This paper addresses the production of volatile fatty acids with fermentation of whey permeate under acidogenic conditions. The coal-immobilized biomass of an anaerobic fluidized bed reactor operated with a fairly constant hydraulic residence time of 12 min transformed the substrate (whey permeate i.e., essentially lactose) into a blend of acetic, propionic, butyric and isobutyric acids corresponding to between 2 and 19, 1 and 6, 11 and 30, 0 and 2% of the initial load (carbon basis), respectively. There was a slight decrease in the sugar transformation efficiency (65 to 48%) with the increase of the organic loading rate (OLR) which varied from 586 to 3339 g sugar/Lreactord. At the highest OLR of 3339 g sugar/Lreactor.d, the biomass transformed 19% of the substrate into a blend of acetic, propionic, butyric and isobutyric acids. Residual sugar and bio-gas were 52 and 2%, respectively, of the initial load (carbon basis). Cet article fait référence L une étude sur la production d’acides gras volatiles par fermentation anaérobie du perméat de lactosérum dans un bioréacteur. La biomasse fixée aux grains de charbon composant le lit fluidisé, opérant avec un temps de rétention hydraulique de 12 minutes, transformait le substrat (perméat i.e., essentiellement lactose) en un mélange d’acide acétique, propionique, n-butyrique et isobutyrique correspondant respectivement L 2 et 19, 1 et 6, 11 et 30, 0 et 2% de la charge initiale (sur la base d’un bilan de carbone). Il a été possible d’observer une légère diminution de l’efficacité de la biodégradation du sucre (65 L 48%) avec une augmentation du taux de charge organique lequel variait de 586 L 3 339 g de sucre/Lréacteurd. L la charge organique la plus forte, soit 3 339 g de sucre/Lréacteur.d, la biomasse transformait le substrat L 19% en un mélange d’acide acétique, propionique, n-butyrique et isobutyrique. La part du sucre résiduel était de 52% et celle du biogaz L 2% (bilan de carbone).

No abstract

In this study, the formation of the biofilm and the temporal change in the bacterial composition at different whey permeate (wastewater) sugar concentrations were assessed inside a fluidized bed bioreactor. At a sugar concentration of 5 g/L, the efficiency of biodégradation was 10%, while at 20 g/L it was 3%. With time, an increase in the ATP concentration of the bacteria on the coal grains was observed, indicating biofilm formation. To estimate the biodegradation activity in the biofilm, expressed as mass of sugar biodegraded per day and per volume of support, the bacterial ATP was determined by the firefly biolu-minescent enzymatic reaction developed by Karl and Larock (1975). At sugar concentrations of 5 and 20 g/L, the ATP concentrations of the bacteria forming the biofilm were, respectively, 11.6 and 36.0 moles ATP/m3 of support, corresponding, respectively, with lactose rates of 343.7 and 515.5 kg/d m3. There were 13 species of bacteria inventoried in the bioreactor. Pseudomonas maltophilia, P. paucimobilis, P. sp., P. fluorescens, Salmonella sp., Acinetobacter calcoaceti-cus var. lwoffi, Aeromonas hydrophila/caviae, Staphylococcus hominis, S. cohnii, S. aureus, Escherichia coli, Enterobacter faecium, and a filamentous species that could be associated with the genus Methanothrix.