Advances in Chitin and Chitosan Science

Immune-enhancing Effects of Chitosan-fermented Feed Additive on Broiler Chickens and Subsequent Protection Conferred against Experimental Infection with Salmonella Gallinarum

Benefits chitosan-fermented feed additives (CFFAs) particularly in the regulation of the immune system and antimicrobial activity. Therefore, we investigated the immune-enhancing and bacterial clearance effects of CFFA (fermented by Bacillus licheniformis) on broiler chickens Salmonella Gallinarum challenge. We administered 2% or 4% CFFA evaluated its immune-enhancing effects using several immunological experiments, including examination of lysozyme activity, lymphocyte proliferation, and expression of cytokines. We also evaluated the bacterial clearance effects of CFFA against S. Gallinarum. CFFA administration markedly enhanced lysozyme activity, lymphocyte proliferation, and the expression of interleukin (IL)-2, IL-12, tumor necrosis factor alpha, and interferon gamma in the spleen. In broilers challenged with S. Gallinarum, the clinical signs of S. Gallinarum infection and the number of viable bacterial colonies in the feces and tissues decreased in both CFFA groups. Therefore, CFFAs could be good candidates for feed additive to improve nonspecific immune responses and bacterial clearance.

Chitin-derived biochar with nitrogen doping to activate persulfate for phenol degradation: Application potential and electron transfer pathway in system

The fast and efficient removal of organic pollutants (e.g., phenolics) remains one of the focus problems in environment pollution. Thus, a chitin-derived biochar with nitrogen doping (N-BC) was successfully prepared at a lower calcination temperature of 600 °C, which is environmentally friendly and energy saving. The N-BC was analyzed by SEM, FTIR, BET, XRD, XPS and Raman spectroscopy to confirm that the doping of nitrogen element provided sufficient defect sites to promote the activation of persulfate (PDS). Quenching experiments and EPR results revealed the presence of •OH and •O₂^- contributed to phenol degradation in N-BC 600/PDS system. In addition, the linear sweep voltammogram experiments also demonstrated the existence of electron transfer pathway. The electrons were donated from phenol and shifted to PDS through N-BC. The graphitic N and carbon defects in N-BC served as the active sites of the reaction and involved absorption and transfer of electrons as the key character. Moreover, the removal rates of phenol and TOC reached 98.8% and 58.2% within 2 h, indicating that N-BC effectively activated the persulfate to degrade phenol. This study provides the theoretical support and potential applications for the activation of persulfate by nitrogen-doped biochar to degrade other phenolic compounds.

Control and prevention of microbially influenced corrosion using cephalopod chitosan and its derivatives: A review

Microbially influenced corrosion (MIC) of metals is an important industrial problem, causing 300-500 billion dollars of economic loss worldwide each year. It is very challenging to prevent or control the MIC in the marine environment. Eco-friendly coatings embedded with corrosion inhibitors developed from natural products may be a successful approach for MIC prevention or control. As a natural renewable resource, cephalopod chitosan has a number of unique biological properties, such as antibacterial, antifungal and non-toxicity effects, which attract scientific and industrial interests for potential applications. Chitosan is a positively charged molecule, and the negatively charged bacterial cell wall is the target of its antimicrobial action. Chitosan binds to the bacterial cell wall and disrupts the normal functions of the membrane by, for example, facilitating the leakage of intracellular components and impeding the transport of nutrients into the cells. Interestingly, chitosan is an excellent film-forming polymer. Chitosan may be applied as an antimicrobial coating substance for the prevention or control of MIC. Furthermore, the antimicrobial chitosan coating can serve as a basal matrix, in which other antimicrobial or anticorrosive substances like chitosan nanoparticles, chitosan silver nanoparticles, quorum sensing inhibitors (QSI) or the combination of these compounds, can be embedded to achieve synergistic anticorrosive effects. A combination of field and laboratory experiments will be conducted to test this hypothesis for preventing or controlling MIC in the marine environment. Thus, the proposed review will identify new eco-friendly MIC inhibitors and will assay their potential in future applications in the anti-corrosion industry.

