scholarly journals Biocatalytic synthesis of the Green Note trans-2-hexenal in a continuous-flow microreactor

2018 ◽  
Vol 14 ◽  
pp. 697-703 ◽  
Author(s):  
Morten M C H van Schie ◽  
Tiago Pedroso de Almeida ◽  
Gabriele Laudadio ◽  
Florian Tieves ◽  
Elena Fernández-Fueyo ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Aqueous Media ◽  
Alcohol Oxidase ◽  
Reaction Rates ◽  
Reaction Scheme ◽  
Pleurotus Eryngii ◽  
Turnover Frequency ◽  
Catalytic Activities ◽  
The Poor ◽  
Flow Microreactor

The biocatalytic preparation of trans-hex-2-enal from trans-hex-2-enol using a novel aryl alcohol oxidase from Pleurotus eryngii (PeAAOx) is reported. As O2-dependent enzyme PeAAOx-dependent reactions are generally plagued by the poor solubility of O2 in aqueous media and mass transfer limitations resulting in poor reaction rates. These limitations were efficiently overcome by conducting the reaction in a flow-reactor setup reaching unpreceded catalytic activities for the enzyme in terms of turnover frequency (up to 38 s−1) and turnover numbers (more than 300000) pointing towards preparative usefulness of the proposed reaction scheme.

scholarly journals Mass and Heat Transfer Coefficients in Automotive Exhaust Catalytic Converter Channels

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 507
Author(s):  
Chrysovalantis C. Templis ◽  
Nikos G. Papayannakos
Keyword(s):  
Heat Transfer ◽  
Flow Reactor ◽  
Catalytic Converter ◽  
Reaction Rates ◽  
Cfd Model ◽  
Automotive Exhaust ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Mass And Heat Transfer

Mass and heat transfer coefficients (MTC and HTC) in automotive exhaust catalytic monolith channels are estimated and correlated for a wide range of gas velocities and prevailing conditions of small up to real size converters. The coefficient estimation is based on a two dimensional computational fluid dynamic (2-D CFD) model developed in Comsol Multiphysics, taking into account catalytic rates of a real catalytic converter. The effect of channel size and reaction rates on mass and heat transfer coefficients and the applicability of the proposed correlations at different conditions are discussed. The correlations proposed predict very satisfactorily the mass and heat transfer coefficients calculated from the 2-D CFD model along the channel length. The use of a one dimensional (1-D) simplified model that couples a plug flow reactor (PFR) with mass transport and heat transport effects using the mass and heat transfer correlations of this study is proved to be appropriate for the simulation of the monolith channel operation.

scholarly journals Ureido Functionalization through Amine-Urea Transamidation under Mild Reaction Conditions

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1583
Author(s):  
Natalia Guerrero-Alburquerque ◽  
Shanyu Zhao ◽  
Daniel Rentsch ◽  
Matthias M. Koebel ◽  
Marco Lattuada ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Reaction Times ◽  
Reaction Rates ◽  
Secondary Amines ◽  
Isocyanic Acid ◽  
Advantages And Disadvantages ◽  
Major Disadvantage ◽  
Wide Range ◽  
Potential Alternative ◽  
Full Conversion

Ureido-functionalized compounds play an indispensable role in important biochemical processes, as well as chemical synthesis and production. Isocyanates, and KOCN in particular, are the preferred reagents for the ureido functionalization of amine-bearing compounds. In this study, we evaluate the potential of urea as a reagent to graft ureido groups onto amines at relatively low temperatures (<100 °C) in aqueous media. Urea is an inexpensive, non-toxic and biocompatible potential alternative to KOCN for ureido functionalization. From as early as 1864, urea was the go-to reagent for polyurea polycondensation, before falling into disuse after the advent of isocyanate chemistry. We systematically re-investigate the advantages and disadvantages of urea for amine transamidation. High ureido-functionalization conversion was obtained for a wide range of substrates, including primary and secondary amines and amino acids. Reaction times are nearly independent of substrate and pH, but excess urea is required for practically feasible reaction rates. Near full conversion of amines into ureido can be achieved within 10 h at 90 °C and within 24 h at 80 °C, and much slower reaction rates were determined at lower temperatures. The importance of the urea/amine ratio and the temperature dependence of the reaction rates indicate that urea decomposition into an isocyanic acid or a carbamate intermediate is the rate-limiting step. The presence of water leads to a modest increase in reaction rates, but the full conversion of amino groups into ureido groups is also possible in the absence of water in neat alcohol, consistent with a reaction mechanism mediated by an isocyanic acid intermediate (where the water assists in the proton transfer). Hence, the reaction with urea avoids the use of toxic isocyanate reagents by in situ generation of the reactive isocyanate intermediate, but the requirement to separate the excess urea from the reaction product remains a major disadvantage.

