Integrative proteomic-metabolomics strategy reveals the regulators and mechanism of enhancing cyclic lipopeptides in the high-cell-density fermentation of Bacillus subtilis S1702

The cyclic lipopeptides (CPs) are synthesized by Bacillus spp. with excellent surface activities, but are limited in the application due to its low yield. More CPs secretion was previously determined in Bacillus subtilis culture under high cell density fermentation (HF). To explore the regulators and mechanism of sporulation and CPs, the proteomic and metabolomics profiles were firstly analyzed. As results, 95 different-regulated proteins were concentrated in TCA cycle, amino acid and fatty acid synthesis and metabolism pathways, promoting the synthesis of precursor peptide chains, inducing fatty acid transformation, and indirectly enhancing the formation of the CPs. Moreover, the correlation proteomic-metabolomics analysis showed that the surfactin and iturin yield were promoted by upregulation of NRPS synthetase (Sfp, Ste), while the downregulation of FenB (log2FC=-2.35) restricted the synthesis of fengycin. Besides, the addition of KH2PO4 increased the expression of two-component system (PhoR/PhoP), and promoted sporulation indirectly. Furthermore, sufficient substrate in HF system promoted energy metabolism pathway to produce more ATP and maintain cell vitality. Overall, our findings firstly provide a basis for further exploring potential regulation of CPs secretion induced by HF, and could be as a novel guild for look for the regulator of target substance in fermentation.