Mixed culture fermentations containing a dextranase-producing yeast, Lipomyces starkeyi, and a dextransucrase-producing bacterium, Leuconostoc mesenteroides, produced dextrans of selected size using sucrose and starch. Dextran and starch hydrolyzates, produced by a Lipomyces starkeyi dextranase and amylase, were incorporated into the dextran and formed small size dextran (Mr = 40kDa). The yields of total and clinical dextran in mixed culture fermentation using 12% sucrose and 3% starch were higher, 84 and 79% of theoretical yield, than those using 15% sucrose only, 73 and 69% of theoretical yield, respectively.