Construction of a lactose-assimilating strain of baker's yeast

A recombinant strain of baker's yeast has been constructed which can assimi late lactose efficiently. This strain has been designed to allow its propag ation in whey, the byproduct resulting from cheese-making. The ability to m etabolize lactose is conferred by the functional expression of two genes fr om Kluyveromyces lactis, LAC12 and LAC4, which encode a lactose permease an d a beta-galactosidase, respectively. To make the recombinant strain more a cceptable for its use in bread-making, the genetic transformation of the ho st baker's yeast was carried out with linear fragments of DNA of defined se quence, carrying as the only heterologous material the coding regions of th e two K. lactis genes. Growth of the new strain on cheese whey affected nei ther the quality of bread nor the yeast gassing power. The significance of the newly developed strain is two-fold: it affords a cheap alternative to t he procedure generally used for the propagation of baker's yeast, and it of fers a profitable use for cheese whey. Copyright (C) 1999 John Wiley & Sons , Ltd.