synthetic propionate pathway was constructed in the budding yeast Saccharomyces cerevisiae , for propionate production under aerobic conditions. Through expression of tdcB and aldH from Escherichia coli and kivD from Lactococcus lactis , L‐threonine was converted to propionate via 2‐ketobutyrate and propionaldehyde. The resulting yeast aerobically produced 0.21 g L ‐1 propionate from glucose in a shake flask. Subsequent overexpression of pathway genes and elimination of competing pathways increased propionate production to 0.37 g L ‐1 . To further increase propionate production, carbon flux was pulled into the propionate pathway by weakened expression of pyruvate kinase ( PYK1 ), together with overexpression of phosphoenolpyruvate carboxylase ( ppc ). The final propionate production reached 1.05 g L ‐1 during fed‐batch fermentation in a fermenter. Conclusions and Implications In this work, a yeast cell factory was constructed using synthetic biology and metabolic engineering strategies to enable propionate production under aerobic conditions. Our study demonstrates engineered S. cerevisiae as a promising alternative for the production of propionate and its derivatives.