⿢A strategy to introduce the sulfonate groups (RSO3⿿) on the chitosan chain has been developed.⿢The resulting polymer was characterized and its antimicrobial activities were investigated.⿢The effect of fungal inhibition was chitsoan type- and fungi-dependent.⿢Sulfonated chitosan exhibited selective antimicrobial activity.Sulfonated chitosan (SCS) was prepared via a facile chemical procedure by using 1,3-propane sultone attached to the backbone of chitosan. The resulting chitosan derivative was characterized by Fourier transform-infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, elemental analysis, and thermo gravimetric analysis. The antibacterial experiments demonstrated that SCS exhibited higher antibacterial activities against Escherichia coli and Staphylococcus aureus with the minimum inhibitory concentration (MIC) of 0.13 mg/mL and 2.00 mg/mL than those of water-soluble chitosan (WCS) with MIC of 0.50 mg/mL and 4.00 mg/mL. However, different antifungal activities of SCS against Arthrinium sacchari (MIC, 64.00 mg/mL) and Botrytis cinerea (MIC, 0.25 mg/mL) were observed. Scanning electron microscopy revealed that WCS and SCS could damage and deform the structure of fungal hyphae with different action modes. It is worth mentioning that SCS exhibited selective antifungal activity, which was an important parameter to control its biological performance in many fields.

•Pyridine moieties were introduced onto the backbone of chitosan.•The solubility and antifungal activity of the resulting polymer were improved.•Non-toxicity was further demonstrated in the acute toxicity study.•It is potential to be used as an antifungal agent in food industry.Pyridine moieties were introduced into chitosan by nucleophilic substitution to afford N-(1-carboxybutyl-4-pyridinium) chitosan chloride (pyridine chitosan). The resulting chitosan derivative was well characterized, and its antifungal activity was examined, based on the inhibition of mycelial growth and spore germination. The results indicated that pyridine chitosan exhibited enhanced antifungal activity by comparison with pristine chitosan. The values of the minimum inhibitory concentration and the minimal fungicidal concentration of pyridine chitosan against Fulvia fulva were 0.13 mg/ml and 1 mg/ml, respectively, while the corresponding values against Botrytis cinerea were 0.13 mg/ml and 4 mg/ml, respectively. Severe morphological changes of pyridine chitosan-treated B. cinerea were observed, indicative that pyridine chitosan could damage and deform the structure of fungal hyphae and subsequently inhibit strain growth. Non-toxicity of pyridine chitosan was demonstrated by an acute toxicity study. These results are beneficial for assessing the potential utilization of this chitosan derivative and for exploring new functional antifungal agents with chitosan in the food industry.

•IMAC-based M2+-AIL/IL systems were developed.•The purification procedure is easy to handle without fussy pre-treatment.•The sorbents could be regenerated in situ with EDTA and fresh metal ions.•It is a practical alternative to the purification of recombinant proteins.A triazacyclononane-ionic liquid (IL)-based sorbent was synthesized, characterized, and applied for rapid and inexpensive purification of hexahistidine tagged (His-tagged) proteins via liquid–liquid extraction. Selective partition of the target proteins between the IL phase and aqueous phase highly depends on a variety of parameters, such as the affinity ionic liquid (AIL), coordinated metal ions, and ionic strength. Compared with the chromatographic properties of Cu2+-AIL/IL and Ni2+-AIL/IL, Zn2+-AIL/IL exhibited relatively higher binding capacity to separate the proteins with high purity (up to 95%). A reclamation method for the AIL/IL extraction sorbent was further established by washing with ethylene diamine tetraacetic acid (EDTA) and then re-immobilization of metal ions. The purification strategies described herein were mild and suitable for a large scale separation of biologically active macromolecules with the possibility of continuous processing and a reduction in operational cost.Graphical abstractDiagram of the procedure of His-tagged proteins separation involved in protein adsorption and desorption.