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Characterizing Biogenic MnOx Produced by Pseudomonas putida MnB1 and Its Catalytic Activity towards Water Oxidation
Elisa Morales1, Sarah E Shaner2, Kari L Stone1
1Department of Chemistry, Lewis University, Romeoville, IL 60446, USA.
Abstract:
Mn-oxidizing microorganisms oxidize environmental Mn(II), producing Mn(IV) oxides. Pseudomonas putida MnB1 is a widely studied organism for the oxidation of manganese(II) to manganese(IV) by a multi-copper oxidase. The biogenic manganese oxides (BMOs) produced by MnB1 and similar organisms have unique properties compared to non-biological manganese oxides. Along with an amorphous, poorly crystalline structure, previous studies have indicated that BMOs have high surface areas and high reactivities. It is also known that abiotic Mn oxides promote oxidation of organics and have been studied for their water oxidation catalytic function. MnB1 was grown and maintained and subsequently transferred to culturing media containing manganese(II) salts to observe the oxidation of manganese(II) to manganese(IV). The structures and compositions of these manganese(IV) oxides were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, inductively coupled plasma optical emission spectroscopy, and powder X-ray diffraction, and their properties were assessed regarding catalytic functionality towards water oxidation in comparison to abiotic acid birnessite. Water oxidation was accomplished through the whole-cell catalysis of MnB1, the results for which compare favorably to the water-oxidizing ability of abiotic Mn(IV) oxides.
Insights
Pseudomonas putida MnB1 biogenic manganese oxides exhibit high reactivity and catalytic potential for water oxidation, comparable to abiotic manganese oxides. This research highlights the unique properties of biologically produced manganese oxides.
Area of Science:
- Environmental Microbiology
- Biogeochemistry
- Catalysis
Background:
- Mn-oxidizing microorganisms transform soluble Mn(II) into insoluble Mn(IV) oxides.
- Biogenic manganese oxides (BMOs) possess distinct structural and reactive properties compared to abiotic counterparts.
- Abiotic manganese oxides are known catalysts for organic oxidation and water oxidation.
Purpose of the Study:
- To characterize the manganese(IV) oxides produced by Pseudomonas putida MnB1.
- To assess the catalytic functionality of these BMOs for water oxidation.
- To compare the water-oxidizing capabilities of BMOs with abiotic acid birnessite.
Main Methods:
- Culturing of Pseudomonas putida MnB1 in manganese(II)-containing media.
- Characterization of BMOs using scanning electron microscopy, energy dispersive X-ray spectroscopy, ICP-OES, and powder X-ray diffraction.
- Assessment of whole-cell catalysis for water oxidation.
Main Results:
- Pseudomonas putida MnB1 effectively oxidized manganese(II) to manganese(IV) oxides.
- The BMOs exhibited amorphous, poorly crystalline structures with high surface areas and reactivity.
- Whole-cell catalysis by MnB1 demonstrated favorable water-oxidizing ability compared to abiotic acid birnessite.
Conclusions:
- Biogenic manganese oxides produced by Pseudomonas putida MnB1 are effective catalysts for water oxidation.
- BMOs present a viable alternative to abiotic manganese oxides for catalytic applications.
- Further research into microbial manganese oxides can unlock novel catalytic functionalities.
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