Signal peptide engineering of a novel M4 family keratinase and the action mechanism in promoting pepper tolerance to salt stress through KerJY23-hydrolyzed feather waste

Microbial keratinase has attracted significant attention for its ability to convert keratin waste into high-value products with substantial application potential in the agricultural field. However, the low yield and potential pathogenicity of native keratinase producers have significantly hindered their large-scale industrial application. In this study, the novel M4 family keratinase KerJY-23 was heterologous expressed in Bacillus subtilis , and a systematic signal peptide engineering was perfor