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ARS Home » Research » Publications at this Location » Publication #92095
Title: ENZYMOLOGY OF XYLAN DEGRADATION

Author
item Saha, Badal
item Bothast, Rodney

Submitted to: American Chemical Society Symposium Series
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Xylan is a major component of hemicellulose, which is the second most common plant material in nature. Xylans from various agricultural residues such as corn fiber, corn cob, wheat straw, and rice straw can serve as renewable feedstock for conversion to fuel ethanol and value-added fermentation products. The structures of xylans are complex, and several enzymes are involved in their breakdown. These enzymes have practical applications in the efficient conversion of xylans to fuels and chemicals, biobleaching of pulp for the paper industry, enhanced digestion of animal feed, clarification of fruit and vegetable juices, and preparation of high fiber bakery goods. Xylan degrading enzymes are produced by a variety of microorganisms. In this paper, a brief review of recent advances in the production, properties, mode of action, and function of each enzyme involved in xylan degradation and their interactions is presented. At present, there is no suitable commercial enzyme preparation that can efficiently convert various pretreated agricultural residues to simple sugars. Advances in enzyme technology are necessary to develop highly efficient and cost effective enzymes for use in agricultural biomass conversion. This manuscript will be of value to both academic and industrial scientists who are currently working, or planning to work, on xylan degrading enzymes and their applications in biotechnology.

Technical Abstract: Xylan is a major component of the hemicellulose portion of plant cell walls and constitutes up to 35% of the total dry weight of higher plants. It consists of a homopolymeric backbone chain of beta-1,4-linked D-xylose units and short side chains including L-arabinofuranosyl, O-acetyl, D-glucuronosyl, or O-methyl-D-glucuronosyl residues. Xylan degrading enzymes are produced by a wide variety of aerobic and anaerobic fungi and bacteria. Enzymatic hydrolysis of xylan involves a multi-enzyme system including endo-xylanase, beta-xylosidase, alpha-arabinofuranosidase, alpha-glucuronidase, acetylxylan esterase, ferulic acid esterase, and p-coumaric acid esterase. Synergistic interactions of all these enzymes are required for the complete degradation of xylans. A brief review of each enzyme involved in xylan degradation is presented.