scholarly journals Asymmetric Whole-Cell Bio-Reductions of (R)-Carvone Using Optimized Ene Reductases

Molecules ◽  
2019 ◽  
Vol 24 (14) ◽  
pp. 2550 ◽  
Author(s):  
Christoph Mähler ◽  
Christian Burger ◽  
Franziska Kratzl ◽  
Dirk Weuster-Botz ◽  
Kathrin Castiglione
Keyword(s):  
Formation Rate ◽  
Product Formation ◽  
Regeneration System ◽  
Initial Product ◽  
Whole Cell ◽  
Stirred Tank Reactors ◽  
E Coli ◽  
Space Time Yield ◽  
Product Formation Rate ◽  
Site Selective

(2R,5R)-dihydrocarvone is an industrially applied building block that can be synthesized by site-selective and stereo-selective C=C bond bio-reduction of (R)-carvone. Escherichia coli (E. coli) cells overexpressing an ene reductase from Nostoc sp. PCC7120 (NostocER1) in combination with a cosubstrate regeneration system proved to be very effective biocatalysts for this reaction. However, the industrial applicability of biocatalysts is strongly linked to the catalysts’ activity. Since the cell-internal NADH concentrations are around 20-fold higher than the NADPH concentrations, we produced E. coli cells where the NADPH-preferring NostocER1 was exchanged with three different NADH-accepting NostocER1 mutants. These E. coli whole-cell biocatalysts were used in batch operated stirred-tank reactors on a 0.7 l-scale for the reduction of 300 mM (R)-carvone. 287 mM (2R,5R)-dihydrocarvone were formed within 5 h with a diasteromeric excess of 95.4% and a yield of 95.6%. Thus, the whole-cell biocatalysts were strongly improved by using NADH-accepting enzymes, resulting in an up to 2.1-fold increased initial product formation rate leading to a 1.8-fold increased space-time yield when compared to literature.

Improved Dynamic System of Microbial Continuous Fermentation and its Parameter Identification

2014 ◽  
Vol 633-634 ◽  
pp. 545-549
Author(s):  
Hong Li Xiao ◽  
Lan Zhang Chong ◽  
Fei Li Hang ◽  
Wang Yong
Keyword(s):  
Dynamic System ◽  
Consumption Rate ◽  
Continuous Fermentation ◽  
Formation Rate ◽  
Product Formation ◽  
Cellular Growth ◽  
Specific Substrate ◽  
Substrate Consumption ◽  
Specific Product ◽  
Product Formation Rate

In this paper, the nonlinear dynamic system of microbe continuous fermentation products 1,3-propanediol (1,3-PD) is rewritten by improving the specific cellular growth rate, specific substrate consumption rate and specific product formation rate. Firstly, under the condition of substrate glycol excess and active trans-membrane transport, according to the dynamic behavior the fermentation process, we consider the glycerol and 1,3–PD concentration within the cell, and improve the specific cellular growth rate, specific substrate consumption rate and specific product formation rate, then rewrite the dynamic system of microbial continuous fermentation process. Secondly, taking the dynamic system as main constraint condition, we establish the parameter identification model and prove the existence of the optimal solution. Lastly, the numerical results calculated by particle swarm algorithm show that the improved model is suitable for describe the dynamic behavior of 1,3-PD, but is not accurate enough for by-products.

Effect of Organometallic Compounds on the Formation of Carbon Nanostructures by Pulsed Electric Discharge of Fluorine-Containing Organic Liquid between Metal Electrodes

2010 ◽  
Vol 459 ◽  
pp. 67-70
Author(s):  
Katsuhiko Hosoi ◽  
Shin-ichi Kuroda
Keyword(s):  
Raman Spectrum ◽  
Electric Discharge ◽  
Carbon Nanostructures ◽  
Organic Liquid ◽  
Formation Rate ◽  
Organometallic Compounds ◽  
Product Formation ◽  
Metal Electrodes ◽  
Carbon Nanoparticle ◽  
Product Formation Rate

