Production and consumption of sorbitol and fructose by saccharomyces cerevisiae ATCC 36859

The production and consumption of sorbitol by Saccharomyces cerevisiae ATCC 36859 have been studied in this work. The results showed that the strain produced ethanol and sorbitol in a fructose medium, but it generated only ethanol while growing in a glucose medium. When the strain was pregrown on fructose and transferred to a sorbitol medium, it consumed that polyol and produced ethanol and fructose. It did not grow on sorbitol when it was transferred from a glucose medium. During the growth of the strain in a glucose-fructose medium, the sorbitol production started some time after the consumption of glucose. Both glucose and ethanol affected the production of sorbitol. Comparing the strain with a wild S. cerevisiae, it was found that the latter one did not produce sorbitol when it grew either on glucose or fructose. Furthermore, the wild strain grew well on sorbitol, regardless of whether it was pregrown on glucose or fructose but it did not produce fructose.     

Increasing isobutanol yield by double-gene deletion of PDC6 and LPD1 in Saccharomyces cerevisiae

As a new biofuel, isobutanol has received more attentions in recent years. Because of its high tolerance to higher alcohols, Saccharomyces cerevisiae has potential advantages as a platform microbe to produce isobutanol. In this study, we investigated integration effects of enhancing valine biosynthesis by overexpression of ILV2 and BAT2 with eliminating ethanol formation by deletion of PDC6 and decreasing acetyl-Co A biosynthesis by deletion of LPD1 on isobutanol titers. Our results showed that deletion of LPD1 in strains overexpressing BAT2 and ILV2 increased isobutanol titer by 5.3-fold compared with control strain. Additional deletion of PDC6 in lpd1Δ strains carrying overexpressed BAT2 and ILV2 further increased isobutanol titer by 1.5 fold. Overexpression of BAT2 and ILV2 in lpd1Δ strains and pdc6Δ strains decreased ethanol titers. Glycerol titers of the engineered strains did not have greater changes than that of control strain, while their acetic acid titers were higher, perhaps due to the imbalance of cofactors in isobutanol synthesis. Our researches suggest that double-gene deletion of PDC6 and LPD1 in strains overexpressing BAT2 and ILV2 could increase isobutanol production dramatically than single-gene deletion of PDC6 or LPD1. This study reveals the integration effects of overexpression of ILV2/BAT2 and double-gene deletion of LPD1 and PDC6 on isobutanol production, and helps understanding future developments of engineered strains for producing isobutanol.     

Tryptophan Derivatives by Saccharomyces cerevisiae EC1118: Evaluation,Optimization, and Production in a Soybean-Based Medium

Given the pharmacological properti es and the potential role of kynurenic acid (KYNA) in human physiology and the pleiotropic activity of the neurohormone melatonin (MEL) involved in physiological and immunological functions and as regulator of antioxidant enzymes, this study aimed at evaluating the capability of Saccharomyces cerevisiae EC1118 to release tryptophan derivatives (dTRPs) from the kynurenine (KYN) and melatonin pathways. The setting up of the spectroscopic and chromatographic conditions for the quantification of the dTRPs in LC-MS/MS system, the optimization of dTRPs’ production in fermentative and whole-cell biotransformation approaches and the production of dTRPs in a soybean-based cultural medium naturally enriched in tryptophan, as a case of study, were included in the experimental plan. Variable amounts of dTRPs, with a prevalence of metabolites of the KYN pathway, were detected. The LC-MS/MS analysis showed that the compound synthesized at highest concentration is KYNA that reached 9.146 ± 0.585 mg/L in fermentation trials in a chemically defined medium at 400 mg/L TRP. Further experiments in a soybean-based medium confirm KYNA as the main dTRPs, whereas the other dTRPs reached very lower concentrations. While detectable quantities of melatonin were never observed, two MEL isomers were successfully measured in laboratory media.     

