This study investigated the feasibility of improved production propionic acid-enriched volatile fatty acid (VFA) from high concentration (C-s) of food waste and waste activated sludge (WAS) via lactic acid pathway by using of Propionibacterium acidipropionici. It was observed that production of L-lactate overwhelmed to D-lactate at first stage, which improved from 3.21 to 35.45 g COD/L with increase of substrate C-s. However, kinetic model analysis indicated that P. acidipropionici growth rate mu(max) was decreased with increase of L-lactate concentration, which explained second stage free cell fermentation of propionic acid was inhibited when fed by first stage liquid from R-40, R-55 and R-70. Then, the fibrous bed bioreactor was employed to eliminate the feed inhibition. The maximal percentage of propionic acid (68.3%) and production (16.31 g COD/L) was obtained by feeding liquid of R-55, which was improved by 3.33 folds compared to the free cell fermentation. (C) 2016 Published by Elsevier Ltd.