Low-molecular-weight chitosans: Preparation and characterization

• Published in: Carbohydrate polymers Vol. 86; no. 2; pp. 1077 - 1081
• Main Authors: Tishchenko, Galina, Šimůnek, Jiří, Brus, Jiří, Netopilík, Miloš, Pekárek, Michal, Walterová, Zuzana, Koppová, Ingrid, Lenfeld, Jiří
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.08.2011; Elsevier
• Subjects: acetic acid; Applied sciences; carbon; Chitooligosaccharides; chitosan; depolymerization; Enzymatic hydrolysis; Exact sciences and technology; Fourier transform infrared spectroscopy; hydrogen bonding; hydrogen peroxide; Low-molecular-weight chitosans; Microwave irradiation; microwave radiation; Natural polymers; nuclear magnetic resonance spectroscopy; Oxidative depolymerization; Physicochemistry of polymers; stable isotopes; Starch and polysaccharides; Low-molecular-weight chitosans; Microwave irradiation; Oxidative depolymerization; Chitooligosaccharides; Enzymatic hydrolysis; Hydrogen peroxide; Microwave; Experimental study; Oligomer; Depolymerization; Preparation; Oxidative degradation; Enzymatic digestion; Oside polymer; Radiochemical degradation; Chitosan; Comparative study; Weight average molecular weight
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2011.04.073

► Oxidative reaction depolymerized chitosan to two fractions of LMW chitosans. ► First fraction with Mw 7–9kDa has lower deacetylation degree (DD) 70–80%. ► Second fraction with Mw 8–10kDa has higher DD 87–94%. ► The content of chitosan oligomers in LMW chitosan fractions was roughly 20–30wt%. ► Enzymatic hydrolysis was the best in preparing chitosan oligomers with polymerization degree 2–10. The chitosan depolymerization products prepared by enzymatic hydrolysis, oxidative reaction or microwave irradiation were characterized by FT-IR, MALDI TOF MS, solid state 13C CP/MAS NMR and GPC. Enzymatic hydrolysis resulted in two fractions of low-molecular-weight (LMW) chitosans with Mw 34kDa (3.9wt%) and 14.6kDa (8.5wt%). In the oxidative reaction at the hydrogen peroxide and acetic acid molar ratio equal to 1.7, two LMW chitosans with Mw 9 and 10kDa (the deacetylation degree 69% and 94%, respectively) were isolated with the total yield 86wt%. In microwave irradiation, the Mw of chitosan (175.5kDa) decreased at most in two times. Two chitosan fractions with Mw 80 and 120kDa (total yield 70wt%) were obtained. In all cases, LMW chitosans served as fortifiers for chitosan oligomers, which were retained with the former through multiple hydrogen bonds. Their content in LMW chitosans was roughly 20–30wt%.