Biochemical characterization and low-resolution SAXS shape of a novel GH11 exo-1,4-β-xylanase identified in a microbial consortium
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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).
KeywordsGH11 exo-β-1,4-xylanase Metatranscriptome Biochemical characterization Synergism Small-Angle X-ray scattering
The authors acknowledge Dr. Marco A. S. Kadowaki for his help with HPAEC analysis and Dr. Evandro Ares de Araújo for assistance with SAXS data collection and processing.
I.P and D.E.E designed the experiments and wrote the manuscript. D.E.E and V.O.A.P performed MetXyn11 biochemical and biophysical characterization. D.E.E performed the SAXS experiments. M.E.S provided pretreated bagasse samples. I.P., S.M.M., N.C.B., D.E.E., and V.O.A.P. contributed to discussion of the results and editing of the manuscript. All the authors approved the final version.
This study was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) via grant nos. 10/52362-5, 11/20505-4, 11/21608-1, and 15/13684-0; the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) via grant nos. 405191/2015-4, 303988/2016-9, 440977/2016-9, and 151963/2018-5; and the BBSRC of the UK Research and Innovation (grant number: BB/I018492/1).
Compliance with ethical standards and ethical approval
This article does not contain any studies with human or animal participants.
Conflict of interest
The authors declare that they have no conflict of interest.
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