The Characteristics Of Lactic Acid Bacteria And The Effect Of Fermented Hawthorn Juice On The Lipid Metabolism Of Rats

Lactic acid bacteria is a kind of not produce spore gram-positive bacteria,widely existing in nature world.Some lactic acid bacteria strains have important physiological functions that are used as probiotics in nutritional supplements or functional foods.However,the probiotic characteristic was significantly influenced by environment,and varied from strain to strain,namely the colonies from same strain may have different physiological and biochemical characteristics and probiotic effects.So safety evaluation need be carried out first.And it is necessary to have a comprehensive understanding for the new separation of lactic acid bacteria,including the biochemical properties,processing characteristics and tolerability,and explore whether it has probiotic characteristics.After that people know how to use the strain.Strains with good processing characteristics are most likely to be separated from natural fermented food.And natural fermented food is one of the important matrix to isolate probiotic strains.Hawthorn,belonging to Rosaceae,is rich in protein,vitamins,minerals,flavonoids and other ingredients that can be used as food and medicine.It has also been listed in Chinese Medicinal and Edible Plant.Because of large amount of organic acid,maslinic acid,tartaric acid and other acidic compounds,direct consumption of hawthorn is easily stimulate the gastric mucosa.Except some species of hawthorn,mostly were processed into food or dried.Nowadays,the studies of functional food are focus on medicinal and edible plant.A lot of studies have been carried out on hawthorn used alone or in combination with other medicine plants.However,there is little study of the effects and mechanism of fermented hawthorn juice which need further study and development.With the the change of lifestyle,the personal daily intake of calories,fat and cholesterol increases significantly.A certain amount of lipid is important of maintaining human health.However,overtaking of lipid will lead to disorders of lipid metabolism,causing cardiovascular diseases.At present,cardiovascular disease has become the top one of the most morbidity and mortality diseases over the world.It not only increases the burden of health,but also causes economic and social pressure.Although the lipid-lowering medicine can effectively regulate the elevated lipid level,it will cause some side effects including the functional change of liver and kidney,elevation of serum transaminase,reaction of digestive tract and other adverse reactions.Therefore,it is urgent to find and develop alternative substitutes for serum lipid regulation with little side effect.Hawthorn has good lipid-lowering effect and has been used in blood lipids regulate medicine.Some Lactobacillus plantarum strains can also regulate serum lipid level.Combination of them may have enhanced effect on regulating blood lipids.Therefore,this study firstly isolated and identified the microorganisms in naturally fermented kimchi.Then safety assessment of L.plantarum PMO has been carried.Following,comparative research of L.plantarum PMO and L.plantarum 102 has been carried,including biological characteristics,tolerance characteristics and probiotic characteristics.Hawthorn was ultrasonic extracted in water and then fermented by L.plantarum PMO.The fermented juice were boiled and centrifuged as different interventions.The changes of viable count and phenolic substance,and anti-oxidant capacity were investigated.Furthermore,high-fat diet rats was intervened by the fermented hawthorn extract liquid and L.plantarum PMO to investigated the hypolipidemic effect,the effect on oxidative stress and the effect on the expression of lipid regulation related gene.These may provide theoretical basises for the development of probiotic strains and functional foods.Here below were the results:?1?There are 9 lactic acid bacteria strains were isolated,including three Lactobacillus plantarum strains,three Lactobacillus brevis strains,two Lactobacillus plantarum strains and a Leuconostoc mesenteroides subsp.mesenteroides.There are five yeast strains including two Candida parapsilosis,two Candida valida and a Saccharomyces cerevisiae.Through the preliminary screening,one strain with good growth performance was selected for further study.?2?L.plantarum PMO was highly sensitive to antibiotics without acute toxicant,and the maximum tolerated dose above 5?10¹¹CFU/?mL·bw?,20mL/?kg·d?.The strain would not cause bacterial translocation.It also did not cause histological changes,or disfunction of liver,heart,kidneys or biliary tract,that can be used in food industry.?3?L.plantarum PMO and L.plantarum 102 could rapidly produced acid during the logarithmic phase with the same acid produce capacity.The maximum viable count of L.plantarum PMO and 102 could reach 10.28±0.12 lg?CFU/mL?and 10.90±0.16lg?CFU/mL?respectively.The