Flocculation and antimicrobial properties of a cationized starch

• Published in: Water research (Oxford) Vol. 119; pp. 57 - 66
• Main Authors: Liu, Zhouzhou, Huang, Mu, Li, Aimin, Yang, Hu
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-08-2017
• Subjects: Anti-Infective Agents; Antibacterial effect; Antibacterial mechanism; Cationized starch-based flocculant; Escherichia coli; Flocculation; Flocculation mechanism; Flocculation performance; Staphylococcus aureus; Starch; Substitution degree of cationic group; Water Purification; Flocculation mechanism; Flocculation performance; Cationized starch-based flocculant; Substitution degree of cationic group; Antibacterial effect; Antibacterial mechanism
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2017.04.043

In this study, a series of cationized starch-based flocculants (starch-3-chloro-2-hydroxypropyl triethyl ammonium chloride, St-CTA) containing various quaternary ammonium salt groups on the starch backbone were prepared using a simple etherification reaction. All of the prepared starch-based flocculants show effective performance for the flocculation of kaolin suspension, two bacterial (Escherichia coli and Staphylococcus aureus) suspensions, and two contaminant mixtures (kaolin and each bacterium) under most pH conditions. St-CTA with a high substitution degree of CTA demonstrates improved contaminant removal efficiency because of the strong cationic nature of the grafted quaternary ammonium salt groups and the charge naturalization flocculation effect. The antibacterial effects of St-CTA were also evaluated, considering that many quaternary ammonium salt compounds elicit bactericidal effects. Three-dimensional excitation–emission matrix spectra and direct cell morphological observation under scanning electron microscopy reveal that the starch-based flocculants exhibit better antibacterial effects on the Gram-negative bacterium E. coli than on the Gram-positive bacterium S. aureus. The thicker cell wall due to the presence of abundant peptidoglycan and teichoic acids of S. aureus than E. coli explains the uneasy breakage of S. aureus cell wall after being attacked by the cationized starch-based flocculants.
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•A dual-function cationic starch-based flocculant (St-CTA) was prepared easily.•St-CTA can remove turbidity and inhibit bacteria in water simultaneously.•The effect of CTA content on the dual functionality of St-CTA was studied.•Charge attraction plays an important role in the flocculation and sterilization.•E. coli is more easily killed than S. aureus due to the different cell wall features.