Xylanase Dosage Research Articles

Effects of dietary cellulase and xylanase addition on digestion, rumen fermentation and methane emission in growing goats

The objective of this study was to evaluate the effectiveness of supplementation of cellulase and xylanase to diets of growing goats to improve nutrient digestibility, utilisation of energy and mitigation of enteric methane emissions. The experiment was conducted in a 5 × 5 Latin square design using five goats with permanent rumen fistulae and five treatments consisted of two levels of cellulase crossed over with two levels of xylanase plus unsupplemented Control. The cellulase (243 U/g) derived from Neocallimastix patriciarum was added at 0.8 and 1.6 g/kg dry matter intake (DMI) and the xylanase (31,457 U/ml) derived from Aspergillus oryzae was fed at 1.4 and 2.2 ml/kg DMI. There were no differences in apparent digestibility of organic matter, neutral detergent fibre, acid detergent fibre and rumen fermentation parameters (i.e. ammonia-nitrogen [N], volatile fatty acids) among all treatments. Dietary cellulase and xylanase addition did not influence energy and N utilisation. But compared to xylanase addition at the higher dose, at the low xylanase dose the retained N, the availability of retained N and digested N were increased (p < 0.01). Moreover, enzyme addition did not affect the enteric methane emission and community diversity of ruminal methanogens. The present results indicated that previous in vitro findings were not confirmed in ruminant trials.

Effects of Dilute Alkali Pretreatment on Chemical Components and Fermentable Sugars and Structure of Bamboo

The pretreatment of bamboo with dilute alkali and the effects on chemical components and enzymatic hydrolysis were studied, and the fiber structural properties of pretreated residues were studied with Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The results showed that dilute alkali was highly effective in delignification of the biomass, reducing the lignin content by 50-70%. Bamboo solid recovery was 74.40%, and cellulose, hemicellulose and lignin content were 60.02%, 25.93% and 9.08%, respectively, when pretreated with 1.0% sodium hydroxide, with a solid-liquid ratio of 1:10 at 100 °C for 40 min. Under the conditions, the pretreated residue was hydrolyzed for 72 h with cellulose and xylanase dosage 40 FPU/g cellulose, and the hydrolysis yield of cellulose was 81.38% and that of hemicelluloses was 84.78%, resulting in a total of 66.74 g fermentable sugars from 100 g dry bamboo. The SEM pictures indicated that the biomass structure was deformed and its fibers were exposed, and FTIR results verified the lignin removal by the pretreatment.

Preparation of acetate-grade dissolving pulp from eucalyptus by processes including alkaline pretreatment and combined post-treatments with xylanase and alkali

In this investigation, alkaline pretreatment before kraft pulping and combined post-treatments with xylanase and alkali after bleaching were applied to obtain an acetate-grade dissolving pulp. Bleaching sequences using oxygen or hydrogen peroxide were also studied. The brightness, α-cellulose content, and degree of polymerization (DP) of the bleached pulps from different bleaching sequences were evaluated. Alkaline pretreatment resulted in a higher α-cellulose content in the pulp. When a D1ED2P bleaching sequence was applied, the pulp obtained had an ISO brightness of 87.5%, a DP of 1050, and an α-cellulose content of 92.7%. The requirements for an acetate-grade dissolving pulp can then be met when followed by combined post-treatments with xylanase and alkali under the optimal conditions of 120 IU•g–1 xylanase dosage and 4% sodium hydroxide concentration.

Effect of Xylanase-Aided Refining on Wet-End Chemistry and Bleachability of Masson Thermomechanical Pulp

The Masson thermomechanical pulp (TMP) which was obtained from the first stage refiner was pretreated with xylanase followed by refining with PFI refiner. The impact of enzymatic refining on wet-end chemistry and bleachability of pulp were studied. The results showed that the enzymatic pretreatment could improve the wet-end chemistry properties and enhance the bleachability of masson TMP. In contrast to the control pulp sample, the beating degree, the zeta potential, the dissolved charge, the filler retention, and the sizing degree was increased respectively by 18.8%, 17.5%, 10%, 19.6%, and 18.8% at the xylanase dosage of 0.3 AXU/g (o.d. pulp); the tensile index, the tearing index and the brightness was increased by 2.3 N·m2/g, 0.19 mN·m2/g, and 1.3%ISO, respectively.

