Electro-separation of chitooligosaccharides with specific degrees of polymerization using electrodialysis ultrafiltration

Abstract

Biological activities of chitooligosaccharides (COSs) are related to their purity and intrinsic structure. However, a wide range of size distribution and degree of polymerization (DP) of COS make it challenging for their meticulous biological research and applications. This research investigated the protonation behavior and the separation mechanism of individual COSs molecules at semi-pilot scale using an electrodialysis-ultrafiltration membrane. Results indicated that COSs were protonated to varying degrees in the pH ranges of 3.28 to 7.95 with a pKa value stand nearly at 6.44. A semi pilot scale investigation of operational parameters successfully separated a fraction with degree of polymerization (DP) ≤ 4 (>93% of total COS migrated) at flow velocity 6.79 cm/s and electric potential of 9 V/cm with highest DP 3 (>36% of the fraction) in 60 min. Additionally, few other fractions (DP ≤ 3 and DP ≤ 5) were efficiently separated from the industrial sample at different processing times. Moreover, the selective conditions also prevent the fouling of ultrafiltration membrane. Conclusively, the inadequate or too high applied electric potential and solution flow velocities have significant influence on migration of target molecules.