Production of Alkalophilic Xylanases by Paenibacillus polymyxa CKWX1 Isolated from Decomposing Wood

Valorization of apple pomace using bio-based technology for the production of xylitol and 2G ethanol

Apple pomace was studied as a raw material for the production of xylitol and 2G ethanol, since this agroindustrial residue has a high concentration of carbohydrate macromolecules, but is still poorly studied for the production of fermentation bioproducts, such as polyols. The dry biomass was subjected to dilute-acid hydrolysis with H₂SO₄ to obtain the hemicellulosic hydrolysate, which was concentrated, detoxified and fermented. The hydrolyzate after characterization was submitted to submerged fermentations, which were carried out in Erlenmeyer flasks using, separately, the yeasts Candida guilliermondii and Kluyveromyces marxianus. High cellulose (32.62%) and hemicellulose (23.60%) contents were found in this biomass, and the chemical hydrolysis yielded appreciable quantities of fermentable sugars, especially xylose. Both yeasts were able to metabolize xylose, but Candida guilliermondii produced only xylitol (9.35 g L^-1 in 96 h), while K. marxianus produced ethanol as the main product (10.47 g L^-1 in 24 h) and xylitol as byproduct (9.10 g L^-1 xylitol in 96 h). Maximum activities of xylose reductase and xylitol dehydrogenase were verified after 24 h of fermentation with C. guilliermondii (0.23 and 0.53 U/mg_prot, respectively) and with K. marxianus (0.08 e 0.08 U/mg_prot, respectively). Apple pomace has shown potential as a raw material for the fermentation process, and the development of a biotechnological platform for the integrated use of both the hemicellulosic and cellulosic fraction could add value to this residue and the apple production chain.

Microbial xylanases and their industrial application in pulp and paper biobleaching: a review

Xylanases are hydrolytic enzymes which cleave the β-1, 4 backbone of the complex plant cell wall polysaccharide xylan. Xylan is the major hemicellulosic constituent found in soft and hard food. It is the next most abundant renewable polysaccharide after cellulose. Xylanases and associated debranching enzymes produced by a variety of microorganisms including bacteria, actinomycetes, yeast and fungi bring hydrolysis of hemicelluloses. Despite thorough knowledge of microbial xylanolytic systems, further studies are required to achieve a complete understanding of the mechanism of xylan degradation by xylanases produced by microorganisms and their promising use in pulp biobleaching. Cellulase-free xylanases are important in pulp biobleaching as alternatives to the use of toxic chlorinated compounds because of the environmental hazards and diseases caused by the release of the adsorbable organic halogens. In this review, we have focused on the studies of structural composition of xylan in plants, their classification, sources of xylanases, extremophilic xylanases, modes of fermentation for the production of xylanases, factors affecting xylanase production, statistical approaches such as Plackett Burman, Response Surface Methodology to enhance xylanase production, purification, characterization, molecular cloning and expression. Besides this, review has focused on the microbial enzyme complex involved in the complete breakdown of xylan and the studies on xylanase regulation and their potential industrial applications with special reference to pulp biobleaching, which is directly related to increasing pulp brightness and reduction in environmental pollution.

Improvement for enhanced xylanase production by Cellulosimicrobium cellulans CKMX1 using central composite design of response surface methodology

