Effect of Surfactant-Mediated Membrane Permeabilization on Menaquinone-7 Production by Engineered Bacillus subtilis

In this study, surfactant-induced mediated cell membrane permeabilization was explored as a strategy to increase the production of menaquinone-7 (MK-7) by an engineered strain, BS168-ΔSinR. Various surfactants were screened for their effectiveness in improving the MK-7 production of BS168-ΔSinR. Cell morphology was observed by scanning electron microscopy (SEM), and cell membrane permeability was detected by flow cytometry and fluorescence microscopy. RNA-seq was used to analyze the expression levels of genes related to MK-7 production. The results showed that the addition of 0.7% Brij-58 significantly increased the yield of MK-7, resulting in a 71.95% and 332.29% increase in the yield of total and extracellular MK-7 when compared with the control strain, respectively. The results from SEM, flow cytometry, and fluorescence microscopy demonstrate that Brij-58-mediated membrane permeabilization was significantly associated with enhanced MK-7 production. RNA-seq analysis showed that the expression levels of genes involved in MK-7 biosynthesis and the antioxidant defense system were generally up-regulated, while the expression levels of genes involved in spore formation were down-regulated. The results of this study provide a theoretical basis for the industrial production of MK-7, and reveal the mechanism by which surfactant-mediated membrane permeabilization increases the yield of MK-7.