The effect of controlled pH and dissolved oxygen (DO) tension on the production of total glucosyltransferase activity (GTF), extracellular GTF and alternansucrase was studied in controlled batch fermentations of Leuconostoc mesenteroides NRRL B-1355. Controlled aeration had a positive effect on the production of extracellular GTF in pH-uncontrolled fermentations. An aerated batch fermentation controlled at 90% DO at controlled pH 6.7 resulted in complete utilisation of the carbon source. At controlled pH 5.5, maximal extracellular GTF (0.6 U cm(-3)), total GTF (3.4 U cm(-3)) and alternansucrase activities (1.2 U cm(-3)) were higher in a controlled aerated (75% DO) batch fermentation than in a non-aerated batch fermentation. Acetic acid production was lowest in the non-aerated fermentation process. Controlled DO batch fermentations carried out at pH 5.5, 6.0 and 6.5 resulted in an increasing energy efficiency. While highest alternansucrase activity (1.5 U cm(-3)) occurred in pH 6.5 controlled batch cultures, the highest total GTF activity (3.4 U cm(-3)) was found in the pH 5.5 controlled fermentation.