Preparation Condition And Characterization Of The Chitosan From Flies Maggots Shell

Flies maggot shell (also known as maggots skin) contains about30%~54.8%chitin, withlow content of limestone, wax, carbonate, heavy metal and less pigment, is an excellent rawmaterial of chitin. Chitosan is the deacetylase product of chitin. Due to its natural non-toxicand functional diversity, chitosan has been widely used in many fields, constantly expandingdemand for chitosan at home and abroad, and it has become one of the hottest areas ofresearch.Flies maggots shell as raw materials, the separation, purification conditions andantibacterial activity of chitosan were studied in the thesis. The main research contents,methods and conclusions are as follows:(1) With flies maggots shell as raw material, the industrial grade white or slightly yellow(a handful darker) flake chitin was acquired after treatment of taking off inorganic salts,deproteinization, decolorization, and the yield was17.58±0.03%.(2) Chitosan with higher deacetylation degree and viscosity was made by removingacetyl from chitin in lye conditions. On the basis of single-factor test, the optimum conditionsof the chitin deacelation reaction were determined by response surface methodology. Theoptimum conditions were as follows: sodium hydroxide concentration of50%,solvent-to-sample ratio of57.49:1, reaction time of7.3h, and reaction temperature of100℃.Under these conditions, the resulting chitosan degree of deacetylation and viscosity were80.24%and50,351.23mPa S, with a difference of1.48%and2.48%from the respectivevalue of the model, respectively, demonstrating the model is reasonable and reliable.(3) The chitosan was extracted by acetate solution from chitin deacetylation products.Effects of acetic acid concentration, time, temperature, pH and the liquid to solid ratio onchitosan yield were studied by single-factor tests. The optimum conditions of extraction ofchitosan were determined by response surface methodology. The optimum conditions were asfollows: acetic acid concentration of10.42%, reaction time of3.33h, solvent-to-sample ratioof40.33:1, reaction temperature of50℃, and pH of7.0. Under these conditions, chitosanyield was87.50±1.05%.(4) On the basis of the above conclusions, a pilot scale test of preparation of chitosanfrom flies maggots shell was carried out. Chitosan products with super high viscosity andmoderate degree of deacetylation was obtained, and its other indicators got up to industrialgrade requirements.(5) Antibacterial activity of chitosan from pilot test to Acetic acid bacteria, Lactic acid bacteria, Escherichia coli, Staphylococcus aureus and Bacillus subtilis was studied at differentconcentrations and pH values. The results indicate that inhibition to Lactic acid bacteria andAcetic acid bacterium was gradually increased, and to Escherichia coli was declined withinthe concentration of1mg/mL to50mg/mL; and the inhibition to Staphylococcus aureus andBacillus subtilis was strongest at the concentration of5mg/mL and10mg/mL, respectively.Antibacterial activity of chitosan to Staphylococcus aureus was strongest among theexperimental microbial at a certain concentration, followed was Escherichia coli, Bacillussubtilis and Lactic acid bacteria.The inhibition of chitosan to both Staphylococcus aureus and Bacillus subtilis wereweaker and weaker within pH values of4.0to7.0, while the antibacterial activity toEscherichia coli was strongest within pH values of5.5to6.0.(6) Maggots shell chitosan was separated and purified by gel chromatography ofSephacrylTM, and the optimal elution conditions determined by single factor test was asfollows: chitosan was eluted with0.05M acetic acid-sodium acetate buffer, sample volumewas15ml of chitosan solution (5mg/mL), and the flow rate was0.5ml per minute. Theeffluent was identified as two components with molecular weight of620kDa and230kDa byHPLC analysis, which showing the effect of this method is good, and then the twocomponents was analyzed by infrared spectrum and crystal structure, both components hadcharacteristic absorption peak of chitosan functional group in the IR spectrum, and degree ofcrystallinity of the component1is low, and degree of crystallinity of the component2is high.