RESUMEN
Among 97 fungal strains isolated from soil collected in the arctic tundra (Spitsbergen), Penicillium chrysogenum 9' was found to be the best lipase producer. The maximum lipase activity was 68 units mL(-1) culture medium on the fifth day of incubation at pH 6.0 and 20 degrees C. Therefore, P. chrysogenum 9' was classified as a psychrotrophic microorganism. The non-specific extracellular lipase showed a maximum activity at 30 degrees C and pH 5.0 for natural oils or at pH 7.0 for synthetic substrates. Tributyrin was found to be the best substrate for lipase, among those tested. The Km and Vmax were calculated to be 2.33 mM and 22.1 units mL(-1), respectively, with tributyrin as substrate. The enzyme was inhibited more by EDTA than by phenylmethylsulfonyl fluoride and was reactivated by Ca2+. The P. chrysogenum 9' lipase was very stable in the presence of hexane and 1,4-dioxane at a concentration of 50%, whereas it was unstable in presence of xylene.
Asunto(s)
Microbiología Industrial , Lipasa/metabolismo , Penicillium chrysogenum/enzimología , Regiones Árticas , Detergentes , Inhibidores Enzimáticos/farmacología , Concentración de Iones de Hidrógeno , Cinética , Lipasa/antagonistas & inhibidores , Lipasa/aislamiento & purificación , Metales/metabolismo , Microbiología del Suelo , Solventes , Especificidad por Sustrato , TemperaturaRESUMEN
A novel method for increasing dissolved oxygen concentration in culture media has been developed. It involves adding hydrogen peroxide (H2O2) to the medium which is then decomposed to oxygen and water by catalase. Some factors affecting oxygenation of culture were investigated. Maximal oxygen concentration occurred in 50 ml of the medium containing 0-2 g wet mycelium and 0.2% glucose at pH 5.0. A new apparatus for automated addition of H2O2 to the bioreactor to keep the dissolved oxygen concentration constant over the range 1-100% +/- 2% was tested. A significant increase (over sixfold) of intracellular catalase activity was obtained while the dissolved oxygen concentration remained stable (30% +/- 2%).
Asunto(s)
Aspergillus niger/enzimología , Catalasa/biosíntesis , Glucosa Oxidasa/biosíntesis , Aspergillus niger/crecimiento & desarrollo , Reactores Biológicos , Medios de Cultivo , Fermentación , Glucosa/metabolismo , Peróxido de Hidrógeno/metabolismo , Concentración de Iones de Hidrógeno , Oxígeno/metabolismo , Consumo de OxígenoRESUMEN
The extracellular catalase (EC 1.11.1.6) produced by Aspergillus niger culture in 5-liter fermentor was isolated and purified by ion-exchange chromatography on DEAE Sepharose (fast flow) column, hydrophobic interaction on phenyl-Sepharose column and chromatofocusing on PBE 94 column. Some physico-chemical properties of two purified catalase forms were also determined (molecular weight, isolelectric point, polysaccharides contents, Km, and Ea).
Asunto(s)
Aspergillus niger/enzimología , Catalasa/aislamiento & purificación , Cromatografía por Intercambio Iónico/métodos , Catalasa/metabolismo , Calor , Concentración de Iones de Hidrógeno , Punto Isoeléctrico , Cinética , Peso Molecular , EspectrofotometríaRESUMEN
The production of gluconic acid, extracellular glucose oxidase and catalase in submerged culture by a number of biochemical mutants has been evaluated. Optimization of stirrer speed, time cultivation and buffering action of some chemicals on glucose oxidase, catalase and gluconic acid production by the most active mutant, AM-11, grown in a 3-L glass bioreactor was investigated. Three hundred rpm appeared to be optimum to ensure good growth and best glucose oxidase production, but gluconic acid or catalase activity obtained maximal value at 500 or 900 rpm, respectively. Significant increase of dissolved oxygen concentration in culture (16-21%) and extracellular catalase activity were obtained when the traditional aeration was employed together with automatic dosed hydrogen peroxide.
Asunto(s)
Aspergillus niger/metabolismo , Catalasa/biosíntesis , Gluconatos/metabolismo , Glucosa Oxidasa/biosíntesis , Aspergillus niger/genética , Aspergillus niger/crecimiento & desarrollo , Reactores Biológicos , Medios de Cultivo , Vidrio , Glucosa/metabolismo , Peróxido de Hidrógeno/metabolismo , Mutación , Oxígeno/farmacología , Silicatos , Hidróxido de Sodio/metabolismoRESUMEN
After mutagenization and selection, mutant Aspergillus niger strains resistant to certain agents were obtained. Seven of the mutants showed increased extracellular glucose oxidase (GOD), the level for individual cases ranged widely from 8.8 to over 138.5% in comparison with the parental strain. Studies of the relationship between method of selection and frequency of mutation showed that the highest frequency of positive mutations (15.8% and 17.3%) was obtained from mutants resistant to ethidium bromide (1 mmol l-1 and sodium gluconate (45%), respectively. The time course of growth and enzyme production by the most active mutant AM-11 showed intra- and extracellular GOD activities to have increased about 2.2- and 2.4-fold, respectively, compared with the parental strain.
