Kinetic model and study of the influence of pH, temperature and undissociated acids on acidogenic fermentation

Acidogenic fermentation is a technology able to produce hydrogen and volatile fatty acids in friendly environmental way. Because of that, it is important to improve the knowledge in this area. In this work, glucose batch fermentations were carried out by a mixed culture at different pH (4, 5, and 6 units) and temperatures (26, 33 and 40 °C). These operating conditions caused an important effect on the fermentation process, such as inhibition of cell growth and substrate consumption. From these results, the critical undissociated acid concentration that caused important shifts in biomass growth and substrate consumption was found. A mathematical model was fitted to the experimental results, and it was observed that the undissociated acid concentrations affected the fermentation in an exponential way, being the process more sensitive when temperature was high. The energy required for cell maintenance increased when pH was low and temperature was high. The specific growth rate increased as pH and temperature increased. Moreover interesting relationships were found between kinetic parameters.

► Acidogenic fermentation of glucose was studied. ► A model describing the kinetics of the fermentation was developed. ► The model developed predicted accurately the fermentation process taking into account the pH, temperature and undissociated acids concentration.