Synthetic fuels could be produced from soil bacterium

Researchers have discovered that an enzyme found in a common soil bacterium can turn carbon monoxide gas into compounds, such as propane, that are useful sources of fuel. This raises the prospect of being able to manufacture synthetic fuels in an environmentally-friendly manner using less energy compared with current industrial processes.

Nitrogen is an essential element for the growth of living organisms, but very few are able to directly use the nitrogen gas found in the atmosphere. Azotobacter vinelandii is a bacterium which lives in the soil and is one of the few microorganisms able to convert nitrogen into a useable form (ammonia) in a process called 'nitrogen fixation'. A. vinelandii produces an enzyme, called nitrogenase, to transform the nitrogen into ammonia, which is part of the natural nitrogen cycle.

Until recently, it has been difficult to extract in the laboratory ample quantities of one form of nitrogenase (vanadium nitrogenase) produced by A. vinelandii. For example, the enzyme easily loses its activity when exposed to the air. But researchers have now been able to obtain a good amount of fully active vanadium nitrogenase and further investigate whether this enzyme can transform other chemicals in addition to nitrogen. The results suggest that it can convert carbon monoxide into other substances.

In this research, vanadium nitrogenase was exposed to carbon monoxide, with no nitrogen present. Small quantities of the short-chain carbon compounds ethylene, ethane and propane were detected. This suggests that the vanadium nitrogenase had been able to transform the carbon monoxide into simple hydrocarbon compounds. Propane, for example, is a gas commonly used as a fuel source for portable stoves.

The researchers caution that their research is at an early stage. Nevertheless, it is feasible that waste, such as car exhausts containing carbon monoxide or by-products of industrial processes, could be turned into useful energy sources, such as propane. It may also be possible to modify vanadium nitrogenase to produce the longer-chain carbon compounds found in petrol.

One of the main benefits of potentially using vanadium nitrogenase to convert carbon monoxide into carbon-containing fuels is that it uses less energy than the industrial Fischer-Tropsch process, which is currently used to synthetically produce liquid carbon fuels from carbon monoxide and hydrogen. This is because the vanadium nitrogenase itself assists the chemical reaction needed for this conversion under normal temperature and pressure conditions.