一种微生物絮团的生化分析及其对对虾免疫力的影响

利用红糖与尿素为碳氮源在自然海水中培养微生物絮团,获得絮团产物,对该产物离心后进行初步的生化分析表明,絮团产物上清液中微生物胞外产物重均分子量为213281Da。絮团沉淀物中多糖含量占29.6%,氨基酸含量占12.6%。将絮团产物按0、0.02、0.1、0.5、2.5%的比例添加至低蛋白饲料中投喂凡纳滨对虾 (Litopenaeus vannamei),14d后分别测定实验对虾血清溶菌活力、抗菌活力和酚氧化酶活力,结果显示在饲料中添加微生物絮团浓度为2.5%的对虾血清中抗菌与溶菌活力最高(P<0.05),添加微生物絮团浓度为0.5%与2.5%的对虾血清中酚氧化酶活力较低蛋白饵料对照组显著提高(P<0.05)。用哈维氏弧菌(Vibrio harveyi)感染实验对虾后,结果显示饵料中添加0.1%微生物絮团产物组对虾的死亡率最低。综合分析认为对虾摄食微生物絮团后,能够显著提高对虾的非特异免疫力,抗微生物感染的能力得到增强。

The biochemical analysis of a microbial flocs and its effect on the immunity of Litopenaeus vannamei

Microbial flocs is a complex of bacteria, residue of feed, algae, protozoa in aquaculture. Biofloc technology (BFT) based on microbial flocs have been applied in the culture of Oreochromis mossambicus, Litopenaeus vannamei, Macrobrachium rosenbergii and so on. In this study, microbial flocs was achieved by artificial culture in natural marine water. In order to investigate the active ingredients in the microbial flocs, molecular weight, content of total polysaccharide and amino acid in the microbial flocs were analyzed by methods of gel permeation chromatography, Phenol sulfuric acid colorimetry and automatic analyzer for amino acid respectively. The results of preliminary biochemical analysis showed that the average molecular weight of extractive from supernatant of microbial flocs was about 213281Da, the polysaccharide and amino acid content of sediment from microbial flocs was 29.57% and 12.63% respectively. Further study was conducted to investigate the function of microbial flocs to enhance the immune activity of shrimp. Microbial flocs were added in the Litopenaeus vannamei diet at a rate of 0%, 0.02%, 0.1%, 0.5%, and 2.5%. Activity of antibacterial, lysozyme and phenoloxidase (PO) in serum of shrimp were analyzed after 14 days of feeding trial. Challenge test was carried out to evaluate the effect of microbial flocs on improving the ability of shrimp against virulent bacterium of Vibrio Harveyi after 30 days of feeding trial. Results show that activity of antibacterial and lysozyme in serum of shrimp fed diet containing microbial flocs at a rate 2.5% were higher than that in other groups (p<0.05). PO activity in serum of shrimp fed diet containing microbial flocs at rates 0.5% and 2.5% were higher than that in other groups(p<0.05). Challenge test show that cumulative mortality of shrimp fed diet containing microbial flocs at a rate of 0.1% was the lowest than that in other groups(p<0.05). The present results suggested that microbial flocs can be utilized by shrimp and can improve the ability of non-specific immunity of shrimp.