Brewing by Immobilized Freeze Dried Cells in a Novel Gas Flow Bioreactor

Abstract

The aim of this study was to examine the novel gas-lift three phase bioreactor with external loop in beer fermentation by immobilized yeast cells on gluten pellets. Cells of Saccharomyces cerevisiae were immobilized on 40 g of gluten pellets, freeze-dried and introduced into a 1.4 L external loop gas-lift bioreactor with 1.1 L of wort. During the fermentation process, nitrogen was inserted in the bioreactor. Several batch repetitive fermentation processes were performed at different temperatures (5, 10 and 20 degrees C). The kinetics of fermentation and beer productivity were determined. Relatively high cell concentrations and presumably, good mass transfer rates in the flowing medium enabled rapid fermentation (48 h fermentation time at 20 degrees C) and high beer productivity of this system, even with such low load of immobilised biocatalyst (3.6% w/w). Further, the final beer product was analyzed on ethanol and volatile compounds important for the organolaptic profile. Contents of ethanol and flavour compounds were in the ranges characteristic for beers of acceptable to fine quality. In addition, preliminary tests on hydrodynamic characteristics of the external loop gas-lift bioreactor were done, providing important information for potential establishing and standardization of this type of fermentors for beer production in prospect.