Abstract: S-Adenosylmethionine (SAM) is highly important for human metabolism, and it can be used as a nutritional supplement to improve human health. During the de novo synthesis of SAM by Bacillus amyloliquefaciens, lipopeptide surfactants usually lead to energy loss and fermentation foaming, which may hinder the accumulation of SAM. In this study, the lipopeptide surfactants synthesis genes of ituD and srfAC were deleted and effects of these genes on SAM synthesis were investigated. The fermentation results showed that deletion of ituD had no significant effect on cell growth and SAM synthesis. On the other hand, deletion of srfAC promoted the SAM titer by 23%, and no significant effect was found on the cell growth. After double mutation of ituD and srfAC, the SAM titer was increased by 32%, and the cell growth was not affected significantly. This study confirms that blocked lipopeptide surfactants synthesis can significantly enhance the SAM production, which provides a new strategy for metabolic engineering breeding of SAM.
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