Evidence for the bulk nature of self-assembled monolayer surface of fluorinated alkyl thiol from hyperthermal energy ion-surface collisions

Kinetic energy distributions of fragment ions from hyperthermal energy collisions of ions with a self-assembled monolayer surface of fluorinated alkyl thiol on gold substrate and a LiF surface (vapor deposited on titanium substrate) have been measured as a function of scattering angle and fragment ion mass. These distributions for the thiol surface show two energetically and angularly distinct pathways for the dissociation of ions while those from LiF show only one peak. A plot of the velocities of the fragment ions as a Newton diagram for these two processes clearly demonstrates that one process is due to the collision of ions with a fraction of the molecular chain of the monolayer surface molecule with scattering over a broader angular range while the other process is due to collision of the projectile ions with the monolayer surface acting as a bulk surface with fragment ions scattering close to the surface parallel and resembles the Newton diagram from the LiF surface.     

BCVEGPY: an event generator for hadronic production of the Bc meson

We have written a Fortran program BCVEGPY, which is an event generator for the hadronic production of the B_c meson through the dominant hard subprocess . To achieve a compact program, we have written the amplitude of the subprocess with the particle helicity technique and made it as symmetric as possible, by decomposing the gluon self couplings and then applying the symmetries. To check the program, various cross sections of the subprocess have been computed numerically and compared with those in the literature. BCVEGPY is written in a PYTHIA-compatible format, thus it is easy to implement in PYTHIA.

Program summary

Title of program: BCVEGPYVersion: 1.0 (September, 2003)Catalogue identifier: ADTJProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTJProgram obtained from: CPC Program Library, Queen's University of Belfast, N. Ireland.Computer: Any computer with FORTRAN 77 compiler. The program has been tested on HP-SC45 Sigma-X workgroups, Linux PCs and Windows PCs with Visual Fortran.Operating systems: UNIX, Linux and Windows.Programming language used: FORTRAN 77.Memory required to execute with typical data: About 2.0 MB.No. of bytes in distributed program, including test data, etc.: 477630No. of lines in distributed program, including test data, etc.: 66461Distribution format: tar gzip fileNature of physical problem: Hadronic production of B_c meson.Method of solution: Improved helicity-approach to the amplitude and symmetries of the amplitude itself have been used to compact the program so as to save cpu as possible as one can. The code with option can generate weighted and un-weighted events. For jet hadronization, an interface to PYTHIA is provided.Restrictions on the complexity of the problem: The hadronic production of the B_c meson in the S-wave states, i.e. pseudo-scalar state () and vector state () are included by the ‘complete calculation’ approach. The hadronic production of B_c meson in P-wave states has not been implemented into the BCVEGPY yet.Typical running time: It depends on which option one chooses to match PYTHIA when generating the B_c events. Typically, if IDWTUP=1, then it takes about 20 hour on a 1.8 GHz Intel P4-processor machine to generate 1000 events; however if IDWTUP=3, to generate 10⁶ events, it takes about 40 minutes only.     

Antagonistic effect on Listeria monocytogenes and L. innocua of a bacteriocin-like metabolite produced by lactic acid bacteria isolated from sucuk

Two Lactobacilli and four Pediococci strains producing bacteriocin-like metabolities isolated from sucuk were tested with agar spot tests and well diffusion assays for their inhibitory activity against 16 Listeria strains, also isolated from sucuk. The production of organic acids and hydrogen peroxide limited, L. sake Lb 706 (used as a bacteriocin producer strain) and the isolated lactic acid bacteria (LAB) showed inhibitory activity against all of the Listeria strains, while L. sake Lb 706-A (used as a bacteriocin non-producer mutant) had the same effects against only two Listeria monocytogenes strains (51, 52) in agar spot tests. In the well diffusion assays, while L sake Lb 706 and four Pediococci isolates (413, 416, 419, 446) exhibited inhibitory activity against all of the Listeria strains tested, L. sake Lb 706-A and two of the Lactobacilli isolates (77, 116) showed no effect on the Listeria strains tested.     

通过抗药性筛选产生广谱高效肽类天然防腐剂的融合菌株

副干酪乳杆菌（Lactobacillus paracaseiHD1.7）与小白链霉菌（Streptomyces albulus）进行原生质体融合,获得种间融合子,通过抗药性进行筛选融合子,获得产生广谱高效肽类天然防腐剂的融合菌株.     

不同处理对Lactobacillus delbrueckii subsp. Bulgaricus LB细胞膜脂肪酸的影响

研究了pH值为6.0(温度为32,37,42和42℃),pH值为5.0和5.5五种培养条件、两个不同生长阶段对Lb.delbrueckii subsp.BulgaricusLB细胞膜脂肪酸组成的影响,以及冷冻干燥过程中细胞膜脂肪酸组成的变化。实验菌株Lb.LB中主要检测到8种脂肪酸。不同处理条件下Lb.LB细胞膜脂肪酸种类一样,但质量分数存在差异。C12:0和C19cyc9质量分数差异最大,变化范围分别为0.86%~2.16%和4.03%~7.51%。冷冻干燥过程中Lb.LB细胞膜中各脂肪酸质量分数变化甚微。     

