Microbial transformation of tectoridin from Pueraria flos by Lactobacillus and bifidobacteria

Tectoridin could be hydrolyzed to tectorigenin by β-glucosidase-producing intestinal bacteria. In this study, nine strains of Lactobacillus and bifidobacteria were screened for high levels of β-glucosidase activity. We investigated their ability to transform tectoridin from Pueraria flos to tectorigenin. Lactobacillus reuteri DSM20016 showed the highest cell-envelope associated β-glucosidase activity, whereas the intracellular β-glucosidase activity from Bifidobacterium adolescentis ATCC15703 was higher than the other screened bacterial strains. L. reuteri DSM20016, Lactobacillus rhamnosus GGB41031 and B. adolescentis ATCC15703 showed high bioconversion rate of tectoridin. L. reuteri DSM20016 showed the highest bioconversion efficiency of tectoridin, 100% tectoridin was hydrolyzed and there was an approximate 185-fold increase in the concentration of tectorigenin after 24 h. The present study suggests that L. reuteri DSM20016, L. rhamnosus GGB41031 and B. adolescentis ATCC15703 have great potential for converting tectoridin from Pueraria flos to more bioactive tectorigenin.     

双歧杆菌基因组DNA提取及其遗传多态性研究

用自行改良的氯化苄法，从液体培养的双歧杆菌菌中提取基因组DNA，用紫外吸收光谱、琼脂糖凝胶电泳等方法进行鉴定。结果表明，该法提取的基因组DNA分子量高，收获量大，蛋白质污染少，而义快速、高效、经济和实用。以该基因组DNA为模板，用随机引物S256通过AP—PCR扩增出清晰的RAPD谱带，并呈现出一定程度的遗传多态性。讨论了RAPD指纹图谱在双歧杆菌分类鉴定及工业菌株分子标记中潜在的应用价值。     

双歧酸牛奶的研制

本文通过对双歧杆菌进行耐氧驯化,选育出耐氧菌株,并且通过正交试验,活菌计数,确定适合工业化生产双歧酸牛奶的工艺及技术参数,该产品在6℃冰箱保存5天后,其双歧杆菌活菌数仍≥10^5efu／ml。     

Hypocholesterolaemic effect of yoghurt containing Bifidobacterium pseudocatenulatum G4 or Bifidobacterium longum BB536

The effect of a yoghurt supplement containing Bifidobacterium pseudocatenulatum G4 or Bifidobacterium longum BB536 on plasma lipids, lipid peroxidation and the faecal excretion of bile acids was examined in rats fed a cholesterol-enriched diet. After 8 weeks, the rats in the positive control (PC) group who were fed the cholesterol-enriched diet showed significant increases in plasma total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, and malondialdehyde (MDA). However, groups fed a cholesterol-enriched diet supplemented with yoghurt containing B. pseudocatenulatum G4 or B. longum BB536 had significantly lower plasma TC, LDL-C, very-low-density lipoprotein (VLDL) cholesterol, and MDA than had the PC group after 8 weeks of treatment. In addition, faecal excretion of bile acids was markedly increased in the rats fed the yoghurt containing B. pseudocatenulatum G4 or B. longum BB536 as compared to the PC and NC groups.     

双歧杆菌发酵胡萝卜汁酸乳贮藏稳定性研究

从健康人体中选育出2株发酵活力高、耐氧性和抗逆性强的双歧杆菌优良发酵菌株两歧双歧杆菌Bbm和长双歧杆菌Blm作为试验菌株,制备了双歧杆菌纯种及双歧杆菌与乳酸菌混种发酵胡萝卜汁酸乳,考察了发酵产品在室温(20~30℃)和冷藏(0~4℃)条件下的贮藏稳定性。试验结果表明:0~4℃冷藏21d,活菌含量仍可达1×109cfu/mL以上,pH值降至4.2~4.3,酸甜适宜。因此,确定发酵产品0~4℃下贮藏期为21d。     

