Microencapsulation

微囊化
  • 文章类型: Journal Article
    开裂是混凝土的必然特征,由于冻融循环,通常会导致嵌入式钢筋的腐蚀和大量变质。已经提出了不同的方法来提高开裂混凝土结构的使用性能。本案例研究涉及胶结材料中包裹的细菌以“治愈”裂缝。这种生物自修复系统需要在水泥基质中保持细菌的活力。许多嵌入的细菌孢子在混凝土养护过程中被破坏,大大降低效率。这项研究调查了在自修复胶结复合材料中固定在海藻酸钙微胶囊中时,常用的非尿素分解细菌孢子的生存能力。本研究使用了三种芽孢杆菌,即,B.伪,B.Cohnii,和B.halodurans。假双歧杆菌表现出最佳的矿化活性;包封后,有足够数量的细菌孢子仍然存活。将微胶囊掺入水泥浆中后,假孢子和超孢子孢子保留了最高的活力,而高杜兰芽孢杆菌孢子在砂浆中保留了最高的生存力。在14至28天内,用细菌碳酸钙填充宽度约为0.13毫米的裂缝,取决于细菌的类型。较大的裂缝没有完全愈合。假B.具有最高的效率,56天后愈合系数为0.497。这项研究还揭示了水泥水化温度对细菌活力的重要作用。因此,进一步研究应优化微胶囊结构中细菌和营养物质的含量。
    Cracking is an inevitable feature of concrete, typically leading to corrosion of the embedded steel reinforcement and massive deterioration because of the freezing-thawing cycles. Different means have been proposed to increase the serviceability performance of cracked concrete structures. This case study deals with bacteria encapsulated in cementitious materials to \"heal\" cracks. Such a biological self-healing system requires preserving the bacteria\'s viability in the cement matrix. Many embedded bacterial spores are damaged during concrete curing, drastically reducing efficiency. This study investigates the viability of commonly used non-ureolytic bacterial spores when immobilized in calcium alginate microcapsules within self-healing cementitious composites. Three Bacillus species were used in this study, i.e., B. pseudofirmus, B. cohnii, and B. halodurans. B. pseudofirmus demonstrated the best mineralization activity; a sufficient number of bacterial spores remained viable after the encapsulation. B. pseudofirmus and B. halodurans spores retained the highest viability after incorporating the microcapsules into the cement paste, while B. halodurans spores retained the highest viability in the mortar. Cracks with a width of about 0.13 mm were filled with bacterial calcium carbonate within 14 to 28 days, depending on the type of bacteria. Larger cracks were not healed entirely. B. pseudofirmus had the highest efficiency, with a healing coefficient of 0.497 after 56 days. This study also revealed the essential role of the cement hydration temperature on bacterial viability. Thus, further studies should optimize the content of bacteria and nutrients in the microcapsule structure.
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  • 文章类型: Journal Article
    Hypercholesterolemia, which is an increase in total and low-density lipoprotein (LDL) serum cholesterol, is an important risk factor for the development of cardiovascular diseases. Lifestyle modifications underpin any action plan for reducing serum cholesterol. Phytosterols are natural compounds belonging to the triterpenes family. Thanks to their structural analogy with cholesterol, phytosterols have the ability to reduce serum LDL-cholesterol levels. Phytosterols are used to enrich or fortify a broad spectrum of food products. Like unsaturated fatty acids and cholesterol, phytosterols are easily oxidized. Microencapsulation could be a useful tool to overcome this and other drawbacks linked to the use of phytosterols in food fortification. In this review, in addition to explaining the phytosterols\' mechanisms of action, a focus on the use of free and encapsulated phytosterols for the formulation of functional foods, taking also into account both technological and legislative issues, is given.
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