Abstract
Six Aspergillus niger strains isolated from semi-desert of Coahuila State (Mexico) were screened for an extracellular catalase (CAT) and glucose oxidase (GOX) production using solid-state and submerged fermentations. The best enzymes producer, A. niger ASPN 1.1, was selected for enzymes production under submerged fermentation condition. The higher activity was observed at 24 and 48 h of submerged fermentation, respectively. The enzymes were partially purified to a yield of 98 and 48%, and fold 9.8 and 5, corresponding to specific activity of 589.60 and 0.60 U/mg, respectively for CAT and GOX, using ultrafiltration with 100 kDa filter. The enzymes showed high affinity for H2O2 and D-glucose with a Km value of 80 and 4.24 mM, respectively. Both enzymes exhibited a greater catalytic activity at pH 6. Optimum temperature for glucose oxidation was 50°C, while for peroxide decomposition, it was 45°C. The enzymes showed a high thermostability at 50°C with a half-life time of 99 and 86 min, respectively, for GOX and CAT. These characteristics suggest the use of xerophytic A. niger strain as a potential producer for both enzymes, which have analytical and industrial application. Key words: Catalase, glucose oxidase, xerophytic, Aspergillus niger.
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