Аннотация:The enzyme beta-galactosidase is widely distributed in plant and animal tissues, however is extremely rare in yeasts. Due to the presence of the beta-galactosidase enzyme, dairy yeasts Kluyveromyces lactis and K. marxianus are able to ferment lactose. Polymeric LAC loci have a complex structure and consist of two closely linked structural genes LAC4 (beta-galactosidase) and LAC12 (lactose permease), and a regulatory sequence (Dickson & Riley 1989; Fairhead & Dujon 2006; Naumov 2008).