The setereoselective preparation ofβ-keto esters using baker's yeast in the presence of rice wine koji

By the addition of rice wine koji, enhancement of the reactivity was observed for the baker＇s yeast reduction of β-keto esters into （S）-β-hydroxy esters with high enantiomeric purity （73-98%）.

Baker's Yeast Mediated Reduction of Optically Active Diketone

Baker's Yeast mediated reduction of optically active diketone has been described.

Reaction Characteristics of Asymmetric Synthesis of (2S,5S)-2,5-Hexanediol Catalyzed with Baker’s Yeast Number 6

Baker’s yeast number 6 was selected by screening. It showed good catalytic activity and enantioselec-tivity for asymmetric reduction of 2,5-hexanedione to produce (2S,5S)-2,5-hexanediol. Gas chromatography-mass spectrometry (GC-MS) revealed that the intermediate was (S)-5-hydroxyhexane-2-one. Reduction of 2,5-hexanedione proceeded in a two-step reaction. The hydroxyketone was initially formed, and this intermediate was further re-duced to the diol. Factors influencing the product yield and the enantiomeric excess of the reduction of 2,5-hexandione catalyzed by baker’s yeast number 6 were investigated. Higher concentration (≤100 mmol·L-1) of 2,5-hexandione did not influence 5-hydroxyhexane-2-one production, but 2,5-hexanediol production was inhibited by excess accumulation (>30 mmol·L-1) of intermediate. The optimal conditions were glucose as the co-substrate at an initial glucose concentration of 20 g·L-1, 34°C, pH 7.0 and cell concentration 60 g·L-1 (cell dry mass). Under the optimal condition and an initial substrate concentration of 30 mmol·L-1, the yield of 2,5-hexandiol was 78.7% and the enantiomeric excess of (2S,5S)-2,5-hexandiol was 94.4% for 24-h reduction.

Effect of β-Glucan (Angel Yeast) Compared to a Placebo on Cold and Flu Incidence and Symptoms in an Adult Population—A Double Blind, Randomised Controlled Trial

Background: 1-3, 1-6 β-glucan derived from Baker’s yeast (Saccharomyces cerevisiae) has been widely studied for its immune stimulatory capabilities and safety. Previous studies found β-glucan to have efficacy at reducing incidence of URTIs as well as being a low risk for negative side effects. The current study aimed to examine the effects of yeast β-glucan (Angel Yeast) on cold and flu incidences and symptoms in healthy adults. Methods: Two hundred and thirty-one males and females aged 18 to 65 years old supplemented with either β-glucan or a placebo for 3-months. Participants completed a general health questionnaire every 4 weeks and in addition, if participants experienced any cold or flu symptoms, these were recorded daily (along with severity) until resolved or up to 2 weeks. Results: Supplementation with β-glucan reduced the self-reported severity of sore throats and improved sleep quality compared to the placebo group. Conclusions: Yeast β-glucan supplementation appears to be able to help reduce certain symptoms experienced during a cold or flu episode and is safe and well tolerated.

Effect of Feeding Different Levels of Dietary Protein and Addition of Baker＇s Yeast （Saccharomyces cerevisiae） on Productive Parameters of Awassi Lambs

Forty eight individually fed Awassi male lambs were used in factorial experiment to investigate their responses to feeding concentrate diets containing three levels of dietary crude protein （CP）, each was offered without or with baker＇s yeast （SC） at rate of 0.5% （on dry matter （DM） basis）. Concentrates were offered at rate of 3% of live body weight with free choice of barley straw. Results revealed that higher （P 〈 0.05） digestible dry matter （DDM） and digestible organic matter （DOM） intakes were achieved due to feeding medium level of CP and to the addition of SC. Addition of SC improved （P 〈 0.05） gain, lambs fed medium and high levels gained higher （P 〈 0.05） than those fed the low level of dietary CP. Feed conversion ratio （FCR） based on DM and organic matter （OM） intakes was not significantly affected by level of dietary CP or addition of yeast. Even though, less amount of N required per unit of gain was achieved with low and medium as compared to high levels. Higher DM, nitrogen free extract （NFE） and hemicellulose （P 〈 0.05）, OM, CP, crude fiber （CF） and cellulose （P 〈 0.01） digestibilities were achieved in lambs fed the medium level of CP, whereas, no significant effect was observed on ether extract （EE）, neutral detergent fiber （NDF） and acid detergent fiber （ADF） digestibilities. Results also revealed that digestibility of almost all nutrients was improved with different extent due to addition of SC. Effect of interaction between levels of dietary CP and addition of SC referred to the preferability of addition of SC with medium level of dietary protein.

