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. (C) 2007 Elsevier Inc. All rights reserved.