two strains showed good storage characteristics at 4°C.Both strain showed no tolerance to high temperature?65°C?.These two strains showed good tolerance to high pH value environment and could be used as starter for fermentation products.Both strains could grow in of MRS medium with bile salt concentration from 0.1%to 1.0%,showing good bile salt tolerance capacity.And the latency time?LT?of L.plantarum 102 was significantly shorter than that of L.plantarum PMO?p<0.05?.Strains showed high survival rates in artificial gastric juice and had the potential of active proliferation ability in intestinal tract.Both strains with better electron donor ability than electron acceptor ability showed good hydrophobicity to trichloromethane and ethyl acetate.The the automatic aggregation rate for 8h reached40%,and for 24h reached 73.79±1.01%and 63.64±1.75%respectively.?4?The two Lactobacillus plantarum strains were biliary salt hydrolyase enzyme negative strains.L.plantarum PMO removes cholesterol in vitro mainly by coprecipitation and assimilation.38.40%of the total concentration in MRS THIO medium could be removed by L.plantarum PMO with 10%inoculation,while the removal rate would drop when inoculation above 10%.The cholesterol scavenging capacity of L.plantarum PMO increased with the concentration of cholesterol in the matrix,and reaching the maximum value of 75.91?g/mL at the concentration of 200?g/mL of the medium.However,L.plantarum 102 only had coprecipitation and the amount of cholesterol adsorption was 10.97-12.36?g/mL,which was significantly lower than that of L plantarum PMO?p<0.05?.Although the DPPH scavenging ability of L.plantarum 102 was higher than that of L plantarum PMO,were both significantly lower than that of reported antioxidant strains?p<0.05?.?5?The viable count of hawthorn juice fermented by domesticated L.plantarum PMO for 18 h could reach 8.26±0.05 lg?CFU/mL?,and the total acid content raised to1.44±0.04g/100g.There was no post-acidification during storage,and the storage time should no more than 28 days.The content of total phenol decreased by 10.46%during the fermentation and the content of total flavonoids increased by 9.48%.The content of total free amino acids increased by 6.2 folds,and arginine,glycine,leucine and isoleucine increased significantly by fermentation?p<0.05?.Lactic acid,acetic acid,chlorogenic acid and hypericin also increased significantly?p<0.05?.The contents of maslinic acid,oleanolic acid,quercetin and vitexin-4-glucoside decreased significantly?p<0.05?.And thermal treatment also could decrease the contents of epicatechin,maslinic acid and oleanolic acid?p<0.05?.?6?Fermentation could enhance the antioxidant capacity of hawthorn juice.The EC₅₀0 of fermented hawthorn juice?FH?was 1.93%that significantly lower than those of treated fermented juice and unfermented juice?p<0.05?.Scavenging ability of hydroxyl radical,superoxide anion and lipid peroxides of fermented groups?FH,BH,CH?with medium doses were significantly higher than those of non-fermented groups?LH,UH??p<0.05?.However,the total reducing capacity of unfermented hawthorn juice at low concentration was significant higher than that of fermented groups.Antioxidant capacity was fermented hawthorn juice?FH?>boiled fermented hawthorn juice?BH??centrifuged fermented hawthorn juice?CH?>hawthorn juice with strain?LH??unfermented hawthorn juice?UH?.?7?Fermented hawthorn juice?FH?could reduce the number of lipid droplets and restored the liver morphology of high-fat diet rats.Other inventions also could alleviate the damage of high fat diet on the liver.The fermented hawthorn juice?FH?could significantly reduce the content of serum total cholesterol and LDL-C?p<0.05?.All interventions had no effect on content of TG,HDL-C and apoA?p>0.05?.The lipid regulation effect was fermented hawthorn juice?FH?>boiled fermented hawthorn juice?BH?>centrifuged fermented hawthorn juice?CH??hawthorn juice with strain?LH?=unfermented hawthorn juice?UH?,which was accordance with antioxidant capacity in vitro.L.plantarum PMO do not have lipid regulation effect in vivo when used alone.?8?High fat diet will cause oxidative stress of body.Fermented hawthorn juice?FH?could increase the antioxidant capacity and reduce the content of MDA.Remove the cell from fermented hawthorn juice would significantly reduce the antioxidant capacity.The antioxidant capacity of each intervention was accordance with the lipid regulation capacity.The fermented hawthorn juice participated in lipid regulation by reducing the absorption of cholesterol,improving antioxidant capacity and reducing oxidative stress.?9?High fat diet inhibited the expression of HMGCR mRNA and LDLR mRNA,and increased the expression of ABCA1 mRNA.Fermented inventions?FH,BH,CH?could reduce the absorption of exogenous cholesterol,up-regulate the expression of LDLR mRNA?p<0.05?.Five hawthorn juice interventions could up-regulate the expression of CYP7A1 mRNA significantly?p<0.05?.