BIOTRANSFORMATION OF GLUCOSE TO FREE GLUCONIC ACID BY GLUCONOBACTER-OXYDANS - SUBSTRATE AND PRODUCT INHIBITION SITUATIONS

Microbial oxidation of glucose to free gluconic acid by Gluconobacter oxydans batch cultures was studied with a special reference to substra te and product inhibition. Process kinetics were evaluated by comparin g different inhibition models. Substrate inhibition can be best descri bed by the equation of Tseng and Wayman predicting linear inhibition o f growth above a characteristic threshold glucose concentration. Non-l inear inhibition kinetics was observed, however, for product inhibitio n and the model of Levenspiel was found to fit the experimental data. The biokinetic model parameters, productivities and conversion degrees on media with different glucose and gluconic acid concentrations were calculated and compared regarding the principal limits of process eff iciency. Probable mechanisms of inhibition and possible techniques for their minimization are also discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.