Saha2003 - J Ind Microbiol Biotechnol (2003) 30: 279291 DOI

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REVIEW PAPER Hemicellulose bioconversion Received: 17 December 2002/ Accepted: 17 February 2003/Published online: 16 April 2003 Ó Society for Industrial Microbiology 2003 Abstract Various agricultural residues, such as corn ±- ber, corn stover, wheat straw, rice straw, and sugarcane bagasse, contain about 20–40% hemicellulose, the sec- ond most abundant polysaccharide in nature. The con- version of hemicellulose to fuels and chemicals is problematic. In this paper, various pretreatment options as well as enzymatic sacchari±cation of lignocellulosic biomass to fermentable sugars is reviewed. Our research dealing with the pretreatment and enzymatic sacchari- ±cation of corn ±ber and development of novel and improved enzymes such as endo-xylanase, b -xylosidase, and a - L -arabinofuranosidase for hemicellulose biocon- version is described. The barriers, progress, and pros- pects of developing an environmentally benign bioprocess for large-scale conversion of hemicellulose to fuel ethanol, xylitol, 2,3-butanediol, and other value- added fermentation products are highlighted. Keywords Hemicellulose Æ Arabinoxylan Æ Bioconversion Æ Hemicellulase Æ Xylanolytic enzymes Introduction Hemicelluloses, the second most common polysaccha- rides in nature, represent about 20–35% of lignocellu- losic biomass. Xylans are the most abundant hemicelluloses. In recent years, bioconversion of hemi- cellulose has received much attention because of its practical applications in various agro-industrial pro- cesses, such as efficient conversion of hemicellulosic biomass to fuels and chemicals, deligni±cation of paper pulp, digestibility enhancement of animal feedstock, clari±cation of juices, and improvement in the consis- tency of beer [134, 139, 144]. Enzymes that degrade, or help to degrade, hemicellulose are of great interest to the paper and pulp industry due to their bleach-boosting properties (biobleaching of pulp), which reduces envi- ronmentally unfriendly chlorine consumption [91, 135]. Cellulase-free xylanase can facilitate lignin removal from paper pulp without any harmful e²ect. The utilization of hemicellulosic sugars is essential for efficient conversion of lignocellulosic materials to fuel ethanol and other value-added fermentation products. Xylan-degrading enzymes hold great promise in saccharifying various pretreated agricultural and forestry residues to fer- mentable sugars. Other potential applications of hemi- cellulases include biopulping of wood, co²ee processing, fruit and vegetable maceration, and preparation of high ±ber baked goods [19]. In addition, xylan-degrading enzymes play a great role in elucidating the structures of complex xylans. In this article, a brief review on the bioconversion of hemicellulose—particularly arabin- oxylans present in various agricultural residues—to fuel ethanol, xylitol and 2,3-butanediol, is presented.
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This note was uploaded on 12/03/2011 for the course BCMB 8020 taught by Professor Staff during the Fall '08 term at University of Georgia Athens.

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Saha2003 - J Ind Microbiol Biotechnol (2003) 30: 279291 DOI

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