Membrane-based fermentation and separation integration system for succinic acid production and chemical synthesis of bio-based Poly (butylene succinate)

Succinic acid was produced in a novel membrane-based fermentation and separation integration system. Fermentation and separation was coupled by the membrane unit in this process. With this coupled system, product inhibition was alleviated by removing acids and replenishing fresh broth. High cell density maintain for a longer time from 75 to 130 h and succinic acid concentration increased from 53 to 73 g/L. Correspondingly, acetic acid and formic acid concentrations decreased by 30 and 100%, respectively. For succinic acid separation, clearer broth was obtained after ultrafiltration. After further decolorization and distillation, colorless succinic acid fermentation broth with higher concentration was obtained. The pH value was adjusted to 2 and succinic acid was crystallized at a recovery of 85–90%. The purity of the obtained succinic acid crystals reached 99.4% as found by HPLC and 1H NMR analysis. A crystallization experiment indicated that glucose had a negative effect on succinic acid crystallization while acetic acid and formic acid had insignificant effects. Poly (butylene succinate) (PBS) was synthesized and 1H NMR analysis confirmed that the composition of the synthesized PBS is in agreement with that from petro-based succinic acid. The Mw of PBS was as high as 150,000 g/mol. The conversion and selectivity of the recovered succinic acid to diethyl succinate were as high as 90 % and 49 %, respectively.