Synergistic Extraction of 1,3-Propanediol from Fermentation Broths Using Multialcohol Extractants

Extraction is a desirable method for the separation of a target product from an aqueous solution due to its simple operation, mild conditions, and easy automation. However, it is very difficult to find suitable extractants for hydrophilic bio-based target products, e.g., 1,3-propanediol (1,3-PDO). In this study, a surprising synergistic extraction separation of 1,3-PDO was achieved by bi- or trialcohol extractants with long carbon chains of 3 carbon difference between two alcohols, which is just equal to the carbon number of 1,3-PDO. The best synergistic effect was found using a bialcohol extractant at a molar ratio of 2:3. The theoretical analysis revealed that hydrophobic interaction and H-bond energy between the long-chain alcohol and 1,3-PDO would increase the stability of a special structure of seven molecules and provide a suitable cavity for 1,3-PDO. After a four-stage extraction, the recovery of 1,3-PDO was 98.86%, and a high recovery of butyrate (98.10%) by a tricomponent extractant composed of n-octanol, undecanol, and tetradecanol at a molar ratio of 15:4:6 was achieved. The removal rates of proteins and inorganic salts were 96.54 and 75.61% using a filtered concentrated fermentation broth, respectively. Efficient extraction and deprotein/desalination were achieved simultaneously, which highlights a potential separation approach to meet the challenges of bio-based 1,3-PDO industrialization.