面包酵母在手性化合物不对称合成中的类型

药物分子的立体化学决定其生物活性，手性已成为药物研究的一个关键因素。利用微生物或酶催化的方法进行手性化合物的不对称合成已经成为一个极具吸引力的方向。综述了近年来利用面包酵母催化不对称合成手性化合物的研究进展，着重讨论了利用面包酵母可进行的多种手性试剂的催化合成的反应类型。     

金属离子对1.6二磷酸果糖合成代谢流量的影响

本文首次建立了１,６－二磷酸果糖（ＦＤＰ）合成代谢途径流量模型,并应用该模型求解ＦＤＰ合成过程中代谢流量分配。研究了ＮＨ＾＋４、Ｋ＾＋、Ｍｇ＾２＋对１,６－二磷酸果糖合成代谢途径流量的分配的影响,结果发现ＮＨ＾＋４、Ｋ＾＋、Ｍｇ＾２＋对代谢途径流量分配均有一定的影响：尤其是在这三者共存的情况下,代谢流量分配发生了重大改变,１,６－二磷酸果糖的累积流量达到４１．９,为化学调节１,６－二磷酸果糖的超量     

甲醇低压羰基合成中金属离子的去除

分析了甲醇低压羰基合成法生产金属离子的来源情况,介绍了金属离子在反应中的副作用及除去金属离子的过程,此项技术对低压羰基合成中催化剂稳定性和防止催化剂沉淀有重要意义。     

双席夫碱衍生物的合成及其对过渡金属离子识别的研究

分别以水合肼、乙二胺、苯甲醛和水杨醛为原料,通过缩合反应合成了4个双席夫碱衍生物,并以荧光光谱法研究化合物对过渡金属离子Cd2+、Co2+、Cu2+、Ni2+的识别作用.实验表明,化合物与金属离子作用后都发生不同程度的猝灭现象.4种化合物与过渡金属离子的猝灭常数在102～ 106数量级,其中Ⅳ,N＇-双(2-羟基亚苄基...     

腺苷的合成与应用进展

腺苷是一种天然存在的遍布人体细胞的内源性嘌呤核苷，是三磷酸腺苷(ATP）的降解产物。腺苷以其扩张血管作用而被人们所熟知，除具有广泛的心脏效应以及快速显著的冠脉扩张作用外，还具有触发或介导缺血预适应、减轻再灌注损伤等心脏保护效应。在美国，腺苷是经FDA批准的转复阵发性室上性心动过速(PSVT)的一线药物，也是经FDA批准的用于心脏药物负荷试验的两种药物之一，     

负载金属离子合成分子筛脱除汽油中硫醇的性能

根据微波条件下负载不同离子的吸附效果选择了适宜金属离子 ,测定了硫醇在吸附剂上的动态吸附数据 ,考察了负载离子交换溶液浓度、温度等条件对吸附剂脱硫醇效果的影响以及吸附剂脱除汽油中总硫的净化效果 ,探讨了吸附剂的再生方法。结果表明该吸附剂具有净化汽油中硫醇和总硫的双重效果 ,为汽油脱硫技术开发提供一定的基础。     

N-对苯甲酸基-1,8-萘酰亚胺的合成及金属离子识别作用研究

以对硝基甲苯为起始原料,通过重铬酸钠氧化再将硝基还原得到对氨基苯甲酸,然后与1,8-萘酐缩合得到标题化合物,并以荧光光谱法研究了标题化合物对Cd2+、Co2+、Cu2+等7种金属离子的识别作用.结果表明,随着各种金属离子的加入,标题化合物的荧光光谱均发生了猝灭现象;标题化合物对Fe3+的识别作用最优,络合常数为1.69...     

