Home About us Contact
|
Home About us Contact | ||
|
|
||
Manganese Peroxidase (manganese + peroxidase)
Selected AbstractsOxidative Degradation of Azo Dyes by Manganese Peroxidase under Optimized ConditionsBIOTECHNOLOGY PROGRESS, Issue 2 2003I. Mielgo The application of enzyme-based systems in waste treatment is unusual, given that many drawbacks are derived from their use, including low efficiency, high costs and easy deactivation of the enzyme. The goal of this study is the development of a degradation system based on the use of the ligninolytic enzyme manganese peroxidase (MnP) for the degradation of azo dyes. The experimental work also includes the optimization of the process, with the objective of determining the influence of specific physicochemical factors, such as organic acids, H2O2 addition, Mn2+ concentration, pH, temperature, enzyme activity and dye concentration. A nearly total decolorization was possible at very low reaction times (10 min) and at high dye concentration (up to 1500 mg L,1). A specific oxidation capacity as high as 10 mg dye degraded per unit of MnP consumed was attained for a decolorization higher than 90%. Among all, the main factor affecting process efficiency was the strategy of H2O2 addition. The continuous addition at a controlled flow permitted the progressive participation of H2O2 in the catalytic cycle through a suitable regeneration of the oxidized form of the enzyme, which enhanced both the extent and the rate of decolorization. It was also found that, in this particular case, the presence of a chelating organic acid (e.g., malonic) was not required for an effective operation. Probably, Mn3+ was chelated by the dye itself. The simplicity and high efficiency of the process open an interesting possibility of using of MnP for solving other environmental problems. [source] Effects of cadmium on manganese peroxidaseFEBS JOURNAL, Issue 6 2000Competitive inhibition of MnII oxidation, thermal stabilization of the enzyme Inhibition of manganese peroxidase by cadmium was studied under steady-state and transient-state kinetic conditions. CdII is a reversible competitive inhibitor of MnII in the steady state with Ki , 10 µm. CdII also inhibits enzyme-generated MnIII,chelate-mediated oxidation of 2,6-dimethoxyphenol with Ki , 4 µm. CdII does not inhibit direct oxidation of phenols such as 2,6-dimethoxyphenol or guaiacol (2-methoxyphenol) in the absence of MnII. CdII alters the heme Soret on binding manganese peroxidase and exhibits a Kd , 8 µm, similar to Mn (Kd , 10 µm). Under transient-state conditions, CdII inhibits reduction of compound I and compound II by MnII at pH 4.5. However, CdII does not inhibit formation of compound I nor does it inhibit reduction of the enzyme intermediates by phenols in the absence of MnII. Kinetic analysis suggests that CdII binds at the MnII -binding site, preventing oxidation of MnII, but does not impair oxidation of substrates, such as phenols, which do not bind at the MnII -binding site. Finally, at pH 4.5 and 55 °C, MnII and CdII both protect manganese peroxidase from thermal denaturation more efficiently than CaII, extending the half-life of the enzyme by more than twofold. Furthermore, the combination of half MnII and half CdII nearly quadruples the enzyme half-life over either metal alone or either metal in combination with CaII. [source] Laccase production by Phanerochaete chrysosporium, an artefact caused by Mn(III)?LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2001H. Podgornik Aims: The possibility of laccase production by Phanerochaete chrysosporium was studied. Methods and Results: A relatively high initial Mn(II) concentration (1,4 mM) in the growth medium leads to the development of reddish-brown coloration and intensive oxidation of 2.2,-azino-bis(3-etilbenz-tiazolin-6-sulfonate) (ABTS). The peak of ABTS oxidation was obtained approximately 1 day after the peak of MnP activity. Conclusions: ABTS oxidation was not caused by manganese peroxidase (MnP) nor by laccase but was the consequence of the action of Mn(III) which was stabilised in the growth medium. Decomposition of the complex took place after the biomass was removed from the growth medium and especially after the aeration of the culture was interrupted. Significance and Impact of the Study: Mn(III) seems to be the cause of false positive laccase reactions. More reliable data on MnP activity can be obtained if the complex is decomposed by the fungus before MnP activity is measured in the medium. [source] Expression of a Phanerochaete chrysosporium Manganese Peroxidase Gene in the Yeast Pichia pastorisBIOTECHNOLOGY