ABSTRACT
The continuous production of polygalacturonases [PGases] that Exo-polygalacturonase [exo-PGase] and Endo-polygalacturonase [endo-PGase] are two members of this group by a strain of Aspergillus awamori in surface culture fermentation was investigated. Surface culture fermentation is usually done in batch mode. Wheat flour acted as a good substrate for the cultivation of the fungus and production of PGases in surface culture fermentation. Fermentation started in batch mode until mycelia completely occupied the medium following growth of the microorganism, after which it was turned to the continuous mode by the introduction of fresh feed. The process continued for 34 days, and the thickness of the microbial layer on the surface of the liquid medium became almost constant after approximately one week. The production of PGases, however, continued throughout the experiment, and maximum activities of 1.2 U/ml and 0.014 U/ml were obtained for exo-polygalacturonase [exo- PGase] and endo-polygalacturonase [endo-PGase], respectively. An increase in production was observed when a similar system was used with a line for medium recycling. Lowering the residence time to 12 h decreased the exo-PGase and endo-PGase activities. Reducing the residence time from 24 h to 12 h almost halved the concentrations of the enzymes at the outlet