Expression and Characterization of Recombinant GH11 Xylanase from Thermotolerant Streptomyces sp. SWU10

Xylans are major hemicellulose components of plant cell wall which can be hydrolyzed by xylanolytic enzymes. Three forms of endo-β-1,4-xylanases (XynSW1, XynSW2A, and XynSW2B) produced by thermotolerant Streptomyces sp. SWU10 have been reported. In the present study, we described the expression and characterization of the fourth xylanase enzyme from this bacteria, termed XynSW3. The gene containing 726 bp was cloned and expressed in Escherichia coli. The recombinant enzyme (rXynSW3) was purified from cell-free extract to homogeneity using Ni-affinity column chromatography. The apparent molecular mass of rXynSW3 was 48 kDa. Amino acid sequence analysis revealed that it belonged to a xylanase of glycoside hydrolase family 11. The optimum pH and temperature for enzyme activity were 5.5–6.5 and 50 °C, respectively. The enzyme was stable up to 40 °C and in wide pH ranges (pH 0.6–10.3). Xylan without arabinosyl side chain is the most preferable substrate for the enzyme. By using birch wood xylan as substrate, rXynSW3 produced several oligosaccharides in the initial stage of hydrolysis, and their levels increased with time, demonstrating that the enzyme is an endo-acting enzyme. The major products were xylobiose, triose, and tetraose. The rXynSW3 can be applied in several industries such as food, textile, and biofuel industries, and waste treatment.     

Synthesis of Molecularly Imprinted Polymers for Nevirapine by Dummy Template Imprinting Approach

Nevirapine (NVP) and its structurally related analogs including nicotinamide (NAM), benzamide (BZM) and benzophenone (BZP) were used as templates in the synthesis of molecularly imprinted polymers for NVP. Molecular modeling was used to estimate binding energy of the complex formation between methacrylic acid (MAA) monomer and the selected templates, while equilibrium binding studies were applied to evaluate the polymer binding efficiency. The data indicated that NAM is the best candidate to prepare MIPs for retaining NVP due to a relatively similar binding energy between the NVP–MAA and NAM–MAA complex. The NAM-imprinted polymer showed a high binding affinity and selectivity toward NVP. When the polymer was applied as a sorbent in solid-phase extraction of NVP from human plasma, high recovery and reproducibility were obtained.

     

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalyst for selective oxidation of toluene to benzoic acid with H2O2

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalysts were developed for the selective oxidation of toluene to benzoic acid in the presence of H₂O₂. The influence of the DVB content on the capacity of immobilized Fe(III) and on the catalytic activities of the polymeric complexes was investigated. The extent of Fe(III) uptake by the copolymers varied slightly with the concentration of DVB. The catalytic activities generally increase with increasing degree of crosslinker from 2 to 10% and decrease further with increasing the DVB content. Under the optimal conditions (80 °C, 6 h), the catalyst containing 10% DVB was found to be highly efficient in conversion of toluene to benzoic acid with 90% conversion and 96% selectivity.     

Microwave-assisted SNAr reaction of 2,4,6-trichloro-1,3,5-triazine for the rapid synthesis of C3-symmetrical polycarboxylate ligands

The microwave-assisted S_NAr reaction of 2,4,6-trichloro-1,3,5-triazine with various unprotected amino acids was developed for the synthesis of C₃-symmetrical polycarboxylate ligands which can be used as structural directing units in metal-organic frameworks. The reactions were performed in water using a domestic microwave oven as the heating device. In comparison to the reactions performed under conventional heating, the reactions under microwave irradiation proceeded much more rapidly within 20 min to afford the desired ligands in comparative yields to those obtained by conventional heating.     

Synthesis of Molecularly Imprinted Polymers for Nevirapine by Dummy Template Imprinting Approach

Nevirapine (NVP) and its structurally related analogs including nicotinamide (NAM), benzamide (BZM) and benzophenone (BZP) were used as templates in the synthesis of molecularly imprinted polymers for NVP. Molecular modeling was used to estimate binding energy of the complex formation between methacrylic acid (MAA) monomer and the selected templates, while equilibrium binding studies were applied to evaluate the polymer binding efficiency. The data indicated that NAM is the best candidate to prepare MIPs for retaining NVP due to a relatively similar binding energy between the NVP–MAA and NAM–MAA complex. The NAM-imprinted polymer showed a high binding affinity and selectivity toward NVP. When the polymer was applied as a sorbent in solid-phase extraction of NVP from human plasma, high recovery and reproducibility were obtained.