PROGRESS, Issue 5 2003Lina Gu A gene encoding manganese peroxidase (mnp1) from Phanerochaetechrysosporium was cloned downstream of a constitutive glyceraldehyde-3-phosphate dehydrogenase promoter in the methylotrophic yeast Pichia pastoris. Three different expression vectors were constructed: pZBMNP contains the native P.chrysosporium fungal secretion signal, p,AMNP contains an ,-factor secretion signal derived from Saccharomyces cerevisiae, and pZBIMNP has no secretion signal and was used for intracellular expression. Both the native fungal secretion signal sequence and ,-factor secretion signal sequence directed the secretion of active recombinant manganese peroxidase (rMnP) from P. pastoris transformants. The majority of the rMnP produced by P. pastoris exhibited a molecular mass (55,100 kDa) considerably larger than that of the wild-type manganese peroxidase (wtMnP, 46 kDa). Deletion of the native fungal secretion signal yielded a molecular mass of 39 kDa for intracellular rMnP in P. pastoris. Treatment of the secreted rMnP with endoglycosidase H (Endo H) resulted in a considerable decrease in the mass of rMnP, indicating N-linked hyperglycosylation. Partially purified rMnP showed kinetic characteristics similar to those of wtMnP. Both enzymes also had similar pH stability profiles. Addition of exogenous MnII, CaII, and FeIII conferred additional thermal stability to both enzymes. However, rMnP was slightly less thermostable than wtMnP, which demonstrated an extended half-life at 55 °C. [source] Oxidative Degradation of Azo Dyes by Manganese Peroxidase under Optimized ConditionsBIOTECHNOLOGY PROGRESS, Issue 2 2003I. Mielgo The application of enzyme-based systems in waste treatment is unusual, given that many drawbacks are derived from their use, including low efficiency, high costs and easy deactivation of the enzyme. The goal of this study is the development of a degradation system based on the use of the ligninolytic enzyme manganese peroxidase (MnP) for the degradation of azo dyes. The experimental work also includes the optimization of the process, with the objective of determining the influence of specific physicochemical factors, such as organic acids, H2O2 addition, Mn2+ concentration, pH, temperature, enzyme activity and dye concentration. A nearly total decolorization was possible at very low reaction times (10 min) and at high dye concentration (up to 1500 mg L,1). A specific oxidation capacity as high as 10 mg dye degraded per unit of MnP consumed was attained for a decolorization higher than 90%. Among all, the main factor affecting process efficiency was the strategy of H2O2 addition. The continuous addition at a controlled flow permitted the progressive participation of H2O2 in the catalytic cycle through a suitable regeneration of the oxidized form of the enzyme, which enhanced both the extent and the rate of decolorization. It was also found that, in this particular case, the presence of a chelating organic acid (e.g., malonic) was not required for an effective operation. Probably, Mn3+ was chelated by the dye itself. The simplicity and high efficiency of the process open an interesting possibility of using of MnP for solving other environmental problems. [source] Olive Oil Mill Waste Waters Decoloration and Detoxification in a Bioreactor by the White Rot Fungus Phanerochaeteflavido-albaBIOTECHNOLOGY PROGRESS, Issue 3 2002P. Blánquez Olive oil mill wastewater (OMW) is produced as waste in olive oil extraction. With the purpose of treating this highly polluting waste, a number of experiments were conducted in a laboratory-scale bioreactor with the white rot fungus Phanerochaete flavido-alba ( P.flavido-alba). It is known that this fungus is capable of decolorizing OMW in static or semistatic cultures at Erlenmeyer scale and at 30 °C. The objective of this work was to prove that P. flavido-alba could decolorize OMW in submerged cultures and that it is capable of reducing OMW toxicity at room temperature (25 °C) and in a laboratory-scale bioreactor. In the experiments conducted, manganese peroxidase (MnP) and laccase enzymes were detected; however, unlike other studies, lignin peroxidase was not found to be present. Decoloration obtained after treatment was 70%. The reduction of aromatic compounds obtained was 51%, and the toxicity of the culture medium was reduced by up to 70%. We can therefore state that P.flavido-alba is capable of reducing important environmental parameters of industrial effluents and that prospects are positive for the use of this process at a larger scale, even when working at room temperature. [source] | ||||||||||