Kefir-yeast technology: Industrial scale-up of alcoholic fermentation of whey, promoted by raisin extracts, using kefir-yeast granular biomass

Industrial scale-up of whey fermentation, promoted by raisin extracts, using free kefir-yeast cells is reported. The fermented whey would be exploited as raw material to produce kefir-like whey-based drinks, potable and fuel alcohol, as well as kefir-yeast biomass for use as baker's yeast. The scale-up process involved the development of a technology transfer scheme from lab-scale experiments to a successive series of increased capacity bioreactors (100, 3000 and 11,000 L). The development of this technology was supported by the six-fold promotion of whey fermentation by the addition of 1% black raisin extracts (optimum concentration found in this investigation), as well as by the formation of kefir-yeast in the form of easily precipitated granular biomass that led to the avoidance of centrifugal separators, which are equipment of high cost. A cost analysis showed a big reduction of the production cost of the aforementioned products in comparison with the market prices, attributed to the negligible cost of raw materials (whey) and the granular biomass formation.