Novel keratinolytic enzymes, discovered from a talented and efficient bacterial keratin degrader

Abstract

Huge quantities of keratinaceous waste are a substantial and almost totally unexploited protein resource which could be upgraded for use as high value-added products by efficient keratinolytic enzymes. In this study, we found that Bacillus sp. 8A6 can efficiently degrade chicken feather after 24 h growth. According to phylogenetic analysis, the strain (formerly identified as Bacillus pumilus 8A6) belongs to the B. pumilus species clade but it is more closely related to B. safensis. Hotpep predicted 233 putative proteases from Bacillus sp. 8A6 genome. Proteomic analysis of culture broths from Bacillus sp. 8A6 cultured on chicken feathers or on a mixture of bristles and hooves showed high abundance of proteins with functions related to peptidase activity. Five proteases (one from family M12, one from family S01A, two from family S08A and one from family T3) and four oligopeptide and dipeptide binding proteins were highly expressed when Bacillus sp. 8A6 was grown in keratin media compared to LB medium. This study is the first to report that bacterial proteases in families M12, S01A and T3 are involved in keratin degradation together with proteases from family S08.