Immobilization of yeast on delignified cellulosic material for low temperature brewing

A biocatalyst was prepared by immobilization of Saccharomyces cerevisiae strain AXAZ-1 on delignified cellulosic (D.C.) material and studied in the fermentation of wort for batch and continuous brewing. The immobilized yeast gave an important operational stability without decrease of its activity, even at low temperatures (0-5 degrees C), compared with free cells. Batch fermentations at various temperatures were faster than those of free cells and those usual in commercial brewing. A traditional bottom fermentation takes 8-10 days. Specifically, at 0 degrees C, the fermentation rate was 4-5 times higher than that of free cells. Diacetyl and polyphenol contents as well as bitterness and pH were lower than those when free cells were used for fermentations; at 0 degrees C, polyphenol content was similar to 30% and bitterness 50% of the values noted when free cells were used for fermentations. The alcohol concentration at 0 degrees C was similar to 20% higher than that of free cells. The continuous system was operated continuously for 3 months with relatively high productivity. However, polyphenols and bitterness were higher than those obtained in batch fermentations with immobilized cells. Preliminary taste tests indicated that the beer produced by the immobilized cell process had an acceptable clarity, aroma, and taste.