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。

富含S-腺苷甲硫氨酸面包酵母的发酵工艺优化

对摇瓶发酵生产富含S-腺苷甲硫氨酸的面包酵母的培养条件和培养基成分进行了优化,单因子实验结果表明,发酵最适pH值为5.0,最适装液量为70/250 mL,最佳接种量为2%。正交优化实验结果表明,最佳培养基成分为12°Brix糖蜜,另加酵母粉6.667g/L,(NH4)2SO4 2.829g/L,MgSO4 0.2g/L,ZnSO4 0.1g/L,KH2PO4 1g/L,在该条件下,S-腺苷甲硫氨酸产量为14.26 mg/L,含量为1.64 mg/g,分别提高了76.5%和84.3%。

面包酵母不对称还原制备(S)-1-苯砜基-2-丙醇

用自制的溴代丙酮与苯亚磺酸钠反应合成1-苯砜基-2-丙酮,然后利用面包酵母在有机溶剂中不对称催化还原1-苯砜基-2-丙酮,制备了光学活性的手性化合物(S)-1-苯砜基-2-丙醇,此反应具有操作简便、光学产率高等优点,其化学产率可达94%以上,对映体过量值为100%。

(S)-4-氯-3-羟基丁酸乙酯的不对称合成

报道了用4 氯 乙酰乙酸乙酯为原料,以面包酵母为还原剂,选择性合成(s) 4 氯 3 羟基丁酸乙酯。分别考察了能源供体、蔗糖浓度、反应温度、底物加量和压榨酵母用量等因素对产物收率和对映体过量值的影响。结果表明,4 氯 乙酰乙酸乙酯不对称生物还原反应的适宜条件为:能源供体40.0g/L蔗糖,反应温度36.5℃,压榨酵母50.0g/L,底物加量12.0g/L,pH为7 0。反应收率可达60 5%,ee收率为98 5%。

微水有机溶剂中面包酵母催化不对称还原(S)-1-苯砜-2-丙酮的动力学研究

探讨在微水有机溶剂中面包酵母催化不对称还原(S)1苯砜2丙酮的动力学,分别求出30℃和35℃下的反应速率常数和米氏常数.实验结果表明面包酵母在35℃时的催化活性比30℃时要高.

The comparison of Cu(II) adsorption capability of baker’s yeast, nano-titania and their composite adsorbent

The anatase nano-TiO2 powder, with crystal size between 40 and 80 nm, was prepared by the liquid phase hydrolysis of TiCl4. At the same time, the nano-TiO2 was utilized with the baker’s yeast biomass as a composite adsorbent to adsorb the Cu ions in the artificial aqueous solution. The investigation showed that the composite adsorbent had a fine adsorption efficiency. The TiO2 in the composite ad- sorbent could cooperate well with baker’s yeast to improve the adsorbing capability of Cu2+ under the following experimental conditions as well: a quantity of composite adsorbent of 5 g·L?1, pH≥4.0, an adsorption time of 40 min and an initial concentration of Cu ions of 10 mg·L?1. In addition, the results of measurements, obtained with a scanning electron microscope, an infrared spectrophotometer and a Zeta potential analyzer, revealed that the baker’s yeast and nano-TiO2 produced the composite ad- sorbent through coordination and hydrogen bonds in particular, etc. The stability of the composite adsorbent and the amount of titania loaded were largely dependent on the concentration of hydrogen ion in the solution.

