ARTP-ALE Optimized Selection of Low Acetaldehyde Producing Brewer's Yeast and Fermentation Validation

Higher levels of acetaldehyde in beer are one of the major concerns in the current beer industry.Yeast produces acetaldehyde during alcoholic fermentation,and its modification significantly affects beer flavor and quality.A different mutant strain with lower acetaldehyde production and improved ethanol tolerance was constructed using the ARTP-ALE mutagenesis strategy with 4-methylpyrazole-disulfiram.As a result of the mutation,the alcohol dehydrogenase activity of the mutant strain decreased to about 71.22%of that of the wild-type strain.At the same time,the fermentation properties and genetic stability of the newly screened strain showed slight differences from the wild-type strain,and there were no safety concerns regarding industrial use of the mutant strain.

Preparations of TiO_2 film coated on foam nickel substrate by sol-gel processes and its photocatalytic activity for degradation of acetaldehyde

Anatase TiO2 films were successfully prepared on foam nickel substrates by sol-gel technique using tetrabutyl titanate as precursor. The characteristics of the TiO2 films were investigated by XPS, XRD, FE-SEM, TEM and UV-Vis absorption spectra. The photocatalytic activities of TiO2 films were investigated by photocatalytic degradation reactions of gaseous acetaldehyde, an indoor pollutant, under ultraviolet light irradiation. It was found that Ni^2＋ doping into TiO2 films due to the foam nickel substrates resulted in the extension of absorption edges of TiO2 films from UV region to visible light region. The pre-heating for foam nickel substrates resulted in the formation of NiO layer, which prevented effectively the injection of photogenerated electrons from TiO2 films to metal nickel. The TiO2 films displayed high photocatalytic activity for the degradation of acetaldehyde, and were enhanced by calcining the substrates and coating TiO2 films repeatedly. The high activity was mainly attributed to the improvement of the characteristics of substrate surface and the increase of active sites on photocatalyst.

Stabilizing copper species using zeolite for ethanol catalytic dehydrogenation to acetaldehyde

The selective dehydrogenation of ethanol to acetaldehyde is a promising route for acetaldehyde production.Although Cu-based catalysts exhibit high activity in ethanol dehydrogenation,a rapid deactivation due to Cu sintering always occurs.In this study,highly dispersed Cu species were stabilized using the silanol defects in Beta zeolite(denoted as Beta)resulting from dealumination,and applied as robust catalysts for ethanol-to-acetaldehyde conversion.Typically,a long catalyst lifetime of 100 h with an acetaldehyde yield of^70%could be achieved over 5%Cu/Beta.The presence of Cu^+and Cu0 species and the agglomeration of Cu particles after a long-term reaction for 180 h were revealed by transmission electron microscopy,thermogravimetric analysis,and CO-diffuse-reflectance infrared Fourier transform spectroscopy,and were responsible for the deactivation of the Cu/Beta catalyst in the ethanol-to-acetaldehyde conversion.

Modification of Surface Reactivity by CO： Effects on Decomposition and Polymerization of Acetaldehyde on Ru（0001）

The adsorption and reaction of acetaldehyde on the clean and CO pre-covered Ru（0001） surfaces have been investigated using temperature programmed desorption method. On the clean Ru（0001） surface, the decomposition of acetaldehyde is the main reaction channel, with little polymerization occurring. However, on the CO pre-covered Ru（0001） surface, the de- composition of acetaldehyde is inhibited considerably with increasing CO coverage. Whereas, the polymerization occurs efficiently, especially at high CO coverage （θco〉0.5 ML）, which is strongly CO coverage dependent. Combined with previous studies, the well-ordered hexagohal structure of CO layer formed on the Ru（0001） surface at high CO coverage that matches the configuration of paraldehyde is likely to be the origin of this remarkable phenomenon.

