The discovery of novel heat-stable keratinases from Meiothermus taiwanensis WR-220 and other extremophiles.

Billions of tons of keratin bio-wastes are generated by poultry industry annually but discarded that result in serious environmental pollution. Keratinase is a broad spectrum protease with the unique ability to degrade keratin, providing an eco-friendly way to convert keratin wastes to valuable amino acids. In this report, a feather-degrading thermophilic bacterium, Meiothermus taiwanensis WR-220, was investigated due to its ability to apparently complete feather decay at 65 °C in two days. By genomics, proteomics, and biochemical approaches, the extracellular heat-stable keratinase (MtaKer) from M. taiwanensis WR-220 was identified. The recombinant MtaKer (rMtaKer) possesses keratinolytic activities at temperatures ranging from 25 to 75 °C and pH from 4 to 11, with a maximum keratinolytic activity at 65 °C and pH 10. The phylogenetic and structural analysis revealed that MtaKer shares low sequence identity but high structural similarity with known keratinases. Accordingly, our findings have enabled the discovery of more keratinases from other extremophiles, Thermus and Deinococcus. Proteins encoded in the extremophiles shall be evolved to be functional in the extreme conditions. Hence, our study expands the current boundary of hunting keratinases that can tolerate extreme conditions for keratin wastes biorecycle and other industrial applications.