Isolation and Identification of Feather-Degrading Bacteria and Cloning of Their Keratinase Gene

Abstract

There are a large number of cross-linked chemical bonds such as tight disulfide bonds, hydrogen bonds,and salt bonds in keratin, which makes it difficult to break the structural stability of the protein using conventional methods. The degradation of feather waste using keratinases produced by microorganisms has the advantage of being efficient and environmentally friendly. In this study, 23 strains capable of producing transparent circles were obtained via preliminary screening with skim milk as the sole carbon and nitrogen source, and 9 strains capable of degrading feathers were obtained via rescreening with feathers as the sole carbon and nitrogen source. Finally, through the determination of enzyme activity, the strain CY-A with a high ability to degrade feathers was obtained. The strain was identified as Bacillus tequilensis via morphological observation, physiological and biochemical identification, and 16 S rRNA molecular biology. The keratinase gene (bta) of Bacillus tequila was cloned, and its full-length gene sequence was 1110 bp, containing an open reading frame of 1089, encoding 369 amino acids (GeneBank accession number OR733336). The physicochemical properties, secondary structure, and tertiary structure of the recombinant protein were analyzed using bioinformatics tools such as ProtParm, SOPMA, MEGA, and SWISS-MODELS. It was found that the relative molecular mass was 37.953 kD and that the isoelectric point was 8.48. The protein was a hydrophilic protein. The keratinase bta gene was ligated to the expression vector pET28a(+) using T4 ligase, and the recombination expression plasmid pET28-bta was constructed and transformed into E. coli BL21(DE3) to obtain recombinant engineered bacteria. The expressed keratinase was purified using a Ni2+ affinity chromatography column to obtain recombinant bta keratinase bta with a molecular weight of 37.953 kD. The identification and characterization of this keratinase gene provides some theoretical basis for the further enhancement of keratinase activity by means of genetic engineering.