A Novel Hydrophobic Thermal Responsive Sponge in Extractive Fermentation for Continuous Butanol Production

Bio- butanol has a number of advantages of having a low volatility, low vapor pressure, water content,and generate more than 25% ethanol energy, the product of only carbon dioxide and water, will notproduce carbon monoxide and harmful byproducts, etc., more desirable than ethanol biofuels. However,the product has a serious inhibitory effect on producing strains, resulting in strains unable to producesignificant amounts of ABE solvent. Thus, if they can be extracted during butanol fermentation, willeffectively reduce the inhibitory effect.Reducing production cost is the key to the direction of technological development and efforts. Currentlythe research bottlenecks of solvent fermentation technology are mainly severe product inhibition andhigh product recovery costs. Therefore, the development of new technologies - such as continuousfermentation integrated system with product recovery technology will be key to the future success ofthe commercialization process: minimize product inhibition, while reducing the cost of productrecovery. However, current existing designs include pre-vaporation, and gas stripping could not satisfythe energy-saving purpose. For instance, separating butanol by stripping distillation (24.2 MJ / kg)energy demand is comparable butanol (36 MJ / kg). Therefore, another technique to find a lower energyrequirement is very important, so that biobutanol production is economically feasible.The first year of this our research proposal has successfully implemented an extractive fermentationsystem using a polydimethylsiloxane (PDMS) sponge in Clostridium acetobutylicum. However,desorption of butanol of the hydrophobic sponge remains energy intensive. Thus, the focus of thisresearch proposal is to modify the hydrophobicity of sponge by coating thermal responsive polymerpoly-N-isopropylacrylamide (PIPAAm). Thus, the energy-saving product recovery could be obtainedwhen elevated temperature will change both vapor pressure of butanol and hydrophobicity of sponge.The innovation of this study are listed as follows:1. Hydrophobic thermal responsive sponge (PDMS＋PIPAAm) is constructed to absorb and to desorbbutanol by changing temperature.2. A novel in-situ extractive/ desorption sponge fermentation system is constructed for continuousbutanol production