Chitin and chitosan: Properties and applications

Antimicrobial properties of chitosan and mode of action: A state of the art review

Chitosan, a versatile hydrophilic polysaccharide derived from chitin, has a broad antimicrobial spectrum to which gram-negative, gram-positive bacteria and fungi are highly susceptible. In the current review, three possible and accepted antimicrobial mechanisms for chitosan are presented and briefly discussed. The activity dependence on polymeric molecular weight (MW) and degree of acetylation (DA) are described. The chitosan minimum inhibitory concentrations (MIC) are summarized according to recent data found in the literature. The potential to improve inhibitory growth of bacteria by using water soluble chitosan derivatives is also discussed. The data indicate that the effectiveness of chitosan varies and is dependent on species of target microorganisms.

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A Review of the Antimicrobial Activity of Chitosan

Chitosan based edible films and coatings: A review

This review concerns the applications of some polysaccharides in the domain of biomaterials and bioactive polymers. Natural polysaccharides from different sources have been studied for a long time, and their main properties are summarized in this paper; some of their derivatives obtained by chemical modification are also described. The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan, hyaluronan and alginates. Alginates are well known for their property of forming a physical gel in the presence of divalent counterions (Ca, Ba, Sr) whereas carrageenans form a thermoreversible gel; these seaweed polysaccharides are mainly used to encapsulate different materials (cells, bacteria, fungi). Other promising systems are the electrostatic complexes formed when an anionic polysaccharide is mixed with a cationic polysaccharide (e.g. alginate/chitosan or hyaluronan/chitosan). An important development of the applications of polysaccharides can be predicted for the next few years in relation to their intrinsic properties such as biocompatibility and biodegradability in the human body for some of them; they are also renewable and have interesting physical properties (film-forming, gelling and thickening properties). In addition, they are easily processed in different forms such as beads, films, capsules and fibres. Copyright © 2007 Society of Chemical Industry

Main properties and current applications of some polysaccharides as biomaterials

Dielectric and interaction behavior of chitosan/polyvinyl alcohol and chitosan/polyvinyl pyrrolidone blends with some antimicrobial activities

Two series of lightly cross-linked copolymer beads based on styrene (St) and 4-(or 2-)rinylpyridine (4VP or 2VP) were synthesized, and their equilibrium swelling behavior in aqueous solution was studied as a function of pH and ionic strength. A wide range of pH-sensitive swelling behavior could be obtained using a range of compositional changes of copolymers. Over a fairly narrow pH range, the polymer swells as the medium becomes more acidic, consistent with protonation of the VP units. With an increase in the ratio of St to 4VP, the pH at which the swelling transition occurs shifts to lower values and the extent of swells as the decreases

Swelling behavior of pH-sensitive copolymers based on styrene and 4-(or 2-)vinylpyridine

Four demulsifiers were prepared in three steps. In the first step, styrene and maleic anhydride were copolymerized. In the second step, a long-chain alcohol (dodecanol) was reacted with the prepared copolymer to form the monoesterified copolymer. In the final step, the resulting product was further esterified with poly(propylene oxide) (PPO)–poly(ethylene oxide) (PEO) block copolymers of different molecular weights (1.1, 2.5, 3.0, 5.0, and 8.0 × 103) and different PPO/PEO ratios. The demulsification efficiency of these demulsifiers was investigated with the bottle test (Sany glass). The effects of the molecular weight and ratio of the PPO–PEO block copolymers on the demulsification efficiency were studied. The demulsification efficiency could be enhanced from 66% by an individual demulsifier to 100% by demulsifier blends. The surface-active and thermodynamic properties of the prepared demulsifiers were measured at 25, 35, and 45°C. The kinematics of the demulsification process were photographed with a binocular microscope. The demulsification mechanism was found to occur in three stages, that is, adsorption and flocculation, coalescence, and channel formation followed by separation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Demulsification efficiency of some novel styrene/maleic anhydride ester copolymers

Four comb-like copolymers derived from styrene-maleic anhydride copolymer were prepared and characterized by FTIR, 1H-NMR and elemental analysis. The molecular weight was determined using GPC and their intrinsic viscosity was measured. The prepared polymers were investigated as pour point depressants and flow improvers for waxy crude oil and it was found that, the maximum depression was obtained by the sample that has long branch chain (PPD4) from 27°C to −3°C (ΔPP = 30°C, at 10000 ppm). While, the minimum depression was exhibited by short branch chain, PPD1 (ΔPP = 21°C) at the same conditions. The effect of these polymers on the rheology and flow properties of Qarun waxy crude oil was investigated. It was found that the Bingham yield value (τβ) decreased from 6.0 pa.s. to 0.5 pa.s. for PPD4 at 27°C and 10,000 ppm. The dynamic viscosity also decreased from 110 m pa.s. to 24 m pa.s. for the same sample and the same conditions.

Styrene-Maleic Anhydride Copolymer Esters as Flow Improvers of Waxy Crude Oil

Modification of chitosan by grafting with vinyl acetate (VAc) was carried out using potassium persulfate and sodium bisulfite as redox initiators. The effect of monomer, initiator concentration, time, and temperature was studied. The grafted samples were subjected to alkaline hydrolysis and the polyvinyl acetate (PVAc) branches were consequently partially converted into polyvinyl alcohol (PVAl) graft, which showed enhanced swelling in water. The graft copolymers showed a better dye uptake for both acidic and basic dyes. Chitosan/VAc and chitosan/VAl copolymers were both subjected to reaction with dimethyl sulfate in alkaline medium to yield quaternized copolymers. The antifungal behavior of chitosan and its graft copolymers was investigated in vitro on the mycelial growth, sporulation, and germination of conidia or sclerotia of the following sugarbeet: Beta vulgaris pathogens isolated in Egypt, Rhizoctonia solani Kuhn (AG2-2) Sclerotium rolfsii Sacc. and Fusarium solani (Mart.) Sacc. These polymers were also screened against several fungi and it has been found that grafting with polyvinyl alcohol branches enhances the antifungal activity dramatically. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1651–1663, 2007

Maher Z. Elsabee

Papers

Dielectric and interaction behavior of chitosan/polyvinyl alcohol and chitosan/polyvinyl pyrrolidone blends with some antimicrobial activities

Swelling behavior of pH-sensitive copolymers based on styrene and 4-(or 2-)vinylpyridine

Demulsification efficiency of some novel styrene/maleic anhydride ester copolymers

Styrene-Maleic Anhydride Copolymer Esters as Flow Improvers of Waxy Crude Oil

Grafting of vinyl acetate onto chitosan and biocidal activity of the graft copolymers