海洋聚球藻源纳米多聚磷酸体中钙、铁和锌的生物可利用性研究

Deficiencies of minerals such as calcium, iron and zinc are among the leading global health risks. Biomineralized nanoparticles possess unique properties, making them suitable for nutrition intervention programs. Polyphosphate bodies (PPB) are mineralized particles mainly composed of long-chain polyphosphates in many biological cells, and can be enriched with essential trace metals (e.g. calcium, iron and zinc). We previously constructed a marine Synechococcus strain with a high yield of nano-sized polyphosphate bodies (nano-PPB), and in this program, this strain will be used to fermentatively produce three types of nano-PPB respectively enriched with calcium, iron and zinc. After extraction, purification and characterization, these three types of nano-PPB will be respectively fed to ovariectomized rats with osteoporosis, iron-deficient anemic rats and weanling rats, so that bioavailability of calcium, iron and zinc from them will be determined. We will also investigate digestion and absorption mechanisms of these three types of nano-PPB by analyzing rat intestinal contents and using the Caco-2 cell monolayer model. This program provides a green and efficient method for the preparation of nano-PPB by using marine cyanobacteria, and for the first time studies the effectiveness and mechanism of nano-PPB in mineral nutrient delivery. This program is not only vital for the development of novel nano-sized mineral supplements and fortificants, but also provides a novel way to utilize marine microalgae resources.

钙、铁和锌等矿物质营养缺乏是当今人类面临的主要健康风险之一，生物矿化纳米微粒在矿物质营养干预实践中具有独特的应用优势。多聚磷酸体（PPB）是存在于许多生物细胞中的一种主要由长链多聚磷酸盐构成的矿物质微粒，可富集钙、铁和锌等人体必需微量金属元素。本课题组前期构建了一株高产纳米PPB的海洋聚球藻，本项目拟利用该藻株发酵生产三种分别富集钙、铁和锌的纳米PPB，并对其进行提纯和理化表征，再将这三种纳米PPB分别饲喂去卵巢骨质疏松大鼠、缺铁性贫血大鼠和刚断乳大鼠，测定其中钙、铁和锌的生物利用率，还将通过大鼠肠道内容物分析和Caco-2细胞体外吸收模型，揭示这三种纳米PPB的肠道消化和吸收机制。本项目利用海洋蓝藻绿色高效制备纳米PPB，并首次对纳米PPB的矿物质营养运送效果和机制进行探索，这对于新型纳米矿物质营养补充剂和强化剂的开发具有重要的指导意义，也将为海洋微藻资源的高值化利用开辟一条新途径。

项目背景/主要研究内容：海洋微藻聚球藻7002能够在胞内形成纳米尺度的多聚磷酸体（PPB）,可富集钙、铁和锌等人体必需矿物元素，本项目旨在探索聚球藻纳米PPB在矿物质营养递送中的潜在应用。本项目研究了聚球藻7002的逐级放大培养、藻体采收工艺和基本营养特性，优化了聚球藻7002光合发酵生产富钙、富铁和富锌纳米PPB的条件，开发了纳米PPB的提取与纯化工艺，开展了纳米PPB理化特性的表征，探讨了纳米PPB中钙、铁和锌的生物可利用性及肠道吸收机制，并对纳米PPB的肠道益生活性进行了探究。.主要结论与科学意义：聚球藻7002的规模培养可通过并联袋式光生物反应器实现；碱法絮凝可以实现其藻体的高效采收；藻粉中蛋白质含量为65.79%，其中藻蓝蛋白含量高达15.81%，而脂质和碳水化合物含量低(分别为8.21%和9.30%)，富含多种矿物质和维生素；纳米PPB最佳发酵条件为Medium A培养基添加磷酸二氢钾0.1g/L、硝酸钠1g/L和硫酸钠4.32g/L；增加培养基中对应矿物质元素的浓度可实现富钙、富锌和富铁纳米PPB的生产；纳米PPB是平均粒径为56.9±15.1nm的带负电的近似球形颗粒，可由沸水破壁抽提、Sephadex G-100凝胶柱层析纯化；纳米PPB具有较好的热稳定性和酸碱稳定性，在消化道中能够耐受消化，可被肠上皮以内吞作用的方式吸收和转运；在骨质疏松、缺铁性贫血和口服药代动力学等动物模型中发现，纳米PPB中钙、铁和锌具有较高的生物利用率；在体外结扎小鼠肠段和体外肠上皮细胞模型中，纳米PPB能够高效递送钙、铁和锌营养素进入肠上皮细胞和跨肠粘膜转运,尤其在对抗植酸抑制剂方面有良好效果；在体外肠上皮细胞、巨噬细胞、结扎小鼠肠段及葡聚糖硫酸钠诱导的小鼠结肠炎模型中，纳米PPB具有保护肠上皮屏障、抗炎、调节肠道菌群等维护肠道健康的活性。本项目的开展为聚球藻在矿物质营养和肠道健康干预中的潜在应用打下理论和技术基础，可推进我国海洋微藻资源的开发利用。