London, Dec 9: In a new study, researchers show that it is possible to genetically rewire bacteria to produce “non-natural” alcohols that would make ideal biofuel.

According to a report in New Scientist, James Liao’s team at the University of California, Los Angeles, has now engineered bacteria to convert standard sugars into unusually long-chained alcohols.

Bacteria such as Escherichia coli – a bug commonly linked to food poisoning outbreaks – naturally convert sugar into alcohol, but those alcohols tend to be short-chain molecules.

Long-chain alcohols, each containing more than six carbon atoms, are more energy dense – packing more power into a smaller space – and hence make better fuels.

They are also easier to isolate than short-chain alcohols because they are less soluble in water.

So, Liao’s team looked closely at the metabolism of E. coli to see if it could be redesigned to produce these longer chains.

Enzymes in the bacterium encourage one particular keto acid – a precursor to an amino acid – to undergo an “elongation cycle”, increasing its carbon content.

The researchers reasoned that those enzymes might be “promiscuous” enough to elongate a different keto acid.

The product could then be converted to a six-carbon alcohol using two more enzymes – one borrowed from another bacterium and another from the yeast Saccharomyces cerevisiae, which is commonly used in baking and brewing.

So, the researchers engineered E. coli to over-express all of these enzymes, and tests confirmed that it could then convert glucose into the target six-carbon alcohol, known as 3-methyl-1-pentanol.

However, production levels were low. When fed 20 grams of glucose, these bacteria produced just 6.5 milligrams of the target alcohol.

To improve that figure and reduce the quantity of unwanted by-products, Liao’s team had to engineer the two foreign enzymes. That enabled the bacteria to produce 384 milligrams of fuel from the same dose of sugar.

According to Liao, though optimising the process is tricky, because this is a non-natural metabolic pathway, further research will improve on the initial success.

“This work shows that one can take a synthetic biology approach – integrating efforts in metabolic engineering and protein engineering – to construct novel biosynthetic pathways,” said Jim Collins at Boston University.

Liao’s work may open the door for engineering microbes to produce many novel chemicals and materials. (ANI)