Objective The study aims to explore the relationship between the protease-producing capacity of Bacillus and the protease genes carried by the bacteria and analyze the important enzyme genes that affect the protease-producing capacity of Bacillus.

Method The protease-producing strain was screened by using the selective medium. The protease activity of the strains was determined by the Folin method. The protease genes carried on the chromosomes of the strains were obtained and classified by sequencing the whole genome of 15 strains of Bacillus. The transcription level of protease gene mRNA was measured by the real-time fluorescent quantitative PCR method. Through comparative genomics and Bacterial Genome-Wide Association Analysis (BGWAS), the reasons that affect the ability of bacteria to produce protease were explored.

Result According to the protease genes carried on the chromosomes of the strains, they could be divided into 7 groups of genotypes (G1-G7). Comparative genomics and BGWAS found that the number of protease genes carried on bacterial chromosomes was directly related to the protease production capacity, and the protease production capacity of strains lacking aprX and aprE was significantly reduced. The difference in the protease production capacity of Bacillus was found to be related to the expression level of aprX by further studying the mRNA level of the gene.

Conclusion There is a correlation between the protease gene carried on the chromosome of the strain and the protease production capacity of the strain. The important enzyme gene that affects the protease production capacity of Bacillus is aprX.