Extracellular and cell-associated forms of Gluconobacter oxydans dextran dextrinase change their localization depending on the cell growth

Gluconobacter oxydans ATCC 11894 produces dextran dextrinase (DDase, EC 2.4.1.2), which synthesizes dextran from the starch hydrolysate, dextrin and is known to cause ropy beer. G. oxydans ATCC 11894 was believed to possess both a secreted DDase (DDext) and an intracellular DDase (DDint), expressed upon cultivation with dextrin and glucose, respectively. However, genomic Southern blot, peptide mass fingerprinting and reaction product-pattern analyses revealed that both DDext and DDint were identical. The activity in the cell suspension and its liberation from the spheroplast cells indicated that DDint was localized on the cell surface. The localization of DDase was altered during the culture depending on the growth phase. During the early growth stage, DDase was exclusively liberated into the medium (DDext), and the cell-associated form (DDint) appeared after depletion of glucose from the medium.