Modeling and Simulation of Substrate and Product Inhibitions of Fermentation of Cassava ( Manihot Esculenta ) Extract

Abstract

The fermentation of cassava extracts in brewing is often hampered by microbial inhibitors and oscillations from product and substrate inhibitions, which often decrease ethanol yields. Previous evaluation of the modeling of ethanol inhibition during fermentation of cassava extracts showed low model accuracy. This low model accuracy is due to substrate inhibition, which increases process control challenges. The inhibition patterns considered in this work were linear, sudden growth stop, and exponential. Mathematical models were developed to simulate substrate and product inhibitions during the fermentation of cassava extracts for alcohol production. The results obtained showed substrate and product inhibitions exist during fermentation of cassava extracts, with inhibition patterns being linear substrate-exponential product, exponential substrate-exponential product, and linear substrate-linear product inhibitions. The obtained models are described with a high degree of accuracy (99% confidence interval). The developed models thus agree well with experimental data.