General objectives In most fermented milks and other dairy drinks, the milk sugar, lactose, is only partly fermented by the starter bacteria. This makes this fermented product an unsuitable part of the diet for the many people who suffer from lactose-intolerance. One subtask is aiming at complete removal of lactose from fermented milk products by increasing the efficiency of lactose utilisation in Lactococcus lactis. A second, objective is to modify lactose metabolism in L. lactis in such a way that the glucose moiety will end up in the product, while galactose will be fully used for growth, in this way providing a natural sweetening process for dairy products. Some fermented dairy products, especially yoghurt and yoghurt-like products, contain significant amounts of galactose. This is a result of incomplete lactose utilisation by the lactic acid bacteria. Consumption of (too much) galactose, especially in combination with alcohol, can create serious health problems in individuals (i.e. cataract stimulation). For this reason strains of Streptococcus thermophilus and Lactococcus lactis will be constructed which have an improved galactose fermenting capacity, and should be able to use low concentrations of galactose in the medium, thereby reducing its final concentration in dairy products to a minimum.