Cloning and constitutive expression of His-tagged xylanase GH 11 from Penicillium occitanis Pol6 in Pichia pastoris X33: Purification and characterization

Expression of Pleurotus ostreatus Laccase Gene in Pichia pastoris and Its Degradation of Corn Stover Lignin

Pleurotus ostreatus is a species of white-rot fungi that effectively degrades lignin. In this study, we aimed to efficiently express the lac-2 gene of Pleurotus ostreatus in the Pichia pastoris X33 yeast strain. The enzymatic properties of recombinant yeast were determined, and its ability to degrade corn stover lignin was determined. The results showed the optimum pH values of recombinant laccase for 2,2’-Azinobis-3-ethylbenzothiazoline-6-sulfonic acid, 2,6-dimethoxyphenol, and 2-methoxyphenol were 3.0, 3.0, and 3.5, respectively. The optimum reaction temperature was 50 °C, and it had good thermal stability and acid and alkali resistance. The degradation rate of lignin in corn stover by recombinant laccase was 18.36%, and the native Pleurotus ostreatus degradation rate was 14.05%, the difference between them is significant (p < 0.05). This experiment lays a foundation for the study of the degradation mechanism of lignin by laccase.

A porous nano-adsorbent with dual functional groups for selective binding proteins with a low detection limit

Porous nano-adsorbent with dual functional groups for selective binding proteins with a low detection limit.

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.

In planta production and characterization of a hyperthermostable GH10 xylanase in transgenic sugarcane

Sugarcane (Saccharum sp. hybrids) is one of the most efficient and sustainable feedstocks for commercial production of fuel ethanol. Recent efforts focus on the integration of first and second generation bioethanol conversion technologies for sugarcane to increase biofuel yields. This integrated process will utilize both the cell wall bound sugars of the abundant lignocellulosic sugarcane residues in addition to the sucrose from stem internodes. Enzymatic hydrolysis of lignocellulosic biomass into its component sugars requires significant amounts of cell wall degrading enzymes. In planta production of xylanases has the potential to reduce costs associated with enzymatic hydrolysis but has been reported to compromise plant growth and development. To address this problem, we expressed a hyperthermostable GH10 xylanase, xyl10B in transgenic sugarcane which displays optimal catalytic activity at 105 °C and only residual catalytic activity at temperatures below 70 °C. Transgene integration and expression in sugarcane were confirmed by Southern blot, RT-PCR, ELISA and western blot following biolistic co-transfer of minimal expression cassettes of xyl10B and the selectable neomycin phosphotransferase II. Xylanase activity was detected in 17 transgenic lines with a fluorogenic xylanase activity assay. Up to 1.2% of the total soluble protein fraction of vegetative progenies with integration of chloroplast targeted expression represented the recombinant Xyl10B protein. Xyl10B activity was stable in vegetative progenies. Tissues retained 75% of the xylanase activity after drying of leaves at 35 °C and a 2 month storage period. Transgenic sugarcane plants producing Xyl10B did not differ from non-transgenic sugarcane in growth and development under greenhouse conditions. Sugarcane xylan and bagasse were used as substrate for enzymatic hydrolysis with the in planta produced Xyl10B. TLC and HPLC analysis of hydrolysis products confirmed the superior catalytic activity and stability of the in planta produced Xyl10B with xylobiose as a prominent degradation product. These findings will contribute to advancing consolidated processing of lignocellulosic sugarcane biomass.

Lignocellulose degrading extremozymes produced by Pichia pastoris: current status and future prospects

In this review article, extremophilic lignocellulosic enzymes with special interest on xylanases, β-mannanases, laccases and finally cellulases, namely, endoglucanases, exoglucanases and β-glucosidases produced by Pichia pastoris are reviewed for the first time. Recombinant lignocellulosic extremozymes are discussed from the perspectives of their potential application areas; characteristics of recombinant and native enzymes; the effects of P. pastoris expression system on recombinant extremozymes; and their expression levels and applied strategies to increase the enzyme expression yield. Further, effects of enzyme domains on activity and stability, protein engineering via molecular dynamics simulation and computational prediction, and site-directed mutagenesis and amino acid modifications done are also focused. Superior enzyme characteristics and improved stability due to the proper post-translational modifications and better protein folding performed by P. pastoris make this host favourable for extremozyme production. Especially, glycosylation contributes to the structure, function and stability of enzymes, as generally glycosylated enzymes produced by P. pastoris exhibit better thermostability than non-glycosylated enzymes. However, there has been limited study on enzyme engineering to improve catalytic efficiency and stability of lignocellulosic enzymes. Thus, in the future, studies should focus on protein engineering to improve stability and catalytic efficiency via computational modelling, mutations, domain replacements and fusion enzyme technology. Also metagenomic data need to be used more extensively to produce novel enzymes with extreme characteristics and stability.

