From the fusion between Lactobacillus casei and Lactobacillus acidophilus, 8 fusants were selected : Four were able to ferment maltose, lactose, galactose and mannose, but two had greater abilities of acid production than parents. Increased values of up to 7.6-8% in beta-galactosidase activity were obtained from two when compared to that of L. acidophilus, whereas another 2 had activities of 800 and 548 nmol/mg protein/min comparable to that of L. casei giving a value of 400 nmol/mg protein/min in phospho-beta-galactosidase activity.