马尾藻海藻多糖生物活性研究新进展

近年来的研究表明,马尾藻中富含多种新型生物活性化合物,如海藻多酚、海藻多糖及多种硫酸多糖衍生物。在分离出的生物活性成分中,海藻多糖因其具有良好的保健作用和药用效果而备受关注。同时,有大量研究已经证明,马尾藻海藻多糖对人类疾病的预防以及恢复具有积极效果。因此,本文对近年来马尾藻海藻多糖的抗凝血、抗氧化、抗肿瘤、抗血管生成和抗炎症活性的最新进展进行了综述,以期能助推马尾藻海藻多糖的研究,并且协助填补理论研究与工业应用之间的知识鸿沟。     

Seaweed polysaccharide mitigates intestinal barrier dysfunction induced by enterotoxigenic Escherichia coli through NF-κB pathway suppression in porcine intestinal epithelial cells

This study aimed to investigate the protective effects and underlying mechanism of seaweed polysaccharide (SWP) on intestinal epithelial barrier dysfunction induced by E. coli in an IPEC-J2 model. A preliminary study was done to screen optimum SWP concentrations by cell viability, cytotoxicity, apoptosis and proliferation evaluation. The regular study was conducted to evaluate the protective effects of SWP against E. coli challenge via the analysis of transepithelial electrical resistance (TEER), tight junction proteins, NF-κB signalling pathway, proinflammatory cytokines and the E. coli adhesion and invasion. Our results show that 4 h E. coli challenge down-regulated tight junction proteins expression, decreased TEER, activated NF-κB signalling pathway and increased proinflammatory response, which indicates that the E. coli infection model was well-established. Pre-treatment with 240 μg/ml SWP for 24 h alleviated the 4 h E. coli -induced intestinal epithelial barrier dysfunction, as evidenced by the up-regulated expression of Occludin, Claudin-1 and ZO-1 at both mRNA and protein level and the increased TEER of IPEC-J2 cells. Pre-incubation with 240 μg/ml SWP for 24 h inhibited the activation of the NF-κB signalling pathway by 4 h E. coli challenge, including the decreased mRNA expression of TLR-4, MyD88, IκBα, p-65, as well as the reduced ratio of protein expression of p-p65/p65. Also, pre-treatment with 240 μg/ml SWP for 24 h decreased proinflammatory response (IL-6 and TNF-α) induced by 4 h E. coli challenge and decreased the E. coli adhesion and invasion. In conclusion, SWP mitigated intestinal barrier dysfunction caused by E. coli through NF-κB pathway in IPEC-J2 cells and 240 μg/ml SWP exhibited better effect. Our results also provide a fundamental basis for SWP in reducing post-weaning diarrhoea of weaned piglets, especially under E. coli -infected or in-feed antibiotic-free conditions.     

Effect of dietary addition of seaweed and licorice on the immune performance of pigs

In pig production, dietary additive antibiotics are usually used for growth stimulation and disease prevention, although there is public concern about the increased incidence of resistant antibiotics and food safety. It is possible that such antibiotics might be replaced by naturally derived products such as seaweed and licorice. In this study, we evaluated the effect of dietary addition of seaweed and licorice on enhancing the immune function in swine. The animals of each group (eight animals per group) were sensitized at day 42 and 49, and the immunoglobulin production and the expression of cytokines were detected by the ELISA and real‐time PCR. As the results, saliva IgA production of the seaweed‐treated group increased around five times compared to that of control (day 56). Delayed hypersensitivity reaction and IgG production of the seaweed‐treated group increased around 1.8–2.0 times. In addition, enhanced saliva IgA production was detected at day 50 (around two times) and day 51 (around five times) by the licorice treatment, and lower expression level of tumor necrosis factor‐α messenger RNA at day 51 (around 1/25) was observed in the licorice treatment. We conclude that the replacement of antibiotics by naturally derived dietary additives might be feasible for immune system enhancement.     

