Elsevier

Carbohydrate Polymers

Volume 83, Issue 3, 30 January 2011, Pages 1169-1173
Carbohydrate Polymers

Preparation, characterization and antibacterial activity of water-soluble O-fumaryl-chitosan

https://doi.org/10.1016/j.carbpol.2010.09.026Get rights and content

Abstract

A novel water-soluble chitosan derivative, O-fumaryl-chitosan (OFCS), was prepared by using the selective partial acylation of chitosan and fumaric acid in the presence of H2SO4. The chemical structure and physical properties of OFCS were characterized by FTIR, 1H NMR, 13C NMR, and TG techniques. Our results showed that the degree of substitution (DS) for the chitosan derivatives was from 0.07 to 0.48 and the prepared derivatives had good solubility over a wide pH range, for example, the solubility of OFCS increased from 10.5 to 52.6 mg/ml as the DS increased. The antibacterial activity of chitosan and OFCS was investigated against Escherichia coli and Staphylococcus aureus. The results indicated that the antibacterial activity of OFCS was much stronger than that of chitosan and it increased with increasing DS increasing. These findings suggest that the OFCS with a DS of 0.48 is preferable for use as a food preservative.

Introduction

Chitosan has attracted considerable interest because of its unique combination of properties, such as biocompatibility (Rinaudo, 2006), biodegradability (Pamela et al., 2002), and antibacterial activity (Rabea, Badawy, Stevens, Smagghe, & Steurbaut, 2003). Therefore, chitosan has a variety of current and potential applications in various fields, for example, biotechnology (Mao et al., 2001), pharmaceutics (Ilium, 1998), waste water treatment (Ramnani & Sabharwal, 2006), cosmetics (Kumar, Muzzarelli, Muzzarelli, Sashiwa, & Domb, 2004), and food science (Chien, Sheu, & Yang, 2007). The antimicrobial activity of chitosan against a variety of bacteria and fungi is well known for its poly-cationic nature (Fujimoto et al., 2006, Hayashi et al., 2007, Li et al., 2008, Liu et al., 2006, Xu et al., 2007). However, this activity is limited to acidic conditions due to its poor solubility above pH 6.5. Recent studies have focused on the preparation of chitosan derivatives soluble in water, such as hydroxyethylacryl-chitosan (Ma et al., 2008), ethylamine-hydroxyethyl chitosan (Xie, Liu, & Chen, 2007), carboxymethyl-chitosan (Anitha et al., 2009), and hydroxypropyl-chitosan (Peng, Han, Liu, & Xu, 2005). However, the antibacterial activities of these water-soluble derivatives are still low. Therefore, synthesizing a new kind of derivatives that contain both antibacterial and water-soluble groups may be helpful for using chitosan as a preservative.

Fumaric acid is a food-grade acidulant with strong bactericidal activity because of its double bond and two carboxylic groups (Chikthimmah, Laborde, & Beelman, 2003). It has been used as an antimicrobial agent against pathogenic bacteria in fresh-cut lettuce and apple cider. Treatment with 50 mM of fumaric acid for 10 min caused a 2-log decrease in populations of Escherichia coli O157:H7 and Salmonella typhimurium attached to fresh-cut lettuce (Kondo, Murata, & Isshiki, 2006). In addition, its esters also have strong antimicrobial activity against food pathogenic microorganism (Wang, Sun, & Kuang, 2001).

Herein we report the preparation of a water-soluble derivative of chitosan by acylation with fumaric acid. The chemical structure and physical properties of the derivative were characterized by FTIR, 1H NMR, 13C NMR, and TG techniques. The solubility in water as well as the antibacterial activity against E. coli and Staphylococcus aureus was also studied.

Section snippets

Materials

Chitosan of low molecular weight from crab shells was purchased from Nantong Shuanglin Biochemical Co. Ltd. (Jiangsu, China) and used as received. According to the company analysis, its molecular weight was 40 kDa and its degree of deacetylation was about 95%. All commercially available solvents and reagents were used without further purification.

Synthesis

The chitosan derivative was synthesized as follows (Scheme 1): 1.7 g chitosan (10 mmol calculated as glucosamine units) was suspended in 100 ml of

FTIR analysis

FTIR spectra of OFCS and chitosan are shown in Fig. 1. From the FTIR spectrum of chitosan, the broad band at around 3422 cm−1 was attributed to –NH and –OH stretching vibration, as well as inter- and extra-molecular hydrogen bonding of chitosan molecules. The characteristic bands at 1657, 1597, and 1320 cm−1 were attributed to the amide one, the amine –NH2 and amide three absorption of chitosan, respectively (Zhang, Ping, Zhang, & Shen, 2003). From the FTIR spectrum of OFCS, the new absorption

Conclusion

O-Fumaryl chitosan (OFCS) derivatives with different DS from 0.07 to 0.48 were prepared by using acylation of chitosan and fumaric acid in the presence of H2SO4. FTIR, 1H NMR, and 13C NMR spectra confirmed that the fumaryl group was selectively acylated onto the hydroxyl group of chitosan. TG analysis showed that the thermal stability of OFCS was lower than that of chitosan. OFCS had good solubility in a wide pH range, which was related to the degree of substitution. OFCS exhibited higher

Acknowledgements

This research was financially supported by the fund for 863 Project (No. 2007AA100401), the National Natural Science Funds of China (20876068), the guidance project of State key Laboratory of Food Science and Technology (No. SKLF-MB-200805), the Fund Project for Transformation of Scientific and Technological Achievements of Jiangsu Province (BA2009082).

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