Characterization of a neutral protease gene of Bacillus subtilis Isolated from the Guts of Bombyx mori

To explore distribution and probiotics function of enzyme-producing bacteria in gut of the silkworm,a bacillus subtilis strain (no.951na) was isolated from the guts of the fourth instar larvae of bombyx mori. the strain was separated using na casein medium and identified by the morphology and the 16s rdna sequences analysis. in vitro assays,the enzyme activity was 24.2uml-1. meanwhile,a gene encoding a kind of neutral protease was cloned and its prokaryotic expression in escherichia coli was also carried out. the cdna of this gene was 2644bp encoding a protein with a molecular weight of about 60 kd,which was confirmed by sds-page. the positive transformant strains were cultured with different concentrations of iptg and their enzymatic activities of expressed proteins was determined by folin-phenol method,which demonstrated that the constructed expression system had an efficient expression capacity for the neutral protease npr. these results provided a foundation for further function study of this neutral protease.