Resilience of microorganisms and aggregation of a sandy calcareous soil to amendment with organic and synthetic fertilizer

Marginal coastal soils are dependent on appropriate land management to prevent soil erosion, as a result of low soil stability combined with exposure to strong winds. An example of such an area is the machair, a fixed dune system utilized for agriculture in the northwest of Scotland, UK. The separate and combined effects of synthetic NPK fertilizer and a traditional soil conditioner (kelp, a seaweed) on soil structure formation, stabilization and biological parameters were studied on a cropped field on the machair. Soil physical properties examined included water retention at 10 kPa matric suction, water stable aggregates (WSA) >1 mm, aggregate stability, and biological properties including ester-linked fatty acid (ELFA) analysis and β-glucosidase activity for microbial biomass and activity, respectively. Significant treatment effects were few and inconsistent between sampling times, but included kelp and/or NPK fertilizer reducing aggregation, water retention, microbial biomass and activity relative to the unamended control treatment. Furthermore, seasonal variation, which could be attributed to changes in soil water content, was stronger than variation in response to fertilizer treatments. Principal components analysis of the ELFA data showed that ploughing promoted fungal biomass relative to bacteria, and confirmed both the absence of consistent synthetic and organic fertilizer effects and the sensitivity of microbial biomass to season. Overall, the study demonstrated the resilience of a calcareous sandy soil to amendment with fertilizer.     

镉在海藻中的化学形态

利用化学试剂逐步提取法研究了紫菜、海带、裙带菜和羊栖菜中镉的存在化学形态。研究结果表明:镉以多种化学形态存在于4种海藻中,1 mol/L氯化钠提取态镉和 2% 醋酸提取态的镉所占比例较大,两者约占总镉含量的76.3%～92.9%。0.6 mol/L盐酸提取态、去离子水提取态和80%乙醇提取态镉所占比例较小,其中乙醇提取态(离子态镉)约仅占总镉含量的0.4%～9.2%,且对于4种海藻,紫菜中的离子态镉所占比例最低(均小于1%)。实验进一步证实以海藻中总镉含量作为检测标准不能准确反映海藻及其制品的食用安全性,因此亟需建立海藻中针对毒性较强的离子态镉的检测标准限量和快速有效的检测方法,以保障我国海藻产业和出口创汇经济的顺利发展。     

不同浓度营养液添加海藻肥对生菜产量及品质的影响

【目的】研究不同浓度营养液添加稀释1 000倍海藻肥对生菜产量和品质的影响,以期为生菜的设施高效栽培提供参考。【方法】采用水培试验,设置4个营养液处理:1/2倍霍格兰营养液(CK)、1/2倍霍格兰营养液+1 000倍海藻肥(T1)、3/8倍霍格兰营养液+1 000倍海藻肥(T2)、1/4倍霍格兰营养液+1 000倍海藻肥(T3)。【结果】相比于不添加海藻肥的1/2倍霍格兰营养液(CK),T1、T2处理在鲜质量上无显著差异,但显著增加干物质的积累和光合色素含量。在各浓度营养液添加海藻肥能提高生菜多酚、类黄酮和可溶性糖含量,降低硝酸盐含量,尤其是T2、T3处理对生菜的品质提升效果更佳。T2、T3处理可溶性糖含量较CK显著提高,分别提高40%和32.06%,硝酸盐含量则分别降低42.9%和42.59%,多酚含量分别增加65.99%和65.06%,DPPH自由基清除率分别提高72.49%和75.77%。与CK相比,3/8霍格兰营养液添加海藻肥能够保持生菜生长不受影响,干物质含量增加;而在1/4霍格兰营养液添加海藻肥,生菜鲜质量较CK降低22.34%。【结论】T2、T3处理对生菜产量和品质提升效果较好。综合考虑生物量与施用成本,T2处理为比较适合水培生菜的高效优质栽培。     

Antioxidant‐related parameters,digestive enzyme activity and intestinal morphology in rainbow trout (Oncorhynchus mykiss) fry fed graded levels of red seaweed,Gracilaria pygmaea

