Enzymatic deconstruction of xylan for biofuel production

A review paper by DODD et al titled "Enzymatic deconstruction of xylan for biofuel production" summarizs current understanding of the molecular basis for substrate specificity and catalysis by enzymes involved in xylan deconstruction.

Xylan is the dominant hemicellulose in hardwood and non-woody biomass. Its deconstruction to monomer sugar not only contributes to the source of sugars but also enhances the exposure of cell wall to enzyme/chemical hydrolysis.
production.

Xylan is known a heteropolymeric substrate consisting of a repeating β-1,4-linked xylose backbone branched with acetyl, arabinofuranosyl, and 4-O-methyl glucuronyl groups (Figure 1).In addition, xylan may be cross linked to lignin by aromatic esters. In order to efficiently depolymerize xylan to the component monosaccharides, a mixture of different enzymatic functionalities are required, including endo-1,4-β-xylanases (EC 3.2.1.8), β-D-xylosidases (EC 3.2.1.37), α-L-arabinofuranosidases (AFs) (EC 3.2.1.55), α-glucuronidases (EC 3.2.1.139),acetyl xylan esterases (EC 3.1.1.72), and ferulic/coumaric acid esterases (EC 3.1.1.73).



A better understanding of the structural diversity in xylan and the corresponding enzymatic strategies employed by microbes will be critical to hydrolyze the linkages within this complex heteropolymer.