Stereoselective bioconversions in continuously operated fixed bed reactors: Modeling and process optimization

Indlekofer, Michael; Brotz, Friedrich; Bauer, Andréa Carla; Reuß, Matthias

doi:10.1002/(sici)1097-0290(19961120)52:4<459::aid-bit2>3.0.co;2-o

Cited by 38 publications

(35 citation statements)

References 24 publications

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“…The stability tests performed in the different experimental conditions show clearly the departure of inactivation kinetics from first order, demonstrating the inadequacy of the linear-kinetics assumption for lipase inactivation in continuous reactors (Indlekofer et al, 1996). Further studies are necessary to perform detailed physico-mathematical modeling of lipase inactivation phenomena in continuous reactors.…”

Section: Discussionmentioning

confidence: 99%

“…Where organic solvents are used, the quantities of these that must be handled presents another limitation, particularly in terms of safety. Furthermore, little information is available on the operational stability of lipases in continuous reactors (Forssel et al, 1993;Indlekofer et al, 1996;Wisdom et al, 1987). In some cases, enzyme poisoning produced by impurities contained in commercial feedstocks is indicated as a possible inactivation mechanism, although a detailed analysis still is lacking.…”

Section: Introductionmentioning

confidence: 96%

“…However, preliminary experiments to design nonaqueous industrial bioreactors are often made using batch reactors. This is because the organic-resistant continuous reactors described to date are complicated and expensive, and require substantial quantities of feed during long-term operation (Balcao et al, 1996;Colombié et al, 1998;Indlekofer et al, 1996;Ison et al, 1994;Mazzotti et al, 1997;Mensah et al, 1998;Rosell et al, 1996;Ujang et al, 1997). Where organic solvents are used, the quantities of these that must be handled presents another limitation, particularly in terms of safety.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Development of small-size tubular-flow continuous reactors for the analysis of operational stability of enzymes in low-water systems

Pirozzi

Halling

2000

Biotechnol. Bioeng.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Development of small-size tubular-flow continuous reactors for the analysis of operational stability of enzymes in low-water systems

Pirozzi

Halling

2000

Biotechnol. Bioeng.

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“…Models based on complex mechanisms contain a number of parameters that exceed the possibility of their experimental determination; therefore, models based on simple ®rst-order kinetics or two-stage series mechanisms have been frequently used, despite its obvious simpli®ca-tion [11,12,13]. Reactor design considering enzyme inactivation frequently disregard the effect of substrates and products on inactivation rate constants [5,14,15,16] or is based on global inactivation rate constants determined under particular operating conditions [3,6,17], not allowing to discriminate the individual modulation effects. Only in a few cases, protection by substrate has been evaluated and considered for reactor design [2,18,19,20] and, even in fewer, product modulation has been included [21,22].…”

Section: List Of Symbolsmentioning

confidence: 99%

Design of immobilized enzyme reactors for the continuous production of fructose syrup from whey permeate

