Continuous whey fermentation using kefir yeast immobilized on delignified cellulosic material.

Abstract

Delignified cellulosic-supported biocatalyst, prepared by immobilization of kefir yeast on delignified cellulosic material (DCM), was found to be suitable for continuous, modified whey fermentation. The modified whey contained 1% raisin extract and molasses. Ethanol productivities ranged from 3.6 to 8.3 g L(-1)day(-1), whereas parameters such as ethanol concentration, residual sugars, and daily fermented whey productivity were acceptable for the production of potable alcohol and alcoholic drinks in industrial fermentations. The continuous fermentation bioreactor was operated for 39 days, stored for 18 days at 4 degrees C, and operated again for another 15 days without any diminution of the ethanol productivity. The concentrations of higher alcohols (propanol-1, isobutyl alcohol, and amyl alcohols) were low. The main volatile byproducts formed in the continuous process were similar to those observed in alcoholic beverages, and the fermented whey had a good aroma. The concentrations of higher alcohols were very low when compared to that of ethyl acetate, therefore resulting in a quality product. The possibility of using such a process for the production of potable alcohol or a novel, low-alcohol content drink is proposed.