Influence of medium composition and pH on the production of polygalacturonases by Aspergillus oryzae

A liquid medium containing wheat bran, salts and a source of inducer (pectin) was found to be suitable for the production of exo- and endo-polygalacturonases by Aspergillus oryzae CCT3940. Induction of polygalacturonases by purified pectin was significantly higher than when rinds of citrus fruits were used as inducer A. oryzae growth was favoured by pH close to 4, although a drop of pH to around 3 was needed for enzymes production. Afterwards, decreasing activities were, observed with the normal increase in pH to near neutrality. The highest activities were achieved with an initial pH of 4 and controlled when it decreased to a value slightly below 3 (159 units endo-PG.mL(-1) at 83 h and 45 units exo-PG.mL(-1) at 64 h), being the loss in polygalacturonases activities strongly reduced at this condition. The best values of pH and temperature for the action of exo-PG (4.5/57degreesC) and endo-PG (4.3/40degreesC) were assessed.