High temperature aqueous ammonia pretreatment and post-washing enhance the high solids enzymatic hydrolysis of corn stover

Aqueous ammonia pretreatment was optimized and the limiting factors in high solids enzymatic hydrolysis were assessed. The recommended pretreatment condition to achieve high enzymatic yield was: 180 °C, 20% (w/w) ammonia, 30 min, and 20% solids content. FT-IR and GC-MS results indicated that most of the lignin was degraded to soluble fragments after pretreatment. The pretreated solids after post-washing showed higher enzymatic digestibility at high solids loading than that without washing. The washed solids required lower cellulase and xylanase dosage than unwashed solids to achieve high sugar yield. Enzymatic conversions were declined with the increased solids loading of pretreated solids, pretreated-washed solids, and filter papers. The results indicated that solids loading in enzymatic hydrolysis was an important factor affecting sugar yield. The increasing concentration of glucose and ligno-phenolics mainly inhibited the enzymatic hydrolysis of aqueous ammonia pretreated corn stover.

Xylanase supplementation on enzymatic saccharification of dilute acid pretreated poplars at different severities

Three pairs of solid substrates from dilute acid pretreatment of two poplar wood samples were enzymatically hydrolyzed by cellulase preparations supplemented with xylanase. Supplementation of xylanase improved cellulose saccharification perhaps due to improved cellulose accessibility by xylan hydrolysis. Total xylan removal directly affected enzymatic cellulose saccharification. Furthermore, xylan removal by pretreatment and xylanase are indifferent to enzymatic cellulose saccharification. However, more enzymatic xylose and glucose yields were obtained for a substrate with lower xylan content after a severer pretreatment at the same xylanase dosage. The effectiveness of xylanase at increased dosages depended on the substrates structure or accessibility. High xylanase dosages were more effective on well pretreated substrates than on under-pretreated substrates with high xylan content. The application sequence of xylanase and cellulase affected cellulose saccharification. This effect varied with substrate accessibility, perhaps due to competition between xylanase and cellulase binding to the substrate.

Properties and Application of a Partially Purified Thermoalkali Stable Xylanase from Cellulosimicrobium sp. MTCC 10645 in Kraft Pulp Bleaching.

The most promising application of xylanases (E.C. 3.2.1.8) is in the prebleaching of kraft pulp. The present paper reports bleaching effects of a thermoalkali stable xylanase from Cellulosimicrobium sp. MTCC 10645. The bacterium produced thermo-alkali stable xylanase in a basal medium supplemented with wheat bran (1% w/v), which was optimally active at pH 7.0 and 50°C. The xylanase was stable at temperature 50°C for 1 h and retained up to 86% of the activity. The xylanase was stable in a broad pH range of 6.0–11.0 for 1 h at 50°C. Metal ions Ca+2, Hg+2, and Pb+2 were inhibitory for xylanase retaining 72.3%, 35.07% and 36.7% relative activity at 10 mM concentration, whereas Fe+2, Cu+2, Mn+2, Na+2, Co+2, and Zn+2 were inducers at concentrations of 5 mM and 10 mM. The enzyme exhibited greater binding affinity exclusively for xylans but not for avicel, CMC, cellobiose, starch, or p-nitrophenyl xylopyranoside. Parachloromercuric benzoate and iodoacetamide were found stimulatory, while potassium permanganate, cysteine, and cystine markedly reduced the activity. The xylanase dose of 2.0 U/g dry weight pulp of 10% consistency gave optimum bleach boosting of kraft pulp at pH 8.0 and temperature 50°C for 5 h reaction time.

Optimization of Xylanase Production fromAspergillus nigerfor Biobleaching of Eucalyptus Pulp

A crude endo-xylanase produced by Aspergillus niger BCC14405 was investigated for its potential in pre-bleaching of chemical pulp from eucalyptus. The optimal fermentation conditions on the basis of optimization using response surface methodology included cultivation in a complex medium comprising wheat bran, rice bran, and soybean meal supplemented with yeast extract, glucose, peptone, and lactose with a starting pH of 6.0 for 7 d. This resulted in production of 89.5 IU/mL of xylanase with minor cellulase activity. Proteomic analysis using LC/MS/MS revealed that the crude enzyme was a composite of hemicellulolytic enzymes, including endo-β-1,4-xylanase and other hemicellulolytic enzymes attacking arabinoxylan and mannan. Pretreatment of the pulp at a xylanase dosage of 10 IU/g increased the brightness ceiling after the C-Eop-H bleaching step up to 3.0% using a chlorine charge with a C-factor of 0.16-0.20. Xylanase treatment also led to reduction in chlorine charge of at least 20%, with an acceptable brightness level. The enzyme pretreatment resulted in a slight increase in pulp viscosity, suggesting an increase in relative cellulose content. The crude enzyme was potent in the enzyme-aided bleaching of chemical pulp in an environmentally friendly pulping process.

