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

• Published in: Carbohydrate polymers Vol. 134; pp. 74 - 81
• Main Authors: Chang, Shun-Hsien, Lin, Hong-Ting Victor, Wu, Guan-James, Tsai, Guo Jane
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 10.12.2015
• Subjects: Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; Antibacterial activity; antibacterial properties; bacteria; Chitosan; Chitosan - analogs & derivatives; Chitosan - pharmacology; endo-1,4-beta-glucanase; Escherichia coli; 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; Staphylococcus aureus - drug effects; Static Electricity; temperature; ultrafiltration; water solubility; Zeta potential; Antibacterial activity; Chitosan; Zeta potential; Molecular weight; Solubility
• ISSN: 0144-8617; 1879-1344; 1879-1344
• DOI: 10.1016/j.carbpol.2015.07.072

•Six chitosans with molecular weights ranging from 3.3 to 300kDa were prepared.•Combined effects of chitosan MW, temperature, pH on bacterial growth were studied.•The pH effects on water solubility and zeta potential of chitosans were examined.•Positive correlation between chitosan ZP and antibacterial activity was obtained. Six chitosans with molecular weights (MWs) of 300, 156, 72.1, 29.2, 7.1, and 3.3kDa were prepared by cellulase degradation of chitosan (300kDa) 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 >29.2kDa. 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 >29.2kDa, which may explain the loss of their antibacterial activity at pH 7.0.