title: pH Effects on solubility, zeta potential, and correlation between antibacterial activity and molecular weight of chitosan.
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.
authors.affiliation: Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC.
authors.forename: Shun-Hsien
authors.initials: SH
authors.lastname: Chang
authors.affiliation: Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC; Center for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan, ROC.
authors.forename: Hong-Ting Victor
authors.initials: HT
authors.lastname: Lin
authors.affiliation: Department of Food Science, National Penghu University of Science and Technology, Penghu, Taiwan, ROC.
authors.forename: Guan-James
authors.initials: GJ
authors.lastname: Wu
authors.affiliation: 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.
authors.forename: Guo Jane
authors.initials: GJ
authors.lastname: Tsai
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D048271:Chitosan / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects; D004927:Escherichia coli Infections / Q000517:prevention & control; D005516:Food Microbiology / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D008970:Molecular Weight; D012995:Solubility; D013203:Staphylococcal Infections / Q000517:prevention & control; D013211:Staphylococcus aureus / Q000187:drug effects; D055672:Static Electricity
chemical_list: D000900:Anti-Bacterial Agents; D048271:Chitosan
keywords: Antibacterial activity; Chitosan; Molecular weight; Solubility; Zeta potential