固定化啤酒酵母细胞催化有机硅酮不对称还原

研究了固定化啤酒酵母细胞催化三甲基硅乙酮不对称还原反应,系统探讨了振荡速度、底物浓度、固定化细胞浓度、pH值和反应温度对反应速度、产率和产物光学纯度的影响。结果表明,上述因素对固定化啤酒酵母细胞催化三甲基硅乙酮不对称还原反应均有较显著的影响。振荡速度以150r/min为宜,底物浓度和固定化细胞浓度分别为14mmol/L和0.15g/mL较佳,适宜的pH值为7.3,最佳反应温度为25℃～30℃。在该优化反应条件下,反应最大产率和产物的光学纯度分别高达84.9%和90.2%ee。     

高分子膜载体固定化酵母催化2-辛酮不对称还原

以戊二醛交联尼龙6膜载体固定化面包酵母DX213,采用固定化酵母细胞催化2-辛酮不对称还原得到(R)-2-辛醇。系统考察了有机溶剂、反应时间、pH、底物、辅助底物和热处理等因素对反应的产率和光学选择性的影响。结果表明,上述因素对酵母细胞催化不对称合成(R)-2-辛醇反应均有显著影响。二氯甲烷为该反应最适有机溶剂,在固定化细胞57 g/L(50℃预热50 min),水相与有机溶剂相体积比4/1,pH 7.0,初始2-辛酮浓度为60 mmoL/L(分别在反应0,10,17 h等分添加),蔗糖5.7 g/L和28℃条件下反应48 h,(R)-2-辛醇的产率和e.e.值分别达到89.3%和96.8%。     

马肝醇脱氢酶催化有机硅酮不对称还原反应动力学

探讨了马肝醇脱氢酶(HLADH)催化三甲基硅乙酮及其碳结构类似物不对称还原反应动力学.结果表明,在酶浓度低于150 mg/L时,底物浓度与反应初速度的关系符合米氏动力学方程;HLADH催化三甲基硅乙酮不对称还原反应的K_m、v_max和E_a分别为2.67 mmol/L、0.118 mmol/(L·min·mg)和37 kJ/mol, 其碳结构类似物的相应值分别为3.56 mmol/L、0.084 mmol/(L·min·mg)和61 kJ/mol.     

离子液体对固定化Saccharomyces cerevisiae细胞催化乙酰基三甲基硅烷不对称还原反应的影响

对比研究了C4MIm.BF4-缓冲液混合体系和缓冲液单相体系中固定化面包酵母Saccharomyces cerevisiae细胞催化乙酰基三甲基硅烷不对称还原反应的特性,系统探讨了离子液体C4MIm.BF4对该反应的初速度、最大转化率和产物对映体纯度的影响规律。在各自最优的反应条件下,固定化面包酵母细胞在缓冲液单相体系中催化乙酰基三甲基硅烷不对称还原反应的初速度、最大转化率及产物e.e.值分别为84.8 mmol/(L.h)、99.2%和≥99.9%;而在C4MIm.BF4-缓冲液混合体系中,该反应的初速度、最大转化率及产物e.e.值分别为87.0 mmol/(L.h)、99.0%和≥99.9%。离子液体的存在,提高了固定化面包酵母细胞催化该反应的速度,但降低了固定化酵母细胞的操作稳定性。     

固定化细胞有机相催化不对称还原β-羰基酯

将酵母细胞用海藻酸钙包埋后用于有机相催化不对称还原4-氯乙酰乙酸乙酯制备光学活性的4-氯-3-羟基丁酸乙酯,从中筛选得到具有较高立体选择性和还原能力的菌株假丝酵母SW0401,将此菌株的细胞固定化细胞作为研究对象,系统考察了固定化条件、固定化细胞大小、反应溶剂、初始底物浓度、辅助底物、固定化细胞热处理和抑制剂对还原反应的影响。结果表明,上述因素对反应的摩尔转化率和产物（S）-CHBE光学纯度有显著影响。固定化时所用缓冲液的pH值为7．0时和固定化细胞颗粒平均直径为2.5mm较合适,以正己烷为反应介质时反应的摩尔转化率和产物光学纯度最优,初始底物浓度以54.7mmol／L为宜,辅助底物以1-己醇为佳。对固定化细胞的热处理和添加抑制剂烯丙醇均能够明显改善产物的光学纯度,但对提高摩尔转化率有负面影响。     

