Abstract
Microbial secondary metabolites from extreme environments like hydrothermal vents are a promising source for industrial applications. In our study the protease gene from Bacillus cereus obtained from shallow marine hydrothermal vents in the East China Sea was cloned, expressed and purified. The protein sequence of 38 kDa protease SLSP-k was retrieved from mass spectrometry and identified as a subtilisin serine proteinase. The novel SLSP-k is a monomeric protein with 38 amino acid signal peptides being active over wide pH (7–11) and temperature (40–80 °C) ranges, with maximal hydrolytic activities at pH 10 and at 50 °C temperature. The hydrolytic activity is stimulated by Ca2+, Co2+, Mn2+, and DTT. It is inhibited by Fe2+, Cd2+, Cu2+, EDTA, and PMSF. The SLSP-k is stable in anionic, non-anionic detergents, and solvents. The ability to degrade keratin in chicken feather and hair indicates that this enzyme is suitable for the degradation of poultry waste without the loss of nutritionally essential amino acids which otherwise are lost in hydrothermal processing. Therefore, the proteinase is efficient in environmental friendly bioconversion of animal waste into fertilizers or value added products such as secondary animal feedstuffs.
Highlights
Microbial secondary metabolites from extreme environments like hydrothermal vents are a promising source for industrial applications
To screen for the bacteria producing the largest amount of protease, a skim milk assay was performed and among all isolates Bacillus cereus showed maximal activity (Fig. 1a)
Several other studies proved that Bacillus strains are optimal targets to study protease enzyme activity since they are known to produce the highest yields of proteases[28,29,30,31]
Summary
Microbial secondary metabolites from extreme environments like hydrothermal vents are a promising source for industrial applications. The crab Xenograpsus testudinatus lives in shallow-water hydrothermal vents which are rich in sulfur, have highly fluctuating pH, and elevated temperatures, near Kueishantao ( called Turtle Island), NE-Taiwan[2]. Enzymes like proteases that can hydrolyse peptide bonds of proteins are valued in the drug designing industry, as well as for the production of detergents, and for environmental waste water treatment. Keratinase degrades keratin which in turn is a protective protein It is highly rigid, recalcitrant and cannot be hydrolysed by other proteases. The objectives of this study were: (1) to amplify the gene for the novel SLSP-k, (2) to purify and characterize this protease enzyme, and (3) to explore the applications of the protease in research, value-added product synthesis, and biological waste treatment
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