Background: The enzymatic degradation of keratin-rich wastes by a keratinolytic microorganism is a preferable and eco-friendly biotechnological alternative for the valorization of these compounds. Despite their recalcitrant behavior, hydrolysis of these wastes can be efficiently done by microbial proteolytic enzyme known as keratinase. Objective: In the present study, a potent keratinolytic bacterial strain with a great potential of feathers’ degradation was isolated and identified by 16S rDNA sequencing as Bacillus sp. NDS-10. Results: After optimization, high-yield of extracellular keratinase (92 U mL⁻¹) and bioconversion of feathers (97%) were achieved in M9 medium (pH 7.0) containing 0.8% (w/v) native chicken feathers after 20 h incubation at 45 °C. The crude keratinase exhibited maximal activity at pH 7.0–8.0 (Tris-Cl buffer) and 65 °C; and showed great stability over a range of pH (6.0–10.0) and temperature (20-60°C) for 6 h. No inhibitory influence was observed with various chemical modulators, commercial detergents and salt but phenylmethanesulfonyl fluoride (PMSF) completely repressed the keratinolytic activity of enzyme. The enzyme effectively dehaired goat hide after 6 h without any damage and completely removed the blood-stain after 5 min incubation. Conclusion: These favorable features indicated that this keratinolytic enzyme seems to be an efficient and eco-friendly candidate for keratin-waste management, detergents formulations and hide-depilation application.

Graphic Abstract

中文翻译：

---

来自耐热分离芽孢杆菌的角质分解酶。NDS-10：一种用于家禽废物管理、洗衣和皮革脱毛应用的高效绿色生物催化剂

背景：角蛋白溶解微生物对富含角蛋白的废物进行酶促降解是使这些化合物增值的优选且环保的生物技术替代方案。尽管它们的行为顽固，这些废物的水解可以通过称为角蛋白酶的微生物蛋白水解酶有效地完成。目的：在本研究中，通过 16S rDNA 测序分离出一株具有巨大羽毛降解潜力的强效角质蛋白溶解细菌菌株，并鉴定为芽孢杆菌属。NDS-10。结果：优化后，细胞外角蛋白酶产量高（92 U mL ^-1) 和羽毛的生物转化 (97%) 在含有 0.8% (w/v) 天然鸡毛的 M9 培养基 (pH 7.0) 中在 45°C 下孵育 20 小时后实现。粗角蛋白酶在 pH 7.0–8.0（Tris-Cl 缓冲液）和 65 °C 下表现出最大活性；并在 pH (6.0-10.0) 和温度 (20-60°C) 范围内保持 6 小时的稳定性。使用各种化学调节剂、商业洗涤剂和盐没有观察到抑制影响，但苯甲磺酰氟 (PMSF) 完全抑制了酶的角质分解活性。该酶在 6 小时后有效地脱毛山羊皮而没有任何损伤，并在孵育 5 分钟后完全去除血迹。结论： 这些有利的特征表明，这种角质分解酶似乎是角蛋白废物管理、洗涤剂配方和皮革脱毛应用的有效且环保的候选者。

图形摘要