Downstream Processing Of1,3-Propanediol From Fermentation Broth And Experiment On Pilot Scale

1,3-Propanediol is an important bulk chemical. It can be used as a monomer to synthesize polyester which has become a research hotspot. Recently, microbial production of1,3-propanediol has reached a high level of fermentation. However, the complexity of the fermentation broths as well as the hydrophilcity and high boiling point of1,3-PD increased the difficulty of product separation. In this paper, microfiltration-alcohol precipitation-rectification process was used to separate1,3-PD from the fermentation broth under laboratory conditions. Furthermore, on the basis of laboratory research, the pilot-plant-scale experiment was conducted. Finally, some researches were carried out to solve the problems encountered in the pilot-plant-scale experiment and solutions were put forward.Firstly, microfiltration-alcohol precipitation-rectification process was used to separate1,3-PD from the fermentation broth under laboratory conditions. The yield of1,3-PD was86.6%, and the purity of99%for1,3-PD was obtained. Good results were achieved using this downstream processing under laboratory conditions.Secondly, the pi lot-plant-scale experiment was conducted on the basis of the lab-scale experiment. The120m3-scale experimental results showed that, the concentration of1,3-PD was47.0g/L; the average mass conversion ratio was43.0%; the average fermentation time was27.5h; the average productivity was1.72g/(L-h). Regardless of the recovery of the distillation section, the yield and purity of1,3-PD was80.1%and93%, respectively.Thirdly, some researches were carried out to solve the problems encountered in the pilot-plant-scale experiment. The results showed that an ultrafiltration membrane with a molecular weight cutoff of5000Da could remove almost all of the protein from the fermentation broth which could reduce the difficulty of subsequent separation. Various organic solvents were used to deal with the secondary condensed broth after alcohol precipitation, and acetone was the best. Acetone had good extraction efficiency to1,3-propanediol, as well as good removal of impurities and pigments from1,3-propanediol fermentation broth.Finally, the removal of impurities and pigments from1,3-propanediol fermentation broth was investigated by two-step precipitation using alcohol and acetone. The optimal ratio of volume of acetone added to mass of secondary condensed broth was determined to be5:1, without adjusting the pH of the solution, leading to reducing50.3%of pigments in the secondary condensed broth. The protein concentration and conductivity of the fermentation broth decreased by95.6%and 88.1%after two-step precipitation, respectively. Compared with rectification after precipitation using ethanol alone, the novel technique of rectification after two-step precipitation could increase the yield of1,3-propanediol by7.9%, and the purity from97.8%to98.7%. Additionally, the residues in the bottom of rectification tower were reduced by75.9%.