中温发酵乳菌株筛选及其发酵特性分析

采用德氏乳杆菌保加利亚亚种、唾液链球菌嗜热亚种和肠膜明串珠菌混合发酵制备中温(35℃)发酵酸乳制品。根据发酵乳的感官品质、黏度及持水力分析,筛选出菌株德氏乳杆菌保加利亚亚种L2、唾液链球菌嗜热亚种S8、肠膜明串珠菌乳脂亚种M4为发酵剂优组合,其最适宜的接种比例为33︰60︰7。此发酵剂35℃发酵5 h得到的中温发酵乳的感官品质和持水力优于普通发酵乳。三菌混合发酵对上述菌种的生长都有一定的促进作用,但发酵后期M4的生长受到一定抑制。三菌混合发酵乳中酸度主要是L2和S8发酵作用的结果。     

Influence of enzyme treatment of rice bran on gamma-aminobutyric acid synthesis by Lacto bacillus

Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the central nervous system. The production GABA from the cheaper glutamic acid is a valuable process. Rice bran is a potential source of glutamic acid decarboxylase which was therefore selected for production of gamma-aminobutyric acid (GABA) using lactic acid bacteria (Lactobacillus brevis (Lb.brevis) VTCC-B397). The influences of treatment of defatted rice bran with α-amylase, Alcalase (Al), Flavourzyme (Fl) and their combinations at different concentration ratios on the GABA synthesis were examined. With α-amylase impacts, concentration of GABA (6.41 mg mL⁻¹) was about 2.38 times higher than the control sample (2.69 mg mL⁻¹) under hydrolysis conditions of pH 6.5, temperature of 95 °C and α-amylase concentration of 0.15% (v/w) for 45 min. The α-amylase hydrolysis as prerequisite for protein hydrolysis using Al: Fl (ratio Al: Fl of 3: 7, concentration of 2% (w/w), pH = 8, temperature of 50 °C) reached the highest GABA synthesis efficiency, at 8.43 mg mL⁻¹. Results showed that the enzyme treatment positively affected the fermentation using Lb. brevis for GABA biosynthesis from defatted rice bran.     

Recommendations for the viability assessment of probiotics as concentrated cultures and in food matrices

Due to the fact that probiotic cells need to be alive when they are consumed, culture-based analysis (plate count) is critical in ascertaining the quality (numbers of viable cells) of probiotic products. Since probiotic cells are typically stressed, due to various factors related to their production, processing and formulation, the standard methodology for total plate counts tends to underestimate the cell numbers of these products. Furthermore, products such as microencapsulated cultures require modifications in the release and sampling procedure in order to correctly estimate viable counts. This review examines the enumeration of probiotic bacteria in the following commercial products: powders, microencapsulated cultures, frozen concentrates, capsules, foods and beverages. The parameters which are specifically examined include: sample preparation (rehydration, thawing), dilutions (homogenization, media) and plating (media, incubation) procedures. Recommendations are provided for each of these analytical steps to improve the accuracy of the analysis. Although the recommendations specifically target the analysis of probiotics, many will apply to the analysis of commercial lactic starter cultures used in food fermentations as well.     

Identification and Partial Characterization of a Bacteriocin‐Like Inhibitory Substance (BLIS) from Lb. Bulgaricus K41 Isolated from Indigenous Yogurts

Forty‐two strains of Lactobacillus bulgaricus isolated from locally made yogurts were examined and compared for bacteriocin producing ability using spot on lawn assay which improved by taking photo and image processing. Lb. bulgaricus K41 exhibited the highest inhibition level against indicators. K41 Bacteriocin‐like inhibitory substance is sensitive to proteolytic enzymes (proteinase K, pepsin, and trypsin) but α‐amylase makes slight reduction in its activity and it is resistant to lipase. This antibacterial peptide is extremely heat‐stable (121 °C for 15 min) and remains active over a wide pH range (pH = 2 to 10); also nonionic detergents (Tween‐20, Tween‐80, and Triton X100) showed no effect on its activity. The inhibitory spectrum is against Gram‐positive bacteria (except Staphylococcus aureus) with extremely antilisterial activity and it is almost ineffective against Gram‐negative bacteria. The mode of its action was identified as bactericidal against Listeria monocytogenes. The properties of K41 bacteriocin‐like inhibitory substance add to its safety as a biopreservative produced by a generally recognized as safe (GRAS) bacterium suggesting it can be used in hurdle technology for ready‐to‐eat foods as one of the main sources of Listeria contaminations.     

乳杆菌Lb.casei.Zhang对小鼠血清中细胞因子水平的影响

目的:观察及评价乳杆菌Lb.caseiZhang对小鼠血清中IFN-γ、IL-12、IL-1α、TNF-α水平的影响。方法:应用分离自酸马奶,并经过耐酸性实验、人工胃肠消化液中存活能力筛选的L.caseiZhang,制备成热致死菌体和活菌制剂各分成高、中、低三个剂量组灌服小鼠至15d,采用ELISA法检测血清中IFN-γ、IL-12、IL-1α、TNF-α的含量。结果:活菌制剂高、中剂量组小鼠血清中IFN-γ、IL-12含量明显高于对照组(p<0.05),IL-1α、TNF-α含量明显低于对照组(p<0.01);灭活菌制剂对细胞因子的影响与对照相比无显著差异。结论:Lb.caseiZhang活菌制剂的免疫调节作用优于热致死菌体制剂。活菌制剂对小鼠的细胞免疫功能产生了多方面的、有利于机体免疫功能状态的调节作用。