影响面包酵母催化还原羰基的因素探究

利用活性微生物细胞催化还原羰基是不对称合成手性醇的重要方法。微生物催化羰基还原反应的效率和立体化学选择性要受多种因素的影响,这些因素包括有机溶剂种类、水分含量、微生物形式、底物结构和辅酶再生等。     

镁锰锌金属离子对γ-CGT酶生产和能量代谢的促进影响

研究了添加镁、锰、锌二价金属离子对Bacillus macorousWSH02-06生产γ-CGT酶的影响。结果表明,在培养基中组合添加镁、锰、锌等二价金属离子能提高酶产量近两倍。这些金属离子的添加同样能促进细胞生长。锰、锌金属离子的存在能促进细胞消耗镁离子的量。γ-CGT酶产量、细胞干重随着镁离子消耗量的增加而增加。镁、锰、锌二价金属离子提高了胞内ATP含量和ATP/ADP比例,从而为产酶提供了更大的能量支持。     

金属离子对彩色成像过程的影响

通过测量和计算彩色单层片中成色剂的照相活性、偶合效率以及漂白前银密度等参数,研究了在分散四当量成色剂青(Ⅰ)时掺入金属离子Mg~(2+)、Zn~(2+)、Fe~(3+)和Cu~(2+)对彩色青单层片的成像过程中各个化学反应的影响。本实验的结果表明,成色剂中加入的金属离子Cu~(2+)和Fe~(3+)对成像过程的初始反应中的Ag影像形成产生不利的影响,但它们能促进偶合过程中青(Ⅰ)与显影剂氧化产物作用所生成的隐色体转变成染料的速率。Mg~(2+)和Zn~(2+)的加入主要是对偶合过程中青(Ⅰ)的偶合效率产生不利的影响。上述原因的综合影响,最终降低了彩色单层片的感光度。     

啤酒酵母吸附去除水中Cd~(2+)的影响因素

生物吸附法是一种经济有效的处理大规模低浓度重金属废水的生物技术,其中啤酒酵母(Saccharomyces cerevisiae)是具有实用潜力的生物吸附剂。本文研究了啤酒酵母对Cd2+吸附效果的主要影响因素,结果表明pH值对Cd2+会产生较大的影响,非固定化和固定化啤酒酵母对Cd2+吸附的最佳pH值都为4,过高和过低均不利于吸附的进行。水中常见的K+、Ca2+、Na+、Mg2+四种离子在低浓度时对Cd2+的吸附无显著影响,但当其浓度高于5mg/L时会影响吸附,其影响顺序为K+Na+Ca2+Mg2+;Zn2+、Fe2+、Cu2+、Pb2+对Cd2+的吸附效果影响顺序为Pb2+Zn2+Fe2+Cu2+;当Cu2+浓度≥50mg/L时,啤酒酵母对Cd2+不产生性吸附,而对Cu2+产生专性吸附。     

Different Reactive Oxygen Species Lead to Distinct Changes of Cellular Metal Ions in the Eukaryotic Model Organism Saccharomyces cerevisiae

Elemental uptake and export of the cell are tightly regulated thereby maintaining the ionomic homeostasis. This equilibrium can be disrupted upon exposure to exogenous reactive oxygen species (ROS), leading to reduction or elevation of the intracellular metal ions. In this study, the ionomic composition in the eukaryotic model organism Saccharomyces cerevisiae was profiled using the inductively-coupled plasma optical emission spectrometer (ICP-OES) following the treatment with individual ROS, including hydrogen peroxide, cumen hydroperoxide, linoleic acid hydroperoxide (LAH), the superoxide-generating agent menadione, the thiol-oxidising agent diamide [diazine-dicarboxylic acid-bis(dimethylamide)], dimedone and peroxynitrite. The findings demonstrated that different ROS resulted in distinct changes in cellular metal ions. Aluminium (Al(3+)) level rose up to 50-fold after the diamide treatment. Cellular potassium (K(+)) in LAH-treated cells was 26-fold less compared to the non-treated controls. The diamide-induced Al(3+) accumulation was further validated by the enhanced Al(3+) uptake along the time course and diamide doses. Pre-incubation of yeast with individual elements including iron, copper, manganese and magnesium failed to block diamide-induced Al(3+) uptake, suggesting Al(3+)-specific transporters could be involved in Al(3+) uptake. Furthermore, LAH-induced potassium depletion was validated by a rescue experiment in which addition of potassium increased yeast growth in LAH-containing media by 26% compared to LAH alone. Taken together, the data, for the first time, demonstrated the linkage between ionomic profiles and individual oxidative conditions.     