Xylanase production by Paenibacillus campinasensis BL11 and its pretreatment of hardwood kraft pulp bleaching

Production of a single component 41 kDa xylanase from Paenibacillus campinasensis BL11 was conducted under various pH and temperature at the shake flask level. Alternative carbon and nitrogen sources were also evaluated. Up to 10.5 IU/mL and 29.39 IU/mg specific activity of xylanase in crude extract was obtained at 24 h, 37 °C, pH 8. In addition, same level of xylanase productions was also obtained on rice husk and rice straw at 2 days of incubation. Relative xylanase activities of 56.8% and 51.9% were found after 4 h incubation in pH 7 and pH 9 at 65 °C, respectively. Xylanase pretreatments (2.5 IU per gram of oven-dry pulp) increased brightness (as much as 4.4 and 3.9%) and viscosity (as much as 0.5 and 0.3 cP) of pulp after full chlorine dioxide bleaching for untreated and oxygen delignified hardwood kraft pulp. Increased benefits of pretreatment were found with increasing xylanase dosage and pretreatment time.

Pretreatment processing of fabrics by alkalothermophilic xylanase from Bacillus stearothermophilus SDX

A highly active alkalothermophilic cellulase free xylanase (3446 U/g of dry substrate) has been produced from newly isolated strain of Bacillus stearothermophilus under solid-state fermentation using wheat bran (2.5%, w/v) pH 7.0 and at 37 °C. The xylanase was stable over broad range of pH (6.0–12.5) and temperature (37–85 °C) and hence was used in the bioprocessing of fabrics as an alternative to conventional chemical method. The desizing and bioscouring treatments were most efficient at 70 °C after 90 and 180 min of incubation respectively using 5 g/l of xylanase dose in the medium of pH 9.5. Enzymatically desized fabrics when subjected to bioscouring resulted in 0.91%, 0.88% weight loss for micropoly and 0.83%, 0.80% for cotton respectively under agitated (50 ± 2 rpm) and non-agitated conditions. Consequently Whiteness index for cotton (11.81%) and micropoly (52.15%) fabrics was increased. Induction in the release of reducing sugars was also observed for cotton (8.37%) and micropoly (16.79%) fabric over conventional method. Enzymatically processed fabric samples possessed 1.12% and 1.95% more tensile strength than reference. Tearness value also increased for bio-treated cotton (1.57%) and micropoly (2.37%) fabric samples as compared to control.

Enhanced production of cellulase-free thermostable xylanase by Bacillus pumilus ASH and its potential application in paper industry

A very high level of cellulase-free, thermostable xylanase has been produced from newly isolated strain of Bacillus pumilus under submerged fermentation in a basal medium supplemented with wheat bran (2%, w/v) pH 8.0 and at 37 °C. After optimization of various production parameters, an increase of nearly 13-fold in xylanase production (5407 IU/ml) was achieved. The produced xylanase is stable in neutral to alkaline pH region at 70 °C. The suitability of this xylanase for use in the bioleaching of eucalyptus Kraft pulp was investigated. A xylanase dose of 5 IU/g of oven dried pulp of 10% consistency exhibited the optimum bleach boosting of the pulp at pH 7.0 and 60 °C after 180 min of treatment. An increase of 5% in brightness along with an increase of 21% and 28% in whiteness and fluorescence respectively, whereas 18% decrease in the yellowness of the biotreated pulp was observed. Enzyme treated pulp when subjected to chemical bleaching, resulted in 20% reduction in chlorine consumption and up to 10% reduction in consumption of chlorine dioxide. Also a reduction of about 16% in kappa number and 83% in permanganate number, along with a reduction in COD value and significant improvement in various pulp properties, viz. viscosity, tensile strength, breaking length, burst factor, burstness, tear factor and tearness were observed in comparison to the conventional chemical bleaching.

Effects of laccase, xylanase and their combination on the rheological properties of wheat doughs

The effects of Trametes hirsuta laccase alone and in combination with Aspergillus oryzae and Bacillus subtilis xylanases on dough extensibility were studied using the Kieffer test to determine the dough extensibility ( E x) and the resistance to stretching ( R max). Laccase treatment resulted in dough hardening: the R max of dough increased and the E x at R max decreased as a function of dosage (5–50 nkat/g flour). Xylanases softened flour and gluten doughs. Hardening by laccases and softening by xylanases was weaker in gluten doughs. Dough hardening, observed in the laccase treatments, decreased as a function of dough resting time. The softening effect occurred especially at higher laccase dosages (≈50 nkat/g flour). The softening phenomenon was related to the laccase-mediated depolymerization of the cross-linked AX network. In combined laccase and xylanase treatments, the effect of laccase was predominant, especially at low xylanase dosage, but when xylanase was added to flour dough at high concentrations, the hardening effect of laccase on dough was decreased. In combined laccase and xylanase treatments in gluten doughs, similar decreases in laccase-mediated hardening were not seen.

