Effect of global redox-sensing transcriptional regulator Rex on acetoin synthesis of Bacillus subtilis

Abstract:

[Background] The global redox-sensing transcriptional regulator Rex (encoded by the ydiH gene) of Bacillus subtilis can regulate intracellular redox balance by sensing NADH/NAD+ levels. [Objective] To study the effect of Rex on the synthesis of acetoin through regulation of cofactor pools in B. subtilis. [Methods] RNA-seq was used to identify the transcriptional diversity of genes that were involved in the bioprocess of reversible transformation between acetoin and 2,3-butanediol, and ydiH, acuA (acetyl AcsA) and acoC (dihydrolipoamide acetyltransferase) were knocked out by Cre/lox gene knockout technology. Subsequently, the transcriptional levels of acetoin-related genes in the knockout strains was analyzed by real-time fluorescence quantitative PCR (RT-qPCR). [Results] Fermentation results indicated that blocking of ydiH could inhibit biomass of B. subtilis to a certain extent, but acetoin yield of unit cell and substrate conversion rate were significantly increased in early stage of fermentation. However, knockout of acuA and acoC had little effect on acetoin synthesis, biomass and glucose consumption rate. After knocking out ydiH, the transcriptional levels of alsR (positive transcriptional regulator of alsSD), alsS (α-acetolactate synthase), alsD (α-acetolactate decarboxylase) and bdhA (2,3-butanediol dehydrogenase), involved in acetoin synthesis, were significantly up-regulated. [Conclusion] Global redox-sensing transcriptional regulator Rex in B. subtilis affect the synthesis of acetoin by down regulation of the transcription levels of acetoin synthesis related genes. This study first reported the correlation between Rex and the synthesis of acetoin in B. subtilis, laying the foundation for exploring how Rex affects intracellular redox balance by regulating the transcription of related genes, and providing reference for improving the industrial production intensity and substrate conversion rate of B. subtilis.

Key words:Bacillus subtilis, acetoin, global redox-sensing transcriptional regulator, fermentation regulation