Fabrication And Property Modulation Of Chitin Functional Carriers

Chitin is the second largest abundant polysaccharide after cellulose in the world,which is derived from a wide range of food processing waste such as shrimp shells.But there is few research based on this polymer in the past because of its insoluble characters under common solvent,while the discovery of new solvent in recent years has brought new opportunities for the research of chitin.This paper studied the new materials based on the solvent of NaOH/Urea and their potential application,including the preparation of chitin microspheres and its application in such areas as food and environment,preparation of chitin films and their application as catalyst supports and potential applications in areas such as food packaging,preparation of nano chitin and its application as food emulsifier.The main results of this study are as follows:Extreme conditions such as strong acid,high temperature,high pressure homogenization are needed for conventional methods to prepare nano-chitin,which results in low yield or much energy consumption,so an alternative method to overcome the above problems is needed.?-chitin cannot be dispersed directly with ultrasonic treatment while ?-chitin regenerated from a NaOH/urea solvent can then be easily dispersed with ultrasonic treatment because the intermolecular forces of chitin were greatly weakened after the regeneration process.Ultrasonic dispersed chitin containing crystalline region and amorphous region can stabilize oil in water emulsions.Moreover,the average particle size of nano-chitin will be smaller,the degree of crystallinity will be lower and the emulsifying ability is stronger for regenerated chitin with longer ultrasonic time.Regenerated chitin with long ultrasonic time can stabilize high internal phase emulsion and the obtained emulsion can withstand extreme pH and high temperature environment,thus showing good stability for long time.The chitin film was prepared by dissolution and regeneration method possess high gas-barrier and high mechanical strength properties.However,the limited function prevents its application in a wider range of fields.Therefore,modification is needed to widen the application field of chitin film.So chitin film was first obtained after regeneration with alcohol,then incorporation of tannic acid into the chitin film through interfacial assembly was realized due to the strong interaction of chitin and tannic acid.Hydrogen bonds and hydrophobic interaction were found to be the main driving forces for the interfacial assembly.The mechanical strength of chitin film was enhanced and the water vapor transmission rate of chitin film was decreased due to the assembly of tannic acid.The antibacterial(both against Gram-positive and Gramnegative bacterial)and antioxidant behavior of chitin film has been greatly enhanced and they increased with increasing concentration of tannic acid.The chitin membrane prepared by dissolution and regeneration method has porous structure,which is a good carrier of inorganic nanomaterials.Introduction of inorganic materials into nanomaterials by in situ synthesis method can expand the application field of chitin,but also control the size and solve the problem of secondary pollution of inorganic nanometer materials by taking advantage of the chitin mesh.Chitin graphene composite film was prepared by regeneration of chitin with alcohol,and cuprous oxide nanoparticles was in situ prepared in the network structure of graphene chitin-film,where the network structure immobilized the particles,controlled the morphology and size of the particles.Chitin cuprous oxide can degrade part of methyl orange,and the network structure of chitin film preserved the catalytic active sites of cuprous oxide,leading to its increasing catalytic efficiency with increasing concentrations of methyl orange.In addition,the introduction of grapheme greatly enhanced the catalytic effect of cuprous oxide due to its good photoelectron transfer capabilities to protect the active sites of cuprous oxide from destruction during the catalytic degradation process.Traditional chitosan microspheres need to be made with the toxic crosslinking agent,glutaraldehyde,or a more expensive crosslinker,genipin which limits its application in the field of food science.Therefore,it is significant to look for green methods for preparing chitin microspheres.New chitin microspheres with different sizes and magnetic chitin microspheres were successfully prepared with the emulsion templating method.?-amylase was successfully immobilized in partly deacetylated magnetic chitin microspheres with the cross-linking of glutaraldehyde and the immobilized enzyme showed good stability and reusability.Gold nanoparticles were in situ prepared in magnetic chitin microspheres,where chitin microspheres controlled the size of gold nanoparticles to prevent aggregation,and the immobilized gold nanoparticles showed good catalytic performance,reusability for the model compound 4-nitrophenol.Taking advantage of nucleophilic substitution reaction of reactive dyes with magnetic chitin beads under alkaline conditions,negatively charged sulfonic acid groups was successfully introduced to magnetic chitin microspheres,and the modified chitin microspheres showed better performance for adsorption of cationic dyes.Anthocyanin has poor stability and limited bioavailability,so looking for new methods to protect and target delivery of anthocyanins to colon is an effective way to improve their bioavailability of anthocyanins.Chitin microspheres with a diameter of 80?m were obtained with the emulsion templating method.The obtained chitin microspheres were found to load anthocyanins with capacity as much as 2688mg/g,which is the largest amount ever reported.Electrostatic interaction,hydrogen bonding and hydrophobic interactions were proved to be the main driving forces for the load of anthocyanins by chitin microspheres under the optimal loading condition.Moreover,only 30% of the loaded anthocyanins was released under the gastrointestinal tract because of the strong interaction between chitin microspheres and anthocyanins,and most of the loaded anthocyanins was delivered to the colon,where anthocyanins will be released when chitin was digested by the bacterial,then anthocyanins will exert its health promoting effects.The strong interaction between chitin microspheres and anthocyanins made chitin microspheres a promising carrier for colon specific delivery of polyphenol compounds.