Methane-Consuming
Bacteria
Could Be the Future of Fuel
Discovery illuminates how bacteria turn methane gas into liquid methanol
By Amanda Morris
Northwestern University – May 9, 2019 -- Known for their ability to remove methane from the environment and convert it into a usable fuel, methanotrophic bacteria have long fascinated researchers. But how, exactly, these bacteria naturally perform such a complex reaction has been a mystery.
Now an interdisciplinary team atNorthwestern
University
This finding could lead to newly designed, human-made catalysts that can convert methane — a highly potent greenhouse gas — to readily usable methanol with the same effortless mechanism.
“The identity and structure of the metal ions responsible for catalysis have remained elusive for decades,” said Northwestern’s Amy C. Rosenzweig, co-senior author of the study. “Our study provides a major leap forward in understanding how bacteria perform methane-to-methanol conversion.”
“By identifying the type of copper center involved, we have laid the foundation for determining how nature carries out one of its most challenging reactions,” said Brian M. Hoffman, co-senior author.
The study will publish on Friday, May 10 in the journal Science. Rosenzweig is the Weinberg Family Distinguished Professor of Life Sciences in Northwestern’s Weinberg College of Arts and Science. Hoffman is the Charles E. and Emma H. Morrison Professor of Chemistry at Weinberg.
By oxidizing methane and converting it to methanol, methanotrophic bacteria (or “methanotrophs”) can pack a one-two punch. Not only are they removing a harmful greenhouse gas from the environment, they are also generating a readily usable, sustainable fuel for automobiles, electricity and more.
Current industrial processes to catalyze a methane-to-methanol reaction require tremendous pressure and extreme temperatures, reaching higher than 1,300 degrees Celsius. Methanotrophs, however, perform the reaction at room temperature and “for free.”
“While copper sites are known to catalyze methane-to-methanol conversion in human-made materials, methane-to-methanol catalysis at a monocopper site under ambient conditions is unprecedented,” said Matthew O. Ross, a graduate student co-advised by Rosenzweig and Hoffman and the paper’s first author. “If we can develop a complete understanding of how they perform this conversion at such mild conditions, we can optimize our own catalysts.”
Methanol, also known as methyl alcohol among others, is a chemical with the formula CH3OH (a methyl group linked to a hydroxyl group, often abbreviated MeOH). Methanol acquired the name wood alcohol because it was once produced chiefly by the destructive distillation of wood. Today, methanol is mainly produced industrially by hydrogenation of carbon monoxide.
Methanol is the simplest alcohol, consisting of a methyl group linked to a hydroxyl group. It is a light, volatile, colorless, flammable liquid with a distinctive odor similar to that of ethanol (drinking alcohol). Methanol is however far more toxic than ethanol. At room temperature, it is a polar liquid. With more than 20 million tons produced annually, it is used as a precursor to other commodity chemicals, including formaldehyde, acetic acid, methyl tert-butyl ether, as well as a host of more specialized chemicals.
Small amounts of methanol are present in normal, healthy human individuals. One study found a mean of 4.5 ppm in the exhaled breath of test subjects. The mean endogenous methanol in humans of 0.45 g/d may be metabolized from pectin found in fruit; one kilogram of apple produces up to 1.4 g methanol.
Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria and is commonly present in small amounts in the environment. As a result, the atmosphere contains a small amount of methanol vapor. Atmospheric methanol is oxidized by air in sunlight to carbon dioxide and water over the course of days.
Methanol is primarily converted to formaldehyde, which is widely used in many areas, especially polymers. The conversion entails oxidation:
Acetic acid can be produced from methanol.
Methanol is a promising energy carrier because, as a liquid, it is easier to store than hydrogen and natural gas. Its energy density is however low reflecting the fact that it represents partially combusted methane. Its energy density is 15.6 MJ/L, whereas ethanol's is 24 and gasoline's is 33 MJ/L.
Further advantages for methanol is its ready biodegradability and low toxicity. It does not persist in either aerobic (oxygen-present) or anaerobic (oxygen-absent) environments. The half-life for methanol in groundwater is just one to seven days, while many common gasoline components have half-lives in the hundreds of days (such as benzene at 10–730 days). Since methanol is miscible with water and biodegradable, it is unlikely to accumulate in groundwater, surface water, air or soil.
Could Be the Future of Fuel
Discovery illuminates how bacteria turn methane gas into liquid methanol
By Amanda Morris
Northwestern University – May 9, 2019 -- Known for their ability to remove methane from the environment and convert it into a usable fuel, methanotrophic bacteria have long fascinated researchers. But how, exactly, these bacteria naturally perform such a complex reaction has been a mystery.