来源于西梅的(R)-醇腈酶促立体选择性转氰合成(R)-酮醇腈

在水/有机溶剂双相反应体系中,研究了来源于西梅的(R)-醇腈酶催化酮与丙酮醇腈合成(R)-酮醇腈的立体选择性转氰反应．系统探讨了不同酶源、酶粉颗粒大小、底物浓度、两底物配比、酶浓度和底物结构对转氰反应的影响．结果发现西梅醇腈酶能高效催化三甲基硅酮与丙酮醇腈的立体选择性转氰．酶粉颗粒大小以直径0.3～0.45 mm为优,底物浓度以21 mmol/L左右为佳,底物丙酮醇腈与三甲基硅酮摩尔浓度比以2∶1为宜,酶浓度以60.9 g/L左右为好．西梅醇腈酶对3, 3-二甲基-2-丁酮几乎没有催化活性,而对其硅结构类似物三甲基硅酮却具有非常高的立体选择性和催化活性,在上述优化反应条件下反应24 h的底物转化率和产物光学纯度均高达99%以上,表明底物中的硅原子对西梅醇腈酶的催化活性有非常显著的促进作用．     

固定化细胞生物催化制备(S)-苯基乙二醇的研究

采用海藻酸钙固定化细胞方法能有效提高近平滑假丝酵母催化(RS)-苯基乙二醇(S-PED)去消旋化反应的稳定性,在优化反应条件下,固定化细胞催化批次由游离细胞的2次提高至6次,产物可保持高光学纯度(>95%)、高产率(>85%)。与化学合成液晶掺杂剂S-1011的理化特性对比结果表明,生物催化法制备获得的(S)-PED能够替代化学法制备的相同产品。     

海藻酸钠-壳聚糖固定化木瓜蛋白酶催化内吗啡肽的合成

反应体系以乙腈作为有机介质,在微水有机溶剂体系中以Boc-Trp-OH和Phe-NH2为底物,用海藻酸钠 壳聚糖固定化木瓜蛋白酶催化合成Trp-Phe-NH2时,产率为27.8%．在这一合成反应中,对pH值、离子强度、溶液含量、反应温度、酶用量和反应时间进行正交试验,证明pH是本合成过程的最重要影响因素．反应体系以乙腈为有机介质,在微水有机溶剂体系中以 Boc-Tyr-Pro-OMe和Trp-Phe-NH2为底物,用IPSAC催化合成Tyr-Pro-Trp-Phe-NH2,产率为35~2%．     

用木瓜蛋白酶及固定化木瓜蛋白酶拆分DL-苯丙氨酸

为了将手性化合物D-苯丙氨酸和L-苯丙氨酸进行分离,利用木瓜蛋白酶及固定化木瓜蛋白酶催化的方法对其拆分．试验结果表明,用DL-苯丙氨酸合成N-乙酰-DL-苯丙氨酸,得率为88.7％．木瓜蛋白酶、海藻酸钠 壳聚糖固定化木瓜蛋白酶(IPSAC)、尼龙布固定化木瓜蛋白酶(IPN)催化合成N-乙酰-L-苯丙氨酰苯胺时,对催化合成过程影响最大的因素分别是溶液中的离子强度、溶液中的离子强度、反应温度;溶液中的离子强度与pH对合成的影响较大．本试验得出分别用木瓜蛋白酶、IPSAC、IPN催化合成N-乙酰-L-苯丙氨酰苯胺的3个最佳方案;用此3个方案合成时,产率分别为61.2%、54.7%、36.3%．N-乙酰-L-苯丙氨酰苯胺水解生成L-苯丙氨酸,产率59.2%,光学纯度为96.6％．N-乙酰-D-苯丙氨酸水解生成D-苯丙氨酸,产率61.7%,光学纯度为95.7％．     

