| Abstract: | The productivity of growth associated fermentations is dependent upon the quantity of biomass contained in the fermenter (microbial hold-up). In contrast, the performance characteristics of a fermenter are dominated by the form in which the microbial hold-up occurs, i.e., whether as films, flocs, or a combination of both. Industrial fermentations using biological films include biological waste-water treatment (trickling filter, rotating disc), the “quick” vinegar process, animal tissue culture, and bacterial leaching. Atkinson and Davies (Trans. Inst. Chem. Eng., 50 , 208 (1972)), proposed a completely mixed microbial film fermenter (CMMFF) based upon the fluidized bed principle, for application to continuous operation when using growth associated systems. The potential performance characteristics of this fermenter are reviewed and the construction of a laboratory scale unit capable ofaseptic operation is described (volume 9 liters, maximum throughput 15 liter/hr). The fermenter has been continuously used for periods up to 2500 hr without contamination when growing brewer's yeast (NCYC 1026 flocculating). The experimental performance characteristics have been interpreted with the aid of the theory for the CMMFF. The knowledge and experience gained to date is used as a basis for speculation as to the future role of microbial film fermenters in the biochemical process industries. |
