Acid Hydrolysis of Chitosan to Oligomers Using Hydrochloric Acid

Abstract

The natural polymer chitosan is widely used for medical and drug delivery applications. Low molecular weight chitosan (LMWC) has superior properties compared to high molecular weight chitosan (HMWC), which open new applications of LMWC, especially in the cosmetics, food, and pharmaceutical industries. LMWC is often produced from HMWC by acid, enzymatic, or oxidative hydrolysis. Industrially, hydrolysis with dilute HCl is preferred, since it is simple, practical, and gives a high yield. In this study 2M HCl was used to prepare LMWC. A high average depolymerization yield of 87% was obtained. The LMWCs were characterized by FTIR spectroscopy, and the molecular weight and degree of deacetylation were determined. The prepared LMWCs are fully deacetylated, and their production by this method is reproducible.

Chitosan Depolymerization: A Simple and Promising Chemical Process for the Preparation of Bioactive Varying Molecular Weight Derivatives

“…To overcome these limitations, chitosan hydrolysis by acids, mainly acetic acid [9], nitrous acid [22], phosphoric acid, hydrogen uoride [8] and hydrochloric acid (HCl) [23,11] has been evaluated as simple, easy and practical method. Industrially, acid hydrolysis with HCl is preferred, since it is relatively simple, easy, practical and gives a high yield [23,24].…”

“…It is previously reported that HCl not only breaks the glycosidic bonds in chitosan chains but also hydrolyzes the Nacetyl amide groups to give chitosan chains with lower Mw and AD. Indeed, the acid concentration, the reaction time and the used temperature are considered among the most crucial factors of the acid hydrolysis process [23,9].…”

“…Physical approaches use the microwave and ultrasound energy for chitosan hydrolysis, but they are not often used commercially because of their energy-intensive nature [13,14].Chito-oligomers preparation can be achieved by enzymatic hydrolysis using speci c enzymes [15, 16,7,17], however, this method is limited due to the high cost and not availability of chitosanases. The hydrolysis of chitosan was further studied using different other commercial non-speci c enzymes, such as chitinase [18,19], lysozyme, papain, cellulose [20], lipase [21], while, these enzymes, were added at high concentrations.To overcome these limitations, chitosan hydrolysis by acids, mainly acetic acid [9], nitrous acid [22], phosphoric acid, hydrogen uoride [8] and hydrochloric acid (HCl) [23,11] has been evaluated as simple, easy and practical method. Industrially, acid hydrolysis with HCl is preferred, since it is relatively simple, easy, practical and gives a high yield [23,24].…”

“…The hydrolysis of chitosan was further studied using different other commercial non-speci c enzymes, such as chitinase [18,19], lysozyme, papain, cellulose [20], lipase [21], while, these enzymes, were added at high concentrations.To overcome these limitations, chitosan hydrolysis by acids, mainly acetic acid [9], nitrous acid [22], phosphoric acid, hydrogen uoride [8] and hydrochloric acid (HCl) [23,11] has been evaluated as simple, easy and practical method. Industrially, acid hydrolysis with HCl is preferred, since it is relatively simple, easy, practical and gives a high yield [23,24]. It is previously reported that HCl not only breaks the glycosidic bonds in chitosan chains but also hydrolyzes the Nacetyl amide groups to give chitosan chains with lower Mw and AD.…”

“…It is previously reported that HCl not only breaks the glycosidic bonds in chitosan chains but also hydrolyzes the Nacetyl amide groups to give chitosan chains with lower Mw and AD. Indeed, the acid concentration, the reaction time and the used temperature are considered among the most crucial factors of the acid hydrolysis process [23,9].In the present study, chitosan derivatives (CDP) with varying characteristics were prepared by chemical hydrolysis of shrimp chitosan using HCl (6 M). The antimicrobial effect of the obtained CDP, compared to chitosan, was investigated against seven pathogenic bacteria and two fungi, which were mostly putrefactive microorganisms in food and aquatic preservation.…”