Modeling of a bioreactor for the fermentation of palmwine by Saccaharomyce cerevisiae (yeast) and lactobacillus (bacteria)

Abstract

A batch reactor model for the fermentation of palm wine to ethanol and acetic acid has been developed. The kinetics of alcohol and acetic acid production from palm wine was carried out in a laboratory scale experimental batch reactor. 1.5 liters of palm wine was reacted with yeast (Saccharomyce cerevisiae) strain for 12 hours for alcohol production, after which bacteria (lactobacillus) was introduced for another 12 hours for acetic acid production. Biomass, ethanol, acetic acid, and glucose concentrations were sampled every 2 hours. A monod type cell growth kinetic model that accounts for product inhibition was used to approximate the fermentation process. Experimental model fitting technique was used to estimate the kinetic parameters in the model. The reactor models developed were a set of coupled ordinary differential equations and were integrated numerically using the 4 th order runge kutta technique. The model equations predicted the experimental results of the concentration of substrate utilized, biomass and products produced accurately with a maximum deviation of 0.402%, hence the models were used for the batch reactor simulation. The effects of initial substrate and biomass concentration on reactor efficiency were investigated.