Study of in situ ethanol recovery via vapor permeation from fermentation

Vapor permeation (VP) is applied to be integrated with ethanol fermentation as an in situ product recovery technique which could avoid the ethanol inhibition in this study. The polydimethylsiloxane o(PDMS) membrane is used in separating ethanol from model ethanol/water mixture and fermentation integrated processes. And the performance of VP-fermentation process is investigated and compared to that of Pervaporation (PV)-Fermentation and batch fermentation processes. Experimental results show that the ethanol removal is successfully achieved, while it still suffers low flux. Then, in order to reduce the mass transfer resistance in gas boundary layer and thus improving the ethanol removal rate, gas stripping is coupled with VP process to form a new configuration of VP process, i.e. external mode. Benefited from its high ethanol removal rate, the ethanol productivity of External VP-Fermentation process reaches 3.33 g/(L·h), much higher than 2.13 g/(L·h) in batch fermentation and 2.90 g/(L·h) in PV-Fermentation under its optimal condition, i.e. vapor cyclic flow of 1.3 L/min and module temperature of 35 ℃. In VP-fermentation process, membrane deterioration is also efficiently alleviated, which commonly occurs in PV-fermentation process. It makes the membrane process more feasible for industrial fermentation process.