| Lactic acid bacteria, referred to a group of bacteria that can ferment hydrocarbons and produce lactic acid, have long been found and used in fermented food, such as fermented milk and meat products. At first, lactic acid bacteria were used in food industry only for technological purpose. As more knowledge about this group of microbes are obtained, people found lactic acid bacteria, especial Bifidobacteria, have some healthy function and ingestion of these bacteria can bring about some beneficial effects to people. Thus more and more scholars are becoming interested in lactic acid bacteria. Nowadays development of new source of lactic acid bacteria and their application in food industry have been gain worldwide interest.In this study, new strains of lactic acid bacteria are isolated from the faeces of old people aged one hundred years in Bama, Guangxi province. Their biological characteristics and physiological functions are also preliminarily investigated in the hope of obtain some valuable proinciples or basic knowledge that can be referred to in the the development of food-grade bifidobacteria starter and microecologics. My research work mainly focused on the following aspects:1. Using colon adenocarcinoma cell line HT-29 as testing material, adhesion test was carried out for 24 strains of Bifidobacteria isolated from dejecta of longevous people aged one hundred years. The results showed that all strains could adhere to colon adenocarcinoma cells HT-29, among which the strains of TTF, Z2, TZ5 and J-1 showed higher adhesive capability. Thus these four strains of Bifidobacteria were further tested for their endurance to stomach acid and bile acid. The production of vitamin B by these bacterial were also tested. All these tests indicated that the strain of TTF has high ability to produce Vitamin B1, B2, B6, B12, The survival rate after the treatment under pH 3.0 for 120 min was 93.11%, at the same time, the strain TTF can survive after being treated with 2% bile acid for 24h. According to its morphology, together with physiologic and biochemical tests, this strain was identified as Bifidobacteria longum.2. The strain of TTF was further characterized in terms of its optimal growth media, temperature, initial pH and growth promoting factors. The results as follows:1) B. longum TTF grows better in modified MRS broth than MRS and PTYG broth. It usually enters logarithm stage after 6 hours of inoculation and enters stability stage after 12 hours. Optimal temperature and initial pH for its growth are 37β and 7.5, respectively.2) Some food materials, used as BF, can promote its growth. According to our study, the best combination of three food materials that can considerably promote the growth of TTF in vitro was 2% CJ, 2% M and 2% LE. Extract of Lentinus edodes can significantly promote the growth of TTF. However, the optimal concentrations of the extracts of carrot and are related to the addition of milk.3. The factors influencing B. long TTF's ability to adhere to colon adenocarcinoma cell HT-29, its sensitivity to antibiotic and herbs, its capability to eliminate active oxygenous free radicals in vitro, its effects on human immune function and intestine microftora were also studied. The main results are:1) With Staphylococcus aureus ATCC 25923 as indicator bacteria, B. longum TTF showed its antibiotic susceptibility to 30 antibiotics of 8 groups: sensitive to macrolide group, cephalosporin group, penicillin group, β-lactamases inhibitors, chloramphenicol, nitrofurantoin and Rifampin, and resistant to aminoglycoside group and peptide group, whileshowing different susceptibility to tetracyciine group. DNA identification of TTF showed it does not possess the drug resistant plasmids, it means that its resistance to the antibiotics wasn't encoded by plasmids and the possibility of intercellular transferring of resistance genes was excluded. Strain TTF can be safely used in fermented foods and microecologics.2) The influence of herbs, including Fructus Lycii, Fructus Schizan...
|
PDF Full Text Request