iAMB-Institute of Applied Microbiology, ABBt-Aachen Biology and Biotechnology, RWTH Aachen University, Worringerweg 1, Aachen D-52074, Germany.
BMC Biotechnol. 2013 Jul 26;13:59. doi: 10.1186/1472-6750-13-59.
The utilization of raw biomass components such as cellulose or hemicellulose for the production of valuable chemicals has attracted considerable research interest in recent years. One promising approach is the application of microorganisms that naturally convert biomass constituents into value added chemicals. One of these organisms--Ustilago maydis--can grow on xylan, the second most abundant polysaccharide in nature, while at the same time it produces chemicals of biotechnological interest.
In this study, we present the identification of an endo-1,4-beta xylanase responsible for xylan degradation. Xylanase activity of U. maydis cells was indirectly detected by the quantification of released reducing sugars and could be confirmed by visualizing oligosaccharides as degradation products of xylan by thin layer chromatography. A putative endo-1,4-beta-xylanase, encoded by um06350.1, was identified in the supernatant of xylan-grown cells. To confirm the activity, we displayed the putative xylanase on the surface of the xylanase negative Saccharomyces cerevisiae EBY100. The presented enzyme converted xylan to xylotriose, similar to the source organism U. maydis.
The xylan degradation ability together with its unicellular and yeast-like growth makes U. maydis MB215 a promising candidate for the production of valuable chemicals such as itaconic acid or glycolipids from lignocellulosic biomass. Therefore, the characterization of the endo-1,4-beta-xylanase, encoded by um06350.1, is a further step towards the biotechnological application of U. maydis and its enzymes.
近年来，利用纤维素或半纤维素等原始生物质成分来生产有价值的化学品引起了相当多的研究兴趣。一种很有前途的方法是应用能够将生物质成分转化为增值化学品的微生物。其中一种微生物——玉米黑粉菌——可以在木聚糖上生长，木聚糖是自然界中第二丰富的多糖，同时它还能产生具有生物技术兴趣的化学品。
在这项研究中，我们鉴定了一种负责木聚糖降解的内切 1,4-β-木聚糖酶。通过定量释放的还原糖间接检测玉米黑粉菌细胞的木聚糖酶活性，并通过薄层层析将木聚糖的降解产物可视化来证实。在木聚糖生长细胞的上清液中鉴定到一个由 um06350.1 编码的假定内切 1,4-β-木聚糖酶。为了确认其活性，我们将假定的木聚糖酶展示在木聚糖酶阴性的酿酒酵母 EBY100 表面上。该酶将木聚糖转化为木三糖，与来源生物玉米黑粉菌相似。
玉米黑粉菌 MB215 具有木聚糖降解能力，并且能够像单细胞酵母一样生长，这使其成为从木质纤维素生物质生产有价值化学品（如衣康酸或糖脂）的有前途的候选生物。因此，um06350.1 编码的内切 1,4-β-木聚糖酶的特性是玉米黑粉菌及其酶在生物技术应用方面的进一步步骤。
