Can Bacteria Produce Diesel?

Since the dawn of industrial revolution we are dependent on fossil fuels for driving the economy. Abundance of fossil fuels and development of technology to extract them economically has linked advancement in mechanization to energy from fossil fuels. The extent of this dependence is a major factor in current economy and geopolitics. Indiscriminate use of fossil fuels has developed additional complications such as pollution. This has led to widespread search for alternate fuel sources that are less polluting and easily available.

Recent developments in solar and wind energy, along with advances in storage technology, have increased their use in several countries. Due to the attention given to these technologies, they have developed much ahead of other alternate energy sources. Use of clean coal and responsible use of nuclear energy are other, though controversial, sources of energy that can supply the ever-hungry world. In several European countries natural gas is the major heating source. Almost all major car manufacturers have started adding electric cars to their catalogues for the discerning customer. Such developments point to a major change in the way world is thinking of energy use.

However all fossil fuel based industries cannot be powered by these alternate energy sources. We still depend on petroleum products for most of the heavy industries. This suggests that petroleum extraction will not end as soon as we expect. Although new technology has made this process easier, it still has adverse geological effects. There is a human face to this problem as well. All countries do not have oil deposits and their national economies become strained when they spend large sums on importing oil.

Scientists have tried to develop genetically modified organisms that can supply us with fuel. Biofuel was developed from such efforts large amounts of starch or sugar-rich crops were used to develop alcohol by fermentation. This alcohol was used themselves or mixed with fossil fuels in vehicles. This process is widely used, but has become controversial due to use of food crops for fuel production and extensive farming for fuel production. Moreover, not all vehicles are compatible with biofuels and engines may need modifications for efficient use.

Recently scientists from University of Exeter have taken another step in developing a substitute diesel. They have used genetically engineered E.coli bacteria, an intestinal bacterium that has become the workhorse of molecular biology, to develop compounds that are identical to fossil fuel hydrocarbons (alkanes and alkenes). They achieved this by coupling the activity of the fatty acid reductase enzyme from bacteria called Photorhabdus luminescens with aldehyde decarbonylase from the cyanobacteria Nostoc punctiforme to use free fatty acids as substrates for alkane biosynthesis. They modified the length and structure of hydrocarbons synthesized by expressing enzymes from other organisms that alter the fatty acid chain.

This work is an exciting development in the field of synthetic biology where the scientists used E.coli cell to bring together different enzymes from different organisms. These enzymes carried out perfectly natural biological reactions to synthesize diesel that is virtually indistinguishable from natural diesel. The work is not complete although the bacteria makes bona fide diesel, it makes it at excruciatingly slow rate 100 liters of bacteria will yield about a spoonful diesel. However, biotechnology has developed advanced techniques to increase yield and optimize bacterial metabolism. So scientists hope that this technology will help to develop an alternate source of diesel.

Another inherent advantage this system is that we can develop different varieties of hydrocarbons by using combinations of enzymes. This technique requires specific kinds of fatty acids to be supplied to E.coli bacteria, but they can be derived from other biological sources. If successful, this technique can replace the harsh techniques that are currently used in the petroleum industry. It can supplement the current petroleum source, and along with the alternate energy sources that we touched up earlier, supply the energy needs of the world in a less toxic way.

Written by : Sujatha S., Canada (PHD Life Sciences)

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Edited by: Rajesh Bihani ( Find me on Google+ )

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