Scientists at the Emory University Health Sciences Centre are hoping to widen the understanding of an enzyme that breaks caffeine down into theophylline, using bacteria that need the breakdown product of the enzyme for survival.
"We don't know much about it [the enzyme] but we do know it works very slowly. Ideally, we would like to speed it up a bit so that we could create coffee plants that are low in caffeine," said Emory chemist Justin Gallivan.
Decaffeinated coffee accounts for about 10 per cent of the world coffee market but industrial methods in operation today to decaffeinate coffee use organic solvents and carbon dioxide to remove the caffeine from the beans, a process that can strip necessary flavour compounds out of the finished drink.
This latest study could lead to the creation of naturally decaffeinated coffee plants, bringing alternative methods to market that retain the full coffee flavour.
Gallivan says that the idea is to supply the bacteria with caffeine, and give each bacterium a piece of DNA from coffee plants that may encode the enzyme that will allow the bacterium to convert the caffeine to the theophylline it needs to survive.
"Bacteria are terrific chemists, but they normally synthesise only molecules they need for their own survival," added the scientists.
The Emory researchers have coupled the life of a bacterium to the presence of theophylline, a compound that is used to treat asthma, and is produced by the breakdown of caffeine in both coffee and tea plants. One of the reasons that coffee has a high level of caffeine is that in the plant, caffeine is synthesised very quickly, but breaks down to theophylline very slowly.
"At the end of the day, we will know that all of the surviving bacteria have 'learned' to convert caffeine to theophylline, and thus have the enzyme that we're interested in. We can then learn about the enzyme and how it works," explained Gallivan.
The researchers hope to use a process known as 'directed evolution' to help speed up the enzyme to break down caffeine faster. Since the bacteria need theophylline for their survival, they are partners in the whole process.
This latest research joins reports earlier this year that scientists in Brazil had identified naturally growing caffeine-free coffee plants, paving the way for cheaper processing methods for makers of decaffeinated coffee.
Part of a breeding programme to come up with low-caffeine strains, the discovery of the decaffeinated version of Coffea arabica, the most cultivated and consumed coffee in the world, at the State University of Campinas in Brazil could lead to full flavoured alternatives to the artificially decaffeinated coffee on the market today.
A further issue is the 'value-added' potential of the natural crops. According to the intergovernmental, UN-backed International Coffee Organisation, although the coffee business is booming in consuming developed countries, current rock bottom prices are causing immense hardship to countries where coffee is a key economic activity, as well as to the farmers who produce it.
Prices on world markets, which averaged around 120 US cents/lb in the 1980s, are now around 50 cents, the lowest in real terms for 100 years.