1,721,001 research outputs found
Advantages of continuous over batch reactors for the kinetic analysis of enzymes inhibited by unknown substrate impurity
No full textA new experimental technique, employing a continuous stirred-tank reactor, for studying enzyme kinetics in the presence of inhibitor-contaminated substrate is described. The proposed method is simulated mathematically for competitive, uncompetitive, and mixed-type noncompetitive inhibition. The step-by-step experimental procedure is described, as is the necessary data analysis for determining the kinetic parameters. Differences in system response for enzyme inhibition by excess substrate and by an impurity are illustrated, and a stability analysis of the system is performed
Green recovery of platform chemicals from hydrothermal carbonization process water
Full text linkThis study explores the side-recovery of platform chemicals in the hydrothermal carbonization waste-to-energy
chain. Up to 90 % of target chemicals, furfural and 5-hydroxymethylfurfural, were green extracted from the
process waters using the hydrophobic deep eutectic solvent decanoic acid/thymol. Wheat straw and rice husk
reacted (1/4 solid/water ratio) for up to 120 min and at 180 and 230 ◦C. The dissolved chemicals built up to 5.9
g/L, accounting for 12 % of the total carbon. Extractions from the process waters and those from reference
solutions behaved similarly. The solvent affinity toward furfural is 3.5 times higher than that of 5-hydroxymethylfurfural.
The aqueous raffinates chromatographic outline demonstrated the recyclability for prosecuting
the HTC. Focused experiments mimicked the functioning of an industrial cascade of two crosscurrent mixer
settlers. Extraction yields were 90.7 and 65.8 % for furfural and 5-hydroxymethylfurfural. The counterflow
arrangement, simulated by the Kremser method, gave corresponding higher yields, 96.9 and 73.4 %,
respectively
Immobilized enzyme tri-phase reactors for oxidation of cephalosporin C
No full textThe enzymatic oxidation of Cephalosporin C (CEPHC) was catalyzed by D-aminoacid oxidase, from the red yeast Trigonopsis variabilis, immobilized on Duolite A365. The study was performed in two different three phase bioreactors, gas-liquid-solid (immobilized enzyme): the fluidized-bed batch reactor, fed continuously with oxygen and discontinuously with CEPHC, and the UF-membrane reactor continuously fed with both substrates. Only the first reactor allowed significant product yield (> 70%) while the second was a very useful tool for laboratory investigation of both bioconversion kinetics and enzyme stability. Optimum reaction temperature was 15°C for the control of CEPHC spontaneous degradation (roughly 15% in 30 h), and enzyme deactivation (half-life greater than 30 h). Immobiliza tion improved (one order of magnitude longer half-life) enzyme resistance to mechanical stresses induced by liquid stirring and gas bubbling. Roughly 0.04 g of CEPHC was adsorbed per gram of enzyme carrier. The limiting step in oxygen transfer was the gas to liquid transport. In order to attain kinetic control of the bioconversion the mildest conditions were atmospheric gas pressure and oxygen flow rate equal to 2 x 10-2 NmLs per mL of liquid phase
DESIGN AND PERFORMANCES OF A PILOT REACTOR FOR ENZYMATIC HYDROLYSIS OF LIGNOCELLULOSIC BIOMASS
No full textExploratory study on separation of water-ethanol vapour mixtures:selective adsorption on natural zeolites
No full textStudying enzyme-catalized depolymerizations in continuous reactors
No full textThe models of Ohmine et al. and Sendra and Carbonell for the enzymatic breakdown of polymers in batch reactors were modified to describe the depolymerization in continuous reactors. The model equations give the time course of the product concentration in the reactor permeate and that of the total product. The model predictions were compared with the experimental results for the hydrolysis of polygalacturonic acid in ultrafiltration membrane reactors. The amount of enzyme in the reactor varied from 0.18 to 1.80 mg. The residence time (100 min), temperature (25 °C), and membrane molecular cutoff (30 kDa) were maintained constant in the experiments. The system response was sensitive to the kinetic pattern of the enzymatic attack and was in reasonable agreement only with the predictions of the model based on the kinetic assumption made by Sendra and Carbonell. An induction period and an asymptotic amount of product were detected, which cannot be explained by the model of Ohmine et al. Copyright © 2001 American Chemical Societ
"Thermodynamic analysis of the stability enhancement of acid phosphatase by gel immobilization in proteins"
No full text- …
