Original Research ARTICLE
A Highly Efficient Xylan-utilization System in Aspergillus niger An76: a Functional-proteomics Study
- 1Shandong University, China
Xylan constituted with β-1,4-D-xylose linked backbone and diverse substituted side-chains is the most abundant hemicellulose component of biomass, which can be completely and rapidly degraded into fermentable sugars by Aspergillus niger. This is of great value for obtaining renewable biofuels and biochemicals. To clarify the underlying mechanisms associated with highly efficient xylan degradation, assimilation, and metabolism by A. niger, we utilized functional proteomics to analyze the secreted proteins, sugar transporters and intracellular proteins of A. niger An76 grown on xylan-based substrates. Results demonstrated that the complete xylanolytic enzyme system required for xylan degradation and composed of diverse isozymes was secreted in a sequential order. Xylan-backbone-degrading enzymes were preferentially induced by xylose or other soluble sugars, which efficiently produced large amounts of xylooligosaccharides (XOS) and xylose; however, XOS was more efficient than xylose in triggering the expression of the key transcription activator XlnR, resulting in higher xylanase activity and shortening xylanase-production time. Moreover, the substituted XOS was responsible for improving the abundance of side-chain-degrading enzymes, specific transporters, and key reductases and dehydrogenases in the pentose catabolic pathway. Our findings indicated that industries might be able to improve the species and concentrations of xylan-degrading enzymes and shorten fermentation time by adding abundant intermediate products of natural xylan (XOS) to cultures of filamentous fungi.
Keywords: xylan-degrading isoenzyme, sugar transporter, transcription activator XlnR, Aspergillus niger An76, Xylan
Received: 15 Dec 2017;
Accepted: 26 Feb 2018.
Edited by:Ozgur Bayram, Maynooth University, Ireland
Reviewed by:Steven Singer, Lawrence Berkeley National Laboratory (LBNL), United States
Jun-ichi MARUYAMA, The University of Tokyo, Japan
Copyright: © 2018 Gong, Dai, Zhang, Zhang and Wang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Prof. Lushan Wang, Shandong University, The State Key Laboratory of Microbial Technology, Shandong University, 27 Shandanan Rd, Jinan, Shand, Jinan, China, firstname.lastname@example.org