Simultaneous Production of MK-7 and Iturin A by Bacillus velezensis ND

Bacillus velezensis can produce various secondary metabolites, such as the antibacterial compound iturin A and the coagulation-promoting menaquinone-7 (MK-7). To enhance the economic feasibility of the fermentation process, a co-production strategy, involving the simultaneous production of MK-7 and iturin A by Bacillus velezensis ND, was investigated in this study. Firstly, the effects of cultivation temperature and initial pH on the synthesis of MK-7 and iturin A were investigated. Considering the co-production of iturin A and MK-7, the optimal temperature and pH were determined as 32 °C and 7, respectively. Subsequently, important nutrients for the co-production process were investigated. It was observed that glycerol, soybean meal, yeast extract, and l-glutamate had a significant effect on the co-produce process. An optimal medium composed of glycerol (72.19 mL L⁻¹), l-glutamate (1.4 g L⁻¹), yeast extract (16.88 g L⁻¹), and soybean meal (130.95 g L⁻¹) was obtained by response surface methodology (RSM). This co-produce process was further scaled up in a biofilm reactor, and the maximum concentration of MK-7 and iturin A reached 46.88 mg L⁻¹ and 5.58 g L⁻¹, respectively. Finally, we established an effective method for separately extracting the two metabolites from the fermentation broth. The superiority of this co-production fermentation strategy demonstrates its significant potential for industrial production.