ENZYME-PRODUCTION IN A CELL RECYCLE FERMENTATION SYSTEM EVALUATED BY COMPUTER-SIMULATIONS

Enzyme production in a cell recycle fermentation system was studied by computer simulations, using a mathematical model of alpha-amylase pro duction by Bacillus amyloliquefaciens. The model was modified so as to enable simulation of enzyme production by hypothetical organisms havi ng different production kinetics at different fermentation conditions important for growth and production. The simulations were designed as a two-level factorial assay, the factor studied being fermentation wit h or without cell recycling, repression of product synthesis by glucos e, kinetic production constants, product degradation by a protease, mo de of fermentation, and starch versus glucose as the substrate carbon source. The main factor of importance for ensuring high enzyme product ion was cell recycling. Product formation kinetics related to the stat ionary growth phase combined with continuous fermentation with cell re cycling also had a positive impact. The effect was greatest when two o r more of these three factors were present in combinations, none of th em alone guaranteeing a good result. Product degradation by a protease decreased the amount of product obtained; however, when combined with cell recycling, the protease effect was overshadowed by the increased production. Simulation of this type should prove a useful tool for an alyzing troublesome fermentations and for identifying production organ isms for further study in integrated fermentation systems.