THE THEORY AND PRACTICE OF INSTAN-TANEOUS SPECIFIC GROWTH RATE DEPENDENT FED-BATCH REGIME FOR BAKER'S YEAST CULTURE

The fed-batch method for baker’s yeast culture is fundamental for compressed and activedry yeast making. As a technical know-how it has not been published hitherto. The pub-lication of our own fed-batch regime, in principle and in practice, may serve the biologistsas well as engineers to get better results in microbial production.

絮凝性强的优良面包酵母菌株的选育

通过初筛、单倍体分离、DES诱变、絮凝基因的克隆表达及杂交等育种技术成功构建了高生物量、耐高糖、强絮凝的优良面包酵母菌株 (Saccharomycescerevisiae)ZLTH 5 8(MATa α,leu ,FLO1 )。菌株ZLTH 5 8具有双亲的优良性状 ,遗传性状稳定。对其生物量、耐高糖能力、絮凝特性进行了检测 ,结果表明 ,菌株ZLTH 5 8的生物量是原始亲株BL5 6的 1 2 1倍 ;耐高糖能力优于原始亲株BL61 ;絮凝性能明显优于原始亲株BL5 6和BL61。对其培养条件进行了优化 ,在优化的培养条件下 ,生物量可以达到 83 0 6g L ,为初始培养条件下的 1 3 5倍。

酵母细胞催化芳香酮的不对称还原反应

研究了酵母细胞催化芳香酮的不对称还原反应,采用正交试验综合考察了反应温度、反应时间、底物浓度和酵母浓度等因素对底物苯乙酮转化率和产物(S)1苯基乙醇对映选择性的影响.结果表明,影响苯乙酮转化率的因素依次为底物浓度、反应时间、反应温度和酵母浓度,影响(S)1苯基乙醇对映选择性的因素依次为反应温度、底物浓度、酵母浓度和反应时间.同时考察了芳香酮结构对产物对映选择性的影响,发现对映选择性的变化规律符合Prelog规则,与羰基相连的两个基团体积差异越大,对映选择性越好,最高的对映体过量值达到了96.4%.

修饰作用对面包酵母细胞形貌及其吸附Cu^2＋性能的影响比较

分别采用无水乙醇、氢氧化钠修饰面包酵母,并将修饰前后的菌样用于含Cu2+废水的吸附研究.通过扫描电镜、Zeta电位仪和红外光谱仪对吸附前后菌样进行了检测分析.结果显示,化学修饰作用使菌细胞不同程度地发生形变,使其个体减小、表面粗糙且细胞粘连,以及Zeta电位改变,同时菌样的红外光谱吸收峰强度、波数也发生变化甚至有新特征吸收谱线产生.这表明,修饰作用不仅改变了酵母细胞的外形结构、表面电荷,而且提高了菌表面有机官能团的数量及吸附活性,其中NaOH修饰作用还使菌细胞中羰基更加暴露.在吸附Cu2+的过程中,菌样表面羧基、羰基、羟基、氨基、酰胺基、磷酰基等官能团发挥了重要作用.

一种酵母细胞生长现象的实时单细胞拉曼光谱观察

用拉曼镊子观察单个即发活性干酵母(Saccharomy cescerevisiae)细胞在2.0%葡萄糖溶液中的活化过程,收集其拉曼光谱。结果发现,在某一批次的产品中,酵母细胞的1364cm-1峰强度随着细胞的活化而显著增加,531cm-1、652cm-1、1053cm-1等源自葡萄糖或葡萄糖基的信号峰也会随细胞的生长而增强,随后增强的还有1432cm-1、1448cm-1、1561cm-1等源自脂类物质的峰,而源自蛋白质及脂类的1000cm-1、1445cm-1、1655cm-1等峰的信号强度基本不变,酵母细胞代谢活跃的标志峰1603cm-1也基本不变。该批次产品中,10次实验有7次观察到上述现象,而在别的批次产品中并没有观察到该现象。用单细胞拉曼光谱实时记录了这一特殊的生长现象。

