Investigation of ion-exchange membranes and erythritol concentration for the desalination of erythritol culture broth by electrodialysis

Abstract

Erythritol is a zero-calorie sugar substitute, safe for people with diabetes, that occurs naturally but is also commercially produced. Erythritol produced by fermentation must be separated from the rest of the cultivation broth. Electrodialysis (ED) may be used to separate and purify extracellular fermentation products, allowing simultaneous salt removal from the cultivation broth and generation of saline concentrate solution for reuse in a subsequent fermentation process. In the first stage, this study tested the performance of three membrane stacks and compared them to a reference membrane for erythritol purification. The diffusion of products and by-products was analyzed for the synthetic broth containing 5–25 g/L of erythritol. Product and by-product losses, current efficiency and energy consumption were compared among the tested membranes for the same salt removal rate. Step-wise voltage approach was demonstrated to have fewer product losses than the ED controlled by the constant current approach. Finally, erythritol culture broth after cultivation was treated with selected membranes and ED control based on the findings from the first part of the study. The erythritol losses were only 2% for the 94.8% desalination rate.