Keratinase Biosynthesis from Waste Poultry Feathers for Proteinaceous Stain Removal

This study is aimed at assessing the keratinase production related to industrial detergent applications from a newly isolated Bacillus cereus IIPK35. The production was optimized through submerged fermentation by a one-variable-at-a-time method, followed by the response surface methodology, using waste chicken feathers as a carbon source and resulted in a 5-fold increase in keratinase production in 48 h (103.79 U/mL) when supplemented with 1.43% w/v feather and other nutrients. Time-course study of 120 h revealed a direct relationship among microbial growth, feather degradation, sulfite generation, production of keratinase, oligopeptide, and total protein. The sulfite generation in the culture filtrate suggested the possible sulfur mineralization by disulfide reductase produced by IIPK35. At optimized conditions, cell free fermented broth was enriched with 12 amino acids copiously: threonine (8.52 μg/mL), serine (7.55 μg/mL), and phenylalanine (7.13 μg/mL). Fourier transform infrared analysis reflected the cleavage of peptide bonds associated with feather keratin degradation. IIPK35 keratinase exhibited 79–88% stability and compatibility with commercial detergents and thus appeared to be a promising approach toward laundry detergents. The washing simulation experiment with low supplementation of keratinase combined with detergent demonstrated good destaining of proteinaceous stains without damaging the fabric structure and strength. Thus, the crude keratinase from B. cereus IIPK35 could be considered as a potential bioadditive in detergent formulation.