微水-有机溶剂两相体系中消旋萘普生的酶法拆分

研究了微水-有机溶剂两相体系中固定化脂肪酶催化的萘普生甲酯的立体选择性水解反应。固定化酶活性受载体极性、水含量、有机溶剂的logP值、产物抑制的影响,据此构建了一种可以连续拆分产生(S)(+)萘普生的微水-有机溶剂两相体系。反应在一个具有回路的连续流搅拌反应器中进行,反应器中添加有采用吸附法固定化的脂肪酶,载体为一种弱极性的合成载体,水相连同固定化酶颗粒一起永久保持在反应器中,有机流动相带入底物,带出产物。固定化酶在该50mL反应器中30℃连续操作60d,仅损失活性25%,产生(S)(+)萘普生900mg,产物对映体过量值(ee_p)为95%。     

ATP/ADP exchange activity of gastric (H+ + K+)-ATPase

The ATP/ADP exchange is shown to be a partial reaction of the $\text{(}\text{H}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ by the absence of measurable nucleoside diphosphokinase activity and the insensitivity of the reaction to $\text{P}{}^1$, $\text{P}{}^5$ -di(adenosine-5′) pentaphosphate, a myokinase inhibitor. The exchange demonstrates an absolute requirement for Mg²⁺ and is optimal at an ADP/ATP ratio of 2. The high ATP concentration ($\text{K}{}_{0.5}\text{= 116 μ}\text{M}$) required for maximal exchange is interpreted as evidence for the involvement of a low affinity form of nucleotide site. The ATP/ADP exchange is regarded as evidence for an ADP-sensitive form of the phosphoenzyme. In native enzyme, pre-steady state kinetics show that the formation of the phosphoenzyme is partially sensitive to ADP while modification of the enzyme by pretreatment with 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) in the absence of Mg²⁺ results in a steady-state phosphoenzyme population, a component of which is ADP sensitive. The ATP/ADP exchange reaction can be either stimulated or inhibited by the presence of K⁺ as a function of pH and Mg²⁺.     

Characterization of cytochrome P-450SCC-containing liposomes

Purified cytochrome $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$ from bovine adrenocortical mitochondria was incorporated into liposomes by the cholate-dilution method utilizing either dialysis or Sephadex gel filtration. Among synthetic phospholipids tested, dioleoylglycerophosphocholine showed the best stability during the incorporation of $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$ into liposomes. A maximum amount of heme was incorporated into liposomes at a molar ratio of phospholipid to the cytochrome of approx. 200. When $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$ was incorporated into the dioleoylglycerophosphocholine liposomes by the cholate-filtration method, the $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}\text{-}\text{containing liposomes}$ showed two major populations on the elution pattern of the Sepharose 4B gel filtration, and were seen at a diameter of 200–600 Å and its aggregated forms. When the cytochrome was incorporated into dioleoylglycerophosphocholine liposomes or cholesterol-free adrenocortical mitochondrial liposomes, $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$ was less stable than $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$ in aqueous solution. Cholesterol or adrenodoxin markedly stabilized the liposomal $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$. Liposomal $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$ required cholesterol for its optimum reduction with adrenodoxin, adrenodoxin reductase, and NADPH in the presence of CO. About 70% of the total heme in the dioleoylglycerophosphocholine liposomes was reduced by the enzymatic reduction in the presence of cholesterol, indicating that 70% of the total molecules are exposed to the surface of the outer monolayer. In order to see the location of the heme in membrane, the dioleoylglycerophosphocholine-liposomal $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$ was subjected to $\text{p-}\text{chloromercuriphenyl sulfonic acid}$ treatment. This reagent destroyed the liposomal $\text{P}{}_{\mathrm{<mtext>450</mtext><mtext>SCC</mtext>}}$. These results suggest that the heme is located in the proximity of the $\text{p-}\text{chloromercuriphenyl sulfonic acid}$ reacting sites which are exposed to the surface, or located on the vincinity of polar heads of the membrane.     