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     

The Multivalent Polyampholyte Domain of Nst1, a P-Body-Associated Saccharomyces cerevisiae Protein,Provides a Platform for Interacting with P-Body Components

The condensation of nuclear promyelocytic leukemia bodies, cytoplasmic P-granules, P-bodies (PBs), and stress granules is reversible and dynamic via liquid–liquid phase separation. Although each condensate comprises hundreds of proteins with promiscuous interactions, a few key scaffold proteins are required. Essential scaffold domain sequence elements, such as poly-Q, low-complexity regions, oligomerizing domains, and RNA-binding domains, have been evaluated to understand their roles in biomolecular condensation processes. However, the underlying mechanisms remain unclear. We analyzed Nst1, a PB-associated protein that can intrinsically induce PB component condensations when overexpressed. Various Nst1 domain deletion mutants with unique sequence distributions, including intrinsically disordered regions (IDRs) and aggregation-prone regions, were constructed based on structural predictions. The overexpression of Nst1 deletion mutants lacking the aggregation-prone domain (APD) significantly inhibited self-condensation, implicating APD as an oligomerizing domain promoting self-condensation. Remarkably, cells overexpressing the Nst1 deletion mutant of the polyampholyte domain (PD) in the IDR region (Nst1_∆PD) rarely accumulate endogenous enhanced green fluorescent protein (EGFP)-tagged Dcp2. However, Nst1_∆PD formed self-condensates, suggesting that Nst1 requires PD to interact with Dcp2, regardless of its self-condensation. In Nst1_∆PD-overexpressing cells treated with cycloheximide (CHX), Dcp2, Xrn1, Dhh1, and Edc3 had significantly diminished condensation compared to those in CHX-treated Nst1-overexpressing cells. These observations suggest that the PD of the IDR in Nst1 functions as a hub domain interacting with other PB components.     

Improvement of ethanol production in Saccharomyces cerevisiae by hetero‐expression of GAPN and FPS1 deletion

BACKGROUND: During anaerobic bioethanol fermentation of Saccharomyces cerevisiae, the main byproduct glycerol is essential to regulate redox balance (reoxidize NADH to NAD⁺), which is necessary to maintain cell growth and fermentation. Hetero‐expression of a NADP⁺‐dependent glyceraldehydes‐3‐phosphate dehydrogenase (GAPN) [EC.1.2.1.9] in S. cerevisiae could redirect the carbon flux from glycerol to ethanol involving a net oxidation of NADH. The present study investigates whether combination of GAPN hetero‐expression and glycerol exporter Fps1p disruption would result in less glycerol and more ethanol production without affecting growth rate during anaerobic fermentations. RESULTS: The results of anaerobic fermentations showed that the fps1Δ mutant with GAPN (named 4FG) produced 21.47% less glycerol and 9.18% more ethanol compared with a parental strain with a control plasmid, while the rates of growth and fermentation were not changed. Moreover, the engineered strain 4FG yielded less glycerol and acetic acid, and more ethanol than the control, fps1Δ mutant or with GAPN only. CONCLUSIONS: During anaerobic fermentations, hetero‐expression of GAPN restored the reduced grow rate of the fps1Δ mutant, and led to less byproducts and more ethanol production. This combination strategy could be used to modulate glycerol metabolism and optimize the anaerobic fermentation of S. cerevisiae. Copyright © 2011 Society of Chemical Industry     

Exploring the substrate specificity of a mycobacterial polyprenol monophosphomannose-dependent alpha-(1-->6)-mannosyltransferase

