pH Effects on solubility, zeta potential, and correlation between antibacterial activity and molecular weight of chitosan

Shun-Hsien Chang; Hong-Ting Victor Lin; Guan-James Wu; Guo Jane Tsai

doi:10.1016/j.carbpol.2015.07.072

pH Effects on solubility, zeta potential, and correlation between antibacterial activity and molecular weight of chitosan

Carbohydr Polym. 2015 Dec 10:134:74-81. doi: 10.1016/j.carbpol.2015.07.072. Epub 2015 Jul 26.

Authors

Shun-Hsien Chang¹, Hong-Ting Victor Lin², Guan-James Wu³, Guo Jane Tsai⁴

Affiliations

¹ Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC.
² Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC; Center for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan, ROC.
³ Department of Food Science, National Penghu University of Science and Technology, Penghu, Taiwan, ROC.
⁴ Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC; Center for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan, ROC. Electronic address: b0090@mail.ntou.edu.tw.

PMID: 26428102
DOI: 10.1016/j.carbpol.2015.07.072

Abstract

Six chitosans with molecular weights (MWs) of 300, 156, 72.1, 29.2, 7.1, and 3.3 kDa were prepared by cellulase degradation of chitosan (300 kDa) and ultrafiltration techniques. We examined the correlation between activity against Escherichia coli and Staphylococcus aureus and chitosan MW, and provided the underlying explanation. In acidic pH conditions, the chitosan activity increased with increasing MW, irrespective of the temperature and bacteria tested. However, at neutral pH, chitosan activity increased as the MW decreased, and little activity was observed for chitosans with MW >29.2 kDa. At pH 5.0 and 6.0, chitosans exhibited good water solubility and zeta potential (ZP) decreased with the MW, whereas the solubility and ZP of the chitosans decreased with increasing MW at pH 7.0. Particularly, low solubility and negative ZP values were determined for chitosans with MW >29.2 kDa, which may explain the loss of their antibacterial activity at pH 7.0.

Keywords: Antibacterial activity; Chitosan; Molecular weight; Solubility; Zeta potential.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Anti-Bacterial Agents / chemistry*
Anti-Bacterial Agents / pharmacology*
Chitosan / analogs & derivatives*
Chitosan / pharmacology*
Escherichia coli / drug effects
Escherichia coli Infections / prevention & control
Food Microbiology* / methods
Humans
Hydrogen-Ion Concentration
Microbial Sensitivity Tests
Molecular Weight
Solubility
Staphylococcal Infections / prevention & control
Staphylococcus aureus / drug effects
Static Electricity

Substances

Anti-Bacterial Agents
Chitosan