Propionic acid and biomass production using continuous ultrafiltration fermentation of whey

Summary This paper presents a study of propionic acid and propionibacteria production from whey by usingPropionibacterium acidi-propionici in continuous fermentation with cell recycle. The highest propionic acid volumetric productivity achieved was 5 g.l^–1.h^–1 with no biomass bleeding. A maximal biomass concentration of 130 g.l^–1 was achieved before initiating biomass bleeding to give a biomass volumetric productivity of 3.2 g.l^–1.h^–1 with a biomass of 75 g.l^–1 and a propionic acid productivity of 3.6 g.l^–1.h^–1 (for about 100 hours i.e. more than 50 residence times).