The production of intracellular dextran dextrinase (DDase) by Gluconobacter oxydans ATCC 11894 was studied in fermentations with various carbon and nitrogen sources. Glycerol and mycological peptone resulted in highest enzyme yields. The effect of glycerol concentration, mycological peptone concentration and initial pH on DDase production was investigated by means of a five-level three-factor central composite rotatable design (CCRD). Only the peptone concentration showed a significant linear main effect on enzyme production. Optimum fermentation parameters were 20.59 g/l of glycerol, 6.67 g/l of mycological peptone and an initial pH of 6.14. The predicted DDase yield was 0.207 U/ml, whereas an actual experimental value of 0.208 +/- 0.025 U/ml was obtained. (C) 2003 Elsevier Ltd. All rights reserved.