抗李斯特细菌植物乳杆菌的抑菌活性物质特性

对植物乳酸杆菌(Lactobacillus plantarum)产生的抑菌物质进行研究.选用琼脂扩散法从5株植物乳酸杆菌中筛选出1株抑菌活性较高的植物乳酸杆菌菌株LP-1.对抑菌物质的理化性质分析结果表明:其抑菌活性对温度的变化不敏感,经过蛋白酶的处理后抑菌活性有所降低.在pH为4.0-5.0时,抑菌活性基本不变,当pH低于4.0或大于5.0时,抑菌活性均有降低.植物乳杆菌LP-1产生的抑菌物质对革兰氏阳性和阴性细菌都有抑制作用.     

柱层析法纯化番茄红素的研究

用氧化铝作柱层析固定相，三步洗脱分离提纯番茄红素油树脂，得番茄红素晶体，经高压液相色谱检测知番茄红素的纯度为90％，同时还得到β-胡萝卜素、叶黄素等产品。     

芽孢乳酸杆菌抑菌物质特性的研究

芽孢乳酸杆菌1033在乳酸发酵过程中能产生抑菌物质,通过对这种抑菌物质的产生与培养基组成关系的分析,对抑菌物质的分离和提取的研究,以及对理化性质和抑菌谱的测定,初步探明了芽孢乳酸杆菌1033产生的这种抑菌物质能抑制常见的肠道病原菌.     

乳酸片球菌素的抑菌方式

以单核细胞增多症李氏杆菌CVCC1595为指示菌,通过对乳酸片球菌素吸附率的研究,发现乳酸片球菌素的吸附受盐浓度、pH和细胞膜的成分影响显著.NaCl和磷酸盐浓度越高,吸附作用越小,在400mmol/LNaCl溶液中,乳酸片球菌素对菌体的吸附率为0;在pH 6.0吸附率最高(100%),pH 2.0和8.0的吸附率为24.4%,pH 10.0时乳酸片球菌素在菌体上无吸附.温度对吸附影响很小,在100℃时吸附率比室温时下降了1.56%;时间对吸附没有影响,乳酸片球菌素对指示菌的吸附作用应是由静电引力引起,其杀菌作用是使细胞膜形成孔洞,胞内物质外泄,从而导致细胞的死亡.     

PRESERVATION OF FISH SPREAD WITH ENTEROCINS 1071A AND 1071B, TWO ANTIMICROBIAL PEPTIDES PRODUCED BY ENTEROCOCCUS FAECALIS BFE 1071

Enterocins 1071A and 1071B, produced by Enterococcus faecalis BFE 1071, kept the total aerobic cell numbers in fish spread between 8 × 10⁴ and 2 × 10⁵ cfu/g for the first 6 days of storage. The total aerobic cell numbers in a batch preserved with a combination of sodium benzoate (0.045%, w/w) and potassium sorbate (0.059%, w/w) remained between 8 × 10⁴ and 2 × 10⁵ cfu/g during the first 18 days of storage. In a batch containing no preservatives, cell numbers gradually increased from 1 × 10⁵ to 1 × 10⁸ cfu/g over 21 days. The spoilage organisms were identified as Staphylococcus epidermidis and atypical Proteus vulgaris. The pH of all batches remained constant over the 21‐day storage period, with minimal variations recorded in textural and organoleptic qualities. The number of microbial cells recorded in fish spread preserved with enterocins 1071A and 1071B was 8 × 10⁶ after 21 days of cold storage (4C), whereas microbial cell numbers of 1 × 10⁸ were recorded in fish spread that had not been preserved.     

THE NATURE OF TOXINS PRODUCED BY BACILLUS CEREUS BIS-59

Eight strains of Bacillus spp. were examined for production of toxin(s). Three strains of Bacillus cereus produced toxins lethal to mice. The culture filtrate of Bacillus cereus BIS-59 contained two lethal toxins. One was a hemolysin and the other a nonhemolytic glycoprotein. The growth of cells in fresh beef infusion broth resulted in high toxin production, compared to growth in tryptone-glucose-yeast extract or nutrient broth. Separate identities for the two toxins from B. vcereus BIS-59 were established on the basis of hemolytic activity, separation profiles on Sephadex gel filtration, responses to heat and radiation and kinetics of their production during the growth of the organism.     

