Debottlenecking product inhibition in 1,3-propanediol fermentation by In-Situ Product Recovery

The present work describes the application of liquid-liquid extraction as an In-Situ product recovery (ISPR) technique to overcome the problem of product inhibition in 1,3-PD fermentation. As a part of initial screening experiments, six solvents were subjected to phase separation and biocompatibility tests to find the best extractant for in-situ removal of 1,3-PD from the bioreactor. These included tributylphosphate, ethyl acetate, butyl acetate, oleyl alcohol, oleic acid and hexanol. Of these, ethyl acetate was found to be the most suitable solvent for 1,3-PD extraction. Use of the selected extractant in continuous integrated fermentation-extraction was established by batch and fed-batch extractive fermentations which demonstrated a significantly improved 1,3-PD production of 35 g/L and 74.5 g/L, respectively. A steady state 1,3-PD concentration of 58 g/L was obtained in continuous extractive system. Continuous cultivation with in-situ cell retention and in-situ 1,3-PD removal demonstrated a 5-fold enhancement in 1,3-PD productivity over non-extractive batch.