Preparation Of High Deacetylated Chitosan And Its Microspheres From Shrimp Shell Chitin

Chitosan,as the only polysaccharide with positive charge,has been widely concerned about because of its good biological activity.Chitosan and its derivatives are widely used in food,chemical,medicine and other fields,because of their excellent biocompatibility and degradability.In industry,shrimp shells,crab shells and other seafood chitin are used as the main raw materials for the preparation of chitosan.Shrimp and crab shell chitin can be prepared by simple acid-base treatment that removed proteins and minerals,but the application of chitin is limited due to its low solubility and chemically inactive.Therefore,preparing shrimp and crab shells chitin into chitosan,which is more widely used,is the focus of scientific research.The chitosan obtained by the traditional preparation method of chitosan is often of poor quality and requires high reaction conditions.In order to obtain high deacetylation degree and quality chitosan,while reducing the conditions required for the reaction.In this study,the chitosan with high degree of deacetylation was prepared by chemical deacetylation of shrimp shell chitin.Then physical and chemical methods were combined to further improve the process and moderate the reaction conditions to obtain chitosan with higher degree of deacetylation.Finally,chitosan microspheres with better quality were prepared for practical applications in the future.In this study,shrimp shell chitin was used as raw material,and glycerol and sodium hydroxide were mixed as reaction reagent.The experiment was carried out within several steps,during which the reaction reagent was replenished and the acetyl groups produced in the process were removed in time so that the following reaction would keep forward.The single factor method was used to discuss the effects of various factors on the properties of chitosan,and the response surface method was used to optimize the reaction conditions.The optimal reaction conditions of the chemical multi-step method were obtained as follows: the concentration of Na OH solution,the reaction time and reaction temperature were 24 M,8 h and 143?,respectively.The chitosan prepared by this method owned higher degree of deacetylation(91.11±1.5%)and lower viscosity average molecular weight(131±8 k Da).The technical characterization showed that the chitosan meet the standard of commercial chitosan.In order to further improve the degree of deacetylation of the chitosan and moderate the reaction conditions,the original shrimp shell chitin was pretreated by ultrasonic wave and then heated by ultrasonic-microwave instead of magnetic stirring.The response surface method was used to optimize the experimental conditions,and the optimal reaction conditions were obtained as follows: the concentration of Na OH solution,the reaction time and the temperature were22.7 M,7.7 h and 134?,respectively.The degree of deacetylation of chitosan was 96.61±1.5%and the viscosity-average molecular weight was 107±10 k Da.The degree of deacetylation of chitosan increased effectively and the molecular weight decreased.In the meantime,the reaction temperature,reaction time and reagent concentration were also decreased.After characterization,it was found that the chitosan prepared by this method still owned good chemical properties.Finally,chitosan microspheres with good quality were prepared by emulsification cross-linking method.The influence of various reaction factors on the morphology of the microspheres was explored to optimize the conditions for the preparation of chitosan microspheres with smooth surface and regular structure without damage.Provide further theoretical and technical support for the practical application of chitosan and its derivatives.