Recovery and concentration of high vapour pressure bioproducts by means of controlled membrane separation.
Rückgewinnung und Konzentrierung flüchtiger Bioprodukte mittels kontrollierter Membrantrennung
This paper describes the continuous production of high vapour pressure bioproducts by coupling a membrane separator to a conventional fermentor. The arising separation problem is analysed using ethanol fermentation with yeasts as an example. Based on the results of this analysis, the membrane process called pervaporation was chosen to recover the product selectively and simultaneously to retain the microorganisms and nutrients in the fermentation broth. Ethanol-selective composite hollow fibre membranes are contacted with active fermentation broth. A transmembrane flux is generated by lowering the partial pressure of the permeants on the downstream side of the membrane. Long-time experiments confirmed that membrane properties were constant. Fluxes were typically 0.6 kg/qm-hr and ethanol enrichment factors reached values of up to 5.5. The ethanol recovery rate can be controlled by varying the downstream pressure of the module.