The carbon nanotube and carbon nanoparticle that contain fluorine on their surfaces were prepared by a pulsed electric discharge in a fluorine-containing organic liquid. The dominant product was nanoparticles with the diameters of ca. 5–100 nm in all experiments, however, the intensity ratio of G-band (1580 cm-1) to D-band (1350 cm-1) of the Raman spectrum of the products increased by addition of a catalyst indicating the formation of crystalline particles. The product formation rate also increased to 39.3 mg/A•s with ferrocene and 79.4 mg/A•s with nickelocene while with no catalyst it resulted in 12.5 mg/A•s.

scholarly journals Mitigation of pretreatment-derived inhibitors during lignocellulosic ethanol fermentation using spent grain as a nitrogen source

2021 ◽  
Author(s):  
Michael Persson ◽  
Mats Galbe ◽  
Ola Wallberg
Keyword(s):  
Cell Growth ◽  
Protein Hydrolysate ◽  
Formation Rate ◽  
Product Formation ◽  
Negative Effects ◽  
Porcine Pancreas ◽  
Nutrient Sources ◽  
Ethanol Formation ◽  
Spent Grain ◽  
Product Formation Rate

AbstractNitrogen-containing nutrient sources can be used to mitigate the negative effects of pretreatment-derived inhibitors on product formation rates during bioethanol production. Process economic limitations require these nutrients to be inexpensive. A method of hydrolyzing the protein in the spent grain fraction remaining after wheat grain saccharification, using porcine pancreas trypsin, is presented. This protein hydrolysate was shown to increase the volumetric productivity of ethanol production, measured after 24 h, during fermentation of a lignocellulosic hydrolysate from 0.24 to 0.60 g/L h. Although the effects on the productivity, on a per gram basis, were lower than with yeast extract, which increased the product formation rate to 1.64 g/L h, amino acid analysis of the soluble polypeptides in the protein hydrolysate showed that the feasibility of using spent grain as a nutrient source could be increased through optimization of the hydrolysis step. Furthermore, it was shown that pretreatment-derived inhibitors could reduce cell growth without affecting ethanol formation rates and that nutrient addition could increase ethanol formation rates without increasing cell growth. Finally, it was shown that the ability of nutrients to affect the product formation rate was limited above a certain inhibitor concentration.

Highly efficient hydroxylation of gaseous alkanes at reduced temperature catalyzed by cytochrome P450BM3 assisted by decoy molecules

2015 ◽  
Vol 19 (01-03) ◽  
pp. 329-334 ◽  
Author(s):  
Norifumi Kawakami ◽  
Zhiqi Cong ◽  
Osami Shoji ◽  
Yoshihito Watanabe
Keyword(s):  
Reaction Temperature ◽  
Consumption Rate ◽  
Formation Rate ◽  
Coupling Efficiency ◽  
Product Formation ◽  
Alkane Hydroxylase ◽  
Highly Efficient ◽  
Perfluorocarboxylic Acids ◽  
Product Formation Rate ◽  
Reduced Temperature

Cytochrome P450BM3 functions as a small-alkane hydroxylase upon the addition of perfluorocarboxylic acids (PFs) as decoy molecules. The coupling efficiency (product formation rate per NADPH consumption rate) for the hydroxylation of small alkanes was improved by reducing the reaction temperature to 0°C.

Effect of Flow Pulsations in Premixed, Swirl Stabilized Combustor

2014 ◽  
Author(s):  
Aayush K. Sharma ◽  
Uddalok Sen ◽  
Pallab Sinha Mahapatra ◽  
Swarnendu Sen ◽  
Achintya Mukhopadhyay
Keyword(s):  
Numerical Model ◽  
Gas Turbine ◽  
Formation Rate ◽  
Combustion Process ◽  
Product Formation ◽  
Primary Objective ◽  
Gas Turbine Combustor ◽  
Ansys Fluent ◽  
Thermoacoustic Instabilities ◽  
Product Formation Rate

In the present work, a numerical model has been developed using ANSYS Fluent 14.5 to simulate the combustion phenomenon in a partially premixed, swirl-stabilized, LPG-fueled gas turbine combustor. In a practical gas turbine combustor, pulsations in the flow at the air side cannot be avoided which can lead to thermoacoustic instabilities. The primary objective of the study is to numerically analyze the effect of such pulsations on the fluid flow and combustion process inside the combustor. Different parameters like static temperature, progress variable and product formation rate are compared at the outlet plane of the combustor. The effect of change in the parameters like amplitude and frequency of the sinusoidal air flow input has also been investigated in the present study. It is observed that the solution changes from periodic to quasi-periodic at a higher amplitude condition. The numerical model was qualitatively validated against experiments performed on a laboratory-scale premixed, swirl-stabilized, gas turbine combustor.