AutoFACT: AnAutomaticFunctionalAnnotation andClassificationTool

Background  

Assignment of function to new molecular sequence data is an essential step in genomics projects. The usual process involves similarity searches of a given sequence against one or more databases, an arduous process for large datasets.     

Ligand-dependent reactivity of (Na+ + K+)-ATPase with showdomycin

Showdomycin inhibited pig brain ($\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ with pseudo first-order kinetics. The rate of inhibition by showdomycin was examined in the presence of 16 combinations of four ligands, i.e., Na⁺, K⁺, Mg²⁺ and ATP, and was found to depend on the ligands added. Combinations of ligands were divided into five groups in terms of the magnitude of the rate constant; in the order of decreasing rate constants these were: (1)$\text{Na}{}^{\mathrm{+}}\text{+}\text{Mg}{}^{\mathrm{2+}}\text{+}\text{ATP}$, (2) $\text{Mg}{}^{\mathrm{2+}}$, $\text{Mg}{}^{\mathrm{2+}}\text{+}\text{K}{}^{\mathrm{+}}$, $\text{K}{}^{\mathrm{+}}$ and none, (3) $\text{Na}{}^{\mathrm{+}}\text{+}\text{Mg}{}^{\mathrm{2+}}\text{,}\text{Na}{}^{\mathrm{+}}$, $\text{K}{}^{\mathrm{+}}\text{+}\text{Na}{}^{\mathrm{+}}$ and $\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{+}\text{Mg}{}^{\mathrm{2+}}$, (4) $\text{Mg}{}^{\mathrm{2+}}\text{+}\text{K}{}^{\mathrm{+}}\text{+}\text{ATP}\text{,}\text{K}{}^{\mathrm{+}}\text{+}\text{ATP}$ and $\text{Mg}{}^{\mathrm{2+}}\text{+}\text{ATP}\text{, (5)}\text{K}{}^{\mathrm{+}}\text{+}\text{Na}{}^{\mathrm{+}}\text{+}\text{ATP}$, $\text{Na}{}^{\mathrm{+}}\text{+}\text{ATP}$, $\text{Na}{}^{\mathrm{+}}\text{+}\text{ATP}$, $\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{+}\text{Mg}{}^{\mathrm{2+}}\text{+}\text{ATP}$ and ATP. The highest rate was obtained in the presence of Na⁺, Mg²⁺ and ATP. The apparent concentrations of Na⁺, Mg²⁺ and ATP for half-maximum stimulation of inhibition ($\text{K}{}_{0.5}{}^{\mathrm{<mtext>s</mtext>}}$) were 3 mM, 0.13 mM and 4μM, respectively. The rate was unchanged upon further increase in Na⁺ concentration from 140 to 1000 mM. The rates of inhibition could be explained on the basis of the enzyme forms present, including E₁, E₂, ES, E₁-P and E₂-P, i.e., E₂ has higher reactivity with showdomycin than E₁, while E₂-P has almost the same reactivity as E₁-P. We conclude that the reaction of ($\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ proceeds via at least four kinds of enzyme form (E₁, E₂, E₁ · nucleotide and EP), which all have different conformations.     

