Succinic acid production by repeated batch fermentation based on high density culture was studied.The result showed that E.coli could convert glucose to succinic acid in aqueous solution of glucose and a neutralizer.When cell density increased approximately to 28 g·L-1(DCW)

the aerobically grown cells were directly brought into anaerobic conditions.Glucose concentration was maintained at about 10 g·L-1 with constant flow feeding.Cells were recycled from final fermentation broth for the next batch of repeated fermentation when the last fermentation was stopped at 30 h .After two-stage fermentation and two cycles of cell reincubation

the concentration of succinic acid was 95.1 g·L-1

79.7 g·L-1 and 64.4 g·L-1 respectively.The average succinic acid yield and productivity were 72.5% and 1.93 g·L-1·h-1 respectively

with an increase of 29.5% and 25.9%

compared with those in the two-stage fermentation .