基于杏鲍菇纤维素纳米晶的Pickering乳液稳定性及消化机理研究

Triterpenes from the edible mushrooms have been widely acknowledged for its health-promoting effects. However, its application is often limited by its poor water solubility and biochemical degradation during physiological transit that restricts its bioavailability. Pickering emulsion was used to capsulate Poria cocos triterpenes in this project, to improve its stability and bioaccessibility. Cellulosic nanoparticles from the Pleurotus eryngii scraps (PeCNCs) after packaging or processing industry, would be carried out using acid hydrolysis methods. Experimental design was used to investigate the effect of the parameters on the fermentation conditions and the nanoparticle preparation methods. The formulation of the Pickering emulsions based on PeCNCs particles would be also optimized. The stability of the Pickering emulsions and the oxidataion/degradation of the Poria cocos triterpenens during in vitro oral to gastrointestinal digestion would be investigated using static and dynamic in vitro rat stomach-intestinal tract system (DIVRST-II), with clear focus of the biochemical conditions, the morphology and the peristalsis of the gastrointestinal tract on the bioaccessibility and the controlled-releasing of the encapsulated Poria cocos triterpenens. Effective evidences of the emulsions stabilized by PeCNCs as edible Pickering particles would be shown in protecting Poria cocos triterpenens during the in vitro digestion. This project could provide new choice of the emulsion carrier for the bioactive substances, new insights into the food-grade Pickering emulsion approach with its stabilizing nanoparticles hydrolyzed from edible mushroom dietary fibers, and also extend the industrial chain of the Pleurotus eryngii processing industry.

食用菌三萜的低水溶性和变性降解性限制了其消化过程的生物利用度。本项目采用食品级的Pickering乳液作为茯苓三萜的载体，考察Pickering乳液在体外消化道中的稳定性和对茯苓三萜的保护和缓释作用，并揭示其中蕴含的消化机理。其中，用来稳定Pickering乳液的杏鲍菇纤维素纳米晶（PeCNCs）采用富含膳食纤维的杏鲍菇初、深加工废菌渣水解制得，考察不同发酵工艺和酸水解工艺对PeCNCs的微结构和物化特性的影响，优化由PeCNCs稳定的Pickering乳液的配方。通过静态和自主研发的动态体外仿生消化系统（DIVRST-II），揭示了消化道的生化条件（消化液配方）、消化道的特有形态和消化道蠕动对茯苓三萜动态缓释过程的影响机理。本项目为基于食用菌膳食纤维的Pickering乳液体系奠定一定的理论基础，为Pickering乳液技术在食品工业的应用和低水溶性食用菌功能食品配料的开发提供新思路。

三萜类化合物的低水溶性和易氧化变性的问题降低了其直接作为口服药物的生物利用度。近年来，被纤维素纳米晶稳定的食品级Pickering乳液为此提供了一种新的解决思路。本研究采用富含膳食纤维的杏鲍菇子实体深加工废渣为原料，制备了杏鲍菇纤维素纳米晶（PeCNs）。通过SEM、TEM、FT-IR、XRD和TGA等检测可知，PeCNs为针状纳米尺度的纤维素颗粒（长469 nm、宽5-10 nm）、结晶度高（84.3%）和热稳定性好。CLSM和cryo-SEM结果证实当油相占比不高于50%时，PeCNs吸附在水油界面，并稳定了o/w型Pickering乳液。对于乳液的水相部分，PeCNs浓度比离子强度对乳液稳定性的影响更大。虽然乳滴的聚集和合并过程都是乳滴在获得足够独立的Pickering粒子的过渡状态，但通过优化乳液水相条件，聚集状态下的乳液也可以抵抗合并获得稳定且均匀的液滴，从而减少工业应用对PeCNs消耗量。为了改善乳液的稳定性、减少化学改性过程可能造成的有毒有害成分残留，本项目采用干酪乳杆菌发酵的方法对原料进行生物改性。改性后的LCFPeCNCs仍为针状纤维素纳米晶，但比PeCNs短（104.1912±53.53 nm），结晶度也比PeCNs高（94.5%），因此更好地稳定了乳液。PeCNs和LCFPeCNCs稳定的乳液对茯苓酸都具有较高的有效包裹率（88.3~91.7%）。相对于葵花籽油运载体系，Pickering乳液体系能更好地保护茯苓三萜免受氧、胃酸、胆盐和消化酶的破坏而导致的失活，这是因为纳米粒子在水油界面的不可逆吸附起到了第二层物理屏障作用。本研究制备了两种新型的真菌纤维素来源的纤维素纳米晶，为基于食用菌纤维素的Pickering食品级乳液体系的设计及其作为低水溶性药物的口服载体在医药工业上的应用提供建议，并为食用菌深加工废渣提供了再利用的新思路。