| Green tea is the largest producer in China.With the improvement of the quality of life,there is an increasing demand for high-quality tea.A large amount of low-grade green tea is unsalable every year,resulting in a waste of resources.Therefore,the processing and utilization of low-grade green tea is an urgent problem to be solved.The relationship between intestinal flora and human health is gradually being paid attention to,and consumers have greater demand for intestinal health products such as probiotics and prebiotics.In this paper,low-grade fried green tea is used as a raw material to extract polysaccharides,and the effects of green tea polysaccharide(g TPC)on the growth of two common intestinal flora E.coli and Lactobacillus acidophilus are studied to develop it as a"prebiotic"Lay the foundation.The following conclusions are drawn:(1)The molecular weight distribution of g TPC is 3.55×10~6Da(19.97%)and1.76×10~5 Da(80.03%).The monosaccharides of g TPC consist of rhamnose,fucose,ribose,xylose,mannose,galactose,and glucuronic acid.The molar ratio is 3.01,15.53,26.12,1.43,3.85,24.35,and 21.78.It consists of 16 kinds of amino acids with a content of 6.47%and a protein content of 5.56%.Fourier infrared spectroscopy analysis shows that there is a pyran-type monosaccharide in g TPC,and the glycosidic bonds are mainly inα-configuration.(2)The antibacterial activity of g TPC against E.coli is dose-dependent,but the sensitivity of two types of E.coli to g TPC is different.For E.coli DH5α,the g TPC concentration is 4mg/m L,the maximum bacteriostatic rate is 55.75%;for E.coli ATCC 25922,the concentration is 1mg/m L,the maximum bacteriostatic rate is50.75%.When the maximum antibacterial concentration is exceeded,the antibacterial ability of g TPC decreases,which may be used as a nutrient by E.coli due to excessive polysaccharide hydrolysis.From the analysis of the scanning electron microscope and transmission electron microscope observation results,it can be seen that the treatment of g TPC destroys the cell structure of E.coli,resulting in the formation of surface pores,cytoplasmic leakage,and poor adhesion.Flow cytometry analysis found that the ability of green tea polysaccharides to damage the integrity of E.coli cells was dose-dependent,and the higher the concentration,the greater the destruction ability.The experimental results on the outer membrane and inner membrane permeability of E.coli cells showed that when the concentration of green tea polysaccharide was 4mg/m L,the effect on the outer membrane permeability of E.coli cells was the largest,but it had no effect on the inner membrane of the cells.Finally,0.50～6.00 mg/m L g TPC-treated E.coli intracellular reactive oxygen concentration increased by 5.11%,26.57%,33.72%,38.19%,10.87%,respectively,resulting in further damage to the cell structure.(3)Research and determine the effect of adding different concentrations of g TPC,sodium alginate and inulin on the number of colonies and OD600nm value in the fermentation broth of Lactobacillus acidophilus,and found that the three polysaccharides all promote the growth and proliferation of Lactobacillus acidophilus The order is inulin>sodium alginate>green tea polysaccharide.The difference in the total acid content of the three polysaccharide fermentation broths is only about0.15g/L,indicating that there is basically no effect on the acid production of L.acidophilus.The measurement results of short-chain fatty acids show that g TPC can promote the production of lactic acid,acetic acid,propionic acid and butyric acid by L.acidophilus,but it is not obvious;after sodium alginate has an effect on the production of propionic acid and has an inhibitory effect on the production of acetic acid;The effect of inulin on the fermentation of Lactobacillus acidophilus to produce lactic acid and acetic acid and the inhibition of propionic acid production are obvious.The addition of g TPC,sodium alginate and inulin can promote the proliferation of Lactobacillus acidophilus.However,the total acid production has not changed significantly.This situation may be attributed to the fact that these three polysaccharides produce certain short-chain fatty acids for Lactobacillus acidophilus.Promote and inhibit the production of another short-chain fatty acid. |
