Experimental devices for stimulating productivity of lactic acid fermentation were installed and a level meter was used to control the volume of fermentation broth. Experiments were carried out by means of continuous EDF with feed medium. It was verified that 175 g/L of glucose concentrations in the feed medium was the best value. In this case, the continuous EDF lasted for above 350h and was stable for above 200 h. The maximum productivity, yield and conversion ratio were 8.18 g/L h, 69.8% and 71%, respectively. Compared with other EDFs. the continuous EDF with a level meter had the highest productivity and produced 2637 g of lactic acid from 4000 g of glucose. The amount of lactic acid produced was, due to the longest fermentation time and the highest productivity, about 19.5 times greater than that of the conventional EDF and was about 9.7 times greater than that of the intermittent EDF. The glucose, however, began to be excessive in fermentation broth after 200 h, resulting in a decrease of lactic acid production. (C) 2004 Elsevier Ltd. All rights reserved.