| Probiotics are frequently utilized in the food business and have a number of probiotic functions,including balancing the host intestinal microbiota and enhancing the health of the host intestinal system.The stomach acid,bile,and digestive enzymes present inside make probiotics less active or even dead during their transportation to the target parts of the gastrointestinal tract,which makes it difficult to achieve their efficient colonization in the intestinal tract and is not conducive to their beneficial effects.Microcapsulation is considered one of the effective methods to solve this problem,however,insufficient activity and ineffective release of cells upon reaching the intestine are still key issues that need to be addressed in microencapsulation.The aim of this study was to prepare high activity probiotic microcapsules using plant prebiotics goji berry extract for the first time and to explore the mechanism of high cell viability under gastric conditions and regulation of intestinal flora,in order to provide a reference for the development and application of new probiotic microcapsules.（1）We investigated the acid resistance,bile salt resistance,adhesion ability,and antioxidant properties of different probiotic strains,studied the preparation process of probiotic microcapsules,and evaluated the effectiveness of microcapsules through in vitro gastrointestinal digestion experiments.The results showed that L.plantarum had good probiotic properties and could be used as a microencapsulated object.The preparation process of sodium alginate-L.plantarum microcapsules was as follows:the concentration of sodium alginate was1.0%（w/v）,the concentration of Ca Cl2 solution was 0.6%（w/v）,the immobilization time was 40min,and the encapsulation efficiency of microcapsules was 83.11%.In addition,the encapsulation efficiency of microcapsules containing plant prebiotic goji berry extract increased by 8.38%,and the cell viability after gastrointestinal digestion was 6.78 log CFU·g-1,an increase of 99.41%.（2）We studied the performance of Goji berry-L.plantarum microcapsules and explored the mechanism of maintaining high cell activity under gastric conditions.When the concentration of goji berry extract was 3%（w/v）,the cell viability after gastrointestinal digestion was the highest(7.17 log CFU·g-1),increasing by 110.88%.The scanning electron microscopy results showed that Goji berry-L.plantarum microcapsules were smoother and had a more uniform and dense texture.Cell viability increased by 23.43%and 28.13%after 4 weeks of storage at 4°C and 25°C,respectively.The validation results of prebiotic effects indicated that goji berry extract could act as a growth factor to exert prebiotic effects,and it did not affect the retention and release of cells in microcapsules during gastrointestinal digestion.In the presence of goji berry extract,L.plantarum membrane integrity was better and membrane permeability was reduced.The relative content of unsaturated fatty acids,especially oleic acid,increased by14.02%.The fluorescence intensity of membrane protein Phe,Trp and Tyr residues was significantly reduced.Real-time fluorescence quantitative PCR（RT-q PCR）analysis showed that the transcription levels of related genes gad A,gad B,arc D,arg G,and arg H in the cellular glutamate and arginine metabolism pathways were significantly upregulated,with intracellular glutamate and arginine content increasing by 119.19%and 68.93%,respectively.This indicated that cells enhanced the osmotic barrier,accumulated intracellular glutamate and arginine by adjusting membrane homeostasis,thereby improving their survival ability under acid stress.（3）The effects of Goji berry-L.plantarum microcapsules on intestinal flora and short-chain fatty acids（SCFAs）in vitro culture were investigated.In vitro culture was performed with chicken cecum contents,RT-q PCR was performed to determine the number of total bacteria,Enterococcus,Enterobacter,Bacteroides and Bifidobacterium,high-throughput sequencing was performed to analyze the effect of microcapsules on the diversity of intestinal flora,and GC-MS was performed to detect the changes of SCFAs in the intestinal tract.The results showed that after 24 h of in vitro intestinal culture,the number of total bacteria,Bacteroides and Bifidobacterium in Goji berry-L.plantarum microcapsules group were significantly increased by 7.74%,6.43%and 15.01%,respectively.The intestinal flora alpha diversity and beta diversity were significantly increased;The intestinal SCFAs acetic acid,propionic acid,butyric acid and isovaleric acid content in the intestine increased significantly by 36.46%,25.63%,24.69%and 42.86%,respectively.The above results indicated that Goji berry-L.plantarum microcapsules could effectively increase the number of beneficial bacteria in the intestinal tract and produce beneficial metabolites,thus maintaining the intestinal microecological balance. |
