Recovery of Propionic and Acetic Acids from Fermentation Broth by Electrodialysis

摘要

AbstractAcetic and propionic acids can be produced by fermentation. In this process, acid recovery is important both for producing a concentrated product from the broth and for removing acid from the broth to reduce product inhibition during the fermentation. The purpose of this work was to characterize the performance of an electrodialysis unit for carrying out both tasks. Current efficiencies, water transport, and product concentrations were determined both for model solutions of the acids and for fermentation broths to determine the limiting factors in using this separation method. In addition, observations were made of fouling behavior of the membranes in this use. The highest concentrations of product were obtained by contacting with the most concentrated feed and doing so in the absence of competing ions. For the range studied here, a maximum concentration of 13.8 (w/v) sodium propionate was obtained. In the batch recycle mode, final concentrations in the concentrate were reduced, but acid recoveries were improved by the presence of other ions because the low‐current shut‐off was delayed. The use of electrodialysis for producing a concentrated acid product is not promising unless salt levels in the medium can be reduced and acid levels increased. However, electrodialysis can be used to maintain low acid levels in the fermentor during extractive fermentat