Interaction between chitosan and alkyl β-d-glucopyranoside and its effect on their antimicrobial activity

The interactions between chitosan and nonionic surfactant–alkyl β-d-glucopyranoside (AG) in solid state and aqueous solution have been investigated by using FT-IR spectroscopy, thermal analysis, powder X-ray diffraction, viscometry and gel permeation chromatography (GPC). The FT-IR spectra demonstrated that interaction between –NH3+ and –OH groups of chitosan and –OH groups of AG occurred by electrostatic force or hydrogen bonding. Results of thermal analysis and X-ray diffraction indicated that higher orders of structure such as aggregation chain conformation etc and crystallinity of chitosan seemed changed by addition of AG. Results of viscometry and GPC showed that, in aqueous solution, AG most likely made the chitosan chains extend and disaggregate. Interestingly, antimicrobial activity of the dynamic association (mixed solution of chitosan and AG) was much higher than that of chitosan and AG separately. Minimum inhibition concentration (MIC) of dynamic association was 2–8 times lower than that of chitosan alone, and it could kill more microorganisms in a shorter time. The reasons for the enhanced antimicrobial activity of the dynamic association mixture are carefully discussed in terms of the interaction between chitosan and AG.