Abstract：
Enzymatic degradation of lignocellulosic biomass provides an eco-friendly approach to produce value-added macromolecules, e.g., bioactive polysaccharides. A novel acidophilic GH5 β-1,4-endoglucanase (termed TaCel5) from Trichoderma asperellum ND-1 was efficiently expressed in Komagataella phaffii (∼1.5-fold increase, 38.42 U/mL). TaCel5 displayed both endoglucanase (486.3 U/mg) and alginate lyase (359.5 U/mg) enzyme activities. It had optimal pH 3.0 and strong pH stability (exceed 86 % activity retained over pH range 3.0-5.0). 80 % activity (both endoglucanase and alginate lyase) was retained in the presence of 15 % ethanol or 3.42 M NaCl. Analysis of action mode revealed that hydrolytic activity of TaCel5 required at least three glucose (cellotriose) residues, yielding mainly cellobiose. Glu241 and Glu352 are essential catalytic residues, while Asp106, Asp277 and Asp317 play auxiliary roles in cellulose degradation. TaCel5 displayed high hydrolysis efficiency for glucan and alginate substrates. ESI-MS analysis indicated that the enzymatic hydrolysates of alginate mainly contained disaccharides and heptasaccharides. This is the first detailed report of a bifunctional GH5 endoglucanase/alginate lyase enzyme from T. asperellum. Thus TaCel5 has strong potential in food and feed industries as a catalyst for bioconversion of cellulose- and alginate-containing waste materials into value-added products oligosaccharides, which was of great benefit both for the economy and environment.
摘要：
木质纤维素生物质的酶促降解提供了一种生态友好的方法来产生增值的大分子，例如，生物活性多糖。来自天蚕木霉ND-1的新型嗜酸GH5β-1,4-内切葡聚糖酶（称为TaCel5）在波氏杆菌属中有效表达（约1.5倍增加，38.42U/mL)。TaCel5显示了内切葡聚糖酶（486.3U/mg）和藻酸盐裂解酶（359.5U/mg）的酶活性。它具有最佳的pH3.0和强的pH稳定性(在pH范围3.0-5.0内保持超过86%的活性)。在15％乙醇或3.42MNaCl存在下，保留了80％的活性（内切葡聚糖酶和藻酸盐裂解酶）。作用模式分析显示，TaCel5的水解活性需要至少三个葡萄糖（细胞三糖）残基，主要产生纤维二糖。Glu241和Glu352是必需的催化残基，而Asp106、Asp277和Asp317在纤维素降解中起辅助作用。TaCel5对葡聚糖和藻酸盐底物显示出高水解效率。ESI-MS分析表明，藻酸盐的酶解产物主要含有二糖和七糖。这是来自天蚕的双功能GH5内切葡聚糖酶/藻酸盐裂解酶的第一个详细报道。因此，TaCel5在食品和饲料工业中具有强大的潜力，可作为将含有纤维素和藻酸盐的废料生物转化为增值产品寡糖的催化剂，这对经济和环境都有很大的好处。
