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

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 Xray 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 oC. The enzyme maintained above 65% of its original activity in the pH range 5 to 6 after being incubated for 72 h at 50 oC. 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)

Targeted metatranscriptomics of compost derived consortia reveals a GH11 exerting an unusual exo-1,4-β-xylanase activity

Background: Using globally abundant crop residues as a carbon source for energy generation and renewable chemicals production stands out as a promising solution to reduce current dependency on fossil fuels. In nature, such as in compost habitats, microbial communities efficiently degrade the available plant biomass using a diverse set of synergistic enzymes. However, deconstruction of lignocellulose remains a challenge for industry due to recalcitrant nature of the substrate and the inefficiency of the enzyme systems available, making the economic production of lignocellulosic biofuels difficult. Metatranscriptomic studies of microbial communities can unveil the metabolic functions employed by lignocellulolytic consortia and identify new biocatalysts that could improve industrial lignocellulose conversion. Results: In this study, a microbial community from compost was grown in minimal medium with sugarcane bagasse sugarcane bagasse as the sole carbon source. Solid-state nuclear magnetic resonance was used to monitor lignocellulose degradation; analysis of metatranscriptomic data led to the selection and functional characterization of several target genes, revealing the first glycoside hydrolase from Carbohydrate Active Enzyme family 11 with exo-1,4-β-xylanase activity. The xylanase crystal structure was resolved at 1.76 Å revealing the structural basis of exo-xylanase activity. Supplementation of a commercial cellulolytic enzyme cocktail with the xylanase showed improvement in Avicel hydrolysis in the presence of inhibitory xylooligomers. Conclusions: This study demonstrated that composting microbiomes continue to be an excellent source of biotechnologically important enzymes by unveiling the diversity of enzymes involved in in situ lignocellulose degradation

Evaluating the Potential of Culms from Sugarcane and Energy Cane Varieties Grown in Argentina for Second-Generation Ethanol Production

The efficient transformation of lignocellulosic biomass into fermentable sugars is essential for building bioeconomies. Sugarcane is an important agricultural crop in a number of Latin American countries, including Brazil and Argentina. Herein culms from two different sugarcane (SC384 and SC724) and two energy cane varieties (EC3116 and EC3118) bred in Argentina were evaluated for sustainable production of second-generation biofuels and green chemicals. Changes in the biomass crystallinity, structure, and morphology introduced by pretreatments were investigated using X-ray diffraction (DRX), confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) techniques. Enzymatic hydrolysis yields of untreated and pretreated sugarcane and energy cane culms were determined and correlated with physical analyses and chemical composition characterizations. Overall, after combined acid and alkali pretreatment, enzymatic convertibility was highly efficient for all studied sugarcane and energy cane varieties, reaching over 97% of theoretical conversion yields. High crystallinity indices and crystallite sizes of pretreated culms and SEM results and CLSM were consistent with the removal of lignin, solubilization of hemicellulose, and amorphous parts of lignocellulose imprinted by the pretreatments. High potential of culms from sugarcane and energy cane varieties cultivated in Argentina for sustainable production of renewable lignocellulosic sugars and their transformation into green chemicals and fuels was demonstrated. Graphic Abstract: [Figure not available: see fulltext.]Fil: Kane, Aissata Ousmane. Universidade de Sao Paulo; BrasilFil: Pellergini, Vanessa O. Arnoldi. Universidade de Sao Paulo; BrasilFil: Espirito Santo, Melissa C.. Universidade de Sao Paulo; BrasilFil: Ngom, Balla Diop. Universite Cheikh Anta Diop; SenegalFil: Garcia, Jose Maria. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero. Estación Experimental Agropecuaria Famaillá; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Acevedo, Alberto. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; ArgentinaFil: Erazzú, Luis Ernesto. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; ArgentinaFil: Polikarpov, Igor. Universidade de Sao Paulo; Brasi