| 1. One lactic acid bacteria strain FML02-8 with high production of exopolysacchaeide was screened from ZangLingGu(ZLG) grains , which produces 187.6mg/L polysaccharide in skimmed milk cultures. FML02-8 was preliminarily identified as Streptococcus in view of its cultural characteristics and part of biological and biochemical characteristics .The growth characteristic of the strain indicates that it produces acid greatly, and grows fast. The optimum temperature to the strain in MRS media is 37 C,and the optimum incipient pH value is 7.0.2. Preliminary evidences were presented to show that the production of EPS from FM02-8 is not controlled by plasmid, and that there exists coherence to some degree between the production of EPS and the growth of the strain.3. The optimum media for the synthesis of EPS from FML02-8 was selected as follows: Glucose 2.0%, Pepton 2%, NaAc 0.5%, ammonium citrate 0.2%, tween-80 0.1%, MgSO40.01%, MnSO4 0.005%,K2HPO4 0.2%. Single-factor test demonstrated that the strain can use different carbon sources to synthesize EPS with different production, and that the optimum dosage of all sources is 20g/L.Among different carbon sources, glucose has the highest production.4. By means of 24 factorial design in SAS8.0 software, remarkable factors affecting the production of EPS were selected as temperature. PH and time. Through a central composite design, a preferable model of the production of EPS was established follows: EPS= - 3764.49 + 79.42 X T + 729.90 X PH + 16.30 X t - 0.97 X T X T - 52.67 X pH X pH - 0.49 X t X t. The model was also verified.5. The constant PH in 3L fermentation indicated that different constant pH values during fermentation affect the yield of EPS from FML02-8. Under the constant pH5.5, the yield of EPS was 503.3mgL, increasing 30% compared without control of pH.6. To remove proteins, two methods were tested: Sevage method and TCA(trichloroacetic acid) method. The results indicating EPS precipitated by alcohol, the conditions are given as follows: final concentration of alcohol is 75%, time for precipitation is 12h, temperature is 4 C, and pH value of solution is 6.0-6.5.7. The conditions of gradient separation of EPS through Sepharose 4B gel filtration chromatography are studied. The optimum parameters for separation are: concentration of sample 750mg/L, volume 5ml, flow speed of solvent 30ml/h. With these parameters, all EPS from FML02-8 using different carbon sources can be purified into two parts, with a proportion of 26.3:1, The rate of recovery is as high as 90.5% and the fraction is identified to be pure.8. EPSG, EPSF, EPSL, EPSs, EPSM, EPSW from different carbon sources were subjected to infrared spectroscopic studies to analyze their structures preliminarily. All of infrared spectroscopic results showed characteristic band of EPS. The bands were identified as pyranose, mostly in the form of a -conformation, but with differences in band shape, characteristic absorption region and intensity of peak. Peak molecular weigh(Mp) of different EPS were measured through HPLC, and the results were 41092, 54029 , 45468, 46996, 46257 , 45468 Daltons respectively. EPS were also subjected to GC to analyze the composition and mole rate of monosaccharides, and the results are. EPSG-Galactose:Rhamnose=l .60:1; EPSF-Glucose:Mannose=l .98:1; EPSL-Galactose:Rhamnose=4.03:l; EPSs-Galactan; EPSM- Glucose: Rhamnose: Mannose=1.41:1.60:l; EPSw- Galactose: glucose: Rhamnose =2.26:1.33:1. The results indicated that besides the yield of EPS, different carbon sources also affect the structures of EPS, including molecular weight, monosaccharide composition and their mole rate etc. difference in intramolecular structure and the linkage pattern among monosaccharides are pending further study.9. Functional tests in vitro on pure EPS from FML02-8 were studies on rodent tumor cell line S180, and indicated that EPS can inhibit the growth and reproduction of tumor cell. Within the concentration of 10~400ug/ml, EP...
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