One of the revolutions in malaria treatment in recent decades has been the advent of artemisinin drugs, whose active ingredient comes from a traditional Chinese herb, Artemisia annua.
But weather can affect harvests of the plant, causing shortages and price spikes.
In a study published in Nature, a team led by Chris Paddon of Amyris Inc., a biotech firm based in Emeryville, California, reported on a way to ferment artemisinic acid -- a precursor to artemisinin -- from genetically-engineered baker's yeast.
