USE OF A FLEXIBLE SPONGE MATRIX TO IMMOBILIZE YEAST FOR BEER FERMENTATION

The use of a flexible spongelike material to immobilize Saccharomyces cerevisiae has been investigated. The open porous network of the sponge provides for extensive and rapid surface attachment throughout the depth of the material. Rate and level of entrapment was related to a strain's flocculation ability. The surface of the matrix can be chemically modified, and it was found that basic characteristics enhanced both initial rate of uptake and final loading (in excess of 10(9) cells per gram [wet weight] of sponge). Beer fermentations conducted with immobilized yeast indicated a route to enhancing rate of fermentation. Continuous circulation of fermentation medium through columns containing both weakly basic and neutral sponge decreased batch fermentation time, possibly aided by sponge-enhanced CO2 removal from solution. Repeated use of the immobilized yeast showed no fall-off in viability over 31 days.