Impact of Three Different Immobilization Techniques on Batch Fermentation Performance and Substrate Inhibition

This paper is focused on comparing three different immobilized yeast fermentations performance and impact of substrate inhibition on the process. The yeast used for this study was a brewing strain of Saccharomyces cerevisiae. The immobilization techniques used were: entrapment and capsulation method in alginate and immobilization in gelatin structure. Objective of this study was to make a comparison in terms of specific growth rate of microorganisms and kinetic constants.  Fermentations were performed also in different substrate concentrations to study substrate inhibition effect. Fermentations were carried out on beer wort in constant conditions. As a result we conclude that the capsulated yeast fermentation was almost similar to the free cell process. Substrate inhibition effect was stronger on high concentration substrate fermentation but was noticed a reduced effect of substrate inhibition on immobilized yeast fermentation process compared to free cell performance, as a result of a reduced diffusion effect due to support matrix.(Key words: Fermentation rate, Immobilized yeast, Entrapment, Capsulation, Gel immobilization, Substrate inhibition effect)