Adaptive Evolution of Saccharomyces cerevisiae with Enhanced Ethanol Tolerance for Chinese Rice Wine Fermentation

High tolerance towards ethanol is a desirable property for the Saccharomyces cerevisiae strains used in the alcoholic beverage industry. To improve the ethanol tolerance of an industrial Chinese rice wine yeast, a sequential batch fermentation strategy was used to adaptively evolve a chemically mutagenized Chinese rice wine G85 strain. The high level of ethanol produced under Chinese rice wine-like fermentation conditions was used as the selective pressure. After adaptive evolution of approximately 200 generations, mutant G85X-8 was isolated and shown to have markedly increased ethanol tolerance. The evolved strain also showed higher osmotic and temperature tolerances than the parental strain. Laboratory Chinese rice wine fermentation showed that the evolved G85X-8 strain was able to catabolize sugars more completely than the parental G85 strain. A higher level of yeast cell activity was found in the fermentation mash produced by the evolved strain, but the aroma profiles were similar between the evolved and parental strains. The improved ethanol tolerance in the evolved strain might be ascribed to the altered fatty acids composition of the cell membrane and higher intracellular trehalose concentrations. These results suggest that adaptive evolution is an efficient approach for the non-recombinant modification of industrial yeast strains.     

渗透汽化型酯化膜反应器研究——PVA/PSSA共混聚合物管式复合膜的膜反应性能

聚合物共混是制备具有预定性能的功能膜材料的有效方法．报道了以惰性素烧陶瓷管为支撑体的ＰＶＡ／ＰＳＳＡ共混聚合物管式复合膜的制备及其在渗透汽化型酯化膜反应器中不同实验条件下的膜催化反应性能．探讨了共混膜的组成,反应温度等对膜反应和分离性能的影响以及同步膜分离过程对反应转化率的促进作用．交联ＰＶＡ／ＰＳＳＡ管式复合膜具有良好的催化和分离性能．     

PDMS Rod-SBSE System Coupled with Gas Chromatography for Determination of PAHs in Aqueous Samples

A method for the analysis of trace polycyclic aromatic hydrocarbons(PAHs) in aqueous samples has been established by polydimethylsiloxane(PDMS) rod aided stir bar sorptive extraction(SBSE). The homemade PDMS rod has a size of 30 mm?3 mm o.d. with a volume of ca. 200 ?L, stable in thermal desorption process. The enriched PAHs by the PDMS rod were released in a homemade thermal desorption system coupled with gas chromatography. Experimental parameters for extraction of six PAHs were optimized including extraction time, pH, ionic strength and temperature of solution. The procedure has good recoveries of 80.0%―100.3% and very low limits of detection of 4.0―33 ng/L. PAHs in rain and river water were analyzed by this method.     

Pectinases Secretion by Saccharomyces cerevisiae: Optimization in Solid-State Fermentation and Identification by a Shotgun Proteomics Approach

A sequential design strategy was applied to optimize the secretion of pectinases by a Saccharomyces cerevisiae strain, from Brazilian sugarcane liquor vat, on passion fruit residue flour (PFRF), through solid-state fermentation (SSF). A factorial design was performed to determine the influence variables and two rotational central composite designs were executed. The validated experimental result was of 7.1 U mL⁻¹ using 50% PFRF (w/w), pH 5, 30 °C for 24 h, under static SSF. Polygalacturonase, pectin methyl esterase, pectin–lyase and pectate–lyase activities were 3.5; 0.08; 3.1 and 0.8 U mL⁻¹, respectively. Shotgun proteomics analysis of the crude extract enabled the identification of two pectin–lyases, one pectate–lyase and a glucosidase. The crude enzymatic extract maintained at least 80% of its original activity at pH values and temperatures ranging from 2 to 8 and 30 to 80 °C, respectively, over 60 min incubation. Results revealed that PFRF might be a cost-effective and eco-friendly substrate to produce pectinases. Statistical optimization led to fermentation conditions wherein pectin active proteins predominated. To the extent of our knowledge, this is the first study reporting the synthesis of pectate lyase by S. cerevisiae.     

