规格与盐度对凡纳滨对虾肌肉营养成分的影响

裂褶菌多糖是裂褶菌 (Schizophyllum communer Fr.) 子实体、菌丝体或发酵液提取的具有β-(1,6) 分支的 β-(1,3)-D葡聚糖。为了探究裂褶菌多糖饲养凡纳滨对虾 (Litopenaeus vannamei) 的效果，选用12口凡纳滨对虾养殖池，按照裂褶菌多糖的添加量 (质量分数)，分别设置0% (C组)、0.5% (S1组)、1.0% (S2组) 和2.0% (S3组) 4组进行56 d的饲养实验，分析对虾的生长、血清理化、免疫指标和肠道菌群等变化。结果显示，S2组的终末体质量、平均体质量增长率和特定生长率均显著高于C、S1和S3组 (P<0.05)；S2、S3组内层上皮细胞的高度显著高于C和S1组 (P<0.05)。与对照组相比，S2和S3组血清中的尿酸含量显著降低 (P<0.05)，S1组则无显著性差异 (P>0.05)。S2和S3组血清中溶菌酶、总一氧化氮合成酶、酚氧化酶和碱性磷酸酶的活性均显著高于对照组 (P<0.05)。S2组过氧化氢酶、超氧化物歧化酶活性和总抗氧化能力显著高于对照组 (P<0.05)；各实验组血清丙二醛含量均有不同程度的降低 (P>0.05)。肠道菌群Ace、Chao1、Shannon、Simpson指数均无显著性差异 (P>0.05)。在门水平上，与对照组相比，添加裂褶菌多糖的各实验组变形菌门相对丰度均下降，软壁菌门升高。在属水平上，与对照组相比，S2组中Formosa、Pseudoruegeria、Muricauda和鲁杰氏菌属 (Ruegeria) 相对丰度均显著升高 (P<0.05)，而弧菌属 (Vibrio) 相对丰度显著降低 (P<0.05)。结果表明，在饲料中添加1.0%的裂褶菌多糖能显著提升凡纳滨对虾的生长性能、免疫力和抗氧化能力，增加肠道有益菌丰度，降低有害菌丰度。

Polysaccharide immunomodulators as therapeutic agents: structural aspects and biologic function

Schizophyllan (SPG) is a type of polysaccharide with β-(1,6) branching β-(1,3)-D-glucan, extracted from the fruiting body, mycelium or fermentation broth of Schizophyllum communer. In order to study the effects of SPG feed on the cultivation of Litopenaeus vannamei, we selected 12 L. vannamei breeding ponds, and set up four groups according to the addition amounts of SPG [Group C (0%), Group S1 (0.5%), Group S2 (1.0%) and Group S3 (2.0%)] for a 56-day experiment, then we investigated the growth, blood clearance, immune indicators and intestinal microflora. The results show that the final body mass, average weight gain rate and specific weight gain rate of Group S2 were significantly higher than those of Group C, S1 and S3 (P<0.05). The height of inner epithelial cells in Group S2 and S3 were significantly higher than those in Group C and S1 (P<0.05). Compared with Group C, the contents of serum uric acid (UC) in Group S2 and S3 were significantly lower (P<0.05), but there was no significant difference in Group S1 (P>0.05). The activities of lysozyme (LZM), total nitric oxide synthase (TNOS), phenol oxidase (PO) and alkaline phosphatase (AKP) in serum of Group S2 and S3 were significantly higher than those in Group C (P<0.05). The activities of catalase (CAT), superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in Group S2 were significantly higher than those of Group C (P<0.05). Compared with the control group, the contents of serum malondialdehyde (MDA) in all experimental groups decreased to different extents (P>0.05). There was no significant difference in Ace, Chao1, Shannon and Simpson indexes of intestinal flora (P>0.05). At phylum level, compared with Group C, the abundance of Proteobacteria in the experimental groups added with SPG decreased, while that of Tenericutes increased. At genus level, compared with Group C, the abundances of Formosa, Pseudoruegeria, Muricauda and Rugella in Group S2 increased significantly (P<0.05), while the abundance of Vibrio decreased significantly (P<0.05). In conclusion, adding 1.0% SPG in feed can improve the growth performance, immunity and antioxidant capacity of L. vannamei, increase the proportion of beneficial bacteria and reduce the proportion of harmful bacteria in intestinal tract.