Like most alcohols, IBT is expected to be toxic to microbial biocatalysts. Removal of the IBT as it is formed will help avoid product inhibition and maintain high reac­tor productivity. Thus, in situ product recovery will be an integral part of the biore­actor design effort. Because the physical properties of IBT are similar to those of

gas inlet

Ho ow fibers with attached ce s

Shell-side gas outlet

Tube-side gas inlet

n-butanol, methods developed to remove n-butanol from fermentation broths are also likely to work for IBT. A variety of adsorbents have proven effective at recover­ing n-butanol from fermentation broths [92-94], including polymeric resins, which adsorb n-butanol through hydrophobic interactions [95]. Hydrophilic polymers, like polyamides, polyurethanes and polyesters showed weak n-butanol adsorption. In addition, low-alumina zeolites, such as silicalite, effectively adsorb alcohols from dilute solutions. After the butanol has been adsorbed, it can be recovered from the resin by heat desorption. This desorption technique is less energy intensive (~2,000 kcal/kg alcohol) than steam stripping (~6,000 kcal/kg alcohol) or gas strip­ping (~5,000 kcal/kg alcohol) [93].