Solid‐state enzyme deactivation in air and in organic solvents

Toscano, Giuseppe; Pirozzi, Domenico; Maremonti, Michele; Greco, Guido

doi:10.1002/bit.260440604

Cited by 12 publications

(6 citation statements)

References 25 publications

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“…Therefore, thermal inactivation yields a final, unconditionally stable enzyme structure, whose activity is unaffected by further exposure to relatively high temperature (up to 80 °C). This result is consistent with those observed on different enzymes, though the final activity attained is a much higher fraction of that pertaining to the native enzyme (Toscano et al, 1994).…”

Section: "~supporting

confidence: 92%

Characterisation of 2,5-diketo-D-gluconic acid reductase from Corynebacterium sp.

1996

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2,5-diketo-D-gluconic acid reductase, that converts 2,5-diketo-D-gluconic acid into 2-keto-L-gulonic acid (the direct precursor of vitamin C) was extracted and purified from Corynebacterium sp.. The enzyme was characterised in terms of kinetic parameters, molecular weight and isoelectric point. Enzyme stability at different operating temperatures was investigated, as well. INTRODUCTIONL-ascorbic acid (vitamin C) is produced on an industrial scale by the ReichsteinGruessner synthesis (Reichstein and Gruessner, 1934). One fermentative step and four chemical steps are required, to convert the substrate (either D-glucose or sorbitol) with a yield of about 50 %. Several alternative processes have been developed in order to increase this yield. Most of them consist in fermentations and are based on the production of 2-keto-L-gulonic acid (2-KLG), the direct precursor of L-ascorbic acid. Sonoyama et al. (1982) proposed a two-stage fermentation for 2-KLG production from glucose. The substrate is converted to 2,5-diketo-D-gluconic acid (2,5-DKG) by a mutant of Erwinia herbicola. 2,5-DKG is then reduced to 2-KLG by a mutant of Corynebacterium sp. 2,5-DKG can be produced by a large variety of different microorganisms with high yields (Wakisaka, 1964;Buse et al., 1990;Qazi et al., 1991). The reduction of 2,5-DKG to 2-KLG is catalysed by a single NADPH-dependent reductase, present in the cytosol of Corynebacterium sp. and it is characterised by relatively low yields. The latter could be attributed to mass-transfer limitations. In order to overcome these difficulties, the use of a purified enzyme might be envisaged. Basic purpose of this work is the extraction, purification and characterisation of 2,5-DKG reductase from Corynebacterium sp., with specific reference to protein structure and its thermal stability. The results are quite encouraging in view of a possible application of the protein in a cell-free system for 2-KLG production.

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confidence: 92%

Characterisation of 2,5-diketo-D-gluconic acid reductase from Corynebacterium sp.

1996

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“…But, in the absence of starch, the residual enzyme activity was decreased by addition of ethanol. Toscano et al [14] in their study mention that the protein dynamics are unaffected by anhydrous hydrophobic solvents, whereas water addition and hydrophilic solvents increase enzyme flexibility. They also indicated the activity-increasing effect of the presence of substrate, inhibitors or substrate-like compounds in the protein solution.…”

Section: Effect Of Ethanol On α-Amylase Activity and Hydrolysismentioning

confidence: 97%

σ-Amylase inactivation during corn starch hydrolysis process

Apar

Özbek

2004

Process Biochemistry

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“…Enzymes suffer irreversible deactivation from a variety of causes, such as pH, temperature, ionic strength, and the presence of toxic impurities. There have been many studies on enzyme deactivation (Chen and Wu, 1987;Erarslan and Kocer, 1992;Palazzi and Converti, 1999;Simon et al, 1986;Toscano et al, 1994). In this work, enzyme activity was assumed to be an exponentially decaying function, as shown in Eq.…”

Section: Effects Of Enzyme Deactivation On Enzyme Effective Enantiosementioning

confidence: 99%

Mass‐transfer limitations for immobilized enzyme‐catalyzed kinetic resolution of racemate in a fixed‐bed reactor

Xiu

Jiang

2001

Biotech & Bioengineering

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A mathematical model has been developed for immobilized enzyme-catalyzed kinetic resolution of racemate in a fixed-bed reactor in which the enzyme-catalyzed reaction (the irreversible uni-uni competitive Michaelis-Menten kinetics is chosen as an example) was coupled with intraparticle diffusion, external mass transfer, and axial dispersion. The effects of mass-transfer limitations, competitive inhibition of substrates, deactivation on the enzyme effective enantioselectivity, and the optical purity and yield of the desired product are examined quantitatively over a wide range of parameters using the orthogonal collocation method. For a first-order reaction, an analytical solution is derived from the mathematical model for slab-, cylindrical-, and spherical-enzyme supports. Based on the analytical solution for the steady-state resolution process, a new concise formulation is presented to predict quantitatively the mass-transfer limitations on enzyme effective enantioselectivity and optical purity and yield of the desired product for a continuous steady-state kinetic resolution process in a fixed-bed reactor.

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Solid‐state enzyme deactivation in air and in organic solvents

Cited by 12 publications

References 25 publications

Characterisation of 2,5-diketo-D-gluconic acid reductase from Corynebacterium sp.

Characterisation of 2,5-diketo-D-gluconic acid reductase from Corynebacterium sp.

σ-Amylase inactivation during corn starch hydrolysis process

Mass‐transfer limitations for immobilized enzyme‐catalyzed kinetic resolution of racemate in a fixed‐bed reactor

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