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Xylanase
About: Xylanase is a research topic. Over the lifetime, 7099 publications have been published within this topic receiving 163793 citations.
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TL;DR: Enzymic formulations with suitable polygalacturonase and FPCAse activities were favourable to extract oil from the pulp of tropical fruits and oleaginous seeds.
106 citations
TL;DR: It was concluded that enzymes enhanced the fermentation of cellulose and xylan by a combination of pre- and postincubation effects, which was reflected in a higher rate of fermentation.
Abstract: A series of in vitro studies was conducted to determine the effects of adding a commercial enzyme product on the hydrolysis and fermentation of cellulose, xylan, and a mixture (1:1 wt/wt) of both. The enzyme product (Liquicell 2500, Specialty Enzymes and Biochemicals, Fresno, CA) was derived from Trichoderma reesei and contained mainly xylanase and cellulase activities. Addition of enzyme (0.5, 2.55 and 5.1 microL/g of DM) in the absence of ruminal fluid increased (P < 0.001) the release of reducing sugars from xylan and the mixture after 20 h of incubation at 20 degrees C. Incubations with ruminal fluid showed that enzyme (0.5 and 2.55 microL/g of DM) increased (P < 0.05) the initial (up to 6 h) xylanase, endoglucanase, and beta-D-glucosidase activities in the liquid fraction by an average of 85%. Xylanase and endoglucanase activities in the solid fraction also were increased (P < 0.05) by enzyme addition, indicating an increase in fibrolytic activity due to ruminal microbes. Gas production over 96 h of incubation was determined using a gas pressure measurement technique. Incremental levels of enzyme increased (P < 0.05) the rate of gas production of all substrates, suggesting that fermentation of cellulose and xylan was enzyme-limited. However, adding the enzyme at levels higher than 2.55 microL/g of DM failed to further increase the rate of gas production, indicating that the maximal level of stimulation was already achieved at lower enzyme concentrations. It was concluded that enzymes enhanced the fermentation of cellulose and xylan by a combination of pre- and postincubation effects (i.e., an increase in the release of reducing sugars during the pretreatment phase and an increase in the hydrolytic activity of the liquid and solid fractions of the ruminal fluid), which was reflected in a higher rate of fermentation.
106 citations
TL;DR: Xylanase was found to be more effective for paper-bleaching than mannanase and dosed together (simultaneously), both enzymes were able to enhance the liberation of reducing sugars and improve pulp bleachability.
Abstract: Enzymatic pretreatment of softwood kraft pulp was investigated using xylanase and mannanase, singly or in combination, either sequentially or simultaneously. Enzymes were obtained from Streptomyces galbus NR that had been cultivated in a medium, containing either xylan of sugar cane bagasse or galactomannan of palm-seeds, when they were used as sole carbon sources from local wastes in fermentation media. No cellulase activity was detected. Incubation period, temperature, initial pH values and nature of nutritive constituents were investigated. Optimum production of both enzymes was achieved after 5 days incubation on a rotary shaker (200 rpm) at 35 °C and initial pH 7.0. Partial purification of xylanase and mannanase in the cultures supernatant were achieved by salting out at 40–60 and 60–80% ammonium sulphate saturation with a purification of 9.63- and 8.71-fold and 68.80 and 62.79% recovery, respectively. The xylanase and mannanase from S. galbus NR have optimal activity at 50 and 40 °C, respectively. Both enzymes were stable at a temperature up to 50 °C. Xylanase and mannanase showed highest activity at pH 6.5 and were stable from 5.0 to 8.0 and from 5.5 to 7.5, respectively. The partial purified enzymes preparations of xylanase and mannanase enzymes showed high bleaching activity, which is an important consideration for industry. Xylanase was found to be more effective for paper-bleaching than mannanase. When xylanase and mannanase were dosed together (simultaneously), both enzymes were able to enhance the liberation of reducing sugars and improve pulp bleachability, possibly as a result of nearly additive interactions. The simultaneous addition of both enzymes was more effective in pulp treatment than their sequential addition.
105 citations
TL;DR: A comparison of hydrolysis products obtained by reacting individually the three enzymes with birchwood xylan showed characteristic endo-activity patterns for xylanases B and C, whereas xylanase A hydrolysed the substrate preferentially into xylobiose and xylotriose.
Abstract: A third extracellular xylanase produced by Streptomyces lividans 66 was isolated from a clone obtained by shotgun cloning through functional complementation of a xylanase- and cellulase-negative mutant using the multicopy vector pIJ702. This enzyme, designated xylanase C, has a relative molecular mass of 22000 and acts on xylan similarly to xylanase B as an endo-type xylanase producing short-chain oligoxylosides. Its specific activity determined at 1100 IU·mg−1 of protein corresponds on a molecular basis to that of xylanase B and is about three times that of xylanase A. The enzyme shows optimal activity at pH 6.0 and 57°C, values that correspond closely to those observed previously for xylanase A and B. Xylanase C appears not to be glycosylated and has a pI > 10.25. Its Km and Vmax on birchwood xylan are 4.1 mg·ml−1 and 3.0 μmol·min−1·mg−1 of enzyme respectively. Whereas specific antibodies raised against xylanase A show no cross-reaction with either xylanase B or with xylanase C, the anti-(xylanase C) antibodies react slightly with xylanase B but not with xylanase A. A comparison of hydrolysis products obtained by reacting individually the three enzymes with birchwood xylan showed characteristic endo-activity patterns for xylanases B and C, whereas xylanase A hydrolysed the substrate preferentially into xylobiose and xylotriose. Sequential xylanase action on the same substrates showed synergistic hydrolysis only when endo-xylanase activity was followed by that of xylanase A.
105 citations
TL;DR: A single multipurpose biocatalyst has been designed which can be used for carrying out three different and independent reactions; 1) hydrolysis of pectin, 2) hydrofullysis of xylan and 3) hydroleysis of cellulose.
Abstract: The use of immobilized enzymes for catalyzing various biotransformations is now a widely used approach. In recent years, cross-linked enzyme aggregates (CLEAs) have emerged as a novel and versatile biocatalyst design. The present work deals with the preparation of a CLEA from a commercial preparation, Pectinex™ Ultra SP-L, which contains pectinase, xylanase and cellulase activities. The CLEA obtained could be used for any of the enzyme activities. The CLEA was characterized in terms of kinetic parameters, thermal stability and reusability in the context of all the three enzyme activities. Complete precipitation of the three enzyme activities was obtained with n-propanol. When resulting precipitates were subjected to cross-linking with 5 mM glutaraldehyde, the three activities initially present (pectinase, xylanase and cellulase) were completely retained after cross-linking. The Vmax/Km values were increased from 11, 75 and 16 to 14, 80 and 19 in case of pectinase, xylanase and cellulase activities respectively. The thermal stability was studied at 50°C, 60°C and 70°C for pectinase, xylanase and cellulase respectively. Half-lives were improved from 17, 22 and 32 minutes to 180, 82 and 91 minutes for pectinase, xylanase and cellulase respectively. All three of the enzymes in CLEA could be reused three times without any loss of activity. A single multipurpose biocatalyst has been designed which can be used for carrying out three different and independent reactions; 1) hydrolysis of pectin, 2) hydrolysis of xylan and 3) hydrolysis of cellulose. The preparation is more stable at higher temperatures as compared to the free enzymes.
105 citations