面包酵母催化乙酰乙酸乙酯的不对称还原反应

利用面包酵母催化的乙酰乙酸乙酯立体选择性还原反应 ,制备了光学活性的手性化合物—— ( S) - 3-羟基丁酸乙酯。分别考察了能源供体、蔗糖浓度、反应温度、底物加量和压榨酵母用量等因素对产物得率和对映体过量值的影响。结果表明 ,乙酰乙酸乙酯不对称生物还原反应的最适条件为 :能源供体 2 0 0 g/L蔗糖 ,反应温度 35℃ ,压榨酵母 1 70 g/L,底物加量 0 .2 mol/L。

灭活面包酵母菌对溶液中铅离子的吸附研究

为研究灭活面包酵母菌对溶液中Pb^2＋的吸附效果和机理,在实验室进行批量实验,通过AAS、SEM/EDS等手段对实验结果进行分析。实验室条件下面包酵母菌吸附Pb^2＋的最佳条件为：pH值4.0-5.5,菌体质量浓度4.0 g/L,初始Pb^2＋浓度1.0 mmol/L,吸附温度30℃。酵母菌实验最大吸附量为45.07 mg/g,吸附效率为92.45%。不同温度下的动力学分析表明,其吸附过程是一个快速过程,且较低温度时吸附平衡过程迟滞。实验结果很好地符合Langmuir等温吸附模型,计算得面包酵母菌在10℃、20℃和30℃时的最大吸附量qmax分别为71.53 mg/g、72.10 mg/g和75.82 mg/g。SEM/EDS分析发现Pb^2＋被吸附到面包酵母菌表面,与细胞壁上有机物结合后以颗粒物形式附着在细胞表面,并随着溶液中Pb^2＋初始浓度的增加而增多。研究表明,灭活酵母菌是一种快速高效的Pb^2＋生物吸附剂。

乙醇和氢氧化钠预处理对面包酵母菌吸附Cu^2＋的影响

研究了面包酵母菌及由无水乙醇和氢氧化钠分别处理的面包酵母菌对Cu2+的生物吸附作用.结果表明,菌样在pH5,菌量1g.l-1,吸附时间20min,Cu2+25mg·l-1时,最大吸附量分别为2.42,3.3和5.73mg·g-1,吸附过程符合Langmuir等温吸附模型.菌主要依靠表面活性基团吸附Cu2+.预处理作用增加了菌表面活性基团的数量及活性.在吸附过程中静电作用可能对吸附有一定的影响.另外,菌样对Cu2+的吸附以可逆吸附为主,并不同程度地存在不可逆吸附.

面包酵母菌对Pb^(2+)和Cd^(2+)单双重金属离子体系的吸附效果

为了探讨灭活面包酵母菌对Pb^(2+)、Cd^(2+)的单、双重金属离子体系(以下简称双离子体系)的吸附效果及影响机制,选择灭活面包酵母菌为吸附剂,对Pb^(2+)、Cd^(2+)的单离子体系和Pb^(2+)-Cd^(2+)双离子体系吸附动力学过程和等温吸附效果进行研究。结果表明,不同离子体系中,在相同初始浓度情况下,面包酵母菌对Pb^(2+)的吸附量总是大于对Cd2+的吸附量。试验条件下,面包酵母菌对Pb^(2+)、Cd^(2+)的单离子体系和Pb^(2+)-Cd^(2+)双离子体系等温吸附符合Langmuir模型,最大吸附量q_(max)分别为0.414 9 mmol/g、0.346 8 mmol/g和0.488 5 mmol/g。SEM/EDS分析表明,Pb^(2+)、Cd^(2+)被吸附到菌体上,造成菌体变形或出现破裂,并使内部物质外泄,这可能是吸附进行一定时间后出现二次吸附过程的主要原因。灭活面包酵母对Pb^(2+)和Cd^(2+)具有良好的吸附效果,对Pb^(2+)-Cd^(2+)双离子体系的吸附,离子间的点位竞争和联合毒性作用是影响体系总体吸附效果的重要因素。