Department of Animal Biosciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
Department of Cellular and Molecular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
Sci Rep. 2019 Sep 20;9(1):13630. doi: 10.1038/s41598-019-50050-1.
Cellulases play important roles in the dietary fibre digestion in pigs, and have multiple industrial applications. The porcine intestinal microbiota display a unique feature in rapid cellulose digestion. Herein, we have expressed a cellulase gene, p4818Cel5_2A, which singly encoded a catalytic domain belonging to glycoside hydrolase family 5 subfamily 2, and was previously identified from a metagenomic expression library constructed from porcine gut microbiome after feeding grower pigs with a cellulose-supplemented diet. The activity of purified p4818Cel5_2A was maximal at pH 6.0 and 50 °C and displayed resistance to trypsin digestion. This enzyme exhibited activities towards a wide variety of plant polysaccharides, including cellulosic substrates of avicel and solka-Floc, and the hemicelluloses of β-(1 → 4)/(1 → 3)-glucans, xyloglucan, glucomannan and galactomannan. Viscosity, reducing sugar distribution and hydrolysis product analyses further revealed that this enzyme was a processive endo-β-(1 → 4)-glucanase capable of hydrolyzing cellulose into cellobiose and cellotriose as the primary end products. These catalytic features of p4818Cel5_2A were further explored in the context of a three-dimensional homology model. Altogether, results of this study report a microbial processive endoglucanase identified from the porcine gut microbiome, and it may be tailored as an efficient biocatalyst candidate for potential industrial applications.
纤维素酶在猪的膳食纤维消化中发挥重要作用，并有多种工业应用。猪的肠道微生物群在快速纤维素消化方面表现出独特的特征。在此，我们表达了一个纤维素酶基因，p4818Cel5_2A，它单独编码一个属于糖苷水解酶家族 5 亚家族 2 的催化结构域，该基因先前是从用纤维素补充饲料喂养生长猪的猪肠道微生物组的宏基因组表达文库中鉴定出来的。纯化的 p4818Cel5_2A 的活性在 pH6.0 和 50°C 时达到最大值，并且对胰蛋白酶消化具有抗性。该酶对多种植物多糖具有活性，包括纤维素底物微晶纤维素和 Solka-Floc，以及半纤维素的 β-(1→4)/(1→3)-葡聚糖、木葡聚糖、葡甘露聚糖和半乳甘露聚糖。粘度、还原糖分布和水解产物分析进一步表明，该酶是一种具有活性的内切-β-(1→4)-葡聚糖酶，能够将纤维素水解成纤维二糖和纤维三糖作为主要的末端产物。这些 p4818Cel5_2A 的催化特性在三维同源模型的背景下得到了进一步的探索。总之，这项研究的结果报告了一种从猪肠道微生物群中鉴定出的微生物过程性内切葡聚糖酶，它可能被定制为一种有效的生物催化剂候选物，用于潜在的工业应用。
