Enhanced vitamin K2 production by engineered Bacillus subtilis during leakage fermentation.

Menaquinone-7 (MK-7), a valuable member of the vitamin K2 series, is an essential nutrient for humans. It is used for treating coagulation disorders, and osteoporosis, promoting liver function recovery, and preventing cardiovascular diseases. In this study, to further improve the metabolic synthesis of MK-7 by the mutant strain, the effect of surfactants on the metabolic synthesis of MK-7 by the mutant strain Bacillus subtilis 168 KO-SinR (BS168 KO-SinR) was analyzed. The scanning electron microscopy and flow cytometry results showed that the addition of surfactants changed the permeability of the cell membrane of the mutant strain and the structural components of the biofilm. When 0.7% Tween-80 was added into the medium, the extracellular and intracellular synthesis of MK-7 reached 28.8 mg/L and 59.2 mg/L, respectively, increasing the total synthesis of MK-7 by 80.3%. Quantitative real-time PCR showed that the addition of surfactant significantly increased the expression level of MK-7 synthesis-related genes, and the electron microscopy results showed that the addition of surfactant changed the permeability of the cell membrane. The research results of this paper can serve as a reference for the industrial development of MK-7 prepared by fermentation.