EFFECT OF A BACTERIOCIN-LIKE SUBSTANCE (BLS) PRODUCED BY STREPTOCOCCUS THERMOPHILUS STRAINS ON LISTERIA SPP. STRAINS

In this study, fifty-two strains of Streptococcus, isolated from Turkish yogurt were tested for their ability to inhibit Listeria strains. Only two isolates exhibited antimicrobial activity (CFF; cell-free filtrate) against eight strains of Listeria innocua, four strains of Listeria monocytogenes and one strain of Listeria welshimeri by agar diffusion. However, bacteriocin-like substance (BLS) producing strains were determined under conditions with the effects of organic acids and hydrogen peroxide eliminated. Inhibitory activities of Streptococcus thermophilus ET5 and S. thermophilus H22 were due to BLS. BLS of S. thermophilus ET5 was observed to exhibit more significant inhibition to the Listeria strains than BLS of S. thermophilus H22.
Inhibitory effect of nisin in 50, 100, 150, 200, 250 and 300 ppm concentrations was compared with BLS producing S. thermophilus strains against Listeria spp. strains. While all Listeria strains were resistant to 50 and 100 ppm concentrations of nisin, some strains of Listeria spp. were only sensitive to 150, 200, 250 and 300 ppm concentrations. The inhibitory activity of S. thermophilus ET5 was more effective against Listeria strains than the inhibitory activity of nisin. It appears that BLS of S. thermophilus ET5 could provide greater potential and usefulness as bacteriocin than nisin. These results indicate that the potential application of antimicrobial-production of S. thermophilus ET5 and H22 as bio-preservatives against Listeria contamination on dairy products could be suggested.     

DEGRADATION OF GUAR GUM BY ENZYMES PRODUCED BY A BACTERIUM FROM THE HUMAN COLON

A strain of Bacteroides ovatus from the human colon was grown on guar gum, a highly-branched galactomannan which is widely used as a food additive. Growth on guar gum induced production o f extracellular enzymes which partially degraded and/or deaggregated guar gum. The enzymes rapidly reduced the viscosity of guar gum solutions, while breaking only a limited number of glycosidic bonds. The molecular weight (versus dextran standards) of the guar gum decreased sharply as the viscosity decreased. No mono-, di- or trisaccharides were produced during enzyme action, although small quantities of higher oligomers were present after longer (5–8 h) incubations. The enzyme had a sharp temperature optimum at 37°C for an incubation time of 60 min, but was stable for only a few hours at this temperature. These results demonstrate how enzymes produced and elaborated by human colon bacteria can markedly alter the physical properties of a dietary component which reaches the colon. Further studies of both substrate and enzymes will be required to establish the mechanism of this alteration and to establish how B. ovatus is able to utilize guar gum for growth.     

PURIFICATION AND MECHANISTIC ACTION OF A BACTERIOCIN PRODUCED BY A BRAZILIAN SAUSAGE ISOLATE, LACTOBACILLUS SAKE 2a

Bacteriocin 2a is produced by a Lactobacillus sake strain isolated from Brazilian sausage. This bacteriocin was purified 72,000 fold by acid extraction from L. sake 2a, followed by cation exchange and reverse phase chromatography. Bacteriocin 2a dissipated the proton motive force in Listeria monocytogenes and reduced the intracellular ATP with no detectable increase in extracellular ATP. Bacteriocin 2a also mediated a concentration-dependent efflux of carboxyfluorescein from liposomes made from L. monocytogenes lipids. These data indicate that bacteriocin 2a forms pores in the membrane of target cells.     

大豆异黄酮的热水提取及其纯化工艺的优化

研究了热水从大豆胚芽中提取异黄酮的工艺，方法简便、可行且提取率、纯度满足实验要求；并采用HPLC法对提取液中异黄酮组分进行鉴定。经大孔树脂纯化、乙酸乙酯萃取三次后，异黄酮纯度超过60％。     

树脂法提取纯化草莓色素的研究

研究以草莓为原料、用大孔树脂提取和纯化草莓色素的工艺条件.试验结果表明,最佳的工艺条件是:提取液为0.1 mol/L的盐酸溶液;最佳树脂是AB-8树脂;最佳吸附条件是:50℃,pH=1.5的条件下吸附,吸附流速为1 BV/h;最佳解吸条件是:用pH=1.5时,50%的乙醇在室温条件下洗脱,洗脱流速为0.5 BV/h.     

保持乳链菌肽热稳定性的保护剂研究

通过在乳链菌肽中加入不同量的添加物,模拟高温灭菌过程,经过115℃热处理15 min,最终确定海藻糖、奶粉为对乳链菌肽有较好保护作用的保护剂,且其保护作用随量的加大而增大,在其添加量都达到4%时,乳链菌肽的活性损失可以由无保护剂时的29.9%分别降低到7.8%和10.2%.     

洋葱汁的酶法制备及其酒精发酵特性研究

研究了洋葱汁的酶法制备工艺及其酒精发酵特性。对果胶酶处理洋葱汁最适条件进行了优化,确定的适宜条件为：酶用量0.04%;作用时间90min;作用温度35℃;最适pH3.8。并对洋葱汁酒精发酵过程中的酒度、酸度、糖度和还原糖等成分的变化规律进行了研究。