Reactive extraction of pyridinedicarboxylic acid (PDCA) with tri-n-octylamine and Aliquat 336 in 1-octanol – A promising approach to access microbially produced PDCA

Abstract

Pyridinedicarboxylic acids (PDCA) are analogues to terephthalic acid and promising molecules for the production of bio-based plastics. Previous work achieved the microbial production of PDCAs from the renewable resource lignin but an efficient and low cost method to recover PDCA from fermentation broth is still missing. Reactive extraction is commonly applied for the extraction of carboxylic acids from aqueous phase. In this study, we investigate reactive extraction of PDCA with the two extractants tri-n-octylamine (TOA) and Aliquat 336 in the diluent 1-octanol. The extraction and re-extraction were optimized with 2,5-PDCA in an aqueous solution leading to up to 98 % extraction for both extractants. Re-extraction by pH swing resulted in > 95 % re-extracted 2,5-PDCA. A scale-up in liquid–liquid centrifuges enabled continuous extraction and re-extraction in liter scale with a yield of 95 %. A concentration factor of 3.6 was achieved and the organic phase was recycled. The approach also showed transferability to the processing of complex fermentation solution. 2,4-PDCA, microbially produced in a bioprocess, could be recovered by 65 % in one single extraction and re-extraction step from biomass-free fermentation broth.