Effects of Nitrite on the Oxygen Consumption and Ammonia Excretion of Tiger Shrimp Penaeus Monodon

Abstract

The objective of the study were to explore the effect of shearing conditions(chitosanconcnetration,shear rate,reaction temperature,type of solvent and shearing time)andstorage in acidic solutions(at ambient temperatures or at 80℃)on molecular weight andpolydispersity of treated chitosans.The results show that chitosans were degradedfaster in dilute solutions and faster with higher shear rate,faster in higher temperature solutions,faster in the solvent systems in which chitosan molecule is more extended,anddegradation increased with prolonged shearing time.Chitosan was degraded to one thirdof the original molecular weight during storage at 80℃ in acetate buffer for 120 min.However,storage at ambient temperatures,degradation of chitosans was faster for highermolecular weight chitosans.The polydispersity decreases with shearing treatment for allshearing conditions studied and during storage in acidic solution.Polydispersitydecreased from 10.10 to 6.05,7.02,7.53,and to 8.80 for 0.2%,0.8%,1.4% and 2.0% solutionsrespectively.Polydispersity decreased to 10.75,9.66,7.25 and 7.53 for sheared at2600,10400,18300,and 26000 sec^(-1)for 30 mim respectively.Polydispersity decreasedto 7.53,5.15 for solution treated at 4℃ and 40℃ respectively.Polydispersity decreasedto 7.53 and 8.16 for chitosan treated in acetic acid buffer and 5% acetic acid,respectively.Polydispersity decreased to 3.14 after prolonged(300 min)shearing treatment.After storage in acetic acid buffer at ambient temperatures for 17 days,polydispersitychanged from 10.10 to 7.01 for untreated and from 8.52 to 7.30,from 7.53 to 4.98 andfrom 4.57 to 2.42 for those chitosans subjected to shear treatment for 5 min,30 min,and120 min,respectively.本研究目的在探討剪力作用條件（溶質濃度、剪速率、反應溫度、溶劑種類與剪力作用時間）與在酸性水溶液（室溫或80℃）儲藏對受剪力作用的幾丁聚醣的分子量與分散度的影響。結果顯示幾丁聚醣在稀溶液下、在高剪速率作用下、在高溫下處理與在使幾丁聚醣分子變得較伸展的溶劑裏降解較快，也隨剪力作用時間的增加、降解程度隨之增加，幾丁聚醣儲存在80℃之醋酸緩衝溶液120分鐘，其分子量降解至原來的1/3，在室溫下儲藏高分子量的幾丁聚醣的降解較快，分散度隨上述處理條件作用後而減低、也隨著酸性水溶液的儲藏而減少。0.2％、0.8％、1.4％、2.0％的幾丁聚醣溶液的分散度經過剪力作用後由10.10分別減低至6.05、7.02、7.53與8.80、而2.0％的幾丁聚醣溶液經2,600、10,400、18,300與26,000 sec^(-1)處理30分鐘後分散度變成10.75、9.66、7.25與7.53，幾丁聚醣溶液在4℃或40℃下受剪力作用30分鐘、分散度由10.10分別降低至7.53與5.15，在醋酸緩衝溶液或5％醋酸溶液的幾丁聚醣的分散度經處理後分別下降至7.53或8.16，經300分鐘的剪力作用、分散度下降至3.14，在醋酸緩衝溶液下儲藏17天沒有受剪力處理的幾丁聚醣溶液的分散度由10.10減至7.01而受剪力處理5分鐘、30分鐘與120分鐘者的分散度分別由8.52、7.53與4.57下降至7.30、4.98與2.42。