Continuous Primary Beer Fermentation with Brewing Yeast Immobilized on Spent Grains

Abstract

This work demonstrated the technological feasibility of the three-phase airlift bioreactor (ALR) with brewing yeast immobilized on spent grains (a brewing by-product) for continuous beer production. The optimum fermentation performance of the one stage immobilized cell bioreactor was achieved at residence times between 18-25 h (dilution rate 0.04-0.055 h -1 ) and was characterized by an apparent degree of attenuation in the range of 70-80%. The productivity of the system in terms of ethanol concentration in green beer (ca. 4.2%) was satisfactory. Although the diacetyl concentration in the young beer was high (0.32 mg L -1 at D = 0.04 h -1 ) it is speculated that the level could be reduced by cell growth control, aeration and temperature optimisation. The immobilized yeast fermentation in the ALR was shown to be robust in recovery after process upsets.

High Gravity Brewing by Continuous Process Using Immobilised Yeast: Effect of Wort Original Gravity on Fermentation Performance

“…100 g) it appears that the ratio between immobilised cells and free cells in the reactor (X immob /X free ) was highest (1.8) with the 13.4°Plato wort. This value is in agreement with the ratio found in a one-stage airlift bioreactor system 5 . From the 15.3 and 16.6°Plato worts the immobilised/free cell ratio was almost the same (1.1), but when the 16.6°Plato wort was replaced by the 18.5°Plato wort, X immob /X free was the lowest (0.6).…”

“…A similar trend was observed by Virkajärvi et al 38 during the continuous fermentation of high-gravity and very-highgravity worts ranging from 15 to 24°Plato. The ADF and RDF obtained in the present work for the 13.4°Plato wort also resembled those previously attained with an airlift reactor system using BSG as the carrier 5,6 . Notwithstanding, the RDF (56.8%) obtained for the highest gravity wort was lower than that found for a one-stage tubular bioreactor with yeast immobilised in porous glass beads (65%) 38 .…”

“…Recent studies [4][5][6] have demonstrated the feasibility of continuous primary fermentation of all-malt worts with original gravities below 14°Plato, using brewing yeast immobilised on BSG. In these studies, the ethanol concentration in the produced green beers was lower than 5% (v/v).…”

"A comparison between sugar consumption and ethanol production in wort by immobilized Saccharomyces Cerevisiae, Saccharomyces Ludwigii and Saccharomyces Rouxii on Brewer's Spent Grain"

“…However, the support used for the to be food grade (2,4,8,9,10). Taking into the account these requirements and trying to meet a low price substrate, the spent grains, a brewing by-product with considerable cellulose content, was studied as a potential carrier for yeast immobilization (1,2,4,9,10).…”

“…Saccharomyces rouxii is one of the most osmotolerant yeasts (16,17) closely related to S. cerevisiae (16 Immobilization of S. cerevisiae has already been repeated in the literature (2,3,4,9,10,20,21,22) but no immobilization was found for the other two species.…”