Pectinase production profile of Aspergillus foetidus in solid state culture at different acidities

CAVALITTO, SEBASTIÁN FERNANDO; ARCAS, JORGE ALFREDO; HOURS, ROQUE ALBERTO

BIOTECHNOLOGY LETTERS

Chapman & Hall

Lugar: London; Año: 1996 vol. 18 p. 251 - 256

0141-5492

Solid-state cultures of a pectinase-producing fungus (Aspergillus foetidus NRRL 341) were performed under different acidic conditions. Glass bottles containing 5 g of wheat bran and 7.5 mL of 0.2, 0.3, 0.4, or 0.5 N HCl were autoclaved (15 min, 121°C), inoculated with a spore suspension appropriately diluted to achieve an initial concentration of 4 x 104 spores per gram of wet substrate (with a 60 % humidity, on wet basis) and incubated at 30°C. Time course of pH and of different pectinase activities were determined in culture extracts. Total pectinase activity (TPA), expressed in terms of viscosimetric units per gram of wet substrate (VU . g-1) was affected by the initial culture acidity. The higher the HCI concentration used, the higher the TPA achieved, but after longer cultivation times. On the other hand, when 0.5 HCI was used, no fungal growth was observed Nevertheless, enzyme productivity increased with culture acidity. When 0.4 HCl was used, TPA reached its maximum after 36 h of cultivation (2,535 VU.g-I). With 0.2 and 0.3 N HCl, TPA was the highest at 24 h (733 VU.g-1) and at 30 h (1,860 VU.g-1) respectively. The composition of the pectinase pool was also affected by culture acidity. The higher the acidity, the lower the pectinesterase activity and the higher both the polymethylgalacturonate lyase and polygalacturonase activities.