Different effects of microwave energy and conventional heat on the activity of a thermophilic �-galactosidase fromBacillus acidocaldarius

Cara, Francesco La; Scarffi, Maria Rosaria; D’Auria, Sabato; Massa, Rita; d’Ambrosio, Guglielmo; Franceschetti, Giorgio; Rossi, Mos È; Rosa, Mario De

doi:10.1002/(sici)1521-186x(1999)20:3<172::aid-bem3>3.0.co;2-h

Cited by 22 publications

(9 citation statements)

References 15 publications

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“…However, with same solvent systems, earlier experiments [18] found that the nonthermal effect of microwave was varied with different initial substrate concentrations. La Cara [11] also tested the effect of microwave irradiation (f010.4 GHz) on a thermostable enzyme, showing that irreversible inactivation was induced and microwave effects disappeared at the enzyme concentrations above 50 μg/mL. These findings indicate that the nonthermal effect may not appear in any range of substrate concentration, regardless the solvent used; therefore, a suitable range of initial substrate concentrations has to be decided.…”

Section: Resultssupporting

confidence: 89%

“…While in reactions accelerated by microwave, substrates and solvents absorb microwave energy with different capacities, which caused varied nonthermal effects. Some nonthermal effects have been claimed such as the affinity changing of the substrate to the enzyme and the thermal stability of enzyme in organic solvent under microwave irradiation [10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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Nonthermal Effect of Microwave Irradiation in Nonaqueous Enzymatic Esterification

Wan

Sun

et al. 2012

Appl Biochem Biotechnol

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Microwave has nonthermal effects on enzymatic reactions, mainly caused by the polarities of the solvents and substrates. In this experiment, a model reaction with caprylic acid and butanol that was catalyzed by lipase from Mucor miehei in alkanes or arenes was employed to investigate the nonthermal effect in nonaqueous enzymatic esterification. With the comparison of the esterification carried by conventional heating and consecutive microwave irradiation, the positive nonthermal effect on the initial reaction rates was found substrate concentration-dependent and could be vanished ostensibly when the substrate concentration was over 2.0 mol L(-1). The polar parameter log P well correlates the solvent polarity with the microwave effect, comparing to dielectric constant and assayed solvatochromic solvent polarity parameters. The log P rule presented in conventional heating-enzymatic esterification still fits in the microwaved enzymatic esterification. Alkanes or arenes with higher log P provided positive nonthermal effect in the range of 2 ≤ log P ≤ 4, but yielded a dramatic decrement after log P = 4. Isomers of same log P with higher dielectric constant received stronger positive nonthermal effect. With lower substrate concentration, the total log P of the reaction mixture has no obvious functional relation with the microwave effect.

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Section: Resultssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Nonthermal Effect of Microwave Irradiation in Nonaqueous Enzymatic Esterification

Wan

Sun

et al. 2012

Appl Biochem Biotechnol

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“…Modest microwave radiation (10 W) at 60 °C accelerated the inactivation, which occurred within the first five minutes. This non‐thermal microwave effect has been reported for other classes of enzymes, along with a proof that the electromagnetic field can cause protein unfolding within few minutes . Fluorescence spectroscopy and CD studies have confirmed that microwaves induce structural rearrangements not associated with temperature .…”

Section: Resultssupporting

confidence: 67%

Investigating the Role of Conformational Effects on Laccase Stability and Hyperactivation under Stress Conditions

et al. 2015

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Fungal laccase from Steccherinum ochraceum 1833 displays remarkable stability under different harsh conditions: organic/buffer mixtures, thermal treatment, and microwave radiation. The behavior is particularly significant in the light of the sharp inactivation observed for two different fungal laccases. Laccase from S. ochraceum 1833 also displays hyperactivation under mild thermal treatment (60 °C). Molecular dynamics simulations at 80 °C explained how this laccase retains the geometry of the electron transfer pathway, thereby assuring electron transfer through the copper ions and thus maintaining its catalytic activity at high temperature. Spectroscopic studies revealed that the thermal activation corresponds to specific conformational changes in the protein. The results indicate that this laccase is potentially applicable under denaturing conditions that might be beneficial for the biotransformation of recalcitrant substrates.

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“…Thermophilic enzymes appear to be more suitable for reactions under MWI due to their higher thermostablity. However, they have also been found to be inactivated by MWI [ 22 , 23 , 24 ] at temperatures where they were highly stable under conventional thermal heating. In contrast, CelB from Pyrococcus furiosus showed hydrolytic activity under MWI at ambient temperatures in comparison to conventional thermal heating being not active [ 12 ].…”

Section: Introductionmentioning

confidence: 99%

Microwave-Assisted Synthesis of Glycoconjugates by Transgalactosylation with Recombinant Thermostable β-Glycosidase from Pyrococcus

Henze¹,

Merker²,

Elling³

2016

IJMS

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The potential of the hyperthermophilic β-glycosidase from Pyrococcus woesei (DSM 3773) for the synthesis of glycosides under microwave irradiation (MWI) at low temperatures was investigated. Transgalactosylation reactions with β-N-acetyl-d-glucosamine as acceptor substrate (GlcNAc-linker-tBoc) under thermal heating (TH, 85 °C) and under MWI at 100 and 300 W resulted in the formation of (Galβ(1,4)GlcNAc-linker-tBoc) as the main product in all reactions. Most importantly, MWI at temperatures far below the temperature optimum of the hyperthermophilic glycosidase led to higher product yields with only minor amounts of side products β(1,6-linked disaccharide and trisaccharides). At high acceptor concentrations (50 mM), transgalactosylation reactions under MWI at 300 W gave similar product yields when compared to TH at 85 °C. In summary, we demonstrate that MWI is useful as a novel experimental set-up for the synthesis of defined galacto-oligosaccharides. In conclusion, glycosylation reactions under MWI at low temperatures have the potential as a general strategy for regioselective glycosylation reactions of hyperthermophilic glycosidases using heat-labile acceptor or donor substrates.

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Different effects of microwave energy and conventional heat on the activity of a thermophilic �-galactosidase fromBacillus acidocaldarius

Cited by 22 publications

References 15 publications

Nonthermal Effect of Microwave Irradiation in Nonaqueous Enzymatic Esterification

Nonthermal Effect of Microwave Irradiation in Nonaqueous Enzymatic Esterification

Investigating the Role of Conformational Effects on Laccase Stability and Hyperactivation under Stress Conditions

Microwave-Assisted Synthesis of Glycoconjugates by Transgalactosylation with Recombinant Thermostable β-Glycosidase from Pyrococcus

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