CALORIMETRIC INVESTIGATIONS ON MICROBIAL ACETIC-ACID PRODUCTION

Acetic acid production by an Acetobacter aceti strain was studied to obtain a kinetic model, useful to describe microbial growth and ethanol bio-oxidation. The process was investigated using conventional techniques (viable cells count, ethanol consumption, acetic acid production and pH evaluation) and the data obtained were compared with those of isothermal (28 degrees C) calorimetric tests. It was therefore possible to calculate the heat involved during bio-transformation. The evolution of growth indices was made using adeguate mathematical models: microbial growth was described by means of a model constituted of two Gompertz functions, while the other indices were interpretated with a modified Gompertz function. The data show two events: the increase of biomass and the production of metabolites. The results attest the possibility of optimizing industrial processes using thermokinetic models, which allows to quantify both growth indices and their interpretation.