Institute of Industrial Biotechnology, GC University, Lahore, 54000, Pakistan.
Folia Microbiol (Praha). 2020 Oct;65(5):823-834. doi: 10.1007/s12223-020-00793-6. Epub 2020 May 16.
Microbial and enzymatic degradation of keratin waste is more preferred over various conventional approaches which are costly and not environmentally suitable. Diverse niches are auspicious for the discovery of new microorganisms. To discover novel keratinolytic bacteria, 60 isolates from different poultry dumping sites were initially screened, and among these found a potent keratinolytic isolate (NKSP-7) that displayed higher feather-degrading ability. The selected isolate was identified as Bacillus sp. NKSP-7 based on 16S rDNA sequencing as well as physiochemical and morphological characteristics. The strain NKSP-7 showed complete hydrolysis of native chicken feathers (10 g/L) in nutrient medium after 24 h of incubation at 37 °C under agitation (150 rev/min) and produced thermostable extracellular keratinase. The crude enzyme displayed maximal keratinolytic activity (34.7 U/mL) in phosphate buffer of pH 7.0, and at 60 °C using keratin azure as a substrate. Keratinolytic enzyme showed stability at 20-65 °C for 4 h over the pH range of 5.5-8.0. No obvious inhibitory influence was perceived by cations, organic solvents, EDTA, and detergents. Whereas, enzyme activity was enhanced by adding β-mercaptoethanol, Na, Cd, and Mn. All these notable features of keratinase make it a promising candidate for various industrial applications especially for dehairing process in leather industry, bioconversion of poultry waste, and in detergents formulations.
与各种昂贵且不环保的传统方法相比,微生物和酶法降解角蛋白废物更受青睐。不同的生态位有利于发现新的微生物。为了发现新的角蛋白降解细菌,从不同的家禽倾倒场筛选了 60 个分离株,其中发现了一种具有较强角蛋白降解能力的有效角蛋白降解分离株(NKSP-7)。根据 16S rDNA 测序以及生理化学和形态特征,将选定的分离株鉴定为芽孢杆菌 NKSP-7。该菌株 NKSP-7 在 37°C 下搅拌(150 转/分)孵育 24 小时后,在营养培养基中完全水解天然鸡羽毛(10 g/L),并产生耐热的细胞外角蛋白酶。粗酶在 pH 7.0 的磷酸盐缓冲液中显示出最大的角蛋白酶活性(34.7 U/mL),并在使用角蛋白天青作为底物时在 60°C 下显示出最大的角蛋白酶活性。角蛋白酶在 pH 5.5-8.0 的范围内,在 20-65°C 下稳定 4 小时。阳离子、有机溶剂、EDTA 和洗涤剂没有明显的抑制作用。然而,添加β-巯基乙醇、Na、Cd 和 Mn 可增强酶活性。角蛋白酶的所有这些显著特性使其成为各种工业应用的有前途的候选物,特别是在皮革工业的脱毛过程、家禽废物的生物转化以及洗涤剂配方中。