Peracetic Acid Synthesis by Acetaldehyde Liquid Phase Oxidation in Trickle Bed Reactor

In this paper,shorter residence time（a few minutes）with high yield in the trickle bed process for per- acetic acid synthesis by acetaldehyde liquid phase oxidation can be realized on the selected packing material SA-5118.For acetaldehyde in acetone with ferric ion as catalyst,the optimized process conditions were presented. The main factors influencing the yield,selectivity and conversion are residence time,temperature and acetaldehyde concentration,respectively.The temperature range checked is from 30 to 65℃.High yield of 81.53%with high se- lectivity of 91.84%can be obtained at higher temperature of 55℃when the residence time is 5.5min and the acet- aldehyde concentration is 9.85%（by mass）.And there is a critical acetaldehyde concentration point（Cccp）between 18%and 19.5%（by mass）.At temperature less than 55℃,the highest yield to peracetic acid at each temperature level increases with temperature when the acetaldehyde concentration is below Cccp and decreases with temperature when the acetaldehyde concentration is above Cccp.

Pervaporation of Aqueous Solution of Acetaldehyde Through ZSM-5 Filled PDMS Composite Membrane

Hydrophobic ZSM-5 zeolite filled polydimethylsiloxane （PDMS） composite membranes with Nylon micro-filtration membrane as the support layer were prepared to separate acetaldehyde from its aqueous solution. The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. Their structural morphology and thermal stability were also examined. The swelling study showed that the composite membranes presented higher degree of swelling in aqueous solution of acetaldehyde than in pure water at 25℃,

High-efficiency acetaldehyde removal during solid-state polycondensation of poly(ethylene terephthalate) assisted by supercritical carbon dioxide

The concentration of acetaldehyde(AA) is the main quality index of poly(ethylene terephthalate)(PET) used in food and drink packaging.A new method for AA removal has been developed by using supercritical carbon dioxide(sc CO2) during the solid-state polycondensation of PET.The influence factors of AA removal including the temperature,pressure,reaction time and the size of pre-polymer particles are systematically studied in this work.The results indicate that it is a highly efficient way to obtain high molecular weight PET with relative low concentration of AA.Correspondingly,the polymerization degree of PET could increase from 27.9 to 85.6 while the concentration of AA reduces from 0.229 × 10^(-6) to 0.055 × 10^(-6) under the optimal operation conditions of 230 °C,8 MPa and size of 0.30–0.45 mm.Thermodynamic performance tests show the increasing extent of PET crystallinity due to the fact that the plasticization of sc CO_2 is not obvious with extended reaction time,therefore the increasing crystallinity has no significant influence on AA removal.SEM observations reveal that the effects of sc CO_(2-) induced plasticization and swelling on PET increase significantly with the decrease of prepolymer size,and the surface of PET becomes more loose and porous in favor of the AA removal.

Smog Chamber Study on the Ozone Formation Potential of Acetaldehyde

Acetaldehyde is one of the important VOC species of O_(3)precursors in the atmospheric environment.The influences of relative humidity(RH)and initial VOC/NOx ratio(R_(CN))on the formation of O_(3)are studied in smog chamber experiments,and the MCM v3.3.1 mechanism of acetaldehyde is modified based on the experimental results.In low-RH conditions(RH=11.6%±1.1%),the O_(3)concentration at 6 h increases first and then decreases with the increase of R_(CN),and the R_(CN)at the inflection point of O_(3)concentrations is 3.2.In high-RH experiments(RH=78.8%±1.0%),variation of the O_(3)concentration at 6 h with R_(CN)is similar to that in low-RH experiments,but the R_(CN)at the inflection point is 2.8.RH has no significant effect on the O_(3)concentrations under low R_(CN)(<3),whereas it has a negative effect under high R_(CN)(>3).Compared with the experimental results,original MCM v3.3.1 greatly underestimates the O_(3)concentrations.Addition of both the photolysis process of peroxyacetyl nitrate and the photolysis process of HNO_(3)on the reactor surface into the original MCM can reduce the difference between the simulated O_(3)concentrations and the experimental results at 6 h from 24%−35%and 17%−49%to 6%−26%and 10%−42%under low-and high-RH conditions,respectively.The maximum incremental reactivity(MIR)of acetaldehyde simulated with the modified MCM is 4.0 ppb ppb−1 without considering the effect of other VOCs.