A series of synthetic alpha-(1-->6)-linked octyl mannopyranoside oligomers was evaluated as potential acceptors of a polyprenol monophosphomannose-dependent alpha-(1-->6)-mannosyltransferase that is involved in the biosynthesis of the mannan core of mycobacterial lipoarabinomannan. Initial evaluation demonstrated that the enzyme recognizes di-, tri- and tetramannosides (5, 6 and 7) as substrates with different activities. While the highest mannosyltransferase activities were observed when the di- and trisaccharide were used as substrates, diminished enzymatic activity was seen with the tetramannoside. As octyl alpha-D-mannopyranosyl-(1-->6)-alpha-D-mannopyranoside (5) appears to be the minimum structural element required for mannosyltransferase catalysis, a panel of methoxy and deoxy disaccharide analogues (8-21) were used to probe the substrate specificity of the enzyme further. In terms of the steric requirements at the active site, the enzyme does not recognize either C2'- and C2-methoxy analogues as substrates, a result that suggests that the alpha-(1-->2)-mannopyranosyl branches, which are present in the mannan core of LAM must be added on a larger alpha-(1-->6)-oligomannan intermediate. In contrast, the presence of a methoxy functionality at the C3', C3, C4' and C4 positions are somewhat tolerated by the enzyme, although diminished enzyme activities were observed with the C4'- and C4-methoxy analogues. Moreover, the 2'- and 4-hydroxyl groups appear not to be critical for substrate binding at the active site, as both 2'- and 4-deoxy analogues are substrates for the enzyme. In contrast, replacement of the hydroxyl groups at other positions essentially abolished enzymatic activity. Further kinetic characterization of the enzyme by using the effective acceptor substrates gave apparent K(M) values ranging from 111 to 437 microM, which are within two-fold higher or lower than that for the parent dimannoside (5). Although the K(M) values indicate that the enzyme binds those acceptors with comparable affinities, the C4'-methoxy analogue (12) turns over more slowly than the others, as indicated by the apparent V(max) values.     

Mechanistic and kinetic investigation of Cu(II)-catalyzed controlled radical polymerization enabled by ultrasound irradiation

Controlled radical polymerization (CRP) under external field has been an attractive research area in these years. In this work, a new electron transfer mechanism, that is, sonochemically induced electron transfer (SET) was introduced to mediate polymerization for the first time. The activator Cu^IX/L complex was (re)generated from Cu^IIX₂/L in dimethylsulfoxide (DMSO) by the SET process in the presence of free ligand tris(2-dimethylaminoethyl)amine (Me₆TREN). The investigation of polymerization including the mechanistic insights and effect of experimental conditions on the rate of reaction has been undertaken. Kinetics of Cu(II)-catalyzed CRPs via SET under different conditions (i.e., Me₆TREN concentration, catalyst loading, targeted degree of polymerization, and sonication power) were conducted in an unprecedentedly controlled manner, yielding polymers with predetermined molar masses and low dispersities (Đ < 1.12). Attractively, the polymerization can be performed without the piezoelectric nanoparticles and exogenous reducing agent. Contamination by nonliving chains formed from sonochemically generated radicals is avoided as well. All of these results supported that Cu(II)-based catalyst activation enabled by ultrasonication has a promising potential in scale-up of CRP.     

N-(6-氯-1-氧-3-吡啶甲基)邻苯二甲酰亚胺的合成

以邻苯二甲酰亚胺为起始原料,在常温条件下与氢氧化钾反应合成了邻苯二甲酰亚胺钾,其熔点352.8~353.4℃,收率95%。然后在70℃和微波辐射条件下,以邻苯二甲酰亚胺钾作为亲核试剂,与2-氯-5-氯甲基吡啶反应20 m in,制备了N-(6-氯-3-吡啶甲基)邻苯二甲酰亚胺,熔点140.3~140.5℃,收率98.5%。最后以双氧水为氧化剂,在75℃条件下,N原子氧化,合成了目标产物N-(6-氯-1-氧-3-吡啶甲基)邻苯二甲酰亚胺,熔点138.2~139.4℃,收率92%。利用红外光谱(FTIR)、核磁共振氢谱(1HNMR)、气-质联用仪(GC-MS)解析并确定了中间产物及目标化合物的结构。     

Synthesis,characterization, and application of yeast-based magnetic bionanocomposite for the removal of Cu(II) from water

