The Study On Chitin Separation And Chitosan Preparation From Periplaneta Americana

Chitin is a kind of natural polysaccharide containing the element of N and it is also the second most abundant natural polysaccharide after cellulose.It exists mainly as a part of exoskeleton of Arthropod.Chitin and its main derivative chitosan possess excellent biocompatibility,biodegradability,absorbability and non-toxicity.They have been applied broadly in medicine,agriculture,food industry,cosmetic,effluent treatment and so on.Insects live in every single corner all around the world and own extraordinarily huge biomass,which means they are important natural resources.Periplaneta americana is one of the biggest kinds of cockroach.Its vitality is so tenacious that it can endure serious starvation.It could also reproduce easily.All these properties meet the requirements of artificial breeding.In China,there have already been several bases of P.americana breeding.In this dissertation,chitin was separated from P.americana and then converted into chitosan by deacetylation.The obtained chitin and chitosan were compared with commercial shrimp chitin and the chitosan prepared from it to examine the qualification of P.americana as a chitin resource.Chitin separation was conducted by the conventional method of acid and alkali,including defatting(DF),deproteinization(DP)and demineralization(DM).After DF through Soxhlet extraction method by hexane,it was observed that there was 25.03% of lipid in P.americana,implying that it could be a great resource of lipid.The single round DP was separated into 4 different rounds to save the usage of NaOH and time and to reduce the damage to the environment.Compared with single round DP,as the results showed,multi-round DP reduced the consumption of NaOH and time to 77.78% and 62.5%,respectively.The purity of final chitin was 97.66%.The obtained chitin and commercial shrimp chitin were all characterized by different methods.It was found that they owned the same essence — the type of ?,implying that P.americana meet the fundamental requirement as a chitin resource.But the crystallinity index and molecular weight of the obtained chitin from P.americana were lower,while its degree of acetylation was higher.As long as the chitin was separated,it was converted into chitosan.In this dissertation,surface response method was utilized to produce mathematical models that explaining the functional relationship between the experiment factors(concentration of NaOH solution,temperature,time)and the properties of chitosan,degree of deacetylation(DD)and molecular weight(Mv).It was found that concentration of NaOH solution impacted DD and Mv the most seriously;temperature impacted Mv more seriously than DD;time did not impact DD and Mv significantly.By applying the functional relationships,chitosan with 96.31% of DD could be produced,with concentration of NaOH solution,temperature and time being 23 M,150? and 18 h,respectively.Then DD and Mv of chitosan were manipulated by adjusting the experiment factors after solving the functional equations.The results were examined by practical tests.It was found that if the requirements on DD were the opposite to that on Mv,the results could be realized more accurately.The commercial shrimp chitin was also converted into chitosan under the same experiment conditions obtained above for comparison.It was exhibited that the chitosan from P.americana could achieve similar maximum DD,but its Mv was smaller.