Leuconostoc mesenteroides NRRL B-1299 dextransucrase production by sucrose fermentation has been studied and compared with that of a more frequently studied strain of L. mesenteroides : strain NRRL B-512F. Regulation of pH and aeration conditions have little effect on the culture profile and enzyme production by strain B-1299 in contrast to the other strain. Moreover, while feedbatch culture experiments result in a significant improvement of dextransucrase activity with strain B-512F, it was not the case with strain B-1299. When sucrose residual concentration is maintained at a high level by fedbatch technique, a large proportion of the sucrose is consumed by the enzyme to produce dextran. This results in a low enzyme yield. This limited enzyme production could also be attributed to a negative effect of fructose and mannitol accumulation. This can be prevented by addition of low concentrations of glucose (<8 g l(-1)). The use of glucose and sucrose as cosubstrates in a fedbatch reactor experiment makes it possible to improve B-1299 final dextransucrase activity up to 9.7 U ml(-1).