Effect of extraction and enzymatic esterification of ethanol on glucose consumption by two Saccharomyces cerevisiae strains: a comparative study

Extractive alcoholic fermentations of high glucose concentrations (300 and 400 g dm^?3) using a flocculent (saké) and a non‐flocculent (DER24) Saccharomyces cerevisiae strain were compared. The introduction of a Rhizomucor miehei lipase, in the extractive fermentations of 300 g dm^?3 of glucose, increased the ethanol extraction due to its esterification with oleic acid, allowing complete glucose consumption at an organic solvent/fermentation medium phase ratio of 1. In these conditions, an increase of ethanol yield was observed. Total glucose consumption was also obtained in enzymatic extractive fermentations of 400 g dm^?3 of glucose, but only when oleic acid was added at the exponential growth phase. From the comparison of the extractive fermentation performances obtained using the two yeast strains it was observed that the flocculent strain led to a lower glucose metabolisation rate. This behaviour was related to the highest diffusional limitations that occur in the presence of flocs. The developed processes showed that the association of alcoholic fermentation with enzymatic extraction led to the reduction of inhibitory effects as well as to the simultaneous production of fatty esters which are compounds with several commercial applications. © 2001 Society of Chemical Industry     

Factors affecting silver biosorption by an industrial strain of Saccharomyces cerevisiae

Factors affecting silver biosorption by Saccharomyces cerevisiae biomass, obtained as a waste product from industry, were examined. Maximum removal of silver from solution was achieved within 5 min. Increasing the concentration of biomass in experimental flasks from 1 to 8 mg cm⁻³ decreased both silver accumulation, from 224·7 to 89·5 μmol Ag g⁻¹ dry wt, and associated H⁺ ion release, from 109·4 to 31·7 μmol H⁺ g⁻¹ dry wt. The presence of 1·0 mol dm⁻³ cadmium or methionine decreased silver biosorption by 40% and 93% respectively. Boiling in 100 mmol dm⁻³ NaOH or 10 mmol dm⁻³ sodium dodecyl sulphate decreased silver biosorption by 54% and 25% respectively. A temperature increase from 4°C to 55°C decreased silver biosorption by 9%. The metabolic state of the yeast had no effect on silver biosorption. Decreasing the pH of the silver solution caused a reduction in metal removal by the biomass.     

Immobilization of Saccharomyces cerevisiae in Gelatin Cross-Linked with Chromium Ions for Conversion of Sucrose by Intracellular Invertase

A novel immobilized biocatalyst with invertase (β-D-fructofuranosidase, E.C.3.2.1.26) activity was prepared by immobilizing Saccharomyces cerevisiae cells into gelatin by using chromium salts. The effect of chromium salts on cell growth of free and immobilized cells was investigated, and optimum concentrations for chromium acetate and chromium sulfate were found to be 0.016 M and 0.008 M, respectively. Since a medium feeding strategy was applied, higher enzymatic activities were obtained with developed biocatalyst compared to free S. cerevisiae cells. Immobilized samples could be used 10 times in a 30-day period with negligible activity loss. After storing it at 25°C for 28 days, our biocatalyst was used 15 times with 2-day intervals with only a slight amount of activity decrease. As a result we managed to produce a very stable biocatalyst with high invertase activity using an inexpensive methodology.     

