Study on the effects of bdhA knockout on coproduction of menaquinone-7 and nattokinase by Bacillus subtilis based on RNA-Seq analysis

A recombinant strain (BS168-Δ bdhA ) that increased co-production of MK-7 and NK was constructed by knocking out the 2,3-butanediol dehydrogenase gene ( bdhA ) of Bacillus subtilis 168 to reduce the carbon spillover. The results showed that the 2,3- butanediol content in the recombinant strain was reduced by 64% to 2.76 g/L. The recombinant strain had an MK-7 production of 30.6 mg/L and an NK activity of 6.5 FU/mL. RNA-Seq analysis showed that: bdhA knockdown blocked the carbon flux of 2,3-butanediol and promoted glycerol uptake, and the carbon flux flowed more to the MK-7 and NK synthesis pathways. The negative regulator of NK, codY , was down-regulated by 2.19-fold. secA , which is responsible for the energy supply of transmembrane proteins, was down-regulated by 0.37-fold, the Tat secretion pathway was up-regulated by 2.8-fold and 0.5-fold for tatAD and tatC , respectively. This study revealed the mechanism of co-production of MK-7 and NK in recombinant strains for the first time and revealed potential molecular targets to promote the co-production of MK-7 and NK, which will provide a new strategy for metabolic engineering to increase the production of MK-7 and NK.