Propionic acid production by whole cells of Propionibacterium freudenreichii

The microbial production of propionic acid by Propionibacterium freudenreic hii NCIM 2111, has been studied in this communication. Shake-flask studies were carried out to determine the optimum combination of various process pa rameters like stab age, inoculum age, inoculum level, medium constituents, temperature, and the initial pH for maximizing the production of propionic acid by using central composite design method. The system was found to exhi bit product inhibition and hence the product inhibition kinetics was studie d. A two parameter kinetic model, taking into account of the product inhibi tion, was proposed. Leudeking and Piret model was used to describe the prod uction kinetics. The result from the shake-flask studies were compared with that obtained from mechanically stirred batch bioreactor and total recycle batch bioreactor.