Recovery of L-glutamic acid from ammonium glutamate by Donnan dialysis: Membrane characteristic and operation parameters

Abstract

A proof-of-concept study using Donnan dialysis with cation-exchange membranes (CEMs) to recover glutamic acid (GA) from ammonium glutamate was herein developed for cleaner production without directly adding sulfate acid to the fermentation broth. Different commercial CEMs were compared and the operation conditions, including flow velocity, temperature and acid concentration, were investigated focusing on GA conversion and recovery in the feed solution as well as NH4+ transport performance. The results showed that the cation-exchange membranes with low water content and large thickness benefited for GA recovery; And the ones allowing for superior ion transport flux were those possessing relatively high fixed charge density combined with low thickness. Under the optimized condition, the GA conversion rate could reach over 83% and ammonium removal rate over 93% at initial concentration ratio of H+ to NH4+ of 1.6. Meanwhile, over 96% of GA was recovered, avoiding wastewater containing high content of ammonium sulfate. This work indicated that Donnan dialysis could be a promising option toward GA cleaner production and provides important knowledge for better understanding of transport phenomena in the system with ionic organic compounds.