Ten Antarctic bacteria strains with higher exopolysaccharide-producing ability were screened from more than 600 strains by phenol-sulfuric acid and alcohol precipitation.Phylogenetic analysis showed that 9 strains belonged to genus of Pseudoalteromonas and 1 strain belonged to genus of Psychrobacter.The crude exopolysaccharide (EPS) was obtained after fermentation broth treated by alcohol precipitation,proteins removal (Sevag method) and lyophilized.Strain 3-3-1-2 had highest EPS-producing ability,and its EPS yield was up to 0.6 g/L.The EPS produced by 4 strains with higher yield was chosen to test their immunologic activity on turbot.Results showed that on the 3 d after injected with EPS 20 # 3,the activities of both AKP and CAT in the serum of turbot increased 39％ and 24％ than those of control groups respectively,the differences were significant (P＜0.05).On the 5 d after injection,the activity of ACP increased 20％ than that of control group,the difference was significant(P＜0.05).The activity of T-SOD increased 24％ than that of control group,the increase was extremely significant than that of control group (P＜0.01).On the 3 d after injected with EPS 3-3-1-2,the activity of AKP in the serum of turbot increased 12％ than that of control group,the increase was not significant(P＞0.05).On the 5 d after injection,the activity of both ACP and CAT increased 24％ and 5％ than those of positive control groups respectively,the increases were significant higher(P＜0.05).All these results indicated that 2 of 4 kinds of EPS had significant effects on immunologic activity of turbot.It indicates that EPS produced by strain 20 # 3 and 3-3-1-2 had significant effects on the nonspecific immunity index of turbot,and they could be used as additives and immunity-stimulants in the aquaculture industry of turbot.%采用苯酚硫酸法和醇沉淀法,从600余株南极微生物中筛选得到10株胞外多糖产量较高的菌株.分子鉴定与系统发育分析表明,9株菌株属于假交替单胞菌属(Pseudoalteromonas),1株属于嗜冷杆菌属(Psych robacter).对10株菌株进行发酵培养,发酵液经醇沉、除蛋白、冷冻干燥后得到粗胞外多糖.其中菌株3-3-1-2的胞外多糖产量达0.6 g/L.对粗多糖产量较高的4株菌所产的胞外多糖进行免疫活性试验,粗胞外多糖20#3在注射3d时,实验组AKP活性比对照组增加了39％,CAT活性比对照组增加了24％,二者均差异显著(P＜0.05),注射5d时,ACP活性比对照组增加了20％,差异显著(P＜0.05),总超氧化物歧化酶(T-SOD)活性比对照组增加了14％,差异极显著(P＜0.01);粗胞外多糖33-1-2在注射3d时,实验组AKP活性比对照组增加了12％,差异不显著(P＞0.05),注射5d时,酸性磷酸酶(ACP)活性比对照组增加了24％,过氧化氢酶(CAT)活性比阳性对照组增加了5％,二者均差异显著(P＜0.05).研究结果表明,菌株20#3与3-3-12产生的胞外多糖对大菱鲆(Scophthalmus maxoimus)具有显著的免疫促进作用.由此可知,筛选出的极地细菌胞外多糖20#3和3-31-2可显著提高大菱鲆非特异性免疫力,可作为水产饲料添加剂应用于大菱鲆的生产养殖.
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