Open AccessOptimization of alkaline extraction of hemicellulose from sweet sorghum bagasse and its direct application for the production of acidic xylooligosaccharides by Bacillus subtilis strain MR44
Author(s) -
Wei Li,
Tongjing Yan,
Yifei Wu,
Hui Chen,
Baoshan Zhang
Publication year - 2018
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0195616
Subject(s) - bagasse , xylose , xylan , xylanase , bacillus subtilis , chemistry , hemicellulose , arabinoxylan , arabinose , sweet sorghum , food science , extraction (chemistry) , microbiology and biotechnology , cellulose , biochemistry , polysaccharide , fermentation , chromatography , agronomy , biology , sorghum , enzyme , bacteria , genetics
As predominant components of hemicelluloses in grasses, methylglucuroarabinoxylans (MeGAX n ) are sources for the production of acidic xylooligosaccharides (U-XOS). Bacillus subtilis MR44, an engineered biocatalyst to secrete only the XynC xylanase and Axh43 arabinoxylan hydrolase is capable of processing MeGAX n to exclusively U-XOS. The present studies are directed at the explosion on direct alkaline extraction serving for production of U-XOS. Response Surface Methodology was used to optimize xylan extraction conditions on the sweet sorghum bagasse to achieve maximum hemicelluloses yield. The optimized condition was as follows: extraction time of 3.91 h, extraction temperature of 86.1°C, and NaOH concentration (w/w) of 12.33%. Crude xylan extracted with NaOH revealed a compositional analysis of xylose (79.0%), arabinose (5.3%), glucose (1.7%), lignin and ash (5.6%). After neutralization this xylan preparation supported growth of MR44, processing MeGAX n from sweet sorghum and accumulating U-XOS. The quality of U-XOS produced by MR44 using alkaline-treated sweet sorghum bagasse was comparable to that obtained from purified MeGAX n . Overall, the present study demonstrates that direct alkaline treatment of sweet sorghum bagasse is useful to improve the bioavailability of MeGAX n for MR44-mediated conversion to U-XOS with average degrees of polymerization of 11–12, providing alternative resources with applications in nutrition and human and veterinary medicine.