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- Osipov, Evgeny, et al.
(författare)
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Effect of the L499M mutation of the ascomycetous Botrytis aclada laccase on redox potential and catalytic properties
- 2014
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Ingår i: Acta Crystallographica Section D. - : International Union of Crystallography. - 0907-4449 .- 1399-0047. ; 70:11, s. 2913-2923
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Tidskriftsartikel (refereegranskat)abstract
- Laccases are members of a large family of multicopper oxidases that catalyze the oxidn. of a wide range of org. and inorg. substrates accompanied by the redn. of dioxygen to water. These enzymes contain four Cu atoms per mol. organized into three sites: T1, T2 and T3. In all laccases, the T1 copper ion is coordinated by two histidines and one cysteine in the equatorial plane and is covered by the side chains of hydrophobic residues in the axial positions. The redox potential of the T1 copper ion influences the enzymic reaction and is detd. by the nature of the axial ligands and the structure of the second coordination sphere. In this work, the laccase from the ascomycete Botrytis aclada was studied, which contains conserved Ile491 and nonconserved Leu499 residues in the axial positions. The three-dimensional structures of the wild-type enzyme and the L499M mutant were detd. by X-ray crystallog. at 1.7 Å resoln. Crystals suitable for X-ray anal. could only be grown after deglycosylation. Both structures did not contain the T2 copper ion. The catalytic properties of the enzyme were characterized and the redox potentials of both enzyme forms were detd.: E 0 = 720 and 580 mV for the wild-type enzyme and the mutant, resp. Since the structures of the wild-type and mutant forms are very similar, the change in the redox potential can be related to the L499M mutation in the T1 site of the enzyme.
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- Rezić, Tonci, et al.
(författare)
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Biosorption of Mn(II), Co(II) and Cr(VI) in a horizontal rotating tubular bioreactor : Experiments and evaluation of the integral bioprocess model
- 2014
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Ingår i: Brazilian journal of chemical engineering. - : Springer. - 0104-6632 .- 1678-4383. ; 31:3, s. 799-814
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Tidskriftsartikel (refereegranskat)abstract
- In this research, a multi heavy metals removal process with mixed microbial culture was examined in a horizontal rotating tubular bioreactor (HRTB) with different combinations of process parameters. Three metals were selected as examples of cations (manganese and cobalt) and oxy-anion (hexavalent chromium). Hydrodynamic conditions and biomass sorption capacity in the HRTB had the main impact on the heavy metals removal efficiencies, which were for Mn2+ 87.0-93.6%, Co2+ 89.0-95.7% and Cr6+ 99.7-100%, respectively. For the bioprocess description in the HRTB, the integral bioprocess model that combines hydrodynamics, mass transfer and kinetics was used. This model was evaluated for the new experimental conditions and average variances between experimental and simulated data were in the range of 0.12 - 3.21.10(-3). The results obtained clearly show that the integral bioprocess model is able to describe the heavy metal removal process in the HRTB.
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