双歧杆菌及其保健机理

本文从双歧杆菌产生有机酸、抑制肠道腐生菌生长出发,对其抗癌作用、对肝脏及人体代谢的保健作用、改善维生素代谢、防止便秘、提高免疫机能以及降低清血胆固醇作用等进行了较详细的论述,确认了双歧杆菌的优良保健性能。     

Effect of dry heated inulin on selected intestinal bacteria

Degradation of a sample of high-molecular (degree of polymerisation, DP, between 13 and 30) and low-molecular (DP below 12) inulin from Jerusalem artichoke during dry heating for 30 min at 165 and 195 °C was analysed using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and thin layer chromatography. Dry heating at 195 °C induced complete degradation of the fructan chains and the concomitant formation of low-molecular degradation products, most likely di-d-fructose dianhydrides. In vitro fermentation studies using mixed faecal samples of eight human volunteers for 24 h at 37 °C showed significant stimulation of the growth of bifidobacteria and Enterobacteriaceae and a significant decrease of possibly pathogenic bacteria of the Clostridium histolyticum and C. lituseburense group by inulin samples heated at 195 °C compared to unheated samples and samples heated at 165 °C. This preliminary data may point to the hypothesis that heat-treated inulin or its degradation products may cause improvements of the gut microflora superior to native inulin.     

X-Gal在双歧杆菌分离与活菌计数方面的应用研究

利用大多教双歧杆菌具有半孔糖苷酶且活性较高的特性,在NPNL培养基中加入X-Cal(5-溴-4-氯-3-吲哚-β-D-半乳糖苷)作为底物,双歧杆菌水解底物释放出吲哚,产生颜色反应。双歧杆菌菌落呈深蓝色,乳酸菌和其它细菌一般为白色或淡蓝色。将X-Gal应用于不同样品中双歧杆菌分离和活菌计数进行对比。这种方法能比较准确的反映双歧制品和婴儿粪便中双歧杆菌的数量,并且大大减少了分离鉴别双歧杆菌的工作量。     

Protective effect of whey cheese matrix on probiotic strains exposed to simulated gastrointestinal conditions

A probiotic whey cheese added with Lactobacillus casei LAFTI®L26, Lactobacillus acidophilus LAFTI®L10 or Bifidobacterium animalis Bo was subject in vitro to sequential conditions that parallel the four major steps of digestion: mouth (artificial saliva), oesophagus-stomach (artificial gastric juice), duodenum (artificial intestinal juice) and ileum; its manufacture followed the traditional cheesemaking protocol of Portuguese Requeijão. MRS broth was inoculated in parallel as reference medium, to ascertain the protective effect of the whey cheese matrix itself upon those strains in every digestion step. Mouth conditions had an almost negligible effect upon all three strains, whereas oesophagus-stomach, duodenum and ileum conditions decreased the viable numbers of L. casei and L. acidophilus; in both systems, B. animalis suffered only slight decreases in viable numbers; and L. casei and L. acidophilus behaved likewise in MRS exposed to duodenum and ileum conditions. Whey cheese matrices thus appeared to protect the aforementioned three strains during transit throughout the simulated gastrointestinal system, so they are promising carriers of those probiotic bacteria.     

Rheological, textural and microstructural features of probiotic whey cheeses

Whey cheeses have been manufactured with probiotic bacteria - viz. Bifidobacterium animalis Bo and Lactobacillus casei LAFTI^®L26, from combinations of bovine whey and milk, following protein denaturation at 90 °C; they were subsequently inoculated (at 10%) with those strains, and homogenized afterwards; additives such as salt and sugar were then incorporated; and the resulting solid matrices were stored at 7° C for up to 21 d. Oscillatory measurements and instrumental texture profile analyses were performed, and sensory analyses were carried out by a trained panel. Microstructural features were in addition ascertained by scanning electron microscopy.L. casei exhibited a higher acidifying activity than B. animalis, which produced distinct textures; higher firmness and viscoelasticity were indeed found in matrices inoculated with the former. Incorporation of sugar and L. casei favoured consumer acceptability, relative to plain matrices. Microstructural differences were detected between matrices at different times of storage and formulated with distinct additives.