Guangxi Key Laboratory for Polysaccharide Materials and Modifications, Guangxi Key Laboratory of Microbial Plant Resources and Utilization, School of Marine Sciences and Biotechnology, Guangxi University for Nationalities, Nanning, 530006, China.
BMC Biotechnol. 2022 Mar 20;22(1):11. doi: 10.1186/s12896-022-00742-w.
Feathers are the most abundant agricultural waste produced by poultry farms. The accumulation of a large number of feathers not only seriously pollutes the environment but also causes the waste of protein resources. The degradation of feather waste by keratinase-producing strains is currently a promising method. Therefore, screening high-producing keratinase strains from marine environment and studying the fermentation conditions, enzymatic properties and feather degradation mechanism are crucial for efficient degradation of feathers.
A novel efficient feather-degrading bacteria, Gxun-17, isolated from the soil sample of a marine duck farm of Beibu Gulf in Guangxi, China, was identified as Bacillus tropicus. The optimum fermentation conditions were obtained by single factor and orthogonal tests as follows: feather concentration of 15 g/L, maltose concentration of 10.0 g/L, MgSO concentration of 0.1 g/L, initial pH of 7.0 and temperature of 32.5 °C. The strain completely degraded the feathers within 48 h, and the highest keratinase activity was 112.57 U/mL, which was 3.18-fold that obtained with the basic medium (35.37 U/mL). Detecting the keratinase activity and the content of sulphur-containing compounds in the fermentation products showed that the degradation of feathers by the strain might be a synergistic effect of the enzyme and sulphite. The keratinase showed optimal enzyme activity at pH 7.0 and temperature of 60 °C. The keratinase had the best performance on the casein substrate. When casein was used as the substrate, the K and V values were 15.24 mg/mL and 0.01 mg/(mL·min), respectively. Mg, Ca, K, Co, Al, phenylmethylsulphonyl fluoride and isopropanol inhibited keratinase activity, which indicated that it was a serine keratinase. Conversely, the keratinase activity strongly increased with the addition of Mn and β-mercaptoethanol.
A novel feather-degrading B. tropicus Gxun-17 was obtained from marine environment. The strain adapted the extreme conditions such as low temperature, high salt and high pressure. Thus, the keratinase had high activity, wide range of temperature and pH, salt tolerance and other characteristics, which had potential application value.
羽毛是家禽养殖场产生的最丰富的农业废弃物。大量羽毛的积累不仅严重污染环境，还造成蛋白质资源的浪费。角蛋白酶产生菌对羽毛废料的降解是目前很有前途的方法。因此，从海洋环境中筛选高产角蛋白酶的菌株，并研究发酵条件、酶学性质和羽毛降解机制，对于羽毛的高效降解至关重要。
从中国广西北部湾地区某海洋养鸭场的土壤样本中分离到一株新型高效羽毛降解菌，命名为 Gxun-17，鉴定为解淀粉芽孢杆菌。通过单因素和正交试验得到最佳发酵条件为：羽毛浓度 15 g/L、麦芽糖浓度 10.0 g/L、MgSO浓度 0.1 g/L、初始 pH 值 7.0、温度 32.5°C。该菌株在 48 h 内完全降解羽毛，角蛋白酶活力最高可达 112.57 U/mL，是基础培养基（35.37 U/mL）的 3.18 倍。检测发酵产物中的角蛋白酶活力和含硫化合物含量表明，该菌株对羽毛的降解可能是酶和亚硫酸盐的协同作用。角蛋白酶在 pH 7.0、60°C 时酶活力最佳。角蛋白酶对酪蛋白底物表现出最佳性能。当以酪蛋白为底物时，K 和 V 值分别为 15.24 mg/mL 和 0.01 mg/（mL·min）。Mg、Ca、K、Co、Al、苯甲基磺酰氟和异丙醇抑制角蛋白酶活性，表明其为丝氨酸角蛋白酶。相反，加入 Mn 和 β-巯基乙醇会强烈增加角蛋白酶的活性。
从海洋环境中获得了一株新型羽毛降解解淀粉芽孢杆菌 Gxun-17。该菌株适应低温、高盐和高压等极端条件。因此，角蛋白酶具有活性高、温度和 pH 范围广、耐盐等特性，具有潜在的应用价值。
