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Sweet cherry is prone to senesce and decay due to high postharvest respiration rate and fungal infection. The effects of natamycin-chitosan coating on physicochemical and microbial properties of sweet cherries stored at 4 °C were investigated. Scanning electron microscopy results revealed that natamycin was more uniformly distributed on sweet cherry pericarps with the help of chitosan coating. Respiration rate of sweet cherries was suppressed by chitosan coating during the storage and as a result, total soluble solids (13.53 %-13.80 %) and titratable acidity (0.91 %-0.93 %) were remained higher values and weight loss (2.54 %-2.85 %) was decreased in chitosan and natamycin-chitosan groups. Although both natamycin and chitosan were effective in inhibiting yeast and mold, sweet cherries treated with the combination of natamycin and chitosan showed significantly lower yeast and mold count (3.31 log CFU/g) and decay rate (1.67 %) compared with control. Natamycin combined chitosan inhibited the pathogenic fungi of sweet cherries, such as Alternaria, Cladosporium and Penicillium. These results indicated that postharvest natamycin-chitosan coating has great advantages in maintaining fruit quality, inhibiting fungi, and reducing decay rate of sweet cherry., (Copyright © 2022. Published by Elsevier B.V.)

Chemical modification of chitosan is increasingly studied for its potential of providing new applications of chitosan. Here, a group of novel chitosan quaternary ammonium derivatives containing pyridine or amino-pyridine were designed and successfully synthesized through chemical modification of chitosan. Pyridine and amino-pyridine were used as functional groups to improve the antifungal activity of chitosan derivatives. The chitosan derivatives' antioxidant activity against hydroxyl-radical and 1,1-Diphenyl-2-picrylhydrazyl (DPPH)-radical was tested in vitro. The results showed that chitosan derivatives had better water solubility and stronger antioxidant activity compared with chitosan in all assays. Especially, compounds 3C and 3E (with 3-amino pyridine and 2,3-diamino pyridine as substitute respectively) exhibited stronger hydroxyl-radical and DPPH-radical scavenging ability than other synthesized compounds. These data demonstrated that the synergistic effect of the amino group and pyridine would improve the antioxidant activity of chitosan derivatives, and the position of the amino group on pyridine could influence the antioxidant property of chitosan derivatives.

Chitosan is an abundant and renewable polysaccharide, which exhibits attractive bioactivities and natural properties. Improvement such as chemical modification of chitosan is often performed prior to further utilization. Three novel water soluble chitosan derivatives containing 1,2,3- triazole with or without halogen was designed and synthesized. Their antifungal activity against three kinds of phytopathogens was estimated by hyphal measurement in vitro. The inhibitory property and water solubility of the synthesized chitosan derivatives exhibited a remarkable improvement over chitosan. It is hypothesized that thiazolyl groups enable the synthesized chitosan to possess obviously better antifungal activity. Moreover, CTCTS and BTCTS, which have halogens at the periphery of polymers, inhibited the growth of tested phytopathogens more effectively with inhibitory indices of 81-93% at 1.0mg/mL. The halogens could have a synergistic effect with triazole as they exhibited antifungal activity and electron-withdrawing capacity, which improve the antifungal activity of chitosan derivatives., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Chemical modification of chitosan is increasingly studied for its potential of providing new application for chitosan. Here, we modify chitosan at its primary hydroxyl via 'click chemistry', and a group of novel water soluble chitosan derivatives with substituted 1,2,3-triazolyl group were designed and synthesized. Aliphatic alcohols with different lengths were used as functional dendrons to improve the antifungal activity of chitosan derivatives. Meanwhile, their antifungal activity against two kinds of phytopathogens was estimated by hypha measurement in vitro. All the chitosan derivatives exhibited excellent activity against tested fungi. It is found that the antifungal activity of chitosan derivatives against the tested fungi increases with augment in the chain length of straight aliphatic alcohols. And the hydrophobic moiety (alkyl) at the periphery of the synthesized chitosan derivatives tends to affect their antifungal activity., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Fresh jujube fruit are confronted with serious quality deterioration after harvest. This study explored the effects of chitosan and potassium sorbate coatings on the physicochemical quality and fungal community of jujube during cold storage. Microscopic observation showed that chitosan can uniformly distribute potassium sorbate on the surface of jujube. Chitosan coating inhibited the increase in respiration rate and total soluble solids and the decrease in titratable acidity and firmness. Jujube fruit treated with chitosan and potassium sorbate showed the lowest decay rate (2.67%) after 35 d of storage. High-throughput sequencing analysis indicated that the largest number of fungal amplicon sequence variants (ASVs) was detected in jujube treated with chitosan and potassium sorbate, exhibiting higher Chao1, Shannon and Simpson diversity indices. Treatment with chitosan or potassium sorbate alone reduced the relative abundance of Cladosporium in jujube fruit. Jujube treated with chitosan and potassium sorbate had the lowest total relative abundance of all potential pathogenic fungi (Cladosporium , Alternaria and Diaporthe). FUNGuild analysis showed that chitosan and potassium sorbate treatment could inhibit the relative abundance of plant pathogenic fungi. As a result, chitosan maintained the physicochemical properties of jujube by inhibiting the respiration rate, and the combination of chitosan and potassium sorbate reduced the decay rate of jujube by inhibiting pathogenic fungi. Therefore, chitosan and potassium sorbate coating is a promising approach to improve the storage quality and delay the decay of jujube fruit after harvest. • Chitosan maintained the physicochemical properties of jujube. • Chitosan coating decreased respiration rate of jujube. • Chitosan and potassium sorbate increased fungal diversity in jujube. • Chitosan and potassium sorbate inhibited pathogenic fungi and decay of jujube. [ABSTRACT FROM AUTHOR]

Abstract: A composite coating was fabricated on home-developed Mg–Zn–Ca alloy to improve its biocorrosion resistance in simulated body fluid (SBF, Kokubo solution). The coating was prepared by micro arc oxidation (MAO) of the alloy, followed by dip-coating in chitosan solution. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The electrochemical performance of the MAO, chitosan and chitosan/MAO coated alloys was evaluated by anodic polarization measurements in SBF. After being coated by composite coating, anticorrosion performance was significantly enhanced, while single MAO or chitosan coating only improved anticorrosion properties within a limited range. The barrier effect and interface condition of composite coating were analyzed and related with the improvement in electrochemical performance. The present result indicates that fabrication of composite coatings is a significant strategy to slow down the degradation of Mg alloys, thus enhancing the potential of using Mg alloys as bio-implants. [Copyright &y& Elsevier]