Bleaching of wheat straw-rich soda pulp with xylanase from a thermoalkalophilic Streptomyces cyaneus SN32

An alkalistable endoxylanase from Streptomyces cyaneus SN32 was applied in bleaching of wheat straw enriched soda pulp. The xylanase dose of 10 IU g −1 moisture free pulp exhibited maximum bleach boosting of soda pulp (pH 9.5–10.0) optimally at 65 °C after 2 h of reaction time. Pre-treatment of pulp with xylanase and its subsequent treatment with 6% hypochlorite reduced the kappa number by 8.7%, enhanced the brightness index by 3.56% and improved other paper properties such as tear index and burst index. The enzymatically-prebleached pulp when treated with 10% reduced level of hypochlorite (5.4%) gave comparable brightness of resultant hand sheets to the fully bleached pulp (6% hypochlorite).

Application of enzymes in producing bleached pulp from wheat straw

Crude enzymes produced by different strains were used in the production of bleached wheat straw pulp. Pre-treatment with enzymes from Penicillium A10 and Aspergillus L22 at a xylanase dosage of 4 IU/g prior to pulping decreased pulp kappa number by 6.29% and 12.07% respectively as compared to the control. High cellulase activity in crude enzymes has a negative influence on pulping. Xylanase pre-bleaching reduced chlorine charge by 20–30%, or increased final brightness by approximately 4–5% ISO, and improved the pulp strength properties. Xylanase could substitute for alkali extraction in CEH sequence, and be used for treating chemical-bleached pulp, which resulted in higher strength properties for bleached pulp. Modification of bleached pulp with enzymes of 3 IU/g (on xylanase) increased pulp brightness and breaking length by 3–6% ISO and 160–790 m respectively, and decreased post color number and beating degree of pulp by 29–36% and 2.5–5.5 °SR respectively, as compared to the original pulp.

Alkaline Peroxide Mechanical Pulping of Wheat Straw With Enzyme Treatment

Alkaline peroxide mechanical pulping (APMP) of wheat straw with enzyme treatment was studied. Instead of direct enzyme pretreatment on wheat straw, an alternative treatment method was used, in which coarse pulps from refiner defibrated wheat straw rather than wheat straw were pretreated with a crude enzyme containing mainly xylanase, then impregnated with alkaline H2O2 solution and further refined. The optimum conditions of enzyme treatment were xylanase dosage of 10-15 IU/g of oven-dried wheat straw, 90 min, 50-60 degrees C, pulp consistency of 5-10%, and initial pH of 5.0, and those for chemical impregnation were 6% NaOH, 70-80 degrees C, 60-90 min, and 4 to 5% H2O2. Enzyme treatment improved pulpability of wheat straw by the APMP process, and final pulp quality such as brightness, breaking length, and burst index of pulp. Pulp from the APMP process with enzyme treatment could be bleached to a brightness of 70.5% ISO by two-stage H2O2 bleaching sequence with only 4% H2O2, and breaking length of the bleach pulp reached 4470 m

Effect of dose of xylanase on bleachability of sugarcane bagasse ethanol/water pulps.

Pulps obtained from the ethanol/water cooking of sugarcane bagasse were bleached with the xylanase enzyme obtained from the fungus Thermomyces lanuginosus IOC-4145 and with the commercial enzyme Cartazyme HS from Sandoz. By changing the enzyme dose from 4.3 to 36 IU/g of pulp, kappa number and viscosity were maintained when the xylanase from T. lanuginosus was used. On the other hand, by using Cartazyme HS, kappa number decreased by 17%, reaching 35.5. This pulp was further extracted with NaOH without a decrease in viscosity (10 cP), and pulp with a kappa number of 13 was obtained. Xylanases had no significant effect on the ethanol/water pulps.