Now an interdisciplinary team at
This finding could lead to newly designed, human-made catalysts that can convert methane — a highly potent greenhouse gas — to readily usable methanol with the same effortless mechanism.
“The identity and structure of the metal ions responsible for catalysis have remained elusive for decades,” said Northwestern’s Amy C. Rosenzweig, co-senior author of the study. “Our study provides a major leap forward in understanding how bacteria perform methane-to-methanol conversion.”
“By identifying the type of copper center involved, we have laid the foundation for determining how nature carries out one of its most challenging reactions,” said Brian M. Hoffman, co-senior author.
The study will publish on Friday, May 10 in the journal Science. Rosenzweig is the Weinberg Family Distinguished Professor of Life Sciences in Northwestern’s Weinberg College of Arts and Science. Hoffman is the Charles E. and Emma H. Morrison Professor of Chemistry at Weinberg.
By oxidizing methane and converting it to methanol, methanotrophic bacteria (or “methanotrophs”) can pack a one-two punch. Not only are they removing a harmful greenhouse gas from the environment, they are also generating a readily usable, sustainable fuel for automobiles, electricity and more.
Current industrial processes to catalyze a methane-to-methanol reaction require tremendous pressure and extreme temperatures, reaching higher than 1,300 degrees Celsius. Methanotrophs, however, perform the reaction at room temperature and “for free.”
“While copper sites are known to catalyze methane-to-methanol conversion in human-made materials, methane-to-methanol catalysis at a monocopper site under ambient conditions is unprecedented,” said Matthew O. Ross, a graduate student co-advised by Rosenzweig and Hoffman and the paper’s first author. “If we can develop a complete understanding of how they perform this conversion at such mild conditions, we can optimize our own catalysts.”
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Methanol, also known as methyl alcohol among others, is a chemical with the formula CH3OH (a methyl group linked to a hydroxyl group, often abbreviated MeOH). Methanol acquired the name wood alcohol because it was once produced chiefly by the destructive distillation of wood. Today, methanol is mainly produced industrially by hydrogenation of carbon monoxide.
Methanol is the simplest alcohol, consisting of a methyl group linked to a hydroxyl group. It is a light, volatile, colorless, flammable liquid with a distinctive odor similar to that of ethanol (drinking alcohol). Methanol is however far more toxic than ethanol. At room temperature, it is a polar liquid. With more than 20 million tons produced annually, it is used as a precursor to other commodity chemicals, including formaldehyde, acetic acid, methyl tert-butyl ether, as well as a host of more specialized chemicals.
Occurrence of Methanol
Small amounts of methanol are present in normal, healthy human individuals. One study found a mean of 4.5 ppm in the exhaled breath of test subjects. The mean endogenous methanol in humans of 0.45 g/d may be metabolized from pectin found in fruit; one kilogram of apple produces up to 1.4 g methanol.
Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria and is commonly present in small amounts in the environment. As a result, the atmosphere contains a small amount of methanol vapor. Atmospheric methanol is oxidized by air in sunlight to carbon dioxide and water over the course of days.
Applications for Methanol
Methanol is primarily converted to formaldehyde, which is widely used in many areas, especially polymers. The conversion entails oxidation:
2 CH3OH + O2 → 2 CH2O + 2 H2O
Acetic acid can be produced from methanol.
Methanol and isobutene
are combined to give methyl tert-butyl ether (MTBE). MTBE is a major octane
booster in gasoline.
The European Fuel
Quality Directive allows fuel producers to blend up to 3% methanol, with an
equal amount of cosolvent, with gasoline sold in Europe .
China
Methanol is a promising energy carrier because, as a liquid, it is easier to store than hydrogen and natural gas. Its energy density is however low reflecting the fact that it represents partially combusted methane. Its energy density is 15.6 MJ/L, whereas ethanol's is 24 and gasoline's is 33 MJ/L.
Further advantages for methanol is its ready biodegradability and low toxicity. It does not persist in either aerobic (oxygen-present) or anaerobic (oxygen-absent) environments. The half-life for methanol in groundwater is just one to seven days, while many common gasoline components have half-lives in the hundreds of days (such as benzene at 10–730 days). Since methanol is miscible with water and biodegradable, it is unlikely to accumulate in groundwater, surface water, air or soil.
Methanol is
occasionally used to fuel internal combustion engines. It burns forming carbon
dioxide and water:
One problem with
high concentrations of methanol in fuel is that alcohols corrode some metals,
particularly aluminium. Methanol fuel has been proposed for ground
transportation. The chief advantage of a methanol economy is that it could be
adapted to gasoline internal combustion engines with minimum modification to
the engines and to the infrastructure that delivers and stores liquid fuel. Its
energy density is however only half that of gasoline, meaning that twice the
volume of methanol would be required.
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