Asunto(s)
Aspergillus niger/enzimología , Glucosa Oxidasa/biosíntesis , Aspergillus niger/genética , Aspergillus niger/crecimiento & desarrollo , Aspergillus niger/aislamiento & purificación , Medios de Cultivo , MutaciónRESUMEN
The production of extracellular catalase in a submerged culture by a number of biochemical mutants has been evaluated. Eight of these mutants showed increased extracellular catalase, the level of which ranged widely in individual cases from 44% to over 94% in comparison with the parental strain. Studies of the relationship between a criterion of selection and the frequency of mutation showed that the highest frequency of positive mutations (15.8% and 24.2%) was obtained with respect to mutants resistant to ethidium bromide (1 mmol/l) and sodium gluconate (45%) respectively. The time course of growth and enzyme production by the most active mutant, AM-20, showed extra- and intracellular catalase activities increasing about 2- and 2.6-fold respectively, compared with the parental strain.
Asunto(s)
Aspergillus niger/enzimología , Catalasa/biosíntesis , Glucosa Oxidasa/metabolismo , MutaciónRESUMEN
The effect of some medium components, viscous substances and metabolic inhibitors, on catalase production by mutant Aspergillus niger has been studied in shake culture. Altering the composition of the basal medium, particularly substituting NaNO3 for KNO3, and peptone for yeast extract brought an increase in extra- and intracellular catalase activity by 1.5- and 3-fold, respectively. The addition of 2.0-6.0 mg sodium alginate or pectin/ml as viscous additive to the medium, containing glucose as carbon source, increased the medium viscosity and catalase production in shake culture by about 2.8- to 3.0-fold. The highest yield of extracellular catalase activity of A. niger was obtained in the presence of sodium orthovanadate and Triton X-100, which improved the activity of this enzyme by about 1.5-2.2-fold. A significant increase in intracellular catalase activity was observed in the presence of hematin, Tween 80 and sodium orthovanadate (1.7-, 1.6- and 1.4-fold respectively). The time course of growth and enzyme production by A. niger in the optimized medium is also reported.
Asunto(s)
Aspergillus niger/enzimología , Aspergillus niger/metabolismo , Catalasa/metabolismo , Alginatos/metabolismo , Aspergillus niger/crecimiento & desarrollo , Medios de Cultivo/metabolismo , Glucosa/metabolismo , Hemina/metabolismo , Nitratos/metabolismo , Octoxinol/metabolismo , Pectinas/metabolismo , Peptonas/metabolismo , Polisorbatos/metabolismo , Compuestos de Potasio/metabolismo , Vanadatos/metabolismoRESUMEN
Factors affecting the beta-galactosidase production by Penicillium notatum 1 were studied using fermentation media of different chemical composition. The medium containing lactose, salts, peptone and yeast extract with initial pH 2.5 was selected as the best for enzyme production. Monobasic ammonium phosphate (0.9%) was found to be the best inorganic nitrogen source for lactase production. Various extraction media and metabolic inhibitors were examined for effective releasing of beta-galactosidase from the fungal cells. Using a simple method of mycelium extraction with 0.1 Triton X-100, it was possible to obtain about 4-fold higher amounts of enzyme in the cell free extracts, than those excreted into the post-culture liquid.
Asunto(s)
Penicillium/enzimología , beta-Galactosidasa/biosíntesis , Medios de Cultivo , Penicillium/crecimiento & desarrolloRESUMEN
The effect of some medium components and metabolic inhibitors on glucose oxidase (GOD) production by mutant Aspergillus niger was studied in shaken culture. Altering the composition of the basal medium, particularly substitution of (NH4)2HPO4 for NaNO3, and lack of Mg2+ ions caused an increase in GOD activity by 269.6%. The highest yield of extracellular GOD activity of A. niger mycelium was obtained in the presence of hematin (1 mM), choline (40 mM) and Tween 80 (0.1%), which improved the activity of this enzyme by about 31.4-53.9%. A significant increase (68.3%) in intracellular GOD activity was found in the presence of sodium orthovanadate (1 mM). The time course of growth and enzyme production by A. niger in the optimized medium is also reported.