Synthesis of Bioactive Materials by In Situ One-Step Direct Loading of Syzygium aromaticum Essential Oil into Chitosan-Based Hydrogels

Hydrogel conjugates based on chitosan and an essential oil were synthetized by an ultrasound-assisted emulsification approach. Rheology studies revealed a gel-type structure with pronounced compactness and flexibility while SEM showed the formation of a two-level ordered network with highly interconnected pores. The swelling studies indicated a pH-dependent behavior with a significant overshooting effect. The synergistic effects of the components in clove essential oil led to a strong antioxidant character and an enhanced antimicrobial activity of the conjugate hydrogels. The bioactivity was maintained for 6 months, despite a slight decrease in the antimicrobial effect. Hydrogel conjugates were found to be very stable even after two months immersed in acidic solutions that would otherwise dissolve the chitosan matrix. Ultrasound emulsification was proved as an efficient one-step loading method of hydrophobic clove essential oil into hydrophilic chitosan matrix. It was found that clove oil and its components have a double role. Besides providing bioactivity, they also behave as gelation-inducing agents, acting as an alternative to the classical chemical cross-linkers to ensure the good physical and chemical stabilization of chitosan.

Polysaccharides and Тheir Derivatives as Potential Antiviral Molecules

In the current context of the COVID-19 pandemic, it appears that our scientific resources and the medical community are not sufficiently developed to combat rapid viral spread all over the world. A number of viruses causing epidemics have already disseminated across the world in the last few years, such as the dengue or chinkungunya virus, the Ebola virus, and other coronavirus families such as Middle East respiratory syndrome (MERS-CoV) and severe acute respiratory syndrome (SARS-CoV). The outbreaks of these infectious diseases have demonstrated the difficulty of treating an epidemic before the creation of vaccine. Different antiviral drugs already exist. However, several of them cause side effects or have lost their efficiency because of virus mutations. It is essential to develop new antiviral strategies, but ones that rely on more natural compounds to decrease the secondary effects. Polysaccharides, which have come to be known in recent years for their medicinal properties, including antiviral activities, are an excellent alternative. They are essential for the metabolism of plants, microorganisms, and animals, and are directly extractible. Polysaccharides have attracted more and more attention due to their therapeutic properties, low toxicity, and availability, and seem to be attractive candidates as antiviral drugs of tomorrow.

Removal of oil spills by novel developed amphiphilic chitosan-g-citronellal schiff base polymer

A novel chitosan grafted citronellal (Ch-Cit) schiff base amphiphilic polymer was developed for the adsorptive removal of oil spills. The chemical structure was verified by FT-IR spectroscopy and ¹H NMR spectrometer, while the morphological changes and surface area were investigated by SEM and BET analysis tools. The amphiphilic character of Ch-Cit schiff base was controlled through variation of the grafting percentage (G%) of citronellal from 11 to 61%. Dramatic changes in the ion exchange capacity (IEC), solubility and water uptake profiles were established, while the oil adsorption capacity was founded in direct relation with the G (%) of citronellal. Operational conditions such as oil amount, adsorption time, adsorbent dose and agitation speed were investigated. The developed Ch-Cit schiff base exhibited a higher surface area (115.94 m²/g) compared to neat chitosan (57.78 m²/g). The oil adsorption capacity of the Ch-Cit schiff base was greatly improved by 166% and 120% for light crude and heavy crude oil, respectively. Finally, the adsorption process was optimized using response surface methodology (RSM).The results substantiate that the amphiphilic Ch-Cit schiff base could be efficiently applied as a low-cost oil-adsorbent for the removal of crude oil spills from sea-water surfaces.

A Complementary and Revised View on the N-Acylation of Chitosan with Hexanoyl Chloride

The modification of the biobased polymer chitosan is a broad and widely studied field. Herein, an insight into the hydrophobization of low-molecular-weight chitosan by substitution of amino functionalities with hexanoyl chloride is reported. Thereby, the influence of the pH of the reaction media was investigated. Further, methods for the determination of the degree of substitution based on ¹H-NMR, FTIR, and potentiometric titration were compared and discussed regarding their accuracy and precision. ¹H-NMR was the most accurate method, while FTIR and the potentiometric titration, though precise and reproducible, underlie the influence of complete protonation and solubility issues. Additionally, the impact of the pH variation during the synthesis on the properties of the samples was investigated by Cd²⁺ sorption experiments. The adjusted pH values during the synthesis and, therefore, the obtained degrees of substitution possessed a strong impact on the adsorption properties of the final material.