Kinetics and Mechanistic Study on the Reaction of Iodo(diethylenetriamine) Platinum(II) with L-Cystine

2009 ◽  
Vol 62 (5) ◽  
pp. 493 ◽  
Author(s):  
Trilochan Swain ◽  
Prakash Mohanty
Keyword(s):  
Rate Constant ◽  
Total Concentration ◽  
Formation Rate ◽  
Activation Parameters ◽  
Order Rate Constant ◽  
Product Formation ◽  
Ring Closure ◽  
Mechanistic Study ◽  
Rescue Agent ◽  
Product Formation Rate

Substitution reactions of the complex [Pt(dien)I]+, where dien = diethylenetriamine or 1,5-diamino-3-azapentane, with the sulfur-containing rescue agent l-cystine have been studied in a 1.0 × 10–1 mol dm–3 aqueous perchlorate medium at various temperatures (25–50°C) and pH (2.30–1.00) using a UV-visible spectrophotometer. The products were characterized by their infrared and 1H NMR data at various temperatures. These data indicate that [Pt(dien)I]+ formed a complex with l-cystine through Pt–S bonds at pH 1.00–2.30. This Pt–S bond is observed at 50°C with ring closure of the dien (δ 3.8–3.9, 2H, CH2) and with open-ring dien (δ 3.2, 3.6–3.8 (dien), 2H, CH2). All reactions follow the rate law –d[mixture]/dt = (k1 + k2[Nu])[PtII], where k2 denotes a second-order rate constant and [Nu] is the total concentration of nucleophile. The product formation rate constant and activation parameters Ea, ΔH#, and ΔS# have been determined.

scholarly journals Tuning a bi-enzymatic cascade reaction in Escherichia coli to facilitate NADPH regeneration for ε-caprolactone production

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Jinghui Xiong ◽  
Hefeng Chen ◽  
Ran Liu ◽  
Hao Yu ◽  
Min Zhuo ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Binding Sites ◽  
Regeneration System ◽  
Nadph Regeneration ◽  
Whole Cell ◽  
Cyclohexanone Monooxygenase ◽  
Ribosome Binding ◽  
Ribosome Binding Sites ◽  
Whole Cell Biocatalyst ◽  
Substrate Tolerance

Abstractε-Caprolactone is a monomer of poly(ε-caprolactone) which has been widely used in tissue engineering due to its biodegradability and biocompatibility. To meet the massive demand for this monomer, an efficient whole-cell biocatalytic approach was constructed to boost the ε-caprolactone production using cyclohexanol as substrate. Combining an alcohol dehydrogenase (ADH) with a cyclohexanone monooxygenase (CHMO) in Escherichia coli, a self-sufficient NADPH-cofactor regeneration system was obtained. Furthermore, some improved variants with the better substrate tolerance and higher catalytic ability to ε-caprolactone production were designed by regulating the ribosome binding sites. The best mutant strain exhibited an ε-caprolactone yield of 0.80 mol/mol using 60 mM cyclohexanol as substrate, while the starting strain only got a conversion of 0.38 mol/mol when 20 mM cyclohexanol was supplemented. The engineered whole-cell biocatalyst was used in four sequential batches to achieve a production of 126 mM ε-caprolactone with a high molar yield of 0.78 mol/mol.

scholarly journals Process Engineering of the Acetone-Ethanol-Butanol (ABE) Fermentation in a Linear and Feedback Loop Cascade of Continuous Stirred Tank Reactors: Experiments, Modeling and Optimization