Abstract

Due to the amount of yeast residues generated by the industries and their high capacity as biosorbent, this work proposes the use of yeast biomass in natura (YB) or modified with ferromagnetic nanoparticles (Fe₃O₄) (YB-MNP) for Cu(II) removal from water. Synthesized YB-MNP, YB, and magnetite alone (MNP) were characterized by FTIR, XRD, and SEM. It was observed the efficient impregnation of magnetite on the surface of the biomass. Copper sorption was evaluated in batch tests using 100?mg/L of Cu(II) solution at pH 5.5, and the supernatant was analyzed by FAAS for Cu determination. Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm models were applied to fit the experimental data. A favorable sorption process was observed for all the materials, mainly for the D–R model adjusted to the bionanocomposite data (YB-MNP), with r² = 0.9950 and a low error (χ² = 0.0427) associated to the model. Theoretical and experimentally Cu(II) sorption capacities were fairly similar, 8.6?±?0.1 and 8.3?±?0.2?mg/g, respectively.     

双-1,6-(二乙基硫代氨甲酰-二硫化)己烷的制备与应用

用1,6－二氯己烷与硫代硫酸钠合成了六亚甲基－1,6－二硫代硫酸二钠盐,进而制备了新型硫化剂双－1,6－（二乙基硫代氨甲酰－二硫化）己烷。有红外光谱和质谱仪对中间体及产物进行了表征,探讨了产物对天然橡胶的抗硫化返原作用机理,并开展了应用研究,结果表明,用双－1,6－（二乙基硫代氨甲酰－二硫化）己烷组成的硫化体系硫化的橡胶具有优异的抗硫化返原性和动态疲劳性能。     

2－乙基－6－甲基－N－（1＇－甲氧基－2＇－甲氧乙基）苯胺的气相色谱分析

本文用气相色谱法对２－乙基－６－甲基－Ｎ－（１＇－甲氧基－２＇－甲氧乙基）苯胺进行定量分析。这种方法简单、快速、准确和实用。标准偏差为０．１１，变异系数为０．１１％，回收率为９９．２８～１００．６１％。     

啤酒酵母中(1→3)-β-D-葡聚糖的提取及其机理研究

分别采用酸法、酸碱法来提取啤酒酵母中的(1→3) β D 葡聚糖,然后对其产品进行多糖成分和紫外光谱分析。结果发现,在用c(CH3COOH)=0 5mol/L的水溶液提取啤酒酵母中的(1→3) β D 葡聚糖时,其产品中除含有葡聚糖外,还含有一定量的甘露聚糖和蛋白质这两种成分。但先用c(NaOH)=1 0mol/L的水溶液提取,再用w(CH3COOH)=4%的醋酸溶液处理时,产品为高纯度的(1→3) β D 葡聚糖。此结论由傅立叶红外光谱和核磁共振碳谱得到进一步的证实。接着从其水解机理上阐述了产生上述两种不同结果的原因,从而说明了酸碱法是从啤酒酵母中提取(1→3) β D 葡聚糖的理想途径。     

Preparation of SAPO-34 catalyst and presentation of a kinetic model for methanol to olefin process (MTO)

Conversion of methanol to light olefins (MTO) using acidic SAPO-34 molecular-sieve as the reaction catalyst was studied in a differential fixed bed reactor within the temperature range of 375-425 °C and under 4 bar pressure. The importance of MTO process is due to the increasing demand for light olefins in recent years. SAPO-34 was synthesized by hydrothermal method, applying morpholine as the template. The latter compound was then changed into protonated form by ion exchange method with ammonium chloride at 80 °C. A simple stoichiometric scheme has been presented for MTO. In addition a mechanism for this process based on Langmuir-Hinshelwood formulation has been put forward and the kinetic parameters have been evaluated as functions of temperature.     