Effects of Propionic Acid and pH on Ethanol Fermentation by Saccharomyces cerevisiae in Cassava Mash

The effects of propionic acid on ethanol and glycerol production by Saccharomyces cerevisiae in cassava mash were examined along with the influence of pH (4.0, 5.0, and 6.0) and of dissolved solids content (22%, 25%, and 27%). Inhibition by propionic acid increased as solids content increased and medium pH declined. Complete inhibition of ethanol fermentation was observed in mashes at pH 4.0 (60 mM propionic acid for 22% solids and 45 mM for 25% and 27%). Glycerol production linearly decreased with increased undissociated propionic acid concentration in all mashes at all pH levels, which partly contributed to increased final ethanol production when propionic acid concentration in mashes was low (≤ 30 mM).     

间歇反应器内醋酸丁酯酯化反应与渗透汽化集成过程的模型计算

 建立了一个间歇反应器内酯化反应与渗透汽化集成过程的数学模型, 用于描述反应和脱水同时进行的过程. 该模型考虑了反应体系中所有组分的渗透量影响以及混合物的非理想热力学行为. 选择乙酸和正丁醇生成醋酸丁酯的酯化反应与 PVA 膜渗透汽化集成过程为研究体系, 将模型结果与文献中已报道的实验数据进行对比, 验证了该模型的有效性. 结果表明, 采用渗透汽化脱除酯化反应的水分将提高酯的产率. 对温度、反应物初始比、膜面积与反应体积比以及催化剂浓度几种操作条件对集成过程性能影响进行了参数的分析. 根据结果讨论得到该膜过程与反应集成过程的优化操作条件.     

载体乳化液膜法同步进行亚稳相PbCrO4纳米粒子的仿生合成与铅铬废水的处理

采用一种新型的纳米材料仿生合成方法——载体乳化液膜法,在煤油-Span-80-N7301乳化液膜体系中,以电镀废水中常见的Cr(Ⅵ)溶液为外相,蓄电池、油漆等行业废水常见的Pb(Ⅱ)溶液为内相,通过对生物体内囊泡结构的形态和离子传输功能模拟,室温下成功合成了能稳定存在的直径为5～15nm的正交亚稳相PbCrO4纳米粒子．使用XRD,TEM对产物结构和形貌进行了表征．首次通过FT-IR和UV-vis对所得产物和普通块体材料的光学性质做了比较．并对乳化液膜体系控制产物晶型和尺寸的机理进行了初步的探讨．此方法也有望用于对不同类型工业废水的耦合处理．     

Bioactivity and Mechanical Properties of Polydimethylsiloxane (PDMS)-CaO-SiO2 Hybrids with Different PDMS Contents

Silica-titania and titania aerogels were prepared by supercritical drying using different solvents such as low temperature CO₂ (353 K), high temperature CO₂ (553 K), ethanol (553 K) and ethanol with zeolite (553 K) and their efficiencies for the removal of benzene from a synthetic air mixture were investigated. The aerogels obtained showed both large capacities for benzene adsorption and high photocatalytic activity for its decomposition in the adsorbed state. The degree of benzene removal by silica-titania aerogel seemed to depend on the crystallinity of the titania and was in the order low temperature CO₂ < high temperature CO₂ < ethanol = ethanol with zeolite. The amount of CO₂ liberated by the photocatalytic decomposition of benzene also followed the same sequence. Titania aerogels showed the greatest efficiency in the decomposition of benzene, while the amount of CO₂ evolved was lower than those of the silica-titania systems investigated. The adsorption capacity of benzene basically depended on the silica matrix and was not greatly influenced by the difference in the crystallinity of titania.     

Continuous Transport of Zn(II) by Ammonium Chloride Media via Supported Liquid Membrane System

With the gradual depletion of traditional zinc resources, the full use of various non-traditional zinc-containing resources has received intensive attention. However, the efficient recovery of zinc ions with low concentrations remains challenging. Here efficient and continuous recovery of zinc ions in ammoniacal chloride media by a flat supported liquid membrane system is achieved, using Cyanex923 and TBP mixed extractant as the membrane phase. This article discusses the synergistic effect between Aliquat336, Cyanex923 and TBP, the effects of feed pH, total ammonia concentration, Cl⁻ concentration and temperature on Zn(II) transport.     

