Downstream Processing Of 1,3-Propanediol From Fermentation Broths

Considering the problem in 1, 3-propanediol separation from fermentation broths, this study explored three following techniques. They can provide a guidance for further research, and also a reference on the separation of other similar products from fermentation broths.Firstly, the pretreatment of 1, 3-propanediol fermentation broth with flocculants and the reuse of Klebsiella pneumoniae in flocs were investigated in this paper. Chitosan was proved to be the best of the twelve flocculants, whose performance was evaluated by cell and protein removal rates. The flocculation performed the best when the temperature was controlled at 37 ℃, pH was 5.0, the concentration of chitosan with molecular weight of 40kD was 0.5g/L, stirring rate was 300r/min, the time of turbidity and settlement were 20min and 15min, respectively. Then, it was confirmed that K. pneumoniae in floc could grow well in fermentation medium.Secondly, ultrafiltration and nanofiltration were applied in downsteam separation of 1, 3-propanediol from fermentation broth. The cell and protein removal rates can be up to 100% and 92.1% by ultrafiltration. The processes of nanofiltration was feasible, but the total yields of 1, 3-propanediol was only 54.8%.Finally, the separation of 1, 3-propanediol from fermentation broth by a combination of ultrafiltration and alcohol precipitation was well investigated. Dilution crystallization was used in this paper, which can remove most of the salts from concentrated fermentation broth. The yield of 1, 3-propanediol and alcohol recovery were 81.2% and 85.4%, respectively. This work should be researched further in the future.