Preparation of a Cu(II)-PVA/PA6 Composite Nanofibrous Membrane for Enzyme Immobilization

PVA/PA6 composite nanofibers were formed by electrospinning. Cu(II)-PVA/PA6 metal chelated nanofibers, prepared by the reaction between PVA/PA6 composite nanofibers and Cu²⁺ solution, were used as the support for catalase immobilization. The result of the experiments showed that PVA/PA6 composite nanofibers had an excellent chelation capacity for Cu²⁺ ions, and the structures of nanofibers were stable during the reaction with Cu²⁺ solution. The adsorption of Cu(II) onto PVA/PA6 composite nanofibers was studied by the Langmuir isothermal adsorption model. The maximum amount of coordinated Cu(II) (q_m) was 3.731 mmol/g (dry fiber), and the binding constant (K_l) was 0.0593 L/mmol. Kinetic parameters were analyzed for both immobilized and free catalases. The value of V_max (3774 μmol/mg·min) for the immobilized catalases was smaller than that of the free catalases (4878 μmol/mg·min), while the K_m for the immobilized catalases was larger. The immobilized catalases showed better resistance to pH and temperature than that of free form, and the storage stabilities, reusability of immobilized catalases were significantly improved. The half-lives of free and immobilized catalases were 8 days and 24 days, respectively.     

N，N＇－二安替比林－1，6－己二酰胺的合成及表征

采用一步法首次合成了Ｎ，Ｎ＇－二安替比林－１，６－己二酰胺（ＢＡＰＨＤＣＡ），通过元素分析，ＵＶ、ＩＲ光谱和１ＨＮＭＲ谱分析对其结构组成进行了确认和表征，并考察了它在几种常见溶剂中的溶解性。     

Development of a kinetic model for the moderate temperature chemical vapor deposition of SiO2 films from tetraethyl orthosilicate and oxygen

An apparent kinetic model for the chemical vapor deposition of SiO₂ from tetraethyl orthosilicate (TEOS) and O₂ was developed in a poorly investigated range of operating conditions, that is, at atmospheric pressure and between 350 and 500°C, based on literature survey and experimental results obtained in a hot wall tubular reactor. The kinetic model was implemented into the computational fluid dynamics code FLUENT and validated both in shape and value by comparison with experimental deposition rate profiles. It reveals that for the conditions tested, a possible mechanism of SiO ₂ deposition involves two intermediate species formed from TEOS homogeneous decomposition, the first one being active from 300°C and the second one contributing to deposition for temperatures higher than 370°C. The calculated local profiles of gas flow, gas temperature, species mass fraction, and silica deposition rate indicate that the first intermediate species leads to marked film thickness gradients, the second one being more stable as producing uniform thicknesses. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3958–3966, 2018     

(3aS,6aR)-1,3-二苄基-四氢-4H-呋喃并[3,4-d]咪唑-2,4(1H)-二酮的立体选择性合成

以顺-1,3-二苄基-5-[(1S,2S)-(+)-苏式-1-羟甲基-2-(对硝基苯基)-2-羟乙基]-四氢-4H-吡咯并[3,4-d]咪唑-2,4,6-三酮为原料,经单乙酰化、NaBH4还原和酸水解得到标题化合物,与直接还原或是先经双乙酰化再还原的工艺相比,单乙酰化后再还原的选择性高达97.25%。并对单乙酰化物和双乙酰化物结构做了X单晶衍射测定,单乙酰化物的原子空间排布更利于选择性还原。     

Witting-Horner反应合成3-甲基-5-（2,6,6-三甲基-1-环己烯-1-基）-2,4-戊二烯基膦酸二烷基酯

3-甲基-5-（2,6,6-三甲基-1-环己烯-1-基）-2,4-戊二烯基膦酸二烷基酯是维生素A的中间体。β-紫罗兰酮与乙二膦酸四乙酯在碱催化下进行Witting-Horner缩合反应得到目标化合物,其含量为90.5%,收率46.1%。