Purification of DP 6 to 8 chitooligosaccharides by nanofiltration from the prepared chitooligosaccharides syrup

Abstract

Background: Chitooligosaccharides (COS) with degrees of polymerization (DP) 6 to 8 are degraded from chitosan, which possess excellent bioactivities. However, technologies that could purify them from hydrolysis mixtures in the narrow DP range (984 to 1,306 Da) are absent. The objective of this research is to purify DP 6 to 8 COS by nanofiltration on the basis of appropriate adjustments of the feed condition. Methods: Syrup containing DP 6 to 8 COS at different concentrations (19.0 to 46.7 g/L) was prepared. A commercial membrane (QY-5-NF-1812) negatively charged was applied. Experiments were carried out in full recycle mode, so that the observed COS retentions were investigated at various transmembrane pressures (6.0 to 20.0 bar), temperatures (10°C to 50°C), and pHs (5.0 to 9.0). Then, the feasibility of separation of DP 6 to 8 COS was further studied by concentration ratio under optimum conditions. Results: The results indicate that the purification of DP 6 to 8 COS by nanofiltration NF is feasible. It was found that the permeate flux was 95.0 L/(m 2 h) at 10.0 bar, while it reached to 140.0 L/(m 2 h) at 20.0 bar, and it increased with feed temperature, but the membrane pores were also swelled by heating and led to an irreversible wastage of target oligomers. Additionally, the retention behaviors of chitooligosaccharides are significantly influenced by pH. Conclusions: Although glucosamine and dimer were permeatable at low pH, their retention ratios were remarkably varied from 0.458 to 0.864 when pH was 9.0. With the interaction of hydrogen bonds, structural curling and overlapping of chitooligosaccharides were formed. Consequently, the rejection of chitooligosaccharides at various pHs is variable. Spray-dried products were finally characterized by the matrix-assisted laser desorption/ionization time-of-flight mass spectrum. The spectrum identified the distributions of hexamer, heptamer, and octamer. Combined with high-performance liquid chromatography profiles, the purity and yield of DP 6 to 8 chitooligosaccharides were up to 82.2% and 73.9%, respectively.

Chemoenzymatic Production and Engineering of Chitooligosaccharides and N-acetyl Glucosamine for Refining Biological Activities

“…Moreover, the utilization of COS and GlcNAc in the biomedical and food industries require high purity, quality, and quantification (Xia et al, 2011 ). Numerous strategies have been reported in the literature for the extraction and purification of COS and GlcNAc, such asgel filtration, ultrafiltration, and nanofiltration (Sørbotten et al, 2005 ; Lopatin et al, 2009 ; Dong et al, 2014 ).…”

Chitin oligosaccharides for the food industry: production and applications

“…The fractionation of COS using an enzymatic membrane reactor coupled with an ultrafiltration membrane (3000 Da) can improve the yields of pentamers and hexamers [139]. Studies have successfully purified COS of DP 6-8 by nanofiltration technology, and the purity and yield are as high as 82.2% and 73.9%, respectively [140].…”

Enzymatic Modification of Native Chitin and Conversion to Specialty Chemical Products

“…Although only small amounts of samples (5 µM) are required for high resolution analysis, the high material costs and the time-consuming process of derivatization with the fluorescence marker limit its large scale application severely. Nanofiltration has moreover been reported to distinguish between COS with a DP of 6-8 [158].…”