Production of fructose and ethanol from media with high sucrose concentrations by a mutant of Saccharomyces cerevisiae

The production of enriched fructose syrups and ethanol from a synthetic medium with high sucrose concentrations was studied in a batch process using Saccharomyces cerevisiae ATCC 36858. The results showed that the fructose yield was above 92% of theoretical values in synthetic media with sucrose concentrations between 180 g dm^?3 and 726 g dm^?3. Ethanol yield was about 82% in media with sucrose concentrations up to 451 g dm^?3. A product containing 178 g dm^?3 fructose, which represents 97% of the total sugar content, and 79 g dm^?3 ethanol was obtained using a medium with 360 g dm^?3 sucrose. The fructose fraction in the carbohydrates content in the produced syrups decreased with increases in the initial sucrose concentration. In a medium with initial sucrose concentration of 574 g dm^?3, the fructose content in the produced broth was 59% of the total carbohydrates. Glycerol and fructo‐oligosaccharides were also produced in this process. The produced fructo‐oligosaccharides started to be consumed when the concentration of sucrose in the media was less than 30% of its initial value. Complete hydrolysis of these sugars was noticed in media with sucrose concentrations below 451 g dm^?3. These findings will be useful in the production of ethanol and high fructose syrups using sucrose‐based raw materials with high concentrations of this carbohydrate. © 2001 Society of Chemical Industry     

化学修饰啤酒酵母菌对铀的吸附特性

以甲醛为交联剂, 将胱氨酸修饰到啤酒酵母菌(SC)上, 并采用海藻酸钠和明胶固定化, 得到一种新型的生物吸附剂--修饰啤酒酵母菌(MSC)。通过红外光谱(IR)分别表征了两种吸附剂的结构, 考察了其吸附铀的主要影响因素即溶液pH值、吸附时间等。结果表明: MSC细胞表面具有大量吸附铀的基团, MSC和SC吸附铀的最佳条件是: pH值为6.0, 相似文献   

Improved Ethanol Production by Saccharomyces cerevisiae with EDTA,Ferrocyanide and Zeolite X Addition to Sugar Beet Molasses

The influence of ethylenediaminetetra acetic acid (EDTA), potassium ferrocyanide and zeolite X on ethanol production from sugar beet molasses by Saccharomyces cerevisiae was studied. For all of the three substances used, the effect was more pronounced when added to the fermentation medium rather than to the growth medium; 1·9 mmol dm⁻³ potassium ferrocyanide caused an increase in the final ethanol concentration of about 16·4% and 47·5% with respect to control culture on addition to growth and fermentation media respectively. The greatest stimulation in product yield was obtained with zeolite X introduced during the fermentation stage; 8·0 g dm⁻³ zeolite X increased ethanol concentration by 53·3%. © 1997 SCI.     

CRISPRi-Guided Metabolic Flux Engineering for Enhanced Protopanaxadiol Production in Saccharomyces cerevisiae

Protopanaxadiol (PPD), an aglycon found in several dammarene-type ginsenosides, has high potency as a pharmaceutical. Nevertheless, application of these ginsenosides has been limited because of the high production cost due to the rare content of PPD in Panax ginseng and a long cultivation time (4–6 years). For the biological mass production of the PPD, de novo biosynthetic pathways for PPD were introduced in Saccharomyces cerevisiae and the metabolic flux toward the target molecule was restructured to avoid competition for carbon sources between native metabolic pathways and de novo biosynthetic pathways producing PPD in S. cerevisiae. Here, we report a CRISPRi (clustered regularly interspaced short palindromic repeats interference)-based customized metabolic flux system which downregulates the lanosterol (a competing metabolite of dammarenediol-II (DD-II)) synthase in S. cerevisiae. With the CRISPRi-mediated suppression of lanosterol synthase and diversion of lanosterol to DD-II and PPD in S. cerevisiae, we increased PPD production 14.4-fold in shake-flask fermentation and 5.7-fold in a long-term batch-fed fermentation.