Zhikui Hao

Cloning, Expression and 3D Structure Prediction of Chitinase from Chitinolyticbacter meiyuanensis SYBC-H1.

Two CHI genes from Chitinolyticbacter meiyuanensis SYBC-H1 encoding chitinases were identified and their protein 3D structures were predicted. According to the amino acid sequence alignment, CHI1 gene encoding 166 aa had a structural domain similar to the GH18 type II chitinase, and CHI2 gene encoding 383 aa had the same catalytic domain as the glycoside hydrolase family 19 chitinase. In this study, CHI2 chitinase were expressed in Escherichia coli BL21 cells, and this protein was purified by ammonium sulfate precipitation, DEAE-cellulose, and Sephadex G-100 chromatography. Optimal activity of CHI2 chitinase occurred at a temperature of 40 °C and a pH of 6.5. The presence of metal ions Fe3+, Fe2+, and Zn2+ inhibited CHI2 chitinase activity, while Na+ and K+ promoted its activity. Furthermore, the presence of EGTA, EDTA, and β-mercaptoethanol significantly increased the stability of CHI2 chitinase. The CHI2 chitinase was active with p-NP-GlcNAc, with the Km and Vm values of 23.0 µmol/L and 9.1 mM/min at a temperature of 37 °C, respectively. Additionally, the CHI2 chitinase was characterized as an N-acetyl glucosaminidase based on the hydrolysate from chitin. Overall, our results demonstrated CHI2 chitinase with remarkable biochemical properties is suitable for bioconversion of chitin waste.

Controlled synthesis of Zn(1−1.5x)FexS nanoparticles via a microwave route and their photocatalytic properties

Fe-doped ZnS photocatalysts synthesized by a conventional hydrothermal method usually have poor crystallinity and low photocatalytic activity. In this study, the Zn(1−1.5x)FexS particles were first directly synthesized by the microwave irradiation method without additional heat treatments. The prepared Zn(1−1.5x)FexS catalysts were characterized using X-ray diffraction (XRD), UV-Vis absorption spectra, scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analyzer, etc. The characterization results show that the morphology and physico-chemical properties of samples are changed depending on the ratio of Fe and Zn. The absorption edges of Zn(1−1.5x)FexS were red-shifted as the value of x decreased. The band gaps were estimated to be from 2.74 to 3.64 eV from the onset of the UV-Vis absorption edges. The results indicated that the photocatalyst of Zn0.97Fe0.02S has the highest photocatalytic activity of dimethyl phthalate (DMP) with a removal of 97.5%. In addition, the crystallite size, band gap and structure for the Zn(1−1.5x)FexS samples have a strong influence on the degradation of DMP from wastewater.

Hydrogen Peroxide-Resistant CotA and YjqC of Bacillus altitudinis Spores Are a Promising Biocatalyst for Catalyzing Reduction of Sinapic Acid and Sinapine in Rapeseed Meal.

For the more efficient detoxification of phenolic compounds, a promising avenue would be to develop a multi-enzyme biocatalyst comprising peroxidase, laccase and other oxidases. However, the development of this multi-enzyme biocatalyst is limited by the vulnerability of fungal laccases and peroxidases to hydrogen peroxide (H2O2)-induced inactivation. Therefore, H2O2-resistant peroxidase and laccase should be exploited. In this study, H2O2-stable CotA and YjqC were isolated from the outer coat of Bacillus altitudinis SYBC hb4 spores. In addition to the thermal and alkali stability of catalytic activity, CotA also exhibited a much higher H2O2 tolerance than fungal laccases from Trametes versicolor and Trametes trogii. YjqC is a sporulation-related manganese (Mn) catalase with striking peroxidase activity for sinapic acid (SA) and sinapine (SNP). In contrast to the typical heme-containing peroxidases, the peroxidase activity of YjqC was also highly resistant to inhibition by H2O2 and heat. CotA could also catalyze the oxidation of SA and SNP. CotA had a much higher affinity for SA than B. subtilis CotA. CotA and YjqC rendered from B. altitudinis spores had promising laccase and peroxidase activities for SA and SNP. Specifically, the B. altitudinis spores could be regarded as a multi-enzyme biocatalyst composed of CotA and YjqC. The B. altitudinis spores were efficient for catalyzing the degradation of SA and SNP in rapeseed meal. Moreover, efficiency of the spore-catalyzed degradation of SA and SNP was greatly improved by the presence of 15 mM H2O2. This effect was largely attributed to synergistic biocatalysis of the H2O2-resistant CotA and YjqC toward SA and SNP.

Development of an HPLC method to analyze and prepare elsinochrome C and hypocrellin A in the submerged fermentation broth of Shiria sp. SUPER-H168

A rapid and sensitive analytical method based on reverse-phase high-performance liquid chromatography was first developed to simultaneously determine elsinochrome C (EC) and hypocrellin A (HA) in the submerged fermentation. The mobile phase consisted of acetonitrile-water 60:40 (v/v) with a flow-rate of 1 mL/min. The calibration curves were as follows: y = 37,625x + 249,775 for EC, y = 30,813x + 556,409 for HA and linear at the investigated concentration. The correlation coefficients (R(2) ) were 0.9989 and 0.9998 respectively for EC and HA. The limits of detection and quantification were 175 and 585 µg/L for EC and 205 and 610 µg/L for HA. The precisions of concentration and retention times were less than 2.5 and 0.3%. The recovery of the method was greater than 95.0%. The methodology was applied to analyze simultaneously EC and HA concentrations in a submerged fermentation, and was adequate for analysis of biosynthesis of perylenequinones. The method was also amplified to separate and purify EC and HA using a semi-preparative C(18) column. In addition, elsinochrome C was first identified in the submerged fermentation broth of Shiraia sp. SUPER-H168.

Synthesis of sucrose acetate using a solvent-stable serine protease from Serratia sp. SYBC H

Sugar esters have several applications in a variety of industrial processes, including their use as biodegradable surfactants in the food, pharmaceutical, and cosmetic industries and as antitumoral agents and plant growth inhibitors. Most of the sucrose monoesters described in the literature have been enzymatically synthesized from the primary hydroxyls (1′‐OH, 6‐OH, and 6′‐OH) of sucrose. In this study, we report a simple procedure for the regioselective acylation of a secondary hydroxyl (4′‐OH) of sucrose. Sucrose‐4′‐acetate was efficiently synthesized from sucrose and vinyl acetate in anhydrous dimethyl sulfoxide using a solvent‐stable serine protease from Serratia sp. SYBC H. When the sucrose/vinyl acetate molar ratio, protease concentrations, and reaction times are equal to or above 1:8, 25 mg/mL, and 21 h at 30°C, respectively, the yield of sucrose‐4′‐acetate can exceed 90%. The described protocol of enzymatic synthesis of sucrose‐4′‐acetate can improve possible applications of sucrose esters in various fields.