Fuels ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 108-129
Author(s):  
Katja Karstens ◽  
Sergej Trippel ◽  
Peter Götz
Keyword(s):  
Feedback Loop ◽  
Early Stage ◽  
Formation Rate ◽  
Abe Fermentation ◽  
Operating Conditions ◽  
Stirred Tank ◽  
Second Phase ◽  
Stirred Tank Reactors ◽  
Continuous Stirred Tank ◽  
Continuous Stirred Tank Reactors

The production of butanol, acetone and ethanol by Clostridium acetobutylicum is a biphasic fermentation process. In the first phase the carbohydrate substrate is metabolized to acetic and butyric acid, in the following second phase the product spectrum is shifted towards the economically interesting solvents. Here we present a cascade of six continuous stirred tank reactors (CCSTR), which allows performing the time dependent metabolic phases of an acetone-butanol-ethanol (ABE) batch fermentation in a spatial domain. Experimental data of steady states under four operating conditions—with variations of the pH in the first bioreactor between 4.3 and 5.6 as well as the total dilution rate between 0.042 h−1 and 0.092 h−1—were used to optimize and validate a corresponding mathematical model. Beyond a residence time distribution representation and substrate, biomass and product kinetics this model also includes the differentiation of cells between the metabolic states. Model simulations predict a final product concentration of 8.2 g butanol L−1 and a productivity of 0.75 g butanol L−1 h−1 in the CCSTR operated at pHbr1 of 4.3 and D = 0.092 h−1, while 31% of the cells are differentiated to the solventogenic state. Aiming at an enrichment of solvent-producing cells, a feedback loop was introduced into the cascade, sending cells from a later state of the process (bioreactor 4) back to an early stage of the process (bioreactor 2). In agreement with the experimental observations, the model accurately predicted an increase in butanol formation rate in bioreactor stages 2 and 3, resulting in an overall butanol productivity of 0.76 g L−1 h−1 for the feedback loop cascade. The here presented CCSTR and the validated model will serve to investigate further ABE fermentation strategies for a controlled metabolic switch.

scholarly journals Construction and characterization of a novel glucose dehydrogenase-leucine dehydrogenase fusion enzyme for the biosynthesis of l-tert-leucine

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Langxing Liao ◽  
Yonghui Zhang ◽  
Yali Wang ◽  
Yousi Fu ◽  
Aihui Zhang ◽  
...  
Keyword(s):  
Glucose Dehydrogenase ◽  
Catalytic Efficiency ◽  
Space Time ◽  
Cofactor Regeneration ◽  
Enzyme Complex ◽  
Regeneration System ◽  
Regeneration Rate ◽  
Leucine Dehydrogenase ◽  
Fusion Enzyme ◽  
Space Time Yield

Abstract Background Biosynthesis of l-tert-leucine (l-tle), a significant pharmaceutical intermediate, by a cofactor regeneration system friendly and efficiently is a worthful goal all the time. The cofactor regeneration system of leucine dehydrogenase (LeuDH) and glucose dehydrogenase (GDH) has showed great coupling catalytic efficiency in the synthesis of l-tle, however the multi-enzyme complex of GDH and LeuDH has never been constructed successfully. Results In this work, a novel fusion enzyme (GDH–R3–LeuDH) for the efficient biosynthesis of l-tle was constructed by the fusion of LeuDH and GDH mediated with a rigid peptide linker. Compared with the free enzymes, both the environmental tolerance and thermal stability of GDH–R3–LeuDH had a great improved since the fusion structure. The fusion structure also accelerated the cofactor regeneration rate and maintained the enzyme activity, so the productivity and yield of l-tle by GDH–R3–LeuDH was all enhanced by twofold. Finally, the space–time yield of l-tle catalyzing by GDH–R3–LeuDH whole cells could achieve 2136 g/L/day in a 200 mL scale system under the optimal catalysis conditions (pH 9.0, 30 °C, 0.4 mM of NAD+ and 500 mM of a substrate including trimethylpyruvic acid and glucose). Conclusions It is the first report about the fusion of GDH and LeuDH as the multi-enzyme complex to synthesize l-tle and reach the highest space–time yield up to now. These results demonstrated the great potential of the GDH–R3–LeuDH fusion enzyme for the efficient biosynthesis of l-tle.

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