Characterization of partially purified (Na+ + K+)-ATPase from porcine lens

The partial purification of $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ from pig lens has been achieved by treatment with deoxycholate followed by density gradient centrifugation. The specific activity of the final preparation, ranging from 300 to 500 nmol/h per mg protein, is increased approx. 100-fold compared to the homogenate. A parallel increase in $\text{p-}\text{nitrophenylphosphatase}$ activity is also observed. Sodium dodecyl sulfate (SDS) gel electrophoresis reveals six major protein bands, one of which is the 93 kDa α subunit of $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ which can be phosphorylated by reaction with [γ-³²P]ATP. A second band contains a glycoprotein which displays an apparent molecular weight of 51 000 and thus appears to be the β subunit of the enzyme. The enzyme is sensitive to ouabain with the $\text{I}{}_{50}$ for $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ and $\text{p-}\text{nitrophenylphosphatase}$ inhibition being 1.2 and 1.3 μM, respectively. Several agents which inhibit $\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ from other tissues such as oligomycin, Ca²⁺, vanadate, $\text{N-}\text{ethylmaleimide}$, $\text{p-}\text{chloromercuribenzenesulfonic acid}$ (PCMBS) and 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) also inhibit the lens enzyme. Monovalent cations other than K⁺ are partially effective in activating the ($\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}$)-ATPase and $\text{p-}\text{nitrophenylphosphatase}$ activities. The K⁺ congeners were relatively more effective in supporting $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ compared to $\text{p-}\text{nitrophenylphosphatase}$ activity. Other kinetic properties of the lens enzyme are also comparable to those of the enzyme from other tissues. Utilizing the partially purified membrane bound enzyme, discontinuities in Arrhenius plots of $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ activity, $\text{p-}\text{nitrophenylphosphatase}$ activity and fluoresence polarization of the fluidity probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), are observed near the physiological temperature of lens. The possible significance of these observations for the mechanism of cataract formation are discussed.     

A/California/7/2009与A/California/4/2009病毒感染力比较

目的甲型H1N1流感病毒A/California/7/2009与A/California/4/2009病毒序列比较同源性在99%以上,本实验旨在比较两株病毒感染BALB/c小鼠研究感染力强弱。方法分别将A/California/7/2009（CA7）与A/California/4/2009（CA4）两株病毒分别连续10倍稀释后,对4~6周龄雌性BALB/c小鼠经乙醚麻醉后进行滴鼻攻毒,每个稀释度接种10只实验小鼠,测定CA7 MLD50为101.24/0.05 mL,检测小鼠感染、致病的多项指标,观察期为14 d。结果相同TCID50的CA7和CA4病毒感染小鼠,CA4感染小鼠后14 d内死亡率为20%,而CA7感染小鼠后8 d内死亡率为100%。CA7 106TCID50感染的小鼠病理表现为重度弥漫性间质性肺炎,CA4 106TCID50感染的小鼠病理表现为中度-重度间质性肺炎。结论在相同条件下,CA7感染力明显强于CA4。     

An electron spin probe study of (Na+ + K+)-ATPase-Containing membranes

The modulating effect of membrane lipids on enzyme function has been described by several investigators. We have used the spin probe $\text{N-}\text{oxyl}\text{-4′,4′-}\text{dimethyloxazolidine}\text{-12-}\text{keto}$ methyl stearate (M 12-NSE) to study this interaction in ox brain membranes enriched with $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$. This methyl ester of stearic acid is practically insoluble in aqueous media, and consequently spectra of M 12-NSE-labelled preparations are free of “liquid lines”.At least two types of spectra may be obtained when ox brain microsomes are spin labelled with M 12-NSE, indicating the presence of two distinct binding sites. At one site the spin label is relatively unrestricted and gives rise to an isotropic spectrum. A second spectrum, which is obtained from spin label at another site, is similar to that which is observed after incorporation of M 12-NSE into phospholipid bilayers. This suggests that this latter site is within the core of the microsomal membrane.The two binding sites differ in their affinity for the spin probe. The low affinity site is both more abundant in crude preparations and is more easily removed by detergent treatment; spin labels at this site produce isotropic spectra. The high affinity sites are fewer in number and produce broad spectra. In addition these high affinity sites increase in concentration as the enzyme undergoes purification.The two sites are quite distinct in their sensitivity to ascorbic acid, the low affinity site showing a considerably greater rate of reduction by this agent.This study also demonstrates that the delipidation effects of sodium dodecyl sulfate and sodium deoxycholate on $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase-enriched}$ microsomes from ox brain are not identical.It is suggested that the two spin probe binding sites represent two different lipid domains, one of which is very closely associated with the $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ enzyme and may reflect a protein-directed phospholipid specificity for this enzyme.     

