A novel strategy for 1,3-propanediol recovery from fermentation broth and control of product colority using scraped thin-film evaporation for desalination

Abstract

The biological production of 1,3-propanediol (1,3-PD) by microbial fermentation is promising because by-product glycerol produced in biodiesel production can be used as a carbon source. However, the salts present in the fermentation broth are negative to the downstream processing, particularly for the product colority. In the present work, we first studied the effects of several salts on the increase of colority and analyzed the possible mechanism. Ammonium salt ((NH₄)₂SO₄) showed the most negative effect, which was probably due to the decrease of pH caused by the hydrolysis of ammonium salt thus facilitating the chromophoric reaction. A novel strategy was thus made by adjusting the initial pH of the feeding liquid for distillation. It was found that high pH (alkali condition) indeed reduced the distillate colority but showed no negative effects on the recovery yields of the main product 1,3-PD and major by-product 2,3-butanediol (2,3-BD). Scraped thin-film evaporation was greatly effective for desalination and recovering 1,3-PD and 2,3-BD with high recovery yields. High pH was also found to be beneficial to reduce the concentration of the impurity, acetic acid, in the distillate, which was of great importance for producing qualified 1,3-PD for polymerization. The novel strategy is thus very promising for recovering 1,3-PD from fermentation broth, particularly for the downstream processing at an industrial scale.