Production, partial purification and efficacy of keratinase from Bacillus halotolerans L2EN1 isolated from the poultry farm of Himachal Pradesh as a potential laundry additive

Abstract To augment the keratinolytic ability of Bacillus halotolerans L2EN1 isolated from the poultry farm (Nahan, District Sirmour) of Himachal Pradesh, different cultural conditions were optimised using One Variable at a Time (OVAT) approach accompanied by Response Surface Methodology (RSM). Optimisation (OVAT) results revealed that after 3rd day of incubation, maximum enzyme activity was attained at 45 °C, pH 11.0 with 12.5% of inoculum size in the presence of Mn2 + and EDTA in the production medium. Sucrose (1.5%) and yeast extract (2.0%) were observed to be best carbon and nitrogen sources, respectively. A significant increase of 73.19 per cent in the keratinase activity was observed using Central Composite Design (CCD) of RSM. The SDS-PAGE results revealed that crude keratinase is a heterotetramer made up of four polypeptide chains with molecular weights of 17, 37, 40 and 60 kDa. Partial purification by 90 − 100 percent ammonium sulphate gave maximum keratinase production of 22.66 U/mL with purification of 1.68 and yield of 11.47 per cent. The enzyme showed compatibility with different commercial detergents and retained its activity in the order: Reshma (97.77%) > Speed (93.44%) > Tide (79.93%) >Ariel (70.18%) > Surf excel (67.98%) at 50 °C after 1 h of incubation. Wash performance analysis demonstrated that washing with tap water at 18, 28, 35 and 45 °C for 30, 45 and 60 min removed some amount of blood stains from the cotton cloth pieces. However, replacement of detergent’s enzyme (Reshma) with crude keratinase achieved complete blood stain removal under same conditions, suggesting its suitability as a potential cleaning additive in detergents for the removal of blood (proteinaceous) stains for long washing cycles (1 h).