The Preparation Of Chitooligosaccharides And The Application In Aquaculture

To determine the effects of chitooligosaccharides on growth and immunity in Litopemaeus vannamei and Portunus trituberculatus.This paper studies the enzymes solution of the preparation of chitooligosaccharides. The chitooligosaccharides are prepared into different degrees and molecular levels from enzymolysis liquid by ultrafiltration and frozen drying. The chitooligosaccharides prepared were used in the culture of Litopemaeus vannamei and Portunus trituberculatus. The effect of addition, degrees and molecular levels were studied to make sure the function of chitooligosaccharides used in Litopemaeus vannamei and Portunus trituberculatus. The study can be the foundation for the chitooligosaccharides in the further application and promotion in aquaculture.Results show that the optimal temperature,pH value,concentration of substrate , reaction time and enzyme concentration are 3%,3mL/g,45℃,5.8,12hours. The different degrees (74.5%,85.3%,93.2%)and different molecular levels (less than 3kDa,3k～5kDa and5k～10kDa)chitooligosaccharides were prepared by ultrafiltration and frozen drying.The research shows that oligosaccharides can significant improve weight gain rate, survival rate , the main hemocyte densities , the activities of acid phosphatase, lysozyme and peroxidase of Litopenaeus vannamei compared with blank group(P<0.05), the effect is better than others when the addition of oligosaccharides is 0.25g/kg and 0.50g/kg. To some extent ,When the addition of oligosaccharides is 0.25g/kg and 0.50g/kg can improve the activity of total superoxide dismutase , but there was no significant difference in total superoxide dismutase activity between test group and blank group(P>0.05).The different degrees and molecular levels have no significant influence in the growth and non-specific immunization of Litopenaeus vannamei(P>0.05)with the increase of degree and the decrease molecular weight the promotive effect rising. By comprehensive consideration, the suitable addition level , degree level and molecular level used in Litopenaeus vannamei are 0.25～0.50 mg/kg, 74.5% and less than 10kda.Chitooligosaccharides added into basal feed can significant increase the growth rate of Portunus trituberculatus(P<0.05).It can also increase the main hemocyte densities and survival rate of Portunus trituberculatus, The degrees and molecular levels have no significant influence in the main hemocyte densities(P>0.05). The result showed that chitooligosaccharides can significant enhance the activities of acid phosphatase, total superoxide dismutase, lysozyme, peroxidase and the blood corpuscle density of Portunus trituberculatus ( P < 0.05 ) , the effect is better than others when the addition of oligosaccharides is 1.0g/kg. The degrees have no significant influence in the growth and non-specific immunization of Portunus trituberculatus. When the molecular weight is less than 5kDa the growth of Portunus trituberculatus are significant improved Compared with 5kDa～10kDa. In conclusion, the suitable addition level, degree level and molecular level used in Portunus trituberculatus are 1.0g/kg, more than74.5%, less than 5kda.