Peiji Gao

Enzyme-modified nanoporous gold-based electrochemical biosensors

On the basis of the unique physical and chemical properties of nanoporous gold (NPG), which was obtained simply by dealloying Ag from Au/Ag alloy, an attempt was made in the present study to develop NPG-based electrochemical biosensors. The NPG-modified glassy carbon electrode (NPG/GCE) exhibited high-electrocatalytic activity toward the oxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H(2)O(2)), which resulted in a remarkable decrease in the overpotential of NADH and H(2)O(2) electro-oxidation when compared with the gold sheet electrode. The high density of edge-plane-like defective sites and large specific surface area of NPG should be responsible for the electrocatalytic behavior. Such electrocatalytic behavior of the NPG/GCE permitted effective low-potential amperometric biosensing of ethanol or glucose via the incorporation of alcohol dehydrogenase (ADH) or glucose oxidase (GOD) within the three-dimensional matrix of NPG. The ADH- and GOD-modified NPG-based biosensors showed good analytical performance for biosensing ethanol and glucose due to the clean, reproducible and uniformly distributed microstructure of NPG. The stabilization effect of NPG on the incorporated enzymes also made the constructed biosensors very stable. After 1 month storage at 4 degrees C, the ADH- and GOD-based biosensors lost only 5.0% and 4.2% of the original current response. All these indicated that NPG was a promising electrode material for biosensors construction.

Cellulose-binding domain of endoglucanase III from Trichoderma reesei disrupting the structure of cellulose

The DNA fragment encoding the cellulose binding domain of endoglucanase III (CBDEG III) from Trichoderma reesei was subcloned and expressed in E. coli. The CBDEG III had a high affinity for cellulose. The morphological and structural changes of cellulose after treatment with CBDEG III indicated a 17% decrease in number of hydrogen bonds and a 16.5% decrease in crystalline index. X-ray diffraction and IR spectra analyses indicated that the destabilization and breakage of the hydrogen bonds in crystalline cellulose accounted for the non-hydrolytic disruption of the structure of cellulose.

A novel function for the cellulose binding module of cellobiohydrolase I

A homogeneous cellulose-binding module (CBM) of cellobiohydrolase I (CBHI) from Trichoderma pseudokoningii S-38 was obtained by the limited proteolysis with papain and a series of chromatographs filtration. Analysis of FT-IR spectra demonstrated that the structural changes result from a weakening and splitting of the hydrogen bond network in cellulose by the action of CBMCBHI at 40°C for 24 h. The results of molecular dynamic simulations are consistent with the experimental conclusions, and provide a nanoscopic view of the mechanism that strong and medium H-bonds decreased dramatically when CBM was bound to the cellulose surface. The function of CBMCBHI is not only limited to locating intact CBHI in close proximity with cellulose fibrils, but also is involved in the structural disruption at the fibre surface. The present studies provided considerable evidence for the model of the intramolecular synergy between the catalytic domain and their CBMs.

Catalytic activities of fungal oxidases in hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate-based microemulsion.

For hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]), an H(2)O-in-[BMIM][PF(6)] microemulsion could be formed in the presence of nonionic surfactant Triton X-100 (TX-100). In such a medium, both lignin peroxidase (LiP) and laccase could express their catalytic activity with the optimum molar ratio of H(2)O to TX-100 at 8.0 for LiP and >20 for laccase, and the optimum pH values at 3.2 for LiP and 4.2 for laccase, respectively. As compared with pure or water saturated [BMIM][PF(6)], in which the two oxidases had negligible catalytic activity due to the strong inactivating effect of [BMIM][PF(6)] on both enzymes, the use of the [BMIM][PF(6)]-based microemulsion had some advantages. Not only the catalytic activities of both fungal oxidases greatly enhanced, but also the apparent viscosity of the medium decreased.

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.

