Abstract：
Some amino acids are known to mediate immune responses through gut microbiota metabolism in both humans and monogastric animals. However, through the diet, most free amino acids are absorbed in the small intestine and only a small quantity reaches the microbiota-rich colon. To enhance microbial metabolism of amino acids and their potential health benefits, encapsulation strategies are developed for their protection and delivery to the colon. So far, the main encapsulation systems for amino acids are based on solid lipid particles, but their fate within the digestive tract has never been fully clarified. In this study, we investigated the release of various amino acids (branched-chain amino acid mixture, or lysine, or tryptophan) loaded in solid lipid particles during in vitro oro-gastrointestinal digestion mimicking the piglet. The loaded solid lipid particles were fully characterized for their composition, thermal behavior, molecular structure, crystalline state, surface morphology, and particle size distribution. Moreover, we investigated the effect of particle size by sieving solid lipid particles into two non-overlapping size fractions. We found that amino acid release was high during the gastric phase of digestion, mainly controlled by physical parameters, namely particle size and crystalline state including surface morphology. Large particle size and/or smooth ordered particle indeed led to slower and lower release. Although lipid hydrolysis was significant during the intestinal phase of digestion, the impact of the crystalline state and surface morphology was also observed in the absence of enzymes, pointing to a dominant water/solute diffusion mechanism through these porous solid lipid particles.
摘要：
已知一些氨基酸通过人和单胃动物的肠道微生物群代谢介导免疫应答。然而,通过饮食，大多数游离氨基酸在小肠中被吸收，只有少量到达富含微生物群的结肠。为了增强氨基酸的微生物代谢及其潜在的健康益处，为了保护和递送至结肠,开发了包封策略。到目前为止,氨基酸的主要封装系统是基于固体脂质颗粒，但是它们在消化道中的命运从未得到完全澄清。在这项研究中,我们研究了各种氨基酸(支链氨基酸混合物，或者赖氨酸，或色氨酸）在模仿仔猪的体外口胃肠消化过程中负载在固体脂质颗粒中。负载的固体脂质颗粒被完全表征其组成，热行为，分子结构,结晶状态，表面形态,和粒度分布。此外，我们通过将固体脂质颗粒筛分成两个不重叠的尺寸部分来研究颗粒尺寸的影响。我们发现在胃部消化阶段氨基酸释放量很高，主要由物理参数控制，即粒度和结晶状态，包括表面形态。大粒度和/或平滑有序颗粒确实导致更慢和更低的释放。尽管在消化的肠道阶段脂质水解是显著的，在没有酶的情况下也观察到结晶状态和表面形态的影响，指向通过这些多孔固体脂质颗粒的主要水/溶质扩散机制。