Role of Reduced Defects for Coupling Reactions of Acetaldehyde on Anatase TiO2（001）-（1×4） Surface

The chemistry of acetaldehyde (CH3CHO) adsorbed on the anatase TiO2(001)-(1×4) surface has been investigated by temperature-programmed desorption (TPD) method. Our experimental results provide the direct evidence that the perfect lattice sites on the anatase TiO2(001)-(1×4) surface are quite inert for the reaction of CH3CHO, but the reduced defect sites on the surface are active for the thermally driven reductive carbon-carbon coupling reactions of CH3CHO to produce 2-butanone and butene. We propose that the coupling reactions of CH3CHO on the anatase TiO2(001)-(1×4) surface should undergo through the adsorption of paired CH3CHO molecules at the reduced defect sites, since the existing reduced Ti pairs provide the suitable adsorption sites.

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.

Ion-Velocity Map Imaging Study of Photodissociation Dynamics of Acetaldehyde

The photodissociation dynamics of acetaldehyde in the radical channel CH3＋HCO has been reinvestigated using time-sliced velocity map imaging technique in the photolysis wavelength range of 275-321 nm. The CH3 fragments have been probed via （2＋1） resonance-enhanced multiphoton ionization. Images are measured for CH3 formed in the ground and excited states （v2=0 and 1） of the umbrella vibrational mode. For acetaldehyde dissociation on T1 state after intersystem crossing from S1 state, the products are formed with high translational energy release and low internal excitation. The rotational and vibrational energy of both fragments increases with increasing photodissociation energy. The triplet barrier height is estimated at 3.8814-0.006 eV above the ground state of acetaldehyde.

Age-related Metabolic Effects of Acetaldehyde on Rats With Reference to Detoxification Enzymes and Sulfhydryl Groups

Induced-acetaldehyde toxic effects on gluatathione [GSH] metabolism and sulfhydryl (SH) groups in liver and in brain of female albino rats with reference to age was studied.The total -SH groups were decreased whereas the specific activities of glutathione-S-transferase [GST] and glutathione peroxidase [GP0] were increased in acetaldehyde treated rats. However, the specific activity levels of glutathione reductase [GR] and Γ-glutamylcysteine synthetase [Γ-GCS] were decreased. In general, acetaldehyde indueed changes in the specific activities of the enzymes that increase with increasing age

Effect of Acetaldehyde on Oxidoreductases in Tissues of Rats at Different Ages

The toxicity of acetaldehyde and age related changes on oxidoreductases in the liver,brain, kidney, and musele of female albino rats (Wistar strain) were studied. The specific activities of lactate [LDH], isocitrate [ICDH (NAD/NADP)], succinate [SDH], malate [MDH], glutamate [GDH] and glucose-6-Phosphate [G-6-PDH] dehydrogenases were signifieantly inereased as a function of age. However, acetaldehyde treatment significantly inhibited oxidoreductases in the tissues of 21, 90 and 180 day old rats. Liver enzymes of young (21 days) rats exhibited greater sensitivity to acetaldehyde toxicity. Similar inhibition of oxidoreductases in brain and kidney of adult (180 days) rats treated with acetaldehyde was observed. LDH and GDH as compared to other enzymes studied showed higher susceptibility to acetaldehyde toxicity. The differential sensitivity of tissues and inhibition of oxidoreductases by acetaldehyde as a function of age could be attributed to hypoxic conditions, energy crisis, and mitochondrial structural changes. The results suggest that acetaldehyde affects oxidation of glucose via HMP shuni pathway, glycolytic pathway and Krebs cycle resulting in the impairment of carbohydrate metabolism

