Nisin production in batch culture and fed-batch cultures ( sucrose feeding rates were 6, 7, 8, and 10 g l(-1) h(-1), respectively) by Lactococcus lactis subsp. lactis ATCC 11454 was investigated. Nisin production showed primary metabolite kinetics, and could be improved apparently by altering the feeding strategy. The nisin titer reached its maximum, 4,185 IU ml(-1), by constant addition of sucrose at a feeding rate of 7 g l(-1) h(-1); an increase in 58% over that of the batch culture ( 2,658 IU ml(-1)). Nisin biosynthesis was affected strongly by the residual sucrose concentration during the feeding. Finally, a mathematical model was developed to simulate the cell growth, sucrose consumption, lactic acid production and nisin production. The model was able to describe the fermentation process in all cases.