Oxygen-Limiting Growth Conditions and Deletion of the Transition State Regulator Protein Abrb inBacillus subtilis6633 Result in an Increase in Subtilosin Production and a Decrease in Subtilin Production

摘要

It has been recently shown, that certain strains/isolates ofBacillus subtiliscan be used as a probiotic for humans. The production of the macrocyclic sactibiotic subtilosin inB. subtilisATCC 6633 is highly regulated. To improve the subtilosin productivity ofB. subtilis, different growth conditions were compared for maximal expression of thesbopromoter that regulates the expression of the subtilosin biosynthetic gene cluster. Oxygen-limiting conditions led to a strong increase ofsbopromoter activities compared to aerobic conditions, and accordingly, the subtilosin amount determined by reversed phase HPLC (7.8 mg/L) was 15-fold superior to the amount of aerobic grown cultures (0.5 mg/L). A further promising enhancement of the subtilosin yield was achieved using a deletion mutant that is avoiding the general transition state regulator protein AbrB. The subtilosin titer of 42 mg/L produced by Delta abrBcells grown under oxygen-limiting conditions corresponds to an 84-fold increase compared to the subtilosin titer obtained fromB. subtiliswild type cells propagated in aerobic conditions. Furthermore, evidence is provided that oxygen-limiting conditions led to a strong decrease in the productivity of the lantipeptide subtilin suggesting contrary regulatory mechanisms for theB. subtilisantimicrobials subtilin and subtilosin.