RESUMEN
The thermostable fungus, Thermoascus aurantiacus M-2, which produces a novel acidophilic and thermostable xylanase was isolated and identified based on its morphology and comparison of the internal transcribed spacer rDNA gene sequence. The culture conditions and components of medium were optimized for T. aurantiacus M-2 to produce xylanase. T. aurantiacus M-2 produced xylanase at a maximum level of 39.07â¯U/mL after 8-d fermentation at 45⯰C in the optimized medium. The purified xylanase produced by T. aurantiacus M-2 has a relative molecular mass of approximately 31.0â¯kD. The characteristics of purified xylanase were investigated. The purified T. aurantiacus xylanase exhibited maximum activity at 75⯰C and pH 5.0, and it was stable after treatment at a pH range from 2.0 to 10.0 or a temperature range from 30⯰C to 80⯰C for 2-h. Mn2+ and Ag+ enhanced xylanase activity to 120.0% and 119.6%, respectively, while Mn2+ had the highest inhibition ratio, with a residual activity of 20.7%. This study provided a foundation for scaled-up production and application of xylanase.
Asunto(s)
Endo-1,4-beta Xilanasas/biosíntesis , Endo-1,4-beta Xilanasas/química , Thermoascus/enzimología , Endo-1,4-beta Xilanasas/genética , Endo-1,4-beta Xilanasas/aislamiento & purificación , Activación Enzimática , Estabilidad de Enzimas , Fermentación , Concentración de Iones de Hidrógeno , Nitrógeno/metabolismo , Fenotipo , Especificidad por Sustrato , Temperatura , Thermoascus/genética , Thermoascus/crecimiento & desarrolloRESUMEN
Thermoascus aurantiacus is able to secrete most of the hemicellulolytic and cellulolytic enzymes. To establish the xylanase inducers of T. aurantiacus, the mycelia were first grown on glucose up until the end of the exponential growth phase, followed by washing and re-suspension in a basal medium without a carbon source. Pre-weighed amounts of xylose (final concentration of 3.5 mg/ml), xylobiose (7 mg/ml) and hydrolyzed xylan from sugarcane bagasse (HXSB) which contained xylose, xylobiose and xylotriose (6.8 mg/ml) were evaluated as inducers of xylanase. It was observed that xylose did not suppress enzyme induction of T. aurantiacus when used in low concentrations, regardless of whether it was inoculated with xylobiose. Xylobiose promoted fast enzyme production stopping after 10 h, even at a low consumption rate of the carbon source; therefore xylobiose appears to be the natural inducer of xylanase. In HXSB only a negligible xylanase activity was determined. Xylose present in HXSB was consumed within the first 10 h while xylobiose was partially hydrolyzed at a slow rate. The profile of α-arabinofuranosidase induction was very similar in media induced with xylobiose or HXSB, but induction with xylose showed some positive effects as well. The production profile for the xylanase was accompanied by low levels of cellulolytic activity. In comparison, growth in HXSB resulted in different profiles of both xylanase and cellulase production, excluding the possibility of xylanase acting as endoglucanases.
Asunto(s)
Celulasa/biosíntesis , Proteínas Fúngicas/biosíntesis , Glicósido Hidrolasas/biosíntesis , Thermoascus/enzimología , Biomasa , Biotecnología , Disacáridos/metabolismo , Inducción Enzimática , Hidrólisis , Cinética , Thermoascus/crecimiento & desarrollo , Thermoascus/metabolismo , Xilanos/metabolismoRESUMEN
Toxic waste generated by Jatropha seed cake after utilization of biodiesel on one hand has stimulated the need to develop new technologies to treat the waste and on the other, forced us to reevaluate the efficient utilization of its nutritive potential for production of various high-value compounds and its conversion to non-toxic forms which could be used as animal feed stock. In this study, Jatropha seed cake was used for production of cellulases by new isolate of Thermoascus aurantiacus under solid-state fermentation. The interaction of nitrogen source concentration, moisture ratio, initial pH of the medium and inoculum size was investigated and modelled using response surface methodology (RSM) using Box-Behnken Design (BBD). Under optimized conditions endo-ß-1,4-glucanase, ß-glucosidase and filter paper activities were found to be 124.44, 28.86, 4.87 U/g of substrate, respectively. Characterization of endo-ß-1,4-glucanase, ß-glucosidase was done after partial purification by ammonium sulfate fractionation followed by desalting. The endo-ß-1,4-glucanase and ß-glucosidase showed maximum activity at 70 °C and pH 4. Saccharification studies performed with different lignocellulosic substrates showed that sugar cane bagasse was most susceptible to enzymatic hydrolysis. The study suggests that Jatropha seed cake can be used as a viable nutrient source for cellulase production without any pretreatment under solid-state fermentation by T. aurantiacus.
Asunto(s)
Biocombustibles , Celulasa , Proteínas Fúngicas , Jatropha/química , Semillas/química , Residuos Sólidos , Thermoascus , Celulasa/química , Celulasa/metabolismo , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo , Lignina/química , Lignina/metabolismo , Thermoascus/enzimología , Thermoascus/crecimiento & desarrollo , Administración de Residuos/métodosRESUMEN
The effect of growth and fermentation conditions on the production of catalase by T. aurantiacus WSH 03-01 was investigated in shaking flasks. Catalase activity reached 1594 u/mL when the culture was grown on a complex carbon source containing 20 g/L dextrin and 1% (V/V) ethanol, which was 23% higher than the sum produced on 20 g/L dextrin and 1% (V/V) ethanol, respectively. It was concluded that dextrin might act as a major carbon source in the complex, while ethanol was rather a stimulator than a carbon source. The stimulation effect of ethanol on catalase production was postulated to be two aspects; catalase-dependent alcohol metabolism is activated by acute alcohol, thus more catalase need to be synthesized for that use, named direct induction. As for indirect induction, which may result from little amount of H2O2 generation in process of NADH regeneration in respiratory chain. Peptone was shown to be a favorable nitrogen source for catalase production and its optimum concentration was found to be 10 g/L. Catalase production by T. aurantiacus WSH 03-01 was further improved by optimizing the initial pH, volume of medium in flasks as well as the concentration of external H2O2. Under the optimum culture conditions, the activity of catalase reached 2762 u/mL, which was nearly 6.8 times higher than that of the initiate conditions. Furthermore, the potential application of this novel catalase in the treatment of textile bleaching effluents was evaluated. Thermo-and alkaline stability of this catalase was compared with the commercial available catalases produced from bovine and Aspergillus niger. The crude enzyme from T. aurantiacus WSH 03-01 showed stronger stabilities at (70 degrees C, 80 degrees C, 90 degrees C) and (pH 9.0, pH 10.0, pH 11.0) than the other two types of catalases, indicating a great application potential in the clean production process of textile industry.