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Studies on Chitosan and Its Derivatives Adsorption for Paralytic Shellfish Poisoning in Ostrea Rivul

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Tutor: YangXiHong
School: Guangdong Ocean University
Course: Of Food Science
Keywords: Ostrea Rivularis Could,Paralytic Shellfish Poisoning toxins,Chitosan,N,O-carboxy
CLC: TS254.4
Type: Master's thesis
Year:  2011
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Ostrea Rivularis Could is the major coastal aquaculture molluscs in the northern China. Paralytic shellfish poisoning (PSP) is a public health and safety hazard concern worldwide and causes severe economic losses globally. It is mainly originated in toxic marine dino?agellates of the genus Alexandrium, and accumulated in shellfish via the food chain and causes sporadic food poisoning in human in many parts of the world including China. Chitosan (CTS) is a crude macromolecular compound, the aetive funetional goups (-NH2 and-OH) of chitosan can chelate heavy metal ions and other groups.Chitosan can be used as a macromolecular adsorbent to rernove heavy metal ions. Further more,chitosan is avirulent and it would not bring secondary pollution, and can be disassemble by biologic catabolism. PSP were obtained by sonicating Alexandrium minutum, and used to adsorpted by CTSD. Through establish oyster contamination model, CTSD were used as an adsorbent to remove the PSP which was consisted in the oyster. The conclusions of this paper just as follows:(1) The methods for culturing of Alexandrium minutum and Alexandrium catenella were established and improved in the lab. Through concentrating and harvesting the cells of algae, Alexandrium minutum was chose as the production of the PSP. Firstly, the logarithmic phase of the algae cell was inoculated, the cell growth rate kept higher in initial 8 days. After it attained the highest density of cell (2.0¡Á10~4cells/mL), the algae was collected by filtration, the crude toxin was extracted by 0.05 mol/L acetic acid. Combined with the mice bioassay, the crude toxin was identified, the result showed the major toxic component from A.catenella were GTX1,GTX2,GTX3 and GTX4 by high performance liquid chromatography (HPLC) and the concentrations of them were about GTX4 (5.04)>GTX3 (4.97)>GTX1 (2.14)>GTX2 (2.08) (fmol/cell), respectively. The crude toxin was purified via Sephadex-G15 column chromatography and detected by fluorescence spectroscopy and the mice bioassay, the result showed that the impurities can be effectively excluded by Sephadex-G15 column chromatography.(2) In this work, adsorption of PSP onto Chitosan and its derivatives (CTSD) were investigated with respect to pH value, contact time, temperature and the volume of CTSD. Then, the kinetic data was tested using pseudo-first-order and pseudo-second-order kinetic models. It is proved that the data correlated well with the pseudo-second-order kinetic model, indicating that the chemical sorption was the rate-limiting step. The best interpretation for the thermodynamics experimental data was explained by the Freundlich isotherm model. Thermo-dynamic parameters like Gibbs free energy (¡÷G~o), enthalpy (¡÷H~o) and entropy (¡÷S~o) were evaluated by applying the Van¡¯t Hoff equation. Values of them¡÷G~o<0,¡÷H~o>0,¡÷S~o>0, indicating that the adsorption was feasible, spontaneous and endothermic adsorption processes in nature.(3) In this paper, we focused on the accumulative rate, discharge rate of paralytic shellfish poisoning produced by Alexandrium minutum in Ostrea Rivularis Could.The experiment consists of two steps, the accumulation step and the elimination step. Furthermore three grades of the algal feeding amount are designed in the accumulation step, grades A is 4.0¡Á10~3 cell/mL, grades B is 8.0¡Á10~3 cell/mL and grades C is 1.2¡Á10~4 cell/mL. The PSP accumulative rate in the Ostrea Rivularis Could increases rapidly till the upper limit with the increase of Alexandrium minutum cell abundance in all cases. In our study, the maximum cumulative amounts respectively for grades A, B, and C are 5692 MU, 6503 MU and 8193 MU, the final amount of PSP was 14.23, 16.26 and 20.48 times over the national standard.(4) Establish oyster contamination model. Put 0.05 g/L of chitosan derivatives in the breeding process have a great role on the promotion of oyster cadmium discharges for the grades B pollution oyster. Through 15 days desorption experiment, the amount of PSP from the initial 6503 MU to the final 93.33 MU.The chitosan micrballon prepared in this study was used by removing PSP from the Ostrea Rivularis Could. The study found that chitosan micrballon is the best adsorbent of PSP. There would be good removal effect of PSP on oyster meat using chitosan micrballon without adjustting pH value, it can be achieved removal rate reached 90%.(5) Besides, we have a further research about the oyster, enzymatic hydrolysis technology by papain protease and Neutral protease of Ostrea Rivularis Could was investigated. Solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) were used to analysis the effects of curing to volatile compounds in Ostrea Rivularis Could with and without enzymatic hydrolysis, and the different affection of the processing were discussed. 57, 60, and 62 kinds of volatile compounds were identified by comparing their mass spectra with those contained in the NIST mass spectral database. Among these compounds, most of them were hydrocarbons, alcohols, aldehydes, kotones, and sulfuric compounds. They cooperate with each other to make up of the specific aroma of oyster and hydrolysates¡¯flavor. The results also indicated kotones contents were more than the hydrolysates, aldehydes and esters were more in oyster hydrolysates flavorings. Compare the determination results of oyster before and after enzymatic hydrolysis reaction, all of them have 19 kinds of alcohols in the three samples, and the contents were 40.24%, 41.20%, and 43.28%, respectively. Therefore, the product manufactured by enzymatic hydrolysis reaction can improve the flavor of the seafoods, and have good application foreground.
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