Screening and Identification of Protease-producing Bacteria from the Intestines of Maricultured Litopenaeus vannamei
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Abstract:
In this study, to obtain marine-derived microbial protease, 27 protease-producing bacterial strains were isolated from the intestines of maricultured Litopenaeus vannamei using protease hydrolysis circle method. Enzyme production by different strains was preliminarily estimated by determining the ratio of transparent circle diameter to colony diameter (D/d). A high-yield protease-producing strain, named as xc10, was isolated during secondary screening by measuring protease activity of fermentation broth. It was identified as Bacillus cereus by cell morphology, physiological, and biochemical characteristics, 16S rDNA gene sequence analysis, and phylogenetic tree analysis.Enzyme properties of crude protease in the fermentation broth were investigated. The optimal temperature and the pH for protease were 50 ℃ and 7.5, respectively. Additionally, the enzyme activity was inhibited by Fe3+, Cu2+, and EDTA, while Zn2+ slightly increased the enzyme activity. Therefore, strain xc10 isolated from the intestine of maricultured Litopenaeus vannamei was confirmed as a bacterial strain producing mesophilic neutral protease. This study provides a theoretical basis for the development and application of marine-derived microbial proteases in the processing of aquatic products.
