Microemulsion extraction of biobutanol from surfactant based-extractive fermentation broth

The present work investigates the microemulsion based butanol extraction from fermentation broth. Extractive butanol fermentation was carried out using a non-ionic surfactant L62.Pentane, hexane and heptane (i.e. n-C-5, n-C-6 and n-C-7) alkanes were used for the extraction of butanol from fermentation broth. Conditions for Winsor microemulsion with n-C-5, n-C-6 and n-C-7 alkanes were established. Hexane and heptane formed Winsor-III microemulsion. Hexane based microemulsion resulted into organic phase (Om) containing more butanol (62 % w/w) than pentane (12.4 % w/w) and heptane (57.3 % w/w) based ones. Bi-continuous phase (i.e. the surfactant phase or BC) had negligible amount of butanol. Surfactant was retained in BC and water (Wm) phases. Thus, hexane was found to be a better microemulsion extractant than the other two alkanes. Studies with two step approach i.e. coacervation followed by back-extraction resulted in just 13 % (w/w) butanol. Thus, the single stage approach with hexane not only avoided a step but also yielded about 4 times more extracted butanol than the two-stage approach.