Illanes

Wilson

Raiman

1999

Bioprocess Engineering

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Biocatalyst inactivation is inherent to continuous operation of immobilized enzyme reactors, meaning that a strategy must exist to ensure a production of uniform quality and constant throughput. Flow rate can be pro®led to compensate for enzyme inactivation maintaining substrate conversion constant. Throughput can be maintained within speci®ed margins of variation by using several reactors operating in parallel but displaced in time. Enzyme inactivation has been usually modeled under non-reactive conditions, leaving aside the effect of substrate and products on enzyme stability. Results are presented for the design of enzyme reactors under the above operational strategy, considering ®rst-order biocatalyst inactivation kinetics modulated by substrate and products. The continuous production of hydrolyzed-isomerized whey permeate with immobilized lactase and glucose isomerase in sequential packed-bed reactors is used as a case study. Kinetic and inactivation parameters for immobilized lactase have been determined by the authors; those for glucose isomerase were taken from the literature. Except for lactose, all other substrates and products were positive modulators of enzyme stability. Reactor design was done by iteration since it depends on enzyme inactivation kinetics. Reactor performance was determined based on a preliminary design considering non-modulated ®rst-order inactivation kinetics and confronted to such pattern. The new pattern of inactivation was then used to redesign the reactor and the process repeated until reactor performance (considering modulation) matched the assumed pattern of inactivation. Convergence was very fast and only two iterations were needed. List of symbolsA m 2 cross sectional area of reactor a kat/kg speci®c activity of catalyst D m reactor diameter d s total operation time for each reactor cycle E kat enzyme activity e kat/m 3 volumetric enzyme activity F m 3 /s total process¯ow rate F 0i m 3 /s initial feed¯ow-rate to each reactor H number of enzyme half-lives used in the reactor H b m catalyst bed height H R m reactor height K eq kg-mole/m 3 equilibrium constant of glucose isomerization to fructose ( V G K F aV F K G ) K F kg-mole/m 3 IGI Michaelis constant for fructose K G kg-mole/m 3 IGI Michaelis constant for glucose K L kg-mole/m 3 CIL Michaelis constant for lactose K P kg-mole/m 3 CIL competitive inhibition constant for galactose k cat catalytic rate constant for lactose hydrolysis k H cat catalytic rate constant for glucose isomerization k D s À1 ®rst-order inactivation rate constant under no modulation k DJ s À1 ®rst-order inactivation rate constant under modulation by J M kg catalyst mass N 1 ± CIL global modulation factor N 2 ± IGI global modulation factor N R ± number of reactors n L ± CIL modulation factor by lactose n P ± CIL modulation factor by galactose n G ± IGI modulation factor by glucose n F ± IGI modulation factor by fructose R F ± ratio of minimum to maximum ow rate s 0 kg-mole/m 3 feed lactose concentration t s time of operation t s s time interval between e...

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“…Enzyme-catalyzed reactions are becoming increasingly important for stereoselective and regioselective transformations of fine chemicals (1)(2)(3)(4)(5)(6). Although early work had focused on aqueous-phase transformations, the relatively recent discovery that many enzymes are active in organic solvents has expanded the scope of biocatalysis to substrates and products that have little or no solubility in water.…”

Section: Introductionmentioning

confidence: 99%

Regioselective Enzymatic Diol Esterification in Batch and Fixed‐Bed Adsorptive Reactors: Experiments and Modeling

Migliorini

Meissner

Mazzotti

et al. 2000

Biotechnology Progress

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The dynamic behavior of batch and fixed-bed adsorptive reactors is studied for the enzyme-catalyzed regioselective esterification of propionic acid and 2-ethyl-1,3-hexanediol in hexane. The reaction is equilibrium-limited with an apparent equilibrium constant of 0.6 +/- 0.1 at 22 degrees C. Moreover, accumulation of water produced in the reaction onto the biocatalyst causes a decrease in the catalytic activity. As a result, improvements in both reaction rate and final conversion can be achieved by operating in an adsorptive-reactor mode. Control of water in the reactor is achieved with a catalytically inert ion-exchange resin in Na-form. The resin prevents an excessive accumulation of water on the biocatalyst and reduces equilibrium limitations. The thermodynamic activity of water is identified as a key parameter for the design of such reactors. A mathematical model capable of predicting the water activity as a function of the varying concentrations of reactants and products is thus developed and found to successfully predict the experimental behavior observed in laboratory reactors. Substantial improvements in performance predicted by the model are seen experimentally in batch reactions and during the transient operation of continuous-flow fixed-bed reactors combining adsorptive and catalytic functions.

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Stereoselective bioconversions in continuously operated fixed bed reactors: Modeling and process optimization

Cited by 38 publications

References 24 publications

Development of small-size tubular-flow continuous reactors for the analysis of operational stability of enzymes in low-water systems

Development of small-size tubular-flow continuous reactors for the analysis of operational stability of enzymes in low-water systems

Design of immobilized enzyme reactors for the continuous production of fructose syrup from whey permeate

Regioselective Enzymatic Diol Esterification in Batch and Fixed‐Bed Adsorptive Reactors: Experiments and Modeling

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