The present work reports the effect of simple feeding strategies to obtain high-cell-density cultures of Kluyveromyces marxianus maximizing beta-galactosidase productivity using cheese whey as basic medium. Linear and exponential feeding strategies, with feeding times of 20, 25 and 35 h, and three different feeding media concentrations (140 g/L, 210 g/L, and 280 g/L lactose concentration), were tested. Final biomass concentration reached 35 g cells dry weight/L and our results showed that continuous lactose addition to culture were able to produce high specific enzyme activities, consequently improving volumetric activities of beta-galactosidase when compared to batch cultivations. The best fed-batch strategy, which was the feeding of three-fold lactose concentration in the cheese whey-medium during 25 h, resulted in beta-galactosidase productivity of 291 U/L h, representing an increase of more than 50% compared to batch cultivations. (C) 2007 Elsevier Ltd. All rights reserved.