State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, People's Republic of China; Wuhan Institute of Design and Sciences, Wuhan 430070, People's Republic of China.
Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan 173 234, India.
Int J Biol Macromol. 2020 Jul 15;155:572-580. doi: 10.1016/j.ijbiomac.2020.03.249. Epub 2020 Apr 1.
Xylanase is a versatile tool in the food, fiber biobleaching and biofuel industries. Here, to discover new enzyme with special properties, we cloned three xylanases (Xyn11A, Xyn11B, and Xyn11C) by mining the genome of the xylanase producing fungus strain Fusarium sp. 21, biochemically characterized these enzyme and explored their potential application in juice processing. Both Xyn11A and Xyn11B had an optimal pH of 6.0 and optimal temperature of 45 °C, and retained >90% of the residual activity at pH range of 5-10.5 for 24 h. Xyn11C displayed the maximum activity at pH 5.0 and 45 °C and outstanding pH stability with a minimal loss of activity in the pH range of 2.0-10.5. These three xylanases displayed a strong specificity towards beechwood and corncob xylan, with no activity for other substrates. Xyn11A showed much a higher activity against corncob xylan, while Xyn11B and Xyn11C presented higher activities against beechwood xylan. Xyn11A catalyzed the hydrolysis of beechwood xylan with a K of 4.25 ± 0.29 mg·mL and k/K of 30.34 ± 0.65 mL·s·mg, while the hydrolysis of corncob xylan had Km and k/K values of 14.73 ± 1.43 mg·mLand 26.48 ± 0.11 mL·s·mg, respectively. Xyn11B and Xyn11C hydrolyzed beechwood xylan with Km of 9.8 ± 0.69 mg·mL, and 4.89 ± 0.38 mg·mLand k/K values of 45.07 ± 1.66 mL·mg, and 26.95 ± 0.67 mL·s·mg, respectively. Beechwood xylan hydrolysates catalyzed by these three xylanases contained xylobiose, xylotriose and xylooligosaccharides (XOS). The clarification of orange juice was improved when treated with these three xylanases. Conclusively, the desirable pH stability and substrate specificity make Xyn11A, Xyn11B and Xyn11C have high potential for application in fiber biobleaching, wine and fruit juice clarification, as well as probiotic XOS production.
木聚糖酶在食品、纤维生物漂白和生物燃料工业中是一种用途广泛的工具。在这里，为了发现具有特殊性质的新酶，我们通过挖掘产木聚糖酶真菌菌株镰孢菌 21 的基因组，克隆了三种木聚糖酶（Xyn11A、Xyn11B 和 Xyn11C），对这些酶进行了生化特性分析，并探索了它们在果汁加工中的潜在应用。Xyn11A 和 Xyn11B 的最适 pH 均为 6.0，最适温度均为 45°C，在 pH 5-10.5 范围内孵育 24 小时后，保留了 >90%的残余活性。Xyn11C 在 pH 5.0 和 45°C 时表现出最大活性，并且在 pH 2.0-10.5 范围内具有出色的 pH 稳定性，活性损失最小。这三种木聚糖酶对山毛榉木聚糖和玉米芯木聚糖具有很强的特异性，对其他底物没有活性。Xyn11A 对玉米芯木聚糖的活性更高，而 Xyn11B 和 Xyn11C 对山毛榉木聚糖的活性更高。Xyn11A 催化山毛榉木聚糖水解的 K 值为 4.25±0.29mg·mL，k/K 值为 30.34±0.65mL·s·mg，而玉米芯木聚糖水解的 Km 和 k/K 值分别为 14.73±1.43mg·mL和 26.48±0.11mL·s·mg。Xyn11B 和 Xyn11C 分别以 Km 为 9.8±0.69mg·mL和 4.89±0.38mg·mL 水解山毛榉木聚糖，k/K 值为 45.07±1.66mL·mg 和 26.95±0.67mL·s·mg。这三种木聚糖酶催化的山毛榉木聚糖水解产物含有木二糖、木三糖和木低聚糖（XOS）。用这三种木聚糖酶处理橙汁可以提高澄清度。总之，理想的 pH 稳定性和底物特异性使 Xyn11A、Xyn11B 和 Xyn11C 在纤维生物漂白、葡萄酒和果汁澄清以及益生菌 XOS 生产方面具有很高的应用潜力。
