Low Molecular Weight Chitosan-Preparation with the Aid of Pepsin, Characterization, and its Bactericidal Activity

Vishu Kumar, Acharya B and Varadaraj, M. C. and Tharanathan, R. N. (2007) Low Molecular Weight Chitosan-Preparation with the Aid of Pepsin, Characterization, and its Bactericidal Activity. Biomacromolecules, 8 (2). pp. 566-572.

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Abstract

Pepsin (EC 3.4.4.1) from porcine stomach mucosa caused depolymerization of a chitosan sample (a copolymer of glucosamine and N-acetylglucosamine linked by -1-4-glycosidic bonds). N-terminal sequence and zymogram analyses confirmed dual (proteolytic and chitosanolytic) activities of pepsin. Optimum depolymerization occurred at pH 5.0 and 45 C with an activity of 4.98 U. Low molecular weight chitosan (LMWC), the major depolymerization product, was obtained in a yield of 75-82%, the degree of polymerization of which depended on reaction time. The LMWC showed a nearly 10-14-fold decrease in the molecular mass as compared to native chitosan, which was also confirmed by GPC and HPLC analyses. IR and 13C NMR spectra indicated a decrease in the degree of acetylation (DA, ~13.4-18.8%) as compared to native chitosan (~25.7%), which was in accordance with the CD analysis. Native chitosan had a crystallinity index (CrI) of ~70%, whereas there was a decrease in the CrI of LMWC (~61%). The latter showed a better bactericidal activity toward both Bacillus cereus and Escherichia coli, which was more toward the former. The bactericidal activity was essentially due to the lytic and not static effect of LMWC, as evidenced by the pore formation on the bacterial cell surface when observed under SEM. This study suggests the possible use of pepsin in place of chitosanase, which is expensive and unavailable in bulk quantities for the production of LMWC of desired molecular mass that has diversified applications in various fields.

Item Type:	Article
Uncontrolled Keywords:	Pepsin Bactericidal Activity chitosan
Subjects:	500 Natural Sciences and Mathematics > 07 Life Sciences > 03 Biochemistry & Molecular Biology > 13 Molecular Biochemistry 600 Technology > 08 Food technology > 11 Food Biochemistry
Divisions:	Dept. of Biochemistry Human Resource Development
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	08 Jan 2008 06:07
Last Modified:	16 May 2012 07:20
URI:	http://ir.cftri.res.in/id/eprint/1607

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