Xylanase pretreatment leads to enhanced soda pulping of wheat straw

Wheat straw was treated with a crude enzyme containing mainly xylanase prior to soda cooking. The enzyme was prepared from the culture filtration of Aspergillus niger strain An-76. The suitable conditions of pretreatment were xylanase dosage of 4 IU/g (on oven dry wheat straw), 48°C, 6–8 h, and pH 5.0, pretreated wheat straw was thorough washed after pretreatment. Xylanase pretreatment can improve pulpability of wheat straw effectively, and produce the pulps with lower kappa number (about 2 units lower), lower rejects and similar yields of screened-pulps under identical pulping conditions. The residual active alkali consistency of black liquor was increased by xylanase pretreatment. The brightness of bleached pulps from the xylanase pretreated wheat straw was about 3%ISO higher than that of the controls using identical bleaching sequence and conditions. The pulps, including unbleached pulps and bleached pulps, from the xylanase pretreated wheat straw had a higher tear index, a lower tensile index, and a lower burst index as compared to the control. The changes in the chemical components of wheat straw, crystallizability degree of cellulose, fiber average length and fines contents in the pulps were investigated in order to interpret differences of pulping results from the xylanase pretreated wheat straw and the controls.

Enhanced production of a thermostable xylanase from Streptomyces sp. QG-11-3 and its application in biobleaching of eucalyptus kraft pulp.

A thermostable and cellulase-free xylanase has been produced from Streptomyces sp. QG-11-3 in solid substrate fermentation using wheat bran and eucalyptus kraft pulp as the prime solid substrates. The maximum xylanase yield obtained using these two substrates were 2360 U/g and 1200 U/g dry solid substrate at substrate:moisture ratios of 1:3 and 1:2.5, respectively. In immobilized cell system using polyurethane foam (PUF) and three nonwoven fabrics, namely, polyester, silk, and cotton, the xylanase yields were enhanced by 2.5-fold (203 U/ml), 1.91-fold (155 U/ml), 1.54-fold (125 U/ml), and 1.47-fold (119 U/ml), respectively, compared to the xylanase yield in liquid-batch fermentation (81 U/ml). In the biobleaching experiments, the xylanase dose of 3.5 U/g moisture free pulp exhibited the optimum bleach boosting of eucalyptus kraft pulp at pH 8.5 and 50 degrees C after 2 h of treatment. When xylanase treated pulp was subsequently treated with 4.5% chlorine, it resulted in reduction of kappa number by 25%, enhanced the brightness (%ISO) by 20% and improved the pulp properties such as tensile strength and burst factor by up to 63% and 8%, respectively.

Toxicological studies on Thermomyces lanuginosus xylanase expressed by Fusarium venenatum, intended for use in food

The xylanase used in this study was produced by a submerged fermentation of Fusarium venenatum and contained a gene code originating from Thermomyces lanuginosus. The enzyme was subject to a 13-week toxicological test in rats and in vitro tests to document its safety in use. The enzyme is to be applied as a processing aid in the baking industry to improve handling and stability of dough. The enzyme was not found to be mutagenic in the Salmonella typhimurium reverse mutation assay, nor did it cause chromosomal aberrations in cultured human lymphocytes. Oral administration to rats of up to 10.0ml/kgbw/day (equivalent to a Total Organic Solids dosage of 1.12g/kgbw/ day or a xylanase dosage of 89422FXU(W)/kgbw/day) for 13 weeks did not cause any adverse effect.

Isolation, purification and characterization of xylanasefrom Staphylococcus sp. SG-13 and its application in biobleaching of kraft pulp.

A haloalkalophilic Staphylococcus sp. SG-13 produced an alkalistable xylanase in wheat bran medium. A 12-fold purification was achieved by using standard purification techniques. The purified xylanase exhibited a dual pH optima of 7.5 and 9.2. The optimum temperature for enzyme activity was 50 degrees C. The enzyme was stable at 50 degrees C for more than 4 h. The xylanase exhibited Km and Vmax values of 4 mg ml-1, 90 micromol min-1 per mg for birchwood xylan and 7 mg ml-1, 55 micromol min-1 per mg for oatspelt xylan, respectively. The substrate binding affinity of xylanase was more for oatspelt xylan but birchwood xylan was hydrolysed more rapidly. The xylanase activity was stimulated by Fe2+, Ni2+, Cu2+ and dithiothreitol up to 60% and was strongly inhibited in the presence of Co2+, Hg2+, Pb2+, phenyl methane sulphonyl fluoride, ethylenediaminetetraacetic acid, and acetic anhydride up to 100%. The xylanase dose of 1.8 U g-1 moisture free pulp, exhibited bleach boosting of kraft pulps optimally at pH 9.5-10.0 and 50 degrees C after 4 h of reaction time. Pretreatment of pulp with xylanase and its subsequent treatment with 8% hypochlorite, reduced the kappa number by 30%, enhanced the brightness and viscosity by 11% and 1.8%, respectively, and improved the paper properties such as tensile strength and burst factor up to 10% and 17%, respectively.