Carbohydrate acting enzymes such as glycoside hydrolases (GH) is one example of an essential group of enzymes used on forest and agricultural materials for this purpose, employed to hydrolyze carbohydrates into shorter oligosaccharides and monosugars ( Gilbert et al. However, significant structural dissimilarities between HhXyn5A and CtXyn5A in the binding cleft of CBM6, due to the lack of important ligand-interacting residues, is suggested to cause the observed differences in substrate specificity and product formation.Įnzymatic processing of biomass is a widespread approach and an important step in biorefineries and food industry, in order to break down recalcitrant structures and valorize individual process streams to various building-block chemicals, speciality chemicals and consumer products ( Silva et al. Results from multiple sequence alignment of GH5_34 enzymes, homology modeling of HhXyn5A and docking simulations with ligands XXXA 3, XXXA 3XX and X 5 concluded that the active site of HhXyl5A catalytic domain is highly conserved and can accommodate both shorter and longer ligands. In contrast to the commercially available homolog CtXyn5A, HhXyn5A gave a more specific HPAEC–PAD oligosaccharide product profile when using wheat arabinoxylan and alkali extracted oat bran fibers as the substrate. HhXyn5A demonstrated no side activity on oat β-glucan.
HhXyn5A demonstrated activity on various commercial cereal arabinoxylans and produced prebiotic AXOS, whereas the sole catalytic domain of HhXyn5A did not demonstrate detectable activity. The purified two-domain HhXyn5A (catalytic domain and CBM6) demonstrated high storage stability, showed a melting temperature T m of 61☌ and optimum reaction conditions were determined to 55☌ and pH 6.5 on wheat arabinoxylan. In this study, a novel GH5_34 subfamily arabinoxylanase from Herbinix hemicellulosilytica, HhXyn5A, was identified, produced and extensively characterized, for the intended exploitation in cereal processing to solubilize potential prebiotic fibers: arabinoxylo-oligosaccharides. By solubilizing hemicellulose and modifying the fiber structure, novel food products with increased nutritional value can be created. Carbohydrate active enzymes are valuable tools in cereal processing to valorize underutilized side streams.
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