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/(m² h) at 10.0 bar, while it reached to 140.0 L/(m² 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.

Keywords

Nanofiltration / Chitooligosaccharides / Degree of polymerization / Separation / MALDI-TOF-MS

References

[1] Xia W, Liu P, Zhang J, Chen J. Biological activities of chitosan and chitooligosaccharides. Food Hydrocolloids, 2011, 25: 170-179.

[2] Kim S, Rajapakse N. Enzymatic production and biological activities of chitosan oligosaccharides (COS): a review. Carbohydr Polym, 2005, 62: 357-368.

[3] Benhabiles MS, Salah R, Lounici H, Drouiche N, Goosen MFA, Mameri N. Antibacterial activity of chitin, chitosan and its oligomers prepared from shrimp shell waste. Food Hydrocolloids, 2012, 29: 48-56.

[4] Huang RH, Du YM, Yang JH, Fan L. Influence of functional groups on the in vitro anticoagulant activity of chitosan sulfate. Carbohy Res, 2003, 338: 483-489.

[5] Lin S, Lin Y, Chen H. Low molecular weight chitosan prepared with the aid of cellulase, lysozyme and chitinase: characterisation and antibacterial activity. Food Chem, 2009, 116: 47-53.

[6] Kim KW, Thomas RL. Antioxidative activity of chitosans with varying molecular weights. Food Chem, 2007, 101: 308-313.

[7] Zhang Y, Huo M, Zhou J, Yu D, Wu Y. Potential of amphiphilically modified low molecular weight chitosan as a novel carrier for hydrophobic anticancer drug: synthesis, characterization, micellization and cytotoxicity evaluation. Carbohydr Polym, 2009, 77: 231-238.

[8] Zhang J, Zhang W, Mamadouba B, Xia W. A comparative study on hypolipidemic activities of high and low molecular weight chitosan in rats. Int J Biol Macromol, 2012, 51: 504-508.

[9] Chang Y, Chang C, Huang T, Chen S, Lee J, Chung Y. Effects of low molecular weight chitosans on aristolochic acid-induced renal lesions in mice. Food Chem, 2011, 129: 1751-1758.

[10] Berth G, Dautzenberg H. The degree of acetylation of chitosans and its effect on the chain conformation in aqueous solution. Carbohydr Polym, 2002, 47: 39-51.

[11] Lee EH, Lee JJ, Jon SY. A novel approach to oral delivery of insulin by conjugating with low molecular weight chitosan. Bioconjugate Chem, 2010, 21: 1720-1723.

[12] Li N, Wang CY, Wang M, Sun X, Nie S, Pan W. Liposome coated with low molecular weight chitosan and its potential use in ocular drug delivery. Int J Pharm, 2009, 379: 131-138.

[13] Chien PJ, Sheu F, Lin HR. Coating citrus (Murcott tangor) fruit with low molecular weight chitosan increases postharvest quality and shelf life. Food Chem, 2007, 100: 1160-1164.

[14] Abd–Elmohdy FA, Sayed ZE, Essam S, Hebeish A. Controlling chitosan molecular weight via bio-chitosanolysis. Carbohydr Polym, 2010, 82: 539-542.

[15] Jeon Y, Kim S. Production of chitooligosaccharides using an ultrafiltration membrane reactor and their antibacterial activity. Carbohydr Polym, 2000, 41: 133-141.

[16] Fan W, Yan W, Xu Z, Ni H. Formation mechanism of monodisperse, low molecular weight chitosan nanoparticles by ionic gelation technique. Colloids Surf B, 2012, 90: 21-27.

[17] Cabrera JC, Custem PV. Preparation of chitooligosaccharides with degree of polymerization higher than 6 by acid or enzymatic degradation of chitosan. Biochem Eng J, 2005, 25: 165-172.

[18] Simonnot MO, Castel C, Nicolai M, Rosin C, Sardin M, Jauffret H. Boron removal from drinking water with a boron selective resin: is the treatment really selective. Water Res, 2000, 34: 109-116.

[19] Nadav N. Boron removal from seawater reverse osmosis permeate utilizing selective ion exchange resin. Desalination, 1999, 124: 131-135.

[20] Han YP, Lin Q, He XW. Research on desalination and purification characteristics of chitobiose solution with nanofiltration membrane. Membrane Science and Technology, 2009, 29: 105-109.

[21] Han YP, Lin Q, Wang XL. Feasibility study on chitooligosaccharides purification by nanofiltration membranes. Ion Exchange and Adsorption, 2012, 28: 86-96.

[22] Xu W, Jiang C, Kong X, Liang Y, Rong M, Liu W. Chitooligosaccharides and N-acetyl-D-glucosamine stimulate peripheral blood mononuclear cell-mediated antitumor immune response. Mol Med Rep, 2012, 6: 385-390.

[23] Zhao HF, Hua X, Yang RJ, Zhao LM, Zhao W, Zhang Z. Diafiltration process on xylo-oligosaccharides syrup using nanofiltration and its modeling. Int J Food Sci Tech, 2012, 47: 32-39.

[24] Zhang Z, Yang RJ, Zhang S, Zhao H, Hua X. Purification of lactose syrup by using nanofiltration in a diafiltration mode. J Food Eng, 2011, 105: 112-118.

[25] Bowen WR, Mohammad AW. Diafiltration by nanofiltration: prediction and optimization. AIChE J, 1998, 44: 1799-1812.