Phenotypic and Genomic Insights into Mutant with High Nattokinase-Producing Activity Induced by Carbon Ion Beam Irradiation of Bacillus Subtilis

Nattokinase (NK) is found in fermented foods and has high fibrinolytic activity, which makes it promising for biological applications. In this study, a mutant strain ( Bacillus subtilis ZT-S1, 5529.56 +/- 183.59 U/mL) with high NK-producing activity was obtained using 12 C 6 + heavy ion beam mutagenesis for the first time. The surface morphology of B. subtilis is also altered by changes in functional groups caused by heavy ion beams. Furthermore, B. subtilis ZT-S1 required more carbon and nitrogen sources and reached stabilization phase later. Comparative genome analysis revealed that most of the mutant implicated genes ( oppA , appA , kinA , spoIIP ) were related to spore formation. And the affected rpoA is related to the synthesis of the NK-coding gene aprE . In addition, the B. subtilis ZT-S1 obtained by mutagenesis had good genetic stability. This study further explores the factors affecting NK activity and provides a promising microbial resource for NK production in commercial applications.