A vacuum membrane distillation process using a microporous polytetrafl
uoro-ethylene (PTFE) membrane was developed to concentrate 2,3-butaned
iol from model 2,3-butanediol solutions and fermentation broths. A 0.2
2-mum PTFE membrane passed water vapor while retaining 2,3-butanediol.
Water flux through the membrane was 4 kg/m2.h at 35-degrees-C and 12-
14 kg/M2.h at 55-degrees-C. Medium components, especially yeast extrac
t and fermentation broth, reduced flux as compared to model solutions.
Using this process, butanediol was concentrated from 40 g/L to about
650 g/L in the model solution, and when integrated to a fed-batch reac
tor, 2,3-butanediol was concentrated to over 430 g/L.