Recent advances in keratinase production via protein engineering, breeding, and fermentation

The gene editing and synthetic biological tools have led to the implementation of diverse metabolic engineering approaches to enhance the production of specific enzymes. Microbial keratinases can convert keratin wastes into valuable compounds for mankind. Since the market for keratinases cannot be satisfied by production from wild hosts, it is obligatory to develop hosts with high keratinase yields. The intention of this review is to evaluate microbial keratinase advancement through protein engineering, breeding techniques, and fermentation optimization. The main aim of protein engineering is to improve the heat resistance ability and catalytic activity of keratinases by employing mutagenesis methods. Moreover, modifying the expression elements and host engineering are also two unique ways to augment the keratinase yield. Intending to accelerate the production of modified keratinase, this review attempts to highlight the optimization of expression elements, such as promoter engineering, UTR, signal peptide, and codon optimization. Moreover, the approaches of host engineering including strengthening precursor supply, membrane surface engineering, and optimization of secretion pathways were also explained here. Furthermore, it is also essential to optimize the medium composition and fermentation condition for high keratinase yield. This review also addressed the present advancements, difficulties, and tendencies in the field of microbial keratinase production, along with its potential. [Display omitted] •Site-directed mutagenesis mutates the amino acid sequence especially the at S-pocket of keratinases leading to a significant escalation in thermostability and catalytic activity.•Promoter engineering is a fruitful tool to overcome the metabolic burden on strain and increase the keratinase production.•Sec-Pathway is most common secretory pathways for keratinases. Keratinases usually adopt the Sec-pathway for their secretion.•Optimization of transcriptional factors, expression elements, precursor and energy supply, and administration of cofactors to host for metabolic engineering, are the major challenges in the production of keratinase from recombinant strains.