Improved dispersibility of nano-graphene oxide by amphiphilic polymer coatings for biomedical applications

RSC Advances ◽  
2016 ◽  
Vol 6 (81) ◽  
pp. 77818-77829 ◽  
Author(s):  
Rana Imani ◽  
Wei Shao ◽  
Shahriar Hojjati Emami ◽  
Shahab Faghihi ◽  
Satya Prakash
Keyword(s):  
Graphene Oxide ◽  
Biomedical Applications ◽  
Aqueous Media ◽  
Polymer Coatings ◽  
Amphiphilic Polymer ◽  
Nano Materials ◽  
Biological Applications ◽  
The Poor ◽  
Nano Graphene

The poor dispersibility of graphene-based nano-materials in aqueous media is a crucial limitation in their biological applications.

INTESTINAL ABSORPTION OF VITAMIN A FROM OILY AND AQUEOUS MEDIA IN PATIENTS WITH THE CELIAC SYNDROME

PEDIATRICS ◽  
1949 ◽  
Vol 3 (5) ◽  
pp. 645-650
Author(s):  
WAYNE H. DANIELSON ◽  
EDWARD L. BINKLEY ◽  
HAROLD D. PALMER
Keyword(s):  
Cystic Fibrosis ◽  
Differential Diagnosis ◽  
Celiac Disease ◽  
Vitamin A ◽  
Aqueous Media ◽  
Aqueous Dispersion ◽  
The Poor ◽  
Naturally Occurring ◽  
Poor Absorption ◽  
In Infants And Children

The absorption of vitamin A from oily and aqueous media has been studied in infants and children with cystic fibrosis of the pancreas and idiopathic celiac disease. Patients with cystic fibrosis of the pancreas can absorb vitamin A acetate and vitamin A alcohol when it is given to them in an aqueous dispersion. The vitamin A acetate curves rose above the vitamin A alcohol curves in three of four patients on whom absorption curves were obtained. Vitamin A is absorbed by patients with idiopathic celiac disease only slightly better from an aqueous dispersion of the alcohol than from an oily concentrate of the naturally occurring esters. The poor absorption from an aqueous media by these patients supports the suggestion that the defect in absorption in this disease lies within the intestinal mucosa. The use of the differences in response to oily and aqueous concentrates in the differential diagnosis of the entities of the celiac syndrome is suggested.

scholarly journals High-level expression of aryl-alcohol oxidase 2 from Pleurotus eryngii in Pichia pastoris for production of fragrances and bioactive precursors

2020 ◽  
Vol 104 (21) ◽  
pp. 9205-9218
Author(s):  
Nina Jankowski ◽  
Katja Koschorreck ◽  
Vlada B. Urlacher
Keyword(s):  
Pichia Pastoris ◽  
Alcohol Oxidase ◽  
Building Blocks ◽  
Pleurotus Eryngii ◽  
Oxidation Products ◽  
Oxidative Enzymes ◽  
Biotechnological Applications ◽  
Positive Health ◽  
Neuroprotective Effects ◽  
Flavor Compound

Abstract The fungal secretome comprises various oxidative enzymes participating in the degradation of lignocellulosic biomass as a central step in carbon recycling. Among the secreted enzymes, aryl-alcohol oxidases (AAOs) are of interest for biotechnological applications including production of bio-based precursors for plastics, bioactive compounds, and flavors and fragrances. Aryl-alcohol oxidase 2 (PeAAO2) from the fungus Pleurotus eryngii was heterologously expressed and secreted at one of the highest yields reported so far of 315 mg/l using the methylotrophic yeast Pichia pastoris (recently reclassified as Komagataella phaffii). The glycosylated PeAAO2 exhibited a high stability in a broad pH range between pH 3.0 and 9.0 and high thermal stability up to 55 °C. Substrate screening with 41 compounds revealed that PeAAO2 oxidized typical AAO substrates like p-anisyl alcohol, veratryl alcohol, and trans,trans-2,4-hexadienol with up to 8-fold higher activity than benzyl alcohol. Several compounds not yet reported as substrates for AAOs were oxidized by PeAAO2 as well. Among them, cumic alcohol and piperonyl alcohol were oxidized to cuminaldehyde and piperonal with high catalytic efficiencies of 84.1 and 600.2 mM−1 s−1, respectively. While the fragrance and flavor compound piperonal also serves as starting material for agrochemical and pharmaceutical building blocks, various positive health effects have been attributed to cuminaldehyde including anticancer, antidiabetic, and neuroprotective effects. PeAAO2 is thus a promising biocatalyst for biotechnological applications. Key points • Aryl-alcohol oxidase PeAAO2 from P. eryngii was produced in P. pastoris at 315 mg/l. • Purified enzyme exhibited stability over a broad pH and temperature range. • Oxidation products cuminaldehyde and piperonal are of biotechnological interest. Graphical abstract

