Biological Activity of Native and Low Molecular Weight Chitosan obtained by Steam Explosion Process

The correlation of molecule weight of chitosan oligomers with the corresponding viscosity and antibacterial activity

In order to explore the correlation between the viscosity of chitosan oligomers-acetic solution and its viscosity average molecular weight (M_v), and determine the M_v range with a strong bactericidal effect. A series of chitosan oligomers were obtained by degraded chitosan (728.5 kDa) with dilute acid and chitosan oligomer (101.5 kDa) was characterized by FT-IR, XRD, H NMR and C NMR. The bactericidal effect of chitosan oligomers with different Mv on E. coli, S. aureus and C. albicans was measured by plate counting method. And the bactericidal rate was taken as the evaluation indicator, the optimum conditions were determined by single-factor experiments. The result showed that the molecular structure of chitosan oligomers and original chitosan (728.5 kDa) were similar. The viscosity of the chitosan oligomers in acetic acid solution was positively correlated with the M_v, and the chitosan oligomers with the M_v of 52.5-145.0 kDa had a strong bactericidal performance. In addition, the bactericidal rate of chitosan oligomers on experimental strains was more than 90% when the concentration of 0.5 g/L (bacteria) and 1.0 g/L (fungi), pH6.0, incubation time of 30 min. Thus, chitosan oligomers had a potential application value when the M_v was in the range of 52.5-145.0 kDa.

Pristine and modified chitosan as solid catalysts for catalysis and biodiesel production: A minireview

Chitosan is one of the readily available polymers with relatively high abundance, biodegradable and sustainable materials with divergent functional groups that are employed in broad range of applications. Chitosan is widely used in many fields like adsorption, drug carrier for therapeutic activity, environmental remediation, drug formulation and among others. One of the unique features of chitosan is that it can be transformed to other forms like beads, films, flakes, sponges and fibres depending upon the applications. This review is aimed at showing the potential applications of chitosan and its modified solids in organic transformations. The number of existing articles is organized based on the nature of materials and subsequently with the types of reactions. After a brief description on the structural features of chitosan, properties, characterization methods including various analytical/microscopic techniques and some of the best practices to be followed in catalysis are also discussed. The next section of this review describes the catalytic activity of native chitosan without any modifications while the subsequent sections provide the catalytic activity of chitosan derivatives, chitosan covalently modified with metal complexes/salts through linkers and chitosan as support for metal nanoparticles (NPs). These sections discuss number of organic reactions that include Knoevenagel condensation, oxidation, reduction, heterocycles synthesis, cross-coupling reactions and pollutant degradation among others. A separate section provides the catalytic applications of chitosan and its modified forms for the production of fatty acid methyl esters (FAME) through esterification/transesterification reactions. The final section summarizes our views on the future directions of this field in the coming years.

Chitosan as a Wound Dressing Starting Material: Antimicrobial Properties and Mode of Action

Fighting bacterial resistance is one of the concerns in modern days, as antibiotics remain the main resource of bacterial control. Data shows that for every antibiotic developed, there is a microorganism that becomes resistant to it. Natural polymers, as the source of antibacterial agents, offer a new way to fight bacterial infection. The advantage over conventional synthetic antibiotics is that natural antimicrobial agents are biocompatible, non-toxic, and inexpensive. Chitosan is one of the natural polymers that represent a very promising source for the development of antimicrobial agents. In addition, chitosan is biodegradable, non-toxic, and most importantly, promotes wound healing, features that makes it suitable as a starting material for wound dressings. This paper reviews the antimicrobial properties of chitosan and describes the mechanisms of action toward microbial cells as well as the interactions with mammalian cells in terms of wound healing process. Finally, the applications of chitosan as a wound-dressing material are discussed along with the current status of chitosan-based wound dressings existing on the market.