Abstract
Conversion of biomass into fermentable sugars is a major requirement for successful and cost-effective biofuels production. The conversion of xylan to sugars requires multiple enzymes including α-glucuronidase. Here we report the cloning, expression, purification and characterization of the α-glucuronidase from Dictyoglomusturgidum(DtuAgu). DtuAgu is an intracellular protein of 685 amino acids and a predicted molecular weight of 79.4 kD. Enzymatic activity was optimum between pH 7.0 and 8.0 and at 85°C. The specific activity of the enzyme was 10 u/mg when measured using mixed aldouronic acids. The specific activity on isolated glucuronoxylan was approximately 20% of the value obtained with xylooligosaccharides. DtuAgu significantly improved xylan conversion to xylose when evaluated using two mixtures of thermostable bacterial enzymes and two sources of xylan. DtuAgu has the potential to be a key player in thermostable enzyme cocktails for the conversion to biomass to biofuels.α
Highlights
Plant-based biomass is made up of two main polysaccharide components, cellulose and hemicellulose.Conversion of these polysaccharides to bio-based fuels and chemicals requires the degradation of the cellulose and hemicellulose to sugar monomers via enzymatic processes
While cellulose is a homopolymer of β-1,4 linked glucose, xylans are a heterogenous collection of molecules sharing only a β-1,4 linked xylose backbone
Arabinoxylans contain xylose residues highly substituted with α-(1,2)-linked arabinose, α-(1,3)- linked arabinose as well as xylose residues substituted with both α-(1,2), α-(1,3)-linked arabinose, with a ratio of arabinose to xylose of 0.5 to 0.6 for wheat arabinoxylan [6]
Summary
Plant-based biomass is made up of two main polysaccharide components, cellulose and hemicellulose. Conversion of these polysaccharides to bio-based fuels and chemicals requires the degradation of the cellulose and hemicellulose to sugar monomers via enzymatic processes. A number of enzymatic systems have been described for achieving these conversions, including systems from bacterial [1] and fungal [2,3,4,5] sources. The degradation of these polysaccharides is made more difficult by the complexity of the substrates. Arabinoxylans contain xylose residues highly substituted with α-(1,2)-linked arabinose, α-(1,3)- linked arabinose as well as xylose residues substituted with both α-(1,2), α-(1,3)-linked arabinose, with a ratio of arabinose to xylose of 0.5 to 0.6 for wheat arabinoxylan [6]
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