scholarly journals Human CD38 is an authentic NAD(P)+ glycohydrolase

1998 ◽  
Vol 330 (3) ◽  
pp. 1383-1390 ◽  
Author(s):  
Valérie BERTHELIER ◽  
Jean-Michel TIXIER ◽  
Hélène MULLER-STEFFNER ◽  
Francis SCHUBER ◽  
Philippe DETERRE
Keyword(s):  
Molecular Mechanisms ◽  
Reaction Scheme ◽  
Reaction Pathways ◽  
Catalytic Activities ◽  
Nad Glycohydrolase ◽  
Cyclization Process ◽  
Adp Ribosyl Cyclase ◽  
Cyclic Adp Ribose ◽  
Water Hydrolysis ◽  
Low Efficiency

The leucoyte surface antigen CD38 has been shown to be an ecto-enzyme with multiple catalytic activities. It is principally a NAD+ glycohydrolase that transforms NAD+ into ADP-ribose and nicotinamide. CD38 is also able to produce small amounts of cyclic ADP-ribose (ADP-ribosyl cyclase activity) and to hydrolyse this cyclic metabolite into ADP-ribose (cyclic ADP-ribose hydrolase activity). To classify CD38 among the enzymes that transfer the ADP-ribosyl moiety of NAD+ to a variety of acceptors, we have investigated its substrate specificity and some characteristics of its kinetic and molecular mechanisms. We find that CD38-catalysed cleavage of the nicotinamide-ribose bond results in the formation of an E·ADP-ribosyl intermediary complex, which is common to all reaction pathways; this intermediate reacts (1) with acceptors such as water (hydrolysis), methanol (methanolysis) or pyridine (transglycosidation), and (2) intramolecularly, yielding cyclic ADP-ribose with a low efficiency. This reaction scheme is also followed when using nicotinamide guanine dinucleotide as an alternative substrate; in this case, however, the cyclization process is highly favoured. The results obtained here are not compatible with the prevailing model for the mode of action of CD38, according to which this enzyme produces first cyclic ADP-ribose which is then immediately hydrolysed into ADP-ribose (i.e. sequential ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase activities). We show instead that the cyclic metabolite was a reaction product of CD38 rather than an obligatory reaction intermediate during the glycohydrolase activity. Altogether our results lead to the conclusion that CD38 is an authentic ‘classical’ NAD(P)+ glycohydrolase (EC 3.2.2.6).

Light stimulation of aryl-alcohol oxidase activity in Pleurotus eryngii

1992 ◽  
Vol 96 (11) ◽  
pp. 984-986 ◽  
Author(s):  
G. Delgado ◽  
F. Guillén ◽  
M.J. Martínez ◽  
A.E. González ◽  
A.T. Martínez
Keyword(s):  
Oxidase Activity ◽  
Alcohol Oxidase ◽  
Pleurotus Eryngii ◽  
Light Stimulation ◽  
Stimulation Of

scholarly journals The Effects of Mixing, Reaction Rates, and Stoichiometry on Yield for Mixing Sensitive Reactions—Part II: Design Protocols

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Syed Imran A. Shah ◽  
Larry W. Kostiuk ◽  
Suzanne M. Kresta
Keyword(s):  
Rate Ratio ◽  
Reaction Rate ◽  
Relative Rate ◽  
Reaction Diffusion ◽  
Reaction Rates ◽  
Reaction Scheme ◽  
Considerable Effect ◽  
Mixing Condition ◽  
Reaction Diffusion Model ◽  
Rate Ratios

Competitive-consecutive and competitive-parallel reactions are both mixing sensitive reactions where the yield of desired product depends on how fast the reactants are brought together. Recent experimental results have suggested that the magnitude of the mixing effect may depend strongly on the stoichiometry of the reactions. To investigate this, a 1D, dimensionless, reaction-diffusion model was developed at the micromixing scale, yielding a single general Damköhler number. Dimensionless reaction rate ratios were derived for both reaction schemes. A detailed investigation of the effects of initial mixing condition (striation thickness), dimensionless reaction rate ratio, and reaction stoichiometry on the yield of desired product showed that the stoichiometry has a considerable effect on yield. All three variables were found to interact strongly. Model results for 12 stoichiometries are used to determine the mixing scale and relative rate ratio needed to achieve a specified yield for each reaction scheme. The results show that all three variables need to be considered when specifying reactors for mixing sensitive reactions.

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