| Litopenaeus vannamei also called Penaeus vannamei,is deeply popular with domestic and international consumers,because of its taste and high nutritional value.Litopenaeus vannamei is mainly transported in living body for sale and frozen processing,with fresh prawns about two times the price of frozen shrimps,Therefore,the live transportation of Litopenaeus vannamei has important economic value.The main methods of living transportation are water transportation and waterless transportation.It is easy to operate,with large capacity,low cost,and is beneficial to long distance transportation,waterless transportation has a broad prospect.low temperature or taking advantage of anaesthesia method to Make the aquatic products dormant to achieve waterless transportation.Under low temperature stress,aquatic products are prone to stress injury and sudden death rate is high.Carbon dioxide(CO2)has been widely used in aquatic products transportation for its innocuity and high safety.The study of waterless transportation of Litopenaeus vannamei by combined stress of low temperature and CO2 anaesthetised,firstly the optimal treatment conditions for waterless transportation of Litopenaeus vannamei by response surface method was obtained,then the determination of glycolysis key enzymes and related immune indices during transportation were measured,finally the expression of muscle protein during transportation using differential proteomics was studied to explore the mechanism of metabolism.The main contents and results are as follows:(1)Based on the principal of Box-Behnken experimental design,temperature(A),p H(B),transit time(C)were chosen as independent variables to explore the impact on survival rate to certain the best dealing condition.The interaction between temperature and p H had the significant impact on survival rate of the shrimps(p<0.05),while the interactions between temperature and transit time and the interactions between p H and transit time had not significant impact on survival rate(p>0.05).Under the appointed transit time(8 h),the optimal processing conditions are as follow: temperature was 18.2 ?,p H was 6.08,the prediction of survival rate was 86.4%.The deviation between the practical survival and predictive value of model was 4.63%.(2)Maked use of colorimetric method and cell counting instrument,these parameters under three different states(untreated,during waterless transportation and recovery)were assessed: glucose(Glu)which is metabolic substrate,Lactic acid(LD)which is the product of aerobic metabolism,succinate dehydrogenase(SDH),lactate dehydrogenase(LDH),total haemocyte counts(THC),superoxide dismutase(SOD),peroxidase(POD).The results showed that the concentration of Glu was lower than the control while the concentration of LD was in contrary.The activities of hexokinase(HK),phosphofructokinase(PFK)and pyruvate kinase(PK)were higher than the control.The activities of SDH were weaker than the control instead the activity of LDH was significantly stronger than the control during the transportation.Although THC decreased,the activities of SOD and POD increased with time.After recovery,the activities of HK,PK,SOD and POD recovered to normal level.But the concentration of Glu and LD,the activities of PFK,SDH,LDH and THC were significantly different from the control.The above facts suggest that during the transportation the glycolysis cycle accelerated and the metabolism of shrimps switches from aerobic to anaerobic;cellular immune was suppressed while humoral immune function still works.(3)The iTRAQ approach was applied to identifying differentially expressed proteins between while shrimp during waterless transportation and the control.The extracted samples were enzymolysis by FASP,identified with iTRAQ reagent couple with LC-MS/MS and then analyzed by Protein Pilot 5 software for database search,by comparing the search for protein quantification of differentially expressed proteins.The analyses of differentially expressed proteins were conducted with GO,KEGG network.A total of 2670 proteins with quantitative information were identified.Compared with the control group,150 proteins were up-regulated and 20 proteins were down-regulated of the experimental group.26 target differential proteins were obtained through bioinformatics analysis,which were divided into 6 categories: the proteins related to glycogenolysis,glycolysis,TCA cycle,oxidative phosphorylation,ATP decomposition and synthesis and immune respectively.The results showed that:compared with the control group,6 proteins related to gluconeogenesis were up-regulated,the proteins related to glycolysis showed an increasing trend of up-regulated,12 proteins related to TCA cycle and oxidative phosphorylation were down regulated in experimental group,4 proteins related to stress were up-regulated.Thus,the aerobic metabolism of Litopenaeus vannamei was weakened duringwaterless transportation,and anaerobic metabolism was dominant.The body reinforced the resistance to the adverse environment. |
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