Ethanol production from deproteinized whey byβ-galactosidase coimmobilized cells ofSaccharomyces cerevisiae

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Abstract
The performance of β-galactosidase coimmobilized cells ofSaccharomyces cerevisiae was evaluated during shake flask fermentation of deproteinized cheese whey lactose to ethanol. The performance of the coimmobilized enzyme treatment was compared to that of a treatment using acid prehydrolyzed whey lactose (a readily available substrate). Enzyme coimmobilization resulted in a slower rate and a lower extent of substrate utilization, thus giving a lower maximum ethanol concentration (13.5 versus 16.7 g/l). It did result, however, in a better ethanol yield (95% vs. 89% theoretical). It appears that, compared to acid prehydrolysis of whey lactose, through β-galactosidase coimmobilization we could succeed in obtaining substantial process simplifications, thus saving in equipment and operating cost, while gaining in ethanol yield at the cost of some reasonable loss in the rate and the extent of lactose utilization.