Comparison of three different thermophilic beta-glucosidases for baicalin transformation / 中国中药杂志

Three different beta-glycosidase sequences of Ttebgl3, Tpebgl1 and Tpengl3 from Thermotoga thermarum DSM 5069 and Thermotoga petrophila RKU-1 were analyzed. Also, the influence of temperature, pH, concentration of DMSO, metal ions and kinetic constant on catalytic conversion of baicalin had been compared. The results indicated that the optimal pH and optimum temperature for transformation of baicalin was 4.5 85 °C, 5.0 80 °C and 5.5 80 °C, respectively. The family GH3 beta-glycosidase Ttebgl3 and Tpebgl3 had the better DMSO tolerance. The activation effect of the metal ions on the catalytic conversion of baicalin was not obvious, and the inhibition of the GH3 family beta glucosidase was significantly stronger than that of the GH1 family. The kinetic constants of three different beta-glucosidases catalyzed baicalin were significantly different. The Km and Vmax values of Tpebgl1, Tpebgl3 and Ttebgl3 were 0.029 2 mmol·L⁻¹ 4.85 U·mg⁻¹, 0.268 6 mmol·L⁻¹ 121.04 U·mg⁻¹ and 0.391 8 mmol·L⁻¹ 308.90 U·mg⁻¹, respectively. Family GH3 beta-glycosidase converted more baicalin than family GH1 with the optimal conditions, 0.02 g baicalin, and the conversion rate was 68%, 97.3%, 97.31% respectively. The results of the study provided a guarantee for the transformation of baicalin.

Preparation of baicalein using thermophilic and sugar-tolerant beta-glucosidase / 中国中药杂志

The reaction conditions of baicalin hydrolyzed into baicalein by a kind of thermophilic and sugar-tolerant beta-glucosidase were studied in this paper. The beta-glucosidase could catalyze baicalin into baicalein well in the acetic acid-sodium acetate buffer. The optimal enzyme activity was at 85 degrees C and pH 5.5. The enzyme was stable at the temperature less than 85 degrees C and pH range of 5-7.5. The maximum reaction rate V. and michaelis constant K. were 0.41 mmol x L(-1) x min(-1) and 3.31 mmol x L(-1) respectively. Different metal ions had different effects on the activity of enzyme. Na+ existing in acetic acid-sodium acetate buffer had an activation effect on enzyme. The enzyme activity was enhanced by the concentrations of glucose below 0.6 mol x L(-1), and was gradually inhibited when monosaccharide concentration was over 0.6 mol x L(-1). When the monosaccharide concentration reached 1.2 mol x L(-1), the inhibition rate of enzyme activity was about 50%, which showed good glucose tolerance. The good reaction conditions through the experiment have been determined as follows, the substrate: enzyme dose was 1 g: 0.2 mL, acetic acid-sodium acetate buffer pH 5.5, reaction temperature 85 degrees C, reaction time 10 h, and the enzymatic hydrolyzation ratio could reach 97%.

Rice Straw Degradation with White Rot Fungi and Cellulose Multienzyme Produced by Aspergillus niger / 中国生物工程杂志

Rice straw degradation with white rot fungi and cellulose multienzyme was studied. The results indicated that the LiP, MnP activity produced by P. chrysosoporium 172 could reach 28.3U/g and 12.6U/g respectively under suitable culture condition. And the lignin was degraded efficiently in contrast with the cellulose and hemicellulose in rice straw solid fermentation. Following treatment with white rot fungi, using multienzyme produced by A. niger NL-1 could greatly accelerate the decomposition of rice straw. The decomposition rate of cellulose, hemicellulose, lignin and the loss rate of dry material were 53.8%,57.8%,44.5% and 46.3% respectivity when hydrolysis rice straw 48h with cellulase multienzyme (including 3 IU /g rice straw) after culture P. chrysosoporium 172 for 10 days. Scanning electron microscope analysis showed the cell wall of rice straw was destroyed severely, and the whole tissue got loosely. These results demonstrated the rice straw had been decomposed efficiently and completely.