Aqueous Two-phase Extraction Of 2,3-Butanediol From Fermentation Broths

2,3-Butanediol(2,3-BD) is an important promising chemical which can be used as a variety of chemical feedstocks and liquid fuel.2,3-BD has been shown to have potential applications in the manufacture of printing inks,perfumes,fumigants,moistening and softening agents,explosives and plasticizers,and as a carrier for pharmaceuticals.2,3-BD is mainly manufactured by microbial route.For the difficulty in separation of 2,3-BD from fermentation broths,some technical problems in separation process were explored from the following aspects.Firstly,the phase separation and extraction ability of different hydrophilic organic solvents/salts aqueous two-phase systems(ATPS) were determined.Many systems showed good extraction results.In order to reduce cost and increase separation efficiency,the dipotassium hydrogen phosphate/ethanol system,ammonium sulfate/ethanol system and sodium carbonate/ethanol system have been selected to be further researched.Through investigating the phase diagram of different systems,these three systems have wide phase separation areas,and the areas of aqueous two-phase would be larger if 2,3-BD appeared in the systems.By comparison,it is found that the hydrophilic organic solvent/salt ATPS exhibits better capability on extraction of 2,3-BD than the hydrophobic organic solvent.Secondly,the operation parameters of aqueous two-phase extraction(ATPE) have been optimized.For the dipotassium hydrogen phosphate/ethanol system,the partition coefficient (K) and recovery(Y) of 2,3-BD reached up to 28.34 and 98.13%,respectively,and the selective coefficient of 2,3-BD to glucose was 615.87 when the system was composed of 24% (w/w) ethanol and 25%(w/w) dipotassium hydrogen phosphate.Simultaneously,cells and proteins could be removed from the fermentation broths and the removal ratio reached 99.63%and 85.9%,respectively.For the ammonium sulfate/ethanol system,the K and Y of 2,3-BD reached up to 6.97 and 89.23%when the system was composed of 27%(w/w) ethanol and 20%(w/w) ammonium sulfate.The composition of fermentation broths,(including sodium acetate,sodium citrate and pH),has no effect on the ATPS.For the sodium carbonate/ethanol system,the K and Y of 2,3-BD reached up to 15.12 and 94.30%when the system was composed of 18%(w/w) ethanol and 15%(w/w) sodium carbonate.The volume of top phase concentrate to 70%of original volume. Furthermore,the ATPE has been scaled up and the downstream process of ATPE has been studied.When the ATPS was scaled up from 10g to 1000g,the extraction efficiency shows little change.More than 90%of solvent(ethanol and methanol) and more than 95%of ammonium sulfate can be recovered,which can be reused again for ATPE.Finally,an integrated operating process has been designed,and the result shows that ATPE is simply operated at low cost.