| Chitin is the second most abundant natural polysaccharide next to cellulose, and is obtained from the cell walls of fungi and yeast and from the shells of crustaceans, such as crabs and shrimps, and has many applications in agriculture, medicine, environment and food. Ingeneral, chitin consists of copolymer repeat units ofβ-(1-4)-linked 2-acetamido-2-deoxy-β-D-glucose andβ-(1-4)-linked 2-amino-2-deoxy-β-D-glucose. As chitin dissolves only in specific solvents, such as N,N-dimethylacetamide-LiCl, hexafluoroacetone, and hexafluoro-2-propanol, its practical uses are limited. Deacetylating chitin to chitosan, which increases the units ofβ-(1-4)-linked 2-amino-2-deoxy-β-D-glucose, is one way to increase of its solubility in normal solvent such as delute HAc.The research was done for establishing a fast deacetylation method for the preparation of chitosan from chitin, and the lipid regulation and immunomodulatory effects on experimental mice of chitosan with different molecular weight was sduied,and the fast dection method of chitin/chitosan in functional food was established.1.The solid-phase rapid preparation technology of chitosan from chitin on high temperature was investigated.Using sodium hydroxide as the pro-nuclear agent, the effects of m(NaOH):m(chitin), reaction temperature,and thereaction time on the DD and intrinsic viscosity[η] of chitosan was studied. The results of single factor experiment suggested that with the increasing of m(NaOH):m(chitin), the reaction temperature, and the reaction time, the DD of chitosan was quickly decreased. The optimum conditions for the fast deacetylation of chitin was studied through a CCD experimental design, where temperature, time and m(NaOH):m(chitin) ratio were varied.Then response surface analysis(RSM) was applied to optimize the deacetylation condition of chintin, and the optimum conditions were as follows: reaction temperature(177℃), mass ratio 1:1[(m(NaOH):m(chitin)],reactio time (28min). Under the optimum condition, the DD of the prepared chitosan was about 90.0%, and the intrisic viscosity was about 27.65 mL·g-1.Based on above sdudies, the properties chitosan prepared by sressing methods using a twin-screw extruder was sdudied, and the working parameter of twin-screw extrude on the DD, viscosity and IR of chitosan prepared by the sressing mothod from chitin was sudied.The result showed that the partical size of chitin, the heating temprature,the mass ratio [(m(NaOH):m(chitin)],and the rotationl speed had significant influence on the properties of chitosan prapared from chitin. The sressing methods using a twin-screw extruder was able to realize the rapid and continuous preparation of chitosan from chitin.2.The chitosan with different molecular weight was prepared with non-specific enzyme hydrolysis, and its immunomodulatory effects on hypoimmune mice was investigated. Chitosan with different molecular weight was given to normal mice and hypoimmune model mice induced by Hydrocortisone, respectively. The spleen and thymus index, DTH, hemolysin content, antibody formaing cells number, phagocytosis ability of peritoneal macrophage and carbon particleclearance index were measured respectively. Chitosan with different molecular weight could significantly increase the spleen and thymus index, hemolysin content obviouslly (P<0.01);heighten delayed allergic level(P<0.01);promote the phagocytosis ability of peritoneal macrophage (P<0.05,P<0.01).The result showed that chitosan hydrolysates can stimulate both specific and non-specific immune function in mice.3.The effect of chitosan with different molecular weight on blood lipid regulation in experimental hyperlipidemia mice was studied. Hyperlipemia model mice were established by feeding the mice with high fat emulsion. Meanwhile they were given the samples with different dosages for 30 days. The contents of TC and TG in serum, liver and feces were examined. Results:The content of serum TC in model group was significantly higher than that of control group (P<0.01),while the model TG content of the control group was significantly lower than the control group (P <0.01).every group could decrease the serum TC(P<0.01)significantly, except for the group of chitosan. Liver TC and TG of Model group were significantly higher than those of normal control group (P<0.01),all sample groups can significantly reduce the liver TC and TG (P<0.01).To compare with the model group, non hydrolysate chitosan group can increase the faeces TC significantly, but the total lipid of faeces was very low. Conclusion:Different chitosan hydrolysates can regulate the level of blood lipid and liver lipid, especially they can decrease the liver TC and TG significantly. The results indicate usability of chitosan hydrolysates as a hypocholesterolemic agent.4.The scavenging effects on superoxide anion radical and hydroxyl radical of chitosans with different weight molecular was sudied by means of the chemiluminescence analysis. The experimental results showed that the four chitosan saples with different molecular weight all exhibited significant scavenging capacity on superoxide anion radical and hydroxyl radical,which was increased with the chitosan. The scavenging effects on superoxide anion radical and hydroxyl radical was increased with the decreasing of the molecular weight of chitosan.Moreover, chitosan with low molecular weight had strong lipids regulatory effcts on Hyperlipemia model mice, showed that low molecular chitosan could be hypolipidemic drug.5.A rapid and sensitive method is developed for determination of the chitosan content in fuctional food. The standard curves for glucosamine hydrochloride showed linearity(r≥0.997) over the selected concentration range from 46μg/L-500μg/L.The limit of detction and the limit of quantitation were 22μg/L and 50μg/L, respectively. The precision(RSD) was 3.08%, and the recovery was between 98.23-103.01%.The sample was hydrolyzed under the optimum condition of 2mol/L HCl at 110℃for 12h, using HPLC with 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization and Variable Wavelength Detection (VWD).
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