This study was conducted to investigate the effects of dietary red seaweed, Gracilaria pygmaea level on growth, antioxidant‐related parameters, digestive enzyme activity and intestinal morphology of rainbow trout (Oncorhynchus mykiss) fry. Five isocaloric and isonitrogenous diets were formulated to contain four G. pygmaea levels (30 (GL‐30), 60 (GL‐60), 90 (GL‐90) and 120 g/kg (GL‐120)), and a control diet was used, without inclusion of seaweed. Results of the feeding trial indicated that final body (FBW: 2.8–3.5 g) and specific growth rate (SGR: 4.8–5.2) were significantly improved when 60 g/kg G. pygmaea was supplemented in the diets. However, there was a significant reduction (p < .05) of final body weight (FBW) and specific growth rate (SGR) in fish fed 120 g/kg G. pygmaea. Protease activity was significantly lower in fish fed GL‐120 diet when compared to GL‐30 or control (p < .05). Lipase was significantly affected by dietary seaweed regardless its level of supplementation (p < .05). The inclusion of the Gracilaria in the diet led to evident changes in the fish antioxidant status with significant reduction of superoxide dismutase, glutathione peroxidase activity and lipid peroxidation products. The histological study demonstrated that all groups of fish displayed normal morphology of anterior intestine and pyloric caeca. Villi absorptive area in the anterior intestine of treatment groups GL‐90 and GL‐120 significantly decreased (p < .05). Overall, the results obtained in this study indicate that dietary G. pygmaea supplementation up to 90 g/kg improves growth performance in rainbow trout fry without compromising antioxidant responses and digestive function.     

室内三种富营养模拟条件下水流调控对羊栖菜和石莼生长及生物质合成的影响

大型海藻养殖是一种低成本、高效、环保的水体富营养化生物修复方法,而水流则是影响大型海藻生长的一个重要因素。研究结果表明,水流交换率为200 vol·d^-1时,羊栖菜(Sargassum fusiforme)比生长率最高达(4.34±0.11) %·d^-1,而水流交换率为100 vol·d^-1、中高浓度营养盐条件下石莼(Ulva pertusa)比生长率最大值分别可达(6.31±1.42) %·d^-1、(8.00±0.79) %·d^-1,营养盐浓度决定了两种大型海藻的生长率,石莼更适宜在高营养盐环境中生长。石莼体内叶绿素a、可溶性蛋白和可溶性碳水化合物在不同应用情境间均存在明显差异,而羊栖菜体内仅可溶性蛋白表现出明显变化。水流交换的增强明显改变了石莼的生长和羊栖菜可溶性碳水化合物含量。陆基中试实验表明,与低水流速度相比,中、高流速条件下羊栖菜的比生长率分别增加80%、14%,石莼则分别增加41.3%、33.3%。     

海藻养殖碳汇渔业发展的政府激励机制研究

建立了基于机制设计理论的政府激励机制模型,分析了在不完全信息情况下政府最优的激励强度应是β=λ2/λ2+tρσ2,政府的激励强度与养殖者的努力程度系数成正比。政府会根据观察到的养殖者行为确定相应的激励强度,进而设立激励合同S(π)=+βπ,引导养殖者按照政府的期望进行养殖,使养殖者追求个人利益的行为正好与政府追求的集体价值最大化的目标相吻合,计算出了2008年的激励强度和激励合同分别为69.3万t和210.154万元。最后提出了包括供求激励机制的构建、融资激励机制的构建、养殖技术激励机制的构建、国际合作激励机制的构建的政府激励机制的构建办法。     

海藻碘肥强化果菜碘富集的田间应用研究

以不同果菜为材料,在露天栽培条件下土施和喷施海藻碘肥,探讨果菜类代表性蔬菜品种对碘的吸收和积累特性,以及两种碘肥施用方式下蔬菜碘吸收的差异。结果表明,供试果菜可食部位对碘的吸收均随着海藻碘肥添加浓度的提高而增加。随着取样时间的延长,蔬菜可食部位对海藻碘的吸收除了大豆外均总体呈现下降的趋势。两种不同的海藻碘肥施用方式中,土施更有利于蔬菜对碘的吸收和积累。在土施条件下,碘在果菜不同部位的分配表现为根＞叶＞茎＞果实;在海藻液体碘肥喷施条件下则是叶子的碘含量最高,其次为茎,而果实和根中碘积累量较低。