Four-compartment configuration electrodialyzer was employed to recover and concentrate lactic acid from kitchen garbage fermentation broth that contains mainly ammonium lactate and reducing sugar. Some parameters were examined under different processes of electrodialysis, such as the changes of lactic acid concentration, pH, the recovery ratio of lactic acid, the electric current efficiency and the permeation ratio of reducing sugar. The recovery ratio of lactic acid was over 89.5% in the case of 12-h electrodialysis under 2.0 A dm(-2) cur-rent density, whereas the permeation ratio of reducing sugar and ammonia was less than 0.97 and 0.15%, respectively. Under this condition, the average current efficiency was over 93%, and concentration of lactic acid in permeate solution after electrodialysis increased by about 2.2-fold than that in feed solution. Furthermore, when lactic acid was fed at intervals, the concentration of lactic acid in permeate solution was increased by 5.1-fold, which was up to 162.8 g dm(-3). The results of experiments indicate that the ammonium lactate in the fermentation broths can be conversed into lactic acid, and the lactic acid can been recovered and concentrated by four-compartment configuration electrodialyzer. (C) 2005 Elsevier Ltd. All rights reserved.