Development Of New Technology For The Total Components Transformation Of Shrimp And Crab Shells

With the rapid development of aquatic industry,a large amount of shrimp and crab shell wastes are produced in its processing and consumption.Shrimp and crab shells are high quality biomass resources,which contain a lot of calcium salts,protein and chitin.At present,the utilization of shrimp and crab shell is mainly to extract chitin,resulting in the waste of biological calcium and protein resources,and the process of environmental pollution.Therefore,the development of a new technology for clean utilization of shrimp and crab shell is of long-term significance to the practical role and sustainable utilization of resources.The optimization of extraction and transformation conditions of all components in shrimp and crab shell was studied.The results of this paper are as follows:(1)In this paper,a new pretreatment method was adopted to improve the internal structure of shrimp and crab shell by puffing,and then the chitosan was prepared by acid decalcification salt,alkali deproteinization and alkali-alkali solution deacetylation,and calcium formate and protein products were obtained.The process parameters were optimized by single factor experiment.The optimal conditions for organic acid decalcification were as follows:the concentration of formic acid was 10.0%,the reaction time was 1 h,the reaction temperature was 60℃,the calcium salt in shrimp shell was almost removed,the filtrate was recovered by alcohol precipitation,and the extraction yield of calcium formate was 98.8%.The optimal deproteinization conditions were as follows:Na OH concentration 15.0%,reaction time 4 h,reaction temperature 60℃,protein was almost removed,filtrate was recovered by alcohol precipitation,the extraction yield of protein was 98.0%.The remaining chitin was deacetylated with alkalic solution.The optimal process conditions are:M alkalic solution:M shrimp(crab)shell=30:2.2,Na OH concentration 15.0%,water content 6.25%,reaction temperature 80℃,reaction time 12 h,the deacetylation degree of product 78.4%,the yield of chitosan 99.5%.The yield of calcium formate,protein and chitosan was 98.8%,98.0%and 99.5%,respectively.(2)In order to extract chitosan with high deacetylation degree and shorten the reaction time,a new process of one-step deacetylation of protein by solvothermal method was developed to prepare chitosan.The product after decalcification of is solvo-thermally treated to simultaneously deproteinizate and deacetylate with alkali-alcohol solution.The optimal process conditions are as follows:m alkali-alcohol solution:M shrimp(crab)shell=30:4.5,Na OH concentration 15.0%,water content 6.0%,reaction temperature 150℃,reaction time 6 h,chitosan deacetylation degree of 85.8%,the yield of 99.3%,the overall process reaction time 7 h.Compared with the traditional process,the time is shortened by58.8%,and the quality of deacetylated product meets the quality standard of food-grade chitosan.The yield of protein was 98.0%and the yield of chitosan was 99.3%.(3)A new technology of direct catalytic carbonization of decalcified shrimp and crab shells to prepare high specific area activated carbon was developed.Calcium formate was extracted from shrimp and crab shells with the remaining solid as carbon source and EDTA Fe as activator.The activator was 0.3 times of raw material and the carbonization temperature was 700℃.Porous carbon with specific surface area of 1062 m~2/g was prepared,and the yield of porous carbon was 30.0%.Porous carbon has excellent adsorption capacity for N,N dimethyl acetamide(DMAC).The adsorption process conforms to the quasi-second-order kinetic model,and the adsorption mechanism is Langmuir adsorption.