Effects of glycerol on alcohol fermentation. Inhibition mechanism and diffusion limitations

Research paper by A. Converti, M. Zilli, M. Rovatti, M. Del Borghi

Indexed on: 01 Oct '95Published on: 01 Oct '95Published in: Bioprocess and Biosystems Engineering


Batch alcohol fermentations have been carried out varying the starting level of glycerol in the broth and keeping constant all the other fermentation parameters, in order to study the effect of the accumulation of this metabolite on the fermentation kinetics. A linear slow decrease of the maximum specific ethanol productivity with increasing glycerol level has been followed by a sharp fall of this parameter over a glycerol concentration threshold. A kinetic study through unstructured integrated models demonstrates that, at low concentrations, glycerol behaves as a non competitive inhibitor of fermentation, while, over a concentration threshold (105 kg/m3), an additional effect takes place, likely ascribable to diffusion limitations provoked by excess viscosity of the broth.