Abstract：
Algae and cyanobacteria, other than their nutritional value, possess different beneficial properties, including antioxidant and antimicrobial ones. Therefore, they can be considered functional ingredients in animal feed and natural substitutes for antibiotics. The aim of this study was to evaluate the antioxidant and antimicrobial capacity against porcine O138 E. coli of Ascophyllum nodosum, Chlorella vulgaris, Lithotamnium calcareum, Schizochytrium spp. as algal species and Arthrospira platensis as cyanobacteria. The antioxidant capacity was determined by ABTS Radical Cation Decolorization Assay testing at three different concentrations (100%; 75%; 50%). The growth inhibition effect of the extracts at concentrations of 25%, 12.5%, 6%, 3% and 1.5% against porcine O138 E. coli was genetically characterized by PCR to detect the presence of major virulence factors; this was evaluated by following the microdilution bacterial growth method. The ABTS assay disclosed that Ascophyllum nodosum was the compound with the major antioxidant properties (57.75 ± 1.44 percentage of inhibition; p < 0.0001). All the extracts tested showed growth inhibition activity at a concentration of 25%. Among all extracts, A. nodosum was the most effective, showing a significant growth inhibition of E. coli; in particular, the log10 cells/mL of E. coli used as a control resulted in a significantly higher concentration of 25% and 12.5% after 4 h (8.45 ± 0.036 and 7.22 ± 0.025 log10 cells/mL, respectively; p < 0.005). This also suggests a dose-dependent relationship between the inhibitory activity and the concentration. Also, a synergistic effect was observed on antioxidant activity for the combination of Ascophyllum nodosum and Lithotamnium calcareum (p < 0.0001). Moreover, to determine if this combination could affect the viability of the IPEC-J2 cells under the normal or stress condition, the viability and membrane integrity were tested, disclosing that the combination mitigated the oxidative stress experimentally induced by increasing the cell viability. In conclusion, the results obtained highlight that the bioactive compounds of algal species are able to exert antioxidant capacity and modulate O138 E. coli growth. Also, the combination of Ascophyllum nodosum and Lithotamnium calcareum species can enhance their bioactivity, making them a promising functional feed additive and a suitable alternative to antibiotics.
摘要：
藻类和蓝细菌，除了它们的营养价值，拥有不同的有益特性，包括抗氧化剂和抗菌。因此,它们可以被认为是动物饲料中的功能性成分和抗生素的天然替代品。本研究的目的是评估猪O138大肠杆菌的抗氧化和抗菌能力。普通小球藻,石灰岩,裂殖菊属。作为藻类物种，并且作为蓝细菌。通过ABTS自由基阳离子脱色测试在三种不同浓度(100%;75%;50%)下测定抗氧化能力。提取物在25%浓度下的生长抑制作用，12.5%,6%,针对猪O138大肠杆菌的3%和1.5%通过PCR进行遗传表征以检测主要毒力因子的存在;这通过遵循微稀释细菌生长方法进行评估。ABTS测定公开了结鞘叶是具有主要抗氧化性质的化合物(57.75±1.44百分比的抑制;p<0.0001)。所有测试的提取物在25%的浓度下显示生长抑制活性。在所有提取物中，A.nodosum是最有效的，显示对大肠杆菌的显著生长抑制；特别是，作为对照的log10细胞/mL的大肠杆菌在4小时后导致显著更高的浓度为25%和12.5%(8.45±0.036和7.22±0.025log10细胞/mL,分别为；p<0.005)。这也表明抑制活性和浓度之间的剂量依赖性关系。此外，观察到对夜蛾和石灰岩的组合的抗氧化活性的协同作用(p<0.0001)。此外，为了确定这种组合是否会影响IPEC-J2细胞在正常或应激条件下的活力，活力和膜的完整性进行了测试，公开了该组合减轻了通过增加细胞活力而实验诱导的氧化应激。总之,获得的结果突出表明，藻类的生物活性化合物能够发挥抗氧化能力并调节O138大肠杆菌的生长。此外，夜蛾和石灰岩的组合可以增强它们的生物活性，使它们成为有前途的功能性饲料添加剂和抗生素的合适替代品。
