Selection and optimization of an aqueous two-phase system for the recovery of 1,3-propandiol from fermentation broth

In this study a suitable alcohol/salt aqueous two-phase (ATP) system was selected for the recovery of 1,3-propandiol (1,3-PD) from fermentation broth. From the different alcohol/salt systems studied the ethanol and dipotassium hydrogen phosphate ATP system appeared to be favorable. To examine the potential of this ATP system the partition coefficient of 1,3-PD in synthetic solutions was first optimized with the response surface methodology. The parameters studied were concentrations of ethanol (21.99-38.81% w/w), dipotassium hydrogen phosphate (14.99-31.81% w/w) and 1,3-PD (6.36-73.64 g/L). The optimum conditions were found to be 35.39% w/w for ethanol, 28.40% w/w for dipotassium hydrogen phosphate and 73.6 g/L for 1,3-PD. Under these conditions the maximum partition coefficient of 1,3-PD and the extraction yield were determined as 23.14 and 97.82%, respectively. The optimum extraction conditions were then used to guide the recovery of 1,3-PD from a real fermentation broth. The partition coefficient and extraction yield of 1,3-PD reached 20.28-97.20% in this case, respectively. A favorable partition of the organic acids lactate, acetate and butyrate in the bottom phase was also achieved. We have also studied the removal of cells and macromolecules from the broth. Removal ratio of cells and proteins were 96.47 and 93.05%, respectively. Thus, the ethanol/dipotassium hydrogen phosphate ATP system appears to be an interesting alternative or can be used as one useful step in the downstream processing of 1,3-PD from fermentation broth.