Z.Q. Jiang

A xylose-tolerant β-xylosidase from Paecilomyces thermophila: Characterization and its co-action with the endogenous xylanase

An extracellular beta-xylosidase from the thermophilic fungus Paecilomyces thermophila J18 was purified 31.9-fold to homogeneity with a recovery yield of 2.27% from the cell-free culture supernatant. It appeared as a single protein band on SDS-PAGE with a molecular mass of approx 53.5 kDa. The molecular mass of beta-xylosidase was 51.8 kDa determined by Superdex 75 gel filtration. The enzyme was a glycoprotein with a carbohydrate content of 61.5%. It exhibited an optimal activity at 55 degrees C and pH 6.5, respectively. The enzyme was stable in the range of pH 6.0-9.0 and at 55 degrees C. The purified enzyme hydrolyzed xylobiose and higher xylooligosaccharides but was inactive against xylan substrates. It released xylose from xylooligosaccharides with a degree of polymerization ranging between 2 and 5. The rate of xylose released from xylooligosaccharides by the purified enzyme increased with increasing chain length. It had a K(m) of 4.3mM for p-nitrophenol-beta-d-xylopyranoside and was competitively inhibited by xylose with a K(i) value of 139 mM. Release of reducing sugars from xylans by a purified xylanase produced by the same organism increased markedly in the presence of beta-xylosidase. During 24-hour hydrolysis, the amounts of reducing sugar released in the presence of added beta-xylosidase were about 1.5-1.73 times that of the reaction employing the xylanase alone. This is the first report on the purification and characterization of a beta-xylosidase from Paecilomyces thermophila.

Characterization of a xylanase from the newly isolated thermophilic Thermomyces lanuginosus CAU44 and its application in bread making

Aims:u2002 A xylanase from the newly isolated thermophilic fungus, Thermomyces lanuginosus CAU44, was characterized and evaluated for its suitability in bread making.

Biobleach boosting effect of recombinant xylanase B from the hyperthermophilic Thermotoga maritima on wheat straw pulp.

The recombinant xylanase B (XynB) of Thermotoga maritima MSB8 was found to be highly specific towards xylans and exhibit very low activity towards carboxymethylcellulose in previous study. XynB was thermostable at neutral to alkaline pH region at 90°C and retained more than 90% activity after 1xa0h over the pH range of pH 6.1 to 11.1. The suitability of XynB for use in the biobleaching of wheat straw pulp was investigated. Pretreatment of the pulp with XynB resulted in a substantial improvement in the bleachability of wheat straw pulp. When XynB at 10xa0U g−1 was used to treat wheat straw pulp, it reduced pulp kappa number by 1.1 point, enhanced pulp brightness by 5.5% (% ISO) and improved other pulp properties, such as tensile index and breaking length. Biobleaching of wheat straw pulp with XynB saved active chlorine up to 34.5% while still maintaining the brightness at the control level. Besides, pretreatment of pulp with XynB was also effective at an alkaline pH as high as pH 10.1. This is the first report on the potential application of XynB from T. maritima MSB8 in the pulp and paper sector.

A novel, ultra-large xylanolytic complex (xylanosome) secreted by Streptomyces olivaceoviridis.

The production of a novel, very large xylanolytic complex (xylanosome) by Streptomyces olivaceoviridis E-86 is reported. The molecular weight was approx. 1200 kDa as determined by native gradient gel electrophoresis. Corncob xylan was the best inducer of xylanosome formation. The xylanosome was produced when the organism was grown for 5 d between pH 4.5–6 and at 27.5 to 35 °C.

Secretory expression of a β-xylosidase gene from Thermomyces lanuginosus in Escherichia coli and characterization of its recombinant enzyme.

Aims:u2002 To characterize a β‐xylosidase from the thermophilic fungus Thermomyces lanuginosus and to investigate its potential in saccharification of hemicellulosic xylans.

Variation of xylanosomal subunit composition of Streptomyces olivaceoviridis by nitrogen sources.

Besides affecting the xylanases production, different nitrogen sources present in the media also caused changes in the xylanosomal subunit composition of Streptomyces olivaceoviridis E-86. Four xylanosome fractions, purified from the culture supernatant of S. olivaceoviridis E-86 grown on different nitrogen sources, exhibited high specificity towards different xylans and were composed of different subunits. Thus, S. olivaceoviridis E-86 regulates the expression of xylanase activity and varies the xylanosome composition according to the nitrogen sources possibly through the action of the secreted proteases.

High‐level production of β‐1,3‐1,4‐glucanase by Rhizomucor miehei under solid‐state fermentation and its potential application in the brewing industry

To improve the β‐1,3‐1,4‐glucanase production by Rhizomucor miehei under solid‐state fermentation (SSF) for industrial application.

Purification and characterization of a novel α-glucosidase from Malbranchea cinnamomea

ObjectivesTo characterize a novel α-glucosidase from the thermophilic fungus Malbranchea cinnamomea.ResultsThe enzyme was purified to homogeneity with purification fold of 40 and a recovery of 7.2xa0%. It was a monomer with molecular mass of 65.7xa0kDa on SDS-PAGE. It was optimally active at pH 6 and 50xa0°C (measured over 10xa0min) and exhibited a wide range of substrate specificity with the highest specific activity of 47.4xa0Uxa0mg−1 for p-nitrophenyl α-d-glucopyranoside (pNPGlu) followed by isomaltose, panose and sucrose, suggesting that the enzyme belongs to the type I α-glucosidases. The Km values of the α-glucosidase for pNPGlu and isomaltose were 1.1 and 19.3xa0mM, respectively.ConclusionBecause of its unique properties, the α-glucosidase may have a potential in several industrial applications.