Process engineering for a membrane recycle fermentor

Membrane recycle fermentors are used successfully on laboratory scale to increase the efficiency of fermentation processes. The design of a process on larger scale however is obstructed by the lack of relevant data in literature. Compared to a stand-alone fermentor a membrane recycle fermentor presents new features which must be considered in the design. These features include the use of high density cultures, the additional volume in the membrane section and the circulation of the broth. In this theoretical study these aspects are analyzed with the characteristic time concept, in case of an ethanol fermentation integrated with microfiltration. The analysis shows that depending on the reactor configuration used concentration gradients can be expected. These gradients may decrease the efficiency of the fermentation, or can be advantageous, for example by letting the substrate conversion approach completion in the membrane section.