Annular and non-annular binding sites on the (Ca2+ + Mg2+)-ATPase

Quenching of the fluorescence of the $\text{(}\text{Ca}{}^{\mathrm{2+}}\text{+}\text{Mg}{}^{\mathrm{2+}}\text{)-}\text{ATPase}$ purified from muscle sarcoplasmic reticulum can be used to measure relative binding constants of hydrophobic compounds to the phospholipid-protein interface. We show that the binding constant for cholesterol is considerably less than that for phosphatidylcholine, so that cholesterol is effectively excluded from the phospholipid annulus around the ATPase. However, dibromocholestan-3β-ol causes quenching of the fluorescence of the ATPase, and so has access to other, non-annular sites. We suggest that these non-annular sites could be at protein/protein interfaces in ATPase oligomers. Oleic acid can bind at the phospholipid/protein interface, although its binding constant is less than that for a phosphatidylcholine, and it can also bind at the postulated non-annular sites. The effects of these compounds on the activity of the ATPase depend on the structure of the phospholipid present in the systems.     

Comparison of parameters estimated from A/Ci and A/Cc curve analysis

The parameters estimated from traditional A/C _i curve analysis are dependent upon some underlying assumptions that substomatal CO₂ concentration (C _i) equals the chloroplast CO₂ concentration (C _c) and the C _i value at which the A/C _i curve switches between Rubisco- and electron transport-limited portions of the curve (C _i-t) is set to a constant. However, the assumptions reduced the accuracy of parameter estimation significantly without taking the influence of C _i-t value and mesophyll conductance (g _m) on parameters into account. Based on the analysis of Larix gmelinii’s A/C _i curves, it showed the C _i-t value varied significantly, ranging from 24 Pa to 72 Pa and averaging 38 Pa. t-test demonstrated there were significant differences in parameters respectively estimated from A/C _i and A/C _c curve analysis (p<0.01). Compared with the maximum ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation rate (V_cmax), the maximum electron transport rate (J_max) and J_max/V_cmax estimated from A/C _c curve analysis which considers the effects of g _m limit and simultaneously fits parameters with the whole A/C _c curve, mean V_cmax estimated from A/C _i curve analysis (V_cmax-C _i) was underestimated by 37.49%; mean Jmax estimated from A/C _i curve analysis (J_max-C _i) was overestimated by 17.8% and (J_max-C _i)/(V_cmax-C _i) was overestimated by 24.2%. However, there was a significant linear relationship between V_cmax estimated from A/C _i curve analysis and V_cmax estimated from A/C _c curve analysis, so was it J_max (p<0.05).     

Comparative study of Bifidobacteriumanimalis, Escherichiacoli, Lactobacilluscasei and Saccharomycesboulardii probiotic properties

The present work investigates some probiotic properties of four different microorganisms (Bifidobacterium animalis var. lactis BB-12, Escherichia coli EMO, Lactobacillus casei and Saccharomyces boulardii). In vitro and in vivo tests were carried out to compare cell wall hydrophobicity, production of antagonistic substances, survival capacity in the gastrointestinal tract of germ-free mice without pathological consequence, and immune modulation by stimulation of Küpffer cells, intestinal sIgA and IL-10 levels. In vitro antagonism against pathogenic bacteria and yeast was only observed for the probiotic bacteria B. animalis and L. casei. The hydrophobic property of the cell wall was higher for B. animalis and E. coli EMO, and this property could be responsible for a better ability to colonize the gastrointestinal tract of germ-free mice. Higher levels of sIgA were observed mainly for S. boulardii, followed by E. coli EMO and B. animalis, and only S. boulardii induced a significant higher level of IL-10. In conclusion, for a probiotic use, S. boulardii presented better characteristics in terms of immunomodulation, and B. animalis and L. casei for antagonistic substance production. The knowledge of the different probiotic properties could be used to choice the better microorganism depending on the therapeutic or prophylactic application.