Enhancement of 2,3-Butanediol Production by <i>Klebsiella pneumoniae</i>: Emphasis on the Mediation of sRNA-SgrS on the Carbohydrate Utilization

The demand for renewable energy is increasing. <i>Klebsiella pneumoniae</i> is one of the most promising strains to produce 2,3-butanediol (2,3-BD). Compared with chemical methods, the biological production of 2,3-BD has the characteristics of substrate safety, low cost, and low energy consumption. However, excessive glucose concentrations can cause damage to cells. Therefore, this study investigated the effect of sRNA-SgrS as a sugar transport regulator on the fermentative production of 2,3-BD by <i>K. pneumoniae</i> in response to sugar stress. We designed multiple mutants of <i>K. pneumoniae</i> HD79 to redistribute its carbon flux to produce 2,3-BD. It was found that the 2,3-BD yield of <i>sgrS</i> overexpressed strain decreased by 44% compared with the original strain. The results showed that a high concentration of sRNA-SgrS could accelerate the degradation of <i>ptsG</i> mRNA (encoding the glucose transporter EIICB^Glc) and downregulate the expression levels of the <i>budA</i> gene (encoding the α-acetyllactate decarboxylase) and the <i>budB</i> gene (encoding the α-acetyllactate synthase) and <i>budC</i> gene (encoding the 2,3-BD dehydrogenase) but had no effect on the <i>ack</i> gene (encoding the acetate kinase) and the <i>ldh</i> gene (encoding the lactate dehydrogenase). It provides a theoretical basis and a technical reference for understanding the complex regulation mechanism of sRNA in microorganisms and the genetics and breeding in industrial fermentation engineering.