Co-production of lactic acid and 2,3-butanediol by genetically engineered Enterobacter cloacae

Microbial fermentation technology has advanced rapidly in the field of green chemical production, showcasing broad application prospects. However, current techniques still face challenges such as low carbon utilization efficiency and excessive accumulation of by-products. Additionally, during the fermentation process, carbon sources are released in the form of CO₂, leading to significant carbon loss. In this study, Enterobacter cloacae CICC 10011 was metabolically engineered to achieve the co-production of 2,3-butanediol (2,3-BDO) and lactic acid, while reducing carbon dioxide emissions and improving carbon utilization. By knocking out key genes (pflB and iclR), the pathways for the formation of by-products such as formate, acetate, and ethanol were attenuated, thereby optimizing carbon flux toward the target products. The results showed that under optimal fermentation conditions (aeration rate of 0.4 vvm, pH 6.5, temperature 35 °C), the double-gene deletion strain ECΔpflBΔiclR achieved lactic acid and 2,3-BDO (mixture of stereoisomers) concentrations of 51.03 g/L and 10.44 g/L, respectively, with a total target product yield of 1.76 mol/mol. Compared to the wild-type strain, the production of by-products succinate, acetate, and ethanol was reduced by 70.04 %, 47.10 %, and 89.76 %, respectively. Additionally, CO₂ emissions were reduced by 68.92 %, and carbon conversion efficiency improved by 116.16 %. This strategy provides a novel approach for carbon emission reduction and the co-production of high-value chemicals in fermentation processes.