A novel xyloglucanase from the white rot fungus Abortiporus biennis and its potential role as an accessory biocatalyst in the enzymatic degradation of xyloglucan-contianing substrates

Lignocellulosic biomass is a composite material consisting of cellulose, hemicellulose, and lignin. Xyloglucan is a complex, highly substituted plant biomass hemicellulose that covers cellulose fibrils. Xyloglucanases, the enzymes responsible for its degradation, can be utilized for the design of efficient bioprocesses by incorporating them in enzyme cocktails that target cellulose-containing substrates. In order to shed light on the enzymatic degradation of xyloglucan, a novel xyloglucanase was studied from the basidiomycete Abortiporus biennis. Initially, a bioinformatic analysis of the xyloglucanase was carried out based on its amino acid sequence, followed by the heterologous production of AbiXega with the methylotrophic yeast P. pastoris acting as the host. Afterwards, the enzyme was purified to determine its biochemical and catalytic properties. Finally, its activity was investigated in 2 lignocellulose substrates (apple pulp, corn bran) to determine the synergism of AbiXega with a commercial cellulase preparation. From the results of these experiments, AbiXega was found to be a monomeric glycoprotein with a β-jelly roll structure with relatively strict substrate specificity, since it is only active in xyloglucan and β-glucan in an endo-dissociative way. The main hydrolysis products were the oligomers XXXG, XLXG/XXLG, and XLLG, and the optimum activity conditions are pH 4.5 and 55 ^oC. AbiXega was applied together with cellulases on the saccharification of corn bran and apple pulp. Overall, the importance of xyloglucanases on the saccharification of xyloglucan-containing substrates was demonstrated in this study. The results could contribute to the design of more efficient, tailor-made enzyme cocktails for the saccharification and subsequent valorization of lignocellulose.