Immobilization of lignin peroxidase on nanoporous gold: Enzymatic properties and in situ release of H2O2 by co-immobilized glucose oxidase

Immobilization of enzymes on porous inorganic materials is very important for biocatalysis and biotransformation. In this paper, nanoporous gold (NPG) was used as a support for lignin peroxidase (LiP) immobilization. NPG with a pore size of 40-50 nm was prepared by dealloying Au/Ag alloy (50:50 wt%) for 17 h. By incubation with LiP aqueous solution, LiP was successfully immobilized on NPG. The optimal temperature of the immobilized LiP was ca. 40, 10 degrees C higher than that of free LiP. After 2h incubation at 45 degrees C, 55% of the initial activity of the immobilized LiP was still retained while the free LiP was completely deactivated. In addition, a high and sustainable LiP activity was achieved via in situ release of H(2)O(2) by a co-immobilized glucose oxidase. The present co-immobilization system was demonstrated to be very effective for LiP-mediated dye decolourization.

Taste improvement of refrigerated meat treated with cold-adapted Protease

The cold-adapted protease produced by a deep-sea cold-adapted bacterium Pseudoaltermonas sp. SM9913 and the mesophilic protease produced by a mesophilic bacterium Bacillus sp. SM98011 were sprayed onto the surfaces of marine fish, pork and shrimp meat, respectively, and then stored at 0 °C for 6 days. The amounts of free amino acids in the hydrolysates of samples were determined. The results showed that the samples treated with cold-adapted protease released more free amino acids than those treated with mesophilic protease at 0 °C. The refrigerated meat samples treated with cold-adapted protease, released more taste amino acids and essential amino acids than those treated with mesophilic protease. Therefore, the cold-adapted protease had potential in improving the taste of refrigerated meat.

Morphologies and Phylogenetic Classification of Cellulolytic Myxobacteria

The evolutionary distances of the 16S rDNA sequences in cellulolytic myxobacteria are less than 3%, which units all the strains into a single genus, Sorangium. The size of myxospores and the shape of sporangioles, rather than fruiting body colors or swarm morphologies are consistent with the changes of the 16S rDNA sequences. It is suggested that there are at least two species in the genus Sorangium: one includes strains with small myxospores and spherical sporangioles, and the color of the fruiting bodies is normally orange or brown, though sometimes yellow or black. The second species has large myxospores, polyhedral sporangioles with many inter-cystic substrates, and normally deep brown to black color.

Effect of bio-treatment on the lipophilic and hydrophilic extractives of wheat straw.

Wheat straw, an important papermaking raw material in China, was treated with a white-rot fungus of Phanerochaete chrysosporium ME446, and the lipophilic and hydrophilic extractives from the control and bio-treated samples were analyzed by GC and GC-MS. Bio-treatment of wheat straw could alter the chemical composition of both the lipophylic and hydrophilic extractives. Sugars and phenolic substances such as coniferyl alcohol, 4-hydroxycinnamic acid, 1-guaiacylglycerol and ferulic acid were substantially degraded or consumed by the fungus. More lipophilic substances such as wax, glycerides and steryl esters were degraded into the corresponding components, resulting in much higher concentrations of fatty acids and sterols in the bio-treated samples. Obviously, the bio-treatment of wheat straw was of benefit to pitch control in pulping and papermaking processes, in the view of degradation of the more lipophilic substances. In addition, the bio-treatment could increase the lignin concentration in hot-water extractives of wheat straw.

16S-23S ribosomal DNA intergenic spacer regions in cellulolytic myxobacteria and differentiation of closely related strains

The diversity of 16S-23S rDNA intergenic spacer regions (ISR) among cellulolytic myxobacterial strains was assayed. Agarose gel electrophoresis of PCR amplification products from ten strains shows that there are at least four copies of rRNA operons in the genus Sorangium, based on their size and restriction enzymatic digest maps. There are two sequence organization patterns: tRNA(Ile)-tRNA(Ala)-containing ISR and tRNA-lacking ISR. The tRNA-containing ISRs are highly similar among strains and within a strain (more than 98% similarity) and contain the essential functional regions, such as a ribonuclease III recognition site and an antiterminator recognition site boxA. The tRNA-lacking ISR has no such functional sites that are important for yielding mature rRNA, which suggests that this type of rRNA operons might be degenerate. The tRNA-lacking ISR is divided into two types based on their sizes and sequences, which exhibits about 90% similarity within each type. Thus, the tRNA-lacking ISR polymorphisms can be used to discriminate among different strains of sorangial species.