Efficient expression of codon-adapted human acetaldehyde dehydrogenase 2 cDNA with 6×His tag in Pichia pastoris

Human mitochondrial acetaldehyde dehydrogenase 2 (ALDH2) catalyzes the oxidation of acetaldehyde to acetic acid. Therefore, ALDH2 has therapeutic potential in detoxification of acetaldehyde. Further-more, ALDH2 catalyzes nitroglycerin to nitrate and 1, 2-glyceryldinitrate during therapy for angina pectoris, myocardial infarction, and heart failure. Large quantities of ALDH2 will be needed for potential clinical practice. In this study, Pichia pastoris was used as a platform for expression of human ALDH2. Based on the ALDH2*1 cDNA sequence, we designed ALDH2 cDNA by choosing the P. pastoris preferred codons and by decreasing the G + C content level. The sequence was synthesized using the overlap extension PCR method. The cDNA and 6×His tags were subcloned into the plasmid pPIC9K. The recombinant protein was expressed in P. pastoris GS115 and purified using Ni2+-Sepharose affinity chromatography. The amount of secreted protein in the culture was 80 mg/L in shake-flask cultivation and 260 mg/L in high-density bioreactor fermentation. Secreted ALDH2 was easily purified from the culture supernatant by using Ni2+-Sepharose affinity chromatography. After purification of the fermentation supernatant, the enzyme had a specific activity of 1.2 U/mg protein. The yield was about 16 mg/L in a shake flask culture of P. pastoris GS115 which contained the original human ALDH2*1 cDNA.

Catalytic Hydrogenation of Acetic Acid to Acetaldehyde: Synergistic Effect of Bifunctional Co/Ce-Fe Oxide Solid Solution Catalysts

The large-scale industrial production of acetic acid (HAc) from carbonylation of methanol has enabled intense research interest from direct hydrogenation of HAc to acetaldehyde (AA).Herein,a series of cerium-iron oxide solid solution supported metallic cobalt catalysts were prepared by modified sol-gel method and were applied in gas-phase hydrogenation of HAc to AA.A synergistic effect between the hydrogenation metal cobalt and Ce-Fe oxide solid solution is revealed.Specifically,oxygen vacancies provide the active sites for adsorption of HAc,while highly uniformly dispersed metallic Co adsorbs H2 and activates the reduction of HAc into AA.Moreover,the metallic Co can also assist the cyclical conversion between Fe3+/Fe2+ and Ce3+/Ce4+ on the surface of Ce1.xFexO2-δ supports.The unique effect substantially enhances the ability of the support material to rapidly capture oxygen atoms from HAc.It is found that the catalyst of 5% Co/Ce0.8Fe0.2O2-δ with the highest concentration of oxygen vacancy presents the best catalytic performance (i.e.acetaldehyde yield reaches 49.9%) under the optimal reaction conditions (i.e.623 K and H2 flow rate =10 mL/min).This work indicates that the Co/Ce-Fe oxide solid solution catalyst can be potentially used for the selective hydrogenation from HAc to AA.The synergy between the metallic Co and Ce1-xFexO2-δ revealed can be extended to the design of other composite catalysts.

Prolonged lifetime and enhanced separation of photo- generated charges of nanosized α-Fe2O3 by coupling SnO2 for efficient visible-light photocatalysis to convert C02 and degrade acetaldehyde

