Xylanase

About: Xylanase is a research topic. Over the lifetime, 7099 publications have been published within this topic receiving 163793 citations.

Hydrolysis of Ammonia-pretreated Sugar Cane Bagasse with Cellulase, β-Glucosidase, and Hemicellulase Preparations

Abstract: Sugar cane bagasse consists of hemicellulose (24%) and cellulose (38%), and bioconversion of both fractions to ethanol should be considered for a viable process. We have evaluated the hydrolysis of pretreated bagasse with combinations of cellulase, β-glucosidase, and hemicellulase. Ground bagasse was pretreated either by the AFEX process (2NH3: 1 biomass, 100 °C, 30 min) or with NH4OH (0.5 g NH4OH of a 28% [v/v] per gram dry biomass; 160 °C, 60 min), and composition analysis showed that the glucan and xylan fractions remained largely intact. The enzyme activities of four commercial xylanase preparations and supernatants of four laboratory-grown fungi were determined and evaluated for their ability to boost xylan hydrolysis when added to cellulase and β-glucosidase (10 filter paper units [FPU]: 20 cellobiase units [CBU]/g glucan). At 1% glucan loading, the commercial enzyme preparations (added at 10% or 50% levels of total protein in the enzyme preparations) boosted xylan and glucan hydrolysis in both pretreated bagasse samples. Xylanase addition at 10% protein level also improved hydrolysis of xylan and glucan fractions up to 10% glucan loading (28% solids loading). Significant xylanase activity in enzyme cocktails appears to be required for improving hydrolysis of both glucan and xylan fractions of ammonia pretreated sugar cane bagasse.

Purification and characterization of a novel thermostable α-L-arabinofuranosidase from a color-variant strain of Aureobasidium pullulans.

Abstract: More than one billion gallons of ethanol are produced annually in the United States, with approximately 95% of it being derived from the fermentation of corn starch (4). Various lignocellulosic agricultural residues such as corn fiber, corn stover, straw, and bagasse can also serve as low-value and abundant feedstocks for the production of fuel alcohol. Currently, the utilization of lignocellulosic biomass to produce fuel ethanol faces significant technical and economic challenges, and its success depends largely on the development of highly efficient and cost-effective enzymes for the conversion of pretreated biomass to fermentable sugars. Hemicelluloses, the second most common polysaccharides in nature, represent about 20 to 35% of lignocellulosic biomass (38). l-Arabinosyl residues are widely distributed in hemicelluloses as they constitute monomeric and/or oligomeric side chains on the β-(1→4)-linked xylose or galactose backbones in xylans, arabinoxylans, and arabinogalactans and are the core in arabinans forming α-(1→5) linkages (26, 36). These side chains restrict the enzymatic hydrolysis of hemicelluloses by xylanases (2). α-l-Arabinofuranosidases (α-l-arabinofuranoside arabinofuranohydrolase, EC 3.2.1.55) (α-l-AFase) are exo-type enzymes which hydrolyze terminal nonreducing α-l-arabinofuranosyl groups from l-arabinose-containing polysaccharides. These enzymes can hydrolyze (1→3)- or (1→5)-α-l-arabinofuranosyl linkages of arabinan or both. The α-l-AFases are part of the microbial xylanolytic systems required for the complete breakdown of heteroxylans (2, 9, 22, 27). In recent years, arabinofuranosidases have received much attention because of their practical applications in various agro-industrial processes such as the efficient conversion of hemicellulosic biomass to fuels and chemicals, delignification of pulp, efficient utilization of plant materials for animal feed, and hydrolysis of grape monoterpenyl glycosides during wine fermentation (3, 8, 10, 35). There is a need to develop a suitable α-l-AFase for use in the conversion of hemicellulose to fermentable sugars for the subsequent production of fuel ethanol and other value-added chemicals. α-l-AFases are produced by several bacteria and fungi, but only a few of these enzymes have been purified and characterized (8, 11, 13, 22, 33). The color-variant strains of the yeast-like fungus Aureobasidium pullulans have been recognized as excellent producers of amylases, xylanase, and β-glucosidase (20, 30, 31). These color-variant strains are differentiated from typically pigmented (off-white to black in appearance) strains of A. pullulans by their brilliant pigments of red, yellow, pink, or purple and their low DNA relatedness (21, 37). We have found that a color-variant strain of A. pullulans produced an extracellular highly thermostable α-l-AFase which was able to hydrolyze both (1→3) and (1→5) linkages in arabinan. In this paper, we report on the purification and characteristics of this novel enzyme.

Xylanase Production by Aspergillus niger LPB 326 in Solid-State Fermentation Using Statistical Experimental Designs

Abstract: Summary Xylanase was produced by Aspergillus niger LPB 326 cultivated on lignocellulosic substrate composed by sugarcane bagasse and soybean meal in solid-state fermentation. The effects of various variables were observed and optimized by applying statistical experimental designs. The best xylanase activity was obtained in a medium containing 10 g of sugarcane bagasse and soybean meal in the ratio of 65 and 35 %, respectively, moistened to 85 % of initial water content with a nutrient salt solution composed of (in g/L): CuSO4 0.4, KH2PO4 1.5 and CoSO4 0.0012, and incubated for 4 days at 30 °C. Under these optimized conditions, a xylanase activity of 3099 IU/g of dry matter was obtained.

Identification and characterization of core cellulolytic enzymes from Talaromyces cellulolyticus (formerly Acremonium cellulolyticus) critical for hydrolysis of lignocellulosic biomass

Abstract: Enzymatic hydrolysis of pretreated lignocellulosic biomass is an essential process for the production of fermentable sugars for industrial use. A better understanding of fungal cellulase systems will provide clues for maximizing the hydrolysis of target biomass. Talaromyces cellulolyticus is a promising fungus for cellulase production and efficient biomass hydrolysis. Several cellulolytic enzymes purified from T. cellulolyticus were characterized in earlier studies, but the core enzymes critical for hydrolysis of lignocellulosic biomass remain unknown. Six cellulolytic enzymes critical for the hydrolysis of crystalline cellulose were purified from T. cellulolyticus culture supernatant using an enzyme assay based on synergistic hydrolysis of Avicel. The purified enzymes were identified by their substrate specificities and analyses of trypsin-digested peptide fragments and were classified into the following glycosyl hydrolase (GH) families: GH3 (β-glucosidase, Bgl3A), GH5 (endoglucanase, Cel5A), GH6 (cellobiohydrolase II, Cel6A), GH7 (cellobiohydrolase I and endoglucanase, Cel7A and Cel7B, respectively), and GH10 (xylanase, Xyl10A). Hydrolysis of dilute acid-pretreated corn stover (PCS) with mixtures of the purified enzymes showed that Cel5A, Cel7B, and Xyl10A each had synergistic effects with a mixture of Cel6A and Cel7A. Cel5A seemed to be more effective in the synergistic hydrolysis of the PCS than Cel7B. The ratio of Cel5A, Cel6A, Cel7A, and Xyl10A was statistically optimized for the hydrolysis of PCS glucan in the presence of Bgl3A. The resultant mixture achieved higher PCS glucan hydrolysis at lower enzyme loading than a culture filtrate from T. cellulolyticus or a commercial enzyme preparation, demonstrating that the five enzymes play a role as core enzymes in the hydrolysis of PCS glucan. Core cellulolytic enzymes in the T. cellulolyticus cellulase system were identified to Cel5A, Cel6A, Cel7A, Xyl10A, and Bgl3A and characterized. The optimized mixture of these five enzymes was highly effective for the hydrolysis of PCS glucan, providing a foundation for future improvement of the T. cellulolyticus cellulase system.