Abstract
Bipolar membrane electrodialysis (ED) was applied for the rapid separation of lactic acid from a bacteria culture grown in a medium comprising food-processing waste derivatives supplied with highly concentrated ammonia, used as the pH regulator. Ammonium and lactic acid were separated in a single ED run from culture broth of Lactobacillus rhamnosus containing a high concentration of lactic acid (ca. 10% (w/v); reflecting industrial practice). The bipolar membrane capability for acid-base separation was maintained through repeated use of ED by washing it with dilute nitric acid after individual runs. Membrane cleaning with nitric acid also prevented back-diffusion of ammonia, which is supposed to occur when large amounts of this compound are included in the culture. The method proposed herein is expected to resolve difficulties with conventional ED fermentation, which causes co-separation of trace elements in the media that are necessary for the growth of lactic acid fermentation bacteria.