High-level expression and characterization of a thermostable xylanase mutant from Trichoderma reesei in Pichia pastoris

A gene encoding xylanase 2 mutant from Trichoderma reesei (T2C/T28C, named mxyn2) was cloned into the Pichia pastoris X33 strain using the vector pPICZαA. Recombinant Mxyn2p was functionally expressed in P. pastoris X33 and secreted into the supernatant. Real time qPCR demonstrated that an increase in gene copy number correlated with higher levels of expression. Supernatant from methanol induced cells was concentrated by ultrafiltration with a 10kDa cut off membrane, and purified with ion exchange chromatography using SP Sepharose Fast Flow chromatography. Recombinant Mxyn2p protein had the highest activity at 75°C, while recombinant protein encoded by the "wild type" xylanase gene xyn2, also expressed in Pichia, was 20°C lower. The Mxyn2p enzyme retained more than 70% of its activity after incubation at 80°C for 10min. The effects of the optimal pH and temperature for higher expression levels in P. pastoris were also determined, 6.0 and 22°C, respectively. The maximum xylanase activity of Mxyn2p was 13,000nkat/mg (9.88g/l) in fed-batch cultivation after 168h induction with methanol in a 50l bioreactor.

Toxicological study and oxidative stress evaluation for safety assessment of xylanase preparations in Wistar rats

Acute and 90-day subchronic oral toxicity studies were conducted to establish the safety evaluation of xylanases preparations. A potential oxidative stress evaluation was also performed through testing the generation of oxidative radicals, depletion of antioxidants via oxidative modification of lipids, proteins and DNA of organ cells. During the subchronic oral toxicity study, no mortality was observed, obvious treatment-related clinical signs and urinalysis parameters were in normal range. Differences in some hematological parameters, biochemistry, relative organ weight, and histopathology examinations between the treated group and the control group were not judged to be adverse. Our results indicated that the no-observed-adverse-effect level for xylanases was 1,500 TXU/kg/day and the plasma antioxidant assays showed that these xylanases did not produce free-radicals nor oxidative injuries. On the basis of the bacterial reverse mutation assay data, it is concluded that the expressed xylanase in Pichia pastoris do not present any mutagenic potential when tested in relevant genotoxicological assays.

Immobilization of His-tagged recombinant xylanase from Penicillium occitanis on nickel-chelate Eupergit C for increasing digestibility of poultry feed

Recombinant xylanase 2 from Penicillium occitanis expressed with an His-tag in Pichia pastoris, termed PoXyn2, was immobilized on nickel-chelate Eupergit C by covalent coupling reaction with a high immobilization yield up to 93.49%. Characterization of the immobilized PoXyn2 was further evaluated. The optimum pH was not affected by immobilization, but the immobilized PoXyn2 exhibited more acidic and large optimum pH range (pH 2.0-4.0) than that of the free PoXyn2 (pH 3.0). The free PoXyn2 had an optimum temperature of 50 °C, whereas that of the immobilized enzyme was shifted to 65 °C. Immobilization increased both pH stability and thermostability when compared with the free enzyme. Thermodynamically, increase in enthalpy and free energy change after covalent immobilization could be credited to the enhanced stability. Immobilized xylanase could be reused for 10 consecutive cycles retaining 60% of its initial activity. It was found to be effective in releasing reducing sugar from poultry feed. Immobilization on Eupergit C is important due to its mechanical resistance at high pH and temperature. Hence, considerable stability and reusability of bound enzyme may be advantageous for its industrial application.

Cloning and expression of a xylanase xynB from Aspergillus niger IA-001 in Pichia pastoris

The high-level expression of the xylanase GH11 gene from Aspergillus niger IA-001 called xynB was successfully completed in Pichia pastoris. The xynB gene encoding a mature xylanase of 225 amino acid was subcloned into the pPICZαA vector and was transformed into P. pastoris X-33 under the control of the alcohol oxidase I (AOX1) promoter. The xynB gene was ligated with a sequence encoding modified α-factor signal peptide (pPICZαmA) and the recombinant xylanase activity, which was measured 1280 U ml(-1), was 1.5-fold higher than when it was inserted into pPICZαA and was 19.39-fold greater than the native xylanase in the original strain. In a 10 L fermenter, the recombinant xylanase activity measured 10,035 U ml(-1) after 114 h. The SDS-PAGE analysis revealed that the purified xynB protein migrated as a single band with an apparent molecular weight of 24 kDa. The specific activity, using beechwood xylan as a substrate, was 1916 U mg(-1). The xylanase activity was optimal at pH 5.0 and at 50 °C. In addition, the xynB was active over a pH range of 2.2 to 10.0. The apparent Km and Vmax values were 4.429 mg ml(-1) and 1429 U mg(-1), respectively.

Cloning, Expression, and Characterization of an GHF 11 Xylanase from Aspergillus niger XZ-3S

A xylanase gene (xynZF-2) from the Aspergillus niger XZ-3S was cloned and expressed in Escherichia coli. The coding region of the gene was separated by only one intron with the 68 bp in length. It encoded 225 amino acid residues of a protein with a calculated molecular weight of 24.04 kDa plus a signal peptide of 18 amino acids. The amino acid sequence of the xynZF-2 gene had a high similarity with those of family 11 of glycosyl hydrolases reported from other microorganisms. The mature peptide encoding cDNA was subcloned into pET-28a(+) expression vector. The resultant recombinant plasmid pET-28a-xynZF-2 was transformed into E. coli BL21(DE3), and finally the recombinant strain BL21/xynZF-2 was obtained. A maximum activity of 42.33 U/mg was gained from cellular of E. coli BL21/xynZF-2 induced by IPTG. The optimum temperature and pH for recombinant enzyme which has a good stability in alkaline conditions were 40 °C and 5.0, respectively. Fe(3+) had an active effect on the enzyme obviously.

WITHDRAWN: Aminoglycoside phosphotransferase II gene as primary selection marker for Pichia pastoris producing full-length monoclonal antibody

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