The effects of yeast extract (X₁), NH₄NO₃ (X₂), peptone (X₃), urea (X₄), CMC (X₅), Tween 20 (X₆), MgSO₄ (X₇), and CaCO₃ (X₈) on production of xylanase from Cellulosimicrobium cellulans CKMX1 were optimized by statistical analysis using response surface methodology (RSM). The RSM was used to optimize xylanase production by implementing the Central composite design. Statistical analysis of the results showed that the linear, interaction and quadric terms of these variables had significant effects. However, only the linear effect of X₄, X₅, interaction effect of X₁X₇, X₁X₈, X₂X₃, X₂X₈, X₃X₆, X₃X₈, X₄X₆, X₄X₇, X₅X₇, X₅X₈ and quadratic effect of X ₃² , X ₅² and X ₇² found to be insignificant terms in the quadratic model and had no response at significant level. The minimum and maximum xylanase production obtained was 331.50 U/g DBP and 1027.65 U/g DBP, respectively. The highest xylanase activity was obtained from Run No. 30, which consisted of yeast extract (X₁), 1.00 g (%); NH₄NO₃ (X₂), 0.20 g (%); peptone (X₃), 1.00 g (%); urea (X₄), 10 mg (%); CMC (X₅), 1.00 g (%); Tween 20 (X₆), 0.02 mL (%); CaCO₃ (X₇), 0.50 g (%) and MgSO₄ (X₈), 9.0 g (%). The optimization resulted in 3.1-fold increase of xylanase production, compared with the lowest xylanase production of 331.50 U/g DBP after 72 h of incubation in stationary flask experiment. Application of cellulase-free xylanase in pulp biobleaching from C. cellulans CKMX1 under C-E_P-D sequence has been shown to bring about a 12.5 % reduction of chlorine, decrease of 0.8 kappa points (40 %), and gain in brightness was 1.42 % ISO points in 0.5 % enzyme treated pulp as compared to control.

Modification in the properties of paper by using cellulase-free xylanase produced from alkalophilic Cellulosimicrobium cellulans CKMX1 in biobleaching of wheat straw pulp

Alkalophilic Cellulosimicrobium cellulans CKMX1 isolated from mushroom compost is an actinomycete that produces industrially important and environmentally safer thermostable cellulase-free xylanase, which is used in the pulp and paper industry as an alternative to the use of toxic chlorinated compounds. Strain CKMX1 was previously characterized by metabolic fingerprinting, whole-cell fatty acids methyl ester analysis, and 16S rDNA and was found to be C. cellulans CKMX1. Crude enzyme (1027.65 U/g DBP) produced by C. cellulans CKMX1, having pH and temperature optima of 8.0 and 60 °C, respectively, in solid state fermentation of apple pomace, was used in the production of bleached wheat straw pulp. Pretreatment with xylanase at a dose of 5 U/g after pulping decreased pulp kappa points by 1.4 as compared with the control. Prebleaching with a xylanase dose of 5 U/g pulp reduced the chlorine charge by 12.5%, increased the final brightness points by approximately 1.42% ISO, and improved the pulp strength properties. Xylanase could be substituted for alkali extraction in C–Ep–D sequence and used for treating chemically bleached pulp, resulting in bleached pulp with higher strength properties. Modification of bleached pulp with 5 U of enzyme/g increased pulp whiteness and breaking length by 1.03% and 60 m, respectively; decreased tear factor of pulp by 7.29%; increased bulk weight by 3.99%, as compared with the original pulp. Reducing sugars and UV-absorbing lignin-derived compound values were considerably higher in xylanase-treated samples. Cellulosimicrobium cellulans CKMX1 has a potential application in the pulp and paper industries.

Purification and characterization of cellulase-free low molecular weight endo β-1,4 xylanase from an alkalophilic Cellulosimicrobium cellulans CKMX1 isolated from mushroom compost

Alkalophilic Cellulosimicrobium cellulans CKMX1 isolated from mushroom compost is first report on actinomycetes that has the ability to produce thermostable cellulase-free xylanase, which is an important industrial enzyme used in the pulp and paper industry. Strain CKMX1 was characterized by metabolic fingerprinting, whole-cell fatty acids methyl ester analysis and 16Sr DNA and found to be C. cellulans CKMX1.The enzyme was purified by gel permeation and anion exchange chromatography and had a molecular mass of 29 kDa. Xylanase activity was optimum at pH 8.0 and 55 °C. The enzyme was somewhat thermostable, retaining 50 % of the original activity after incubation at 50 °C for 30 min. The xylanase had K m and V max values of 2.64 mg/ml and 2,000 µmol/min/mg protein in oat spelt xylan, respectively. All metal ions except HgCl2, CoCl2 as well as CdCl2 were well tolerated and did not adversely affect xylanase activity. The deduced internal amino acid sequence of C. cellulans CKMX1 xylanase by matrix assisted laser desorption ionization-time of flight mass spectrometry resembled the sequence of β-1,4-endoxylanase, which is a member of glycoside hydrolase family 11. Some of the novel characteristics that make this enzyme potentially effective in xylan biodegradation could be useful for pulp and paper biobleaching are discussed in this manuscript.