Biochemical characterization and low-resolution SAXS shape of a novel GH11 exo-1,4-β-xylanase identified in a microbial consortium

• Published in: Applied microbiology and biotechnology 2019-10, Vol.103 (19), p.8035-8049
• Main Authors: Evangelista, Danilo Elton, de Oliveira Arnoldi Pellegrini, Vanessa, Santo, Melissa Espirito, McQueen-Mason, Simon, Bruce, Neil C., Polikarpov, Igor
• Format: Article
• Language: English
• Subjects: Bagasse; Biomedical and Life Sciences; Biotechnologically Relevant Enzymes and Proteins; Biotechnology; Catalysis; Cell walls; Consortia; Depolymerization; Disaccharides - metabolism; Endo-1,4-beta Xylanases - chemistry; Endo-1,4-beta Xylanases - isolation & purification; Endo-1,4-beta Xylanases - metabolism; Enzyme Stability; Enzymes; Gene Expression Profiling; Glycoside hydrolase; Hemicellulose; Hydrogen-Ion Concentration; Hydrolase; Hydrolysis; Life Sciences; Lignocellulose; Metagenomics; Microbial Consortia; Microbial Genetics and Genomics; Microbiology; Microorganisms; Oligomers; Organic chemistry; pH effects; Protein Conformation; Recombinant Proteins - chemistry; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Renewable fuels; Scattering, Small Angle; Small angle X ray scattering; Sugar; Sugarcane; Temperature; X-ray scattering; Xylan; Xylanase; Xylans - metabolism
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-019-10033-8

Biotechnologies that aim to produce renewable fuels, chemicals, and bioproducts from residual ligno(hemi)cellulosic biomass mostly rely on enzymatic depolymerization of plant cell walls (PCW). This process requires an arsenal of diverse enzymes, including xylanases, which synergistically act on the hemicellulose, reducing the long and complex xylan chains to oligomers and simple sugars. Thus, xylanases play a crucial role in PCW depolymerization. Until recently, the largest xylanase family, glycoside hydrolase family 11 (GH11) has been exclusively represented by endo-catalytic β-1,4- and β-1,3-xylanases. Analysis of a metatranscriptome library from a microbial lignocellulose community resulted in the identification of an unusual exo-acting GH11 β-1,4-xylanase (MetXyn11). Detailed characterization has been performed on recombinant MetXyn11 including determination of its low-resolution small-angle X-ray scattering (SAXS) molecular envelope in solution. Our results reveal that MetXyn11 is a monomeric globular enzyme that liberates xylobiose from heteroxylans as the only product. MetXyn11 has an optimal activity in a pH range from 6 to 9 and an optimal temperature of 50 °C. The enzyme maintained above 65% of its original activity in the pH range 5 to 6 after being incubated for 72 h at 50 °C. Addition of the enzyme to a commercial enzymatic cocktail (CelicCtec3) promoted a significant increase of enzymatic hydrolysis yields of hydrothermally pretreated sugarcane bagasse (16% after 24 h of hydrolysis).