Heat-treated Saccharomyces cerevisiae for antimony speciation and antimony(III) preconcentration in water samples

An analytical method was developed for antimony speciation and antimony(III) preconcentration in water samples. The method is based on the selective retention of Sb(III) by modified Saccharomyces cerevisiae in the presence of Sb(V). Heat, caustic and solvent pretreatments of the biomass were investigated to improve the kinetics and thermodynamics of Sb(III) uptake process at room temperature. Heating for 30 min at 80 degrees C was defined as the optimal treatment. Antimony accumulation by the cells was independent of pH (5-10) and ionic strength (0.01-0.1 mol L(-1)). 140 mg of yeast and 2h of contact were necessary to ensure quantitative sequestration of Sb(III) up to 750 microg L(-1). In these conditions, Sb(V) was not retained. Sb(V) was quantified in sorption supernatant by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectrometry (ICP-OES). Sb(III) was determined after elution with 40 mmol L(-1) thioglycolic acid at pH 10. A preconcentration factor close to nine was achieved for Sb(III) when 100mL of sample was processed. After preconcentration, the detection limits for Sb(III) and Sb(V) were 2 and 5 ng L(-1), respectively, using ICP-MS, 7 and 0.9 microg L(-1) using ICP-OES. The proposed method was successfully applied to the determination of Sb(III) and Sb(V) in spiked river and mineral water samples. The relative standard deviations (n=3) were in the 2-5% range at the tenth microg L(-1) level and less than 10% at the lowest Sb(III) and Sb(V) tested concentration (0.1 microg L(-1)). Corrected recoveries were in all cases close to 100%.     

Biomethylation of tin (II) complexes in the presence of pure strains of Saccharomyces cerevisiae

The methylation of several tin compounds by strains of Saccharomyces cerevisiae strains (yeast) is described. The production of the methyl tin species was established by gas chromatography and mass spectrometry. Monomethyl tin (IV) products dominated but some dimethyl tin products were observed. This appears to be the first report of a tin methylation by a pure strain of a methylating species rather than a complex mixture obtained from an environmental source.     

Molecular characterization of a gene for aldose reductase (CbXYL1) from Candida boidinii and its expression in Saccharomyces cerevisiae

Candida boidinii produces significant amounts of xylitol from xylose, and assays of crude homogenates for aldose (xylose) reductase (XYL1p) have been reported to show relatively high activity with NADH as a cofactor even though XYL1p purified from this yeast does not have such activity. A gene coding for XYL1p from C. boidinii (CbXYL1) was isolated by amplifying the central region using primers to conserved domains and by genome walking. CbXYL1 has an open reading frame of 966 bp encoding 321 amino acids. The C. boidinii XYL1p is highly similar to other known yeast aldose reductases and is most closely related to the NAD(P)H-linked XYL1p of Kluyveromyces lactis. Cell homogenates from C. boidinii and recombinant Saccharomyces cerevisiae were tested for XYL1p activity to confirm the previously reported high ratio of NADH:NADPH linked activity. C. boidinii grown under fully aerobic conditions showed an NADH:NADPH activity ratio of 0.76, which was similar to that observed with the XYL1p from Pichia stipitis XYL1, but which is much lower than what was previously reported. Cells grown under low aeration showed an NADH:NADPH activity ratio of 2.13. Recombinant S. cerevisiae expressing CbXYL1 showed only NADH-linked activity in cell homogenates. Southern hybridization did not reveal additional bands. These results imply that a second, unrelated gene for XYL1p is present in C. boidinii.     

Separation and speciation of Cr(III) and Cr(VI) with Saccharomyces cerevisiae immobilized on sepiolite and determination of both species in water by FAAS

A rapid, sensitive and accurate method for the separation, preconcentration and determination of Cr(III) and Cr(VI) in water samples is described. Chromium species can be separated by biosorption on Saccharomyces cerevisiae immobilized on sepiolite and determined by flame atomic absorption spectrometry (FAAS). The optimum conditions for separation and preconcentration (pH, bed height, flow rate and volume of sample solution) were evaluated. Recovery of the chromium was 96.3+/-0.2% at 95% confidence level. The breakthrough capacity of the adsorbent was found as 228 mumol g(-1) for Cr(III). The proposed method was applied successfully to the determination of Cr(III) and Cr(VI) in spiked and river water samples.     

