Novel Xylanase from a Holstein Cattle Rumen Metagenomic Library and Its Application in Xylooligosaccharide and Ferulic Acid Production from Wheat Straw
ABSTRACT A novel gene fragment containing a xylanase was identified from a Holstein cattle rumen metagenomic library. The novel xylanase (Xyln-SH1) belonged to the glycoside hydrolase family 10 (GH10) and exhibited a maximum of 44% identity to the glycoside hydrolase from Clostridium thermocellum ATCC 27405. Xyln-SH1 was heterologously expressed, purified and characterized. A high level of activity was obtained under the optimum conditions of pH 6.5 and 40°C. A substrate utilization study indicated that Xyln-SH1 was cellulase-free and strictly specific to xylan from softwood. The synergistic effects of Xyln-SH1 and feruloyl esterase (FAE-SH1) were observed for the release of xylooligosaccharides (XOS) and ferulic acid (FA) from wheat straw. In addition, a high dose of Xyln-SH1 alone was observed to improve the release of FA from wheat straw. These features suggest that this enzyme has substantial potential to improve biomass degradation and industrial applications.
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- "The properties like thermostability and tolerance to extreme pH conditions are inevitable for such purposes. The studies of Chang et al. , Cheng et al. , and Jeong et al.  yielded significant results with xylanases having immense biotechnological applications for lignocellulosic deconstruction and bioethanol production. Moreover, Verma et al. also isolated a novel metagenomic xylanase from compost-soil metagenome that shows alkali stability and thermostability, thus bearing a potential application in paper and pulp industry in pulp bleaching . "
ABSTRACT: Metagenomics deals with the isolation of genetic material directly recovered from environmental samples. Metagenomics as an approach has emerged over the past two decades to elucidate a host of microbial communities inhabiting a specific niche with the goal of understanding their genetic diversity, population structure, and ecological role played by them. A number of new and novel molecules with significant functionalities and applications have been identified through this approach. In fact, many investigators are engaged in this field to unlock the untapped genetic resources with funding from governments sector. The sustainable economic future of modern industrialized societies requires the development of novel molecules, enzymes, processes, products, and applications. Metagenomics can also be applied to solve practical challenges in the field of medicine, agriculture, sustainability, and ecology. Metagenomics promises to provide new molecules and novel enzymes with diverse functions and enhanced features compared to the enzymes from the culturable microorganisms. Besides the application of metagenomics for unlocking novel biocatalysts from nature, it also has found applications in fields as diverse as bioremediation, personalized medicine, xenobiotic metabolism, and so forth.08/2014; 2014:1-7. DOI:10.1155/2014/146030
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ABSTRACT: We identified two family-11 xylanase genes (xynC81 and xynC83) in Achaetomium sp. Xz-8, a thermophilic strain from a desert area with substantial xylanase activity, and successfully expressed them in Pichia pastoris. Their deduced amino acid sequences showed the highest identity of ≤90% to known fungal xylanases and of ≤62% with each other. The purified recombinant xylanases showed optimal activities at pH 5.5 and 60-65 °C, and exhibited stability over pH 5.0-10.0 and temperatures at 55 °C and below. XynC81 had high catalytic efficiency (6082 mL/s/mg), and XynC83 was favorable for xylooligosaccharide production. Under simulated mashing conditions, combination of XynC83 and a commercial β-glucanase improved the filtration rate by 34.76%, which is much better than Novozymes Ultraflo (20.71%). XynC81 and XynC83 had a synergistic effect on viscosity reduction (7.08%), which is comparable with Ultraflo (8.47%). Thus XynC81 and XynC83 represent good candidates for application in the brewing industry.Journal of Agricultural and Food Chemistry 06/2013; 61(28). DOI:10.1021/jf4001296 · 3.11 Impact Factor
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ABSTRACT: Metagenomics has been widely employed for discovery of new enzymes and pathways to conversion of lignocellulosic biomass to fuels and chemicals. In this context, the present study reports the isolation, recombinant expression, biochemical and structural characterization of a novel endoxylanase family GH10 (SCXyl) identified from sugarcane soil metagenome. The recombinant SCXyl was highly active against xylan from beechwood and showed optimal enzyme activity at pH 6,0 and 45°C. The crystal structure was solved at 2.75 Å resolution, revealing the classical (β/α)8-barrel fold with a conserved active-site pocket and an inherent flexibility of the Trp281-Arg291 loop that can adopt distinct conformational states depending on substrate binding. The capillary electrophoresis analysis of degradation products evidenced that the enzyme displays unusual capacity to degrade small xylooligosaccharides, such as xylotriose, which is consistent to the hydrophobic contacts at the +1 subsite and low-binding energies of subsites that are distant from the site of hydrolysis. The main reaction products from xylan polymers and phosphoric acid-pretreated sugarcane bagasse (PASB) were xylooligosaccharides, but, after a longer incubation time, xylobiose and xylose were also formed. Moreover, the use of SCXyl as pre-treatment step of PASB, prior to the addition of commercial cellulolytic cocktail, significantly enhanced the saccharification process. All these characteristics demonstrate the advantageous application of this enzyme in several biotechnological processes in food and feed industry and also in the enzymatic pretreatment of biomass for feedstock and ethanol production.PLoS ONE 07/2013; 8(7):e70014. DOI:10.1371/journal.pone.0070014 · 3.53 Impact Factor