To develop efficient visible-light photocatalysis on α-Fe2O3, it is highly desirable to promote visible-light-excited high-energy-level electron transfer to a proper energy platform thermodynamically. Herein, based on the transient-state surface photovoltage responses and the atmosphere-controlled steady-state surface photovoltage spectra, it is demonstrated that the lifetime and separation of photogenerated charges of nanosized α-Fe2O3 are increased after coupling a proper amount of nanocrystalline SnO2. This naturally leads to greatly improved photocatalytic activities for CO2 reduction and acetaldehyde degradation. It is suggested that the enhanced charge separation results from the electron transfer from α-Fe2O3 to SnO2, which acts as a proper energy platform. Based on the photocurrent action spectra, it is confirmed that the coupled SnO2 exhibits longer visible-light threshold wavelength （-590 nm） compared with the coupled TiO2 （-550 nm）, indicating that the energy platform introduced by SnO2 would accept more photogenerated electrons from α-Fe2O3. Moreover, electrochemical reduction experiments proved that the coupled SnO2 possesses better catalytic ability for reducing CO2 and O2. These are well responsible for the much efficient photocatalysis on SnO2-coupled α-Fe2O3.

Catalytic liquid-phase oxidation of acetaldehyde to acetic acid over a Pt/CeO_2–ZrO_2–SnO_2/γ-alumina catalyst

Pt/CeO2–ZrO2–SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2–ZrO2–SnO2 were successfully dispersed on the γ-Al2O3 support.Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt（6.4 wt.%）/Ce0.68Zr0.17Sn0.15O2.0（16 wt.%）/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8 hr, and the selectivity to acetic acid reached to 95%and higher after the reaction for 4 hr and longer.

Catalytic Aerobic Oxidation of Acetaldehyde over Keggin-type Molybdovanadophosphoric Acid/SBA-15 under Ambient Condition

Keggin-type molybdovanadophosphoric acids （HPA）, H4PMo11VO40 （1）, H5PMo10V2O40 （2） and H6PMo9V3O40 （3） were anchored onto γ-aminopropyltriethoxysilane （APTS） aminosilylated silica mesoporous SBA-15 through acid-base neutralization and the resulting HPA/APTS/SBA-15 were characterized by BET, TEM, XRD, ICP, FFIR and ^31p MAS NMR. The characterization results indicate that the Keggin-structure of these HPAs is preserved within the mesoporous silica host. The samples were tested for catalytic aerobic oxidation of acetaldehyde heterogeneously in liquid phase under ambient condition. The electrostatic force between heteropoly acid and amino groups grafted on the silica channel surface leads to strong immobilization of HPA inside SBA-15 which is against the leaching during the reaction. The good catalytic performance and easy recycle of these catalysts make them as potential environmental friendly catalysts for elimination of indoor air pollutants.

Quantum Chemical Study on Reaction of Acetaldehyde with Hydroxyl Radical

The reaction of acetaldehyde with hydroxyl radical was studied by means of quantum chemical methods. The geometries for all the stationary points on the potential energy surfaces were optimized fully, respectively, at the G3MP2, G3, and MP2/6-311++G(d,p) levels. Single-point energies of all the species were calculated at the QCISD/6-311++G(d,p) level. The mechanism of the reaction studied was confirmed. The predicted product is acetyl radical that is in agreement with the experiment.

Liquid-phase oxidation of ethylamine to acetaldehyde oximes over tungsten-doped zeolites

The liquid-phase oxidation of ethylamine with hydrogen peroxide was studied over tungsten-doped zeolites to develop a clean and simple route for producing acetaldehyde oxime. The investigations were firstly performed over W/MOR, where the coordinated state as well as the acidity of the W species were characterized. The reaction parameters, including H_2O_2 amount, solvent,temperature, tungsten content as well as catalyst amount, governed the activity and oxime selectivity. Under optimized reaction conditions, W/MOR showed an ethylamine conversion and corresponding oxime selectivity of 18.3% and 88.9%. W/MOR showed a superior performance in comparison to other tungsten-containing zeolites of W/Beta, W/MWW and W/Y. Although W/MOR exhibited lower amine conversion than titanosilicates of TS-1 and Ti-MWW, it gave higher selectivity to the main product of oxime. Moreover, W/MOR proved to be a robust catalyst, exhibiting a stable catalytic performance after being reused at least for 5 times.