一种新型超临界流体萃取-高效液相色谱在线联用系统的构建

天然产物研究一直是植物学、化学和药学的重要研究领域．通过从天然产物中寻找生物活性成分和先导物是创制新药的有效途径之一．有效成分的提取是天然产物研究中最基本和最关键的环节．超临界流体萃取（Supercritical fluid extraction,简称SFE）是近年来发展较快的一种新型样品提取技术．超临界CO2作为最常用的萃取剂已被用于天然药物中非极性和弱极性有效成分的提取,尤其是挥发性和热敏性的物质．此外,通过加入适当的添加剂还可有效地萃取极性化合物,和传统的化学方法相比,     

Expression of the small tyrosine phosphatase (Stp1) in Saccharomyces cerevisiae: a study on protein tyrosine phosphorylation

Small tyrosine phoshatase 1 (Stp1) is a Schizosaccharomyces pombe low-molecular-mass phosphotyrosine-phosphatase 50% identical to Saccharomyces cerevisiae Ltp1. In order to investigate the role of Stp1 in yeast, a mutant was generated having the characteristic of a dominant negative molecule. Changes in protein tyrosine phosphorylation in S. cerevisiae proteome in response to Stp1 or its dominant negative mutant expression were analyzed by high-resolution two-dimensional (2-D) electrophoresis. The most remarkable result is the modification by phosphorylation on tyrosine of several proteins involved in carbohydrate metabolism. Twelve proteins were identified on the basis of their positions in the anti-phosphotyrosine immunoblot of the 2-D electrophoresis. Ten of these present tyrosyl residues that are within the consensus sequence for protein kinase CK2 (casein kinase-2). These data open the possibility for the identification of Stp1 substrates in yeast and provide hints about the nature of tyrosine phosphorylating agents in yeast and in other organisms where bona fide tyrosine kinases are lacking.     

Fermentation kinetics of ethanol production from glucose and xylose by recombinant Saccharomyces 1400(pLNH33)

Fermentation kinetics of ethanol production from glucose, xylose, and their mixtures using a recombinant Saccharomyces 1400 (pLNH33) are reported. Single-substrate kinetics indicate that the specific growth rate of the yeast and the specific ethanol productivity on glucose as the substrate was greater than on xylose as a substrate. Ethanol yields from glucose and xylose fermentation were typically 95 and 80% of the theoretical yield, respectively. The effect of ethanol inhibition is more pronounced for xylose fermentation than for glucose fermentation. Studies on glucose-xylose mixtures indicate that the recombinant yeast co-ferments glucose and xylose. Fermentation of a 52.8 g/L glucose and 56.3 g/L xylose mixture gave an ethanol concentration of 47.9 g/L after 36 h. Based on a theoretical yield of 0.51 g ethanol/g sugars, the ethanol yield from this experiment (for data up to 24 h) was calculated to be 0.46 g ethanol/g sugar or 90% of the theoretical yield. The specific growth rate of the yeast on glucose-xylose mixtures was found to lie between the specific growth rate on glucose and the specific growth rate on xylose. Kinetic studies were used to develop a fermentation model incorporating the effects of substrate inhibition, product inhibition, and inoculum size. Good agreements were obtained between model predictions and experimental data from batch fermentation of glucose, xylose, and their mixtures.     

Production of single cell protein (SCP) from food and agricultural waste by using Saccharomyces cerevisiae

Food waste is the single-largest component of the waste stream, in order to protect and safeguard the public health, useful and innovative recycling methods are investigated. The conversion of food wastes in value-added products is becoming a more economically viable and interesting practice. Food waste, collected in the distribution sector and citrus industries, was characterised for its potential as a raw material to use in fermentation processes. In this study, the production of single-cell protein (SCP) using food waste as a substrate was investigated. The purpose of this study has been to produce SCP from mixtures of food waste using Saccharomyces cerevisiae. The main fermentation test was carried out using a 25 l bioreactor. The utilisation of food waste can allow us to not only to reduce environmental pollution, but also to obtain value-added products such as protein supply for animal feed.     

Effect of Cs(I) and Cr(III) on the adsorption of strontium ion by living irradiated Saccharomyces cerevisiae

Journal of Radioanalytical and Nuclear Chemistry - In this paper, the effects of three coexisting ion systems (Cs, Sr), (Cr, Sr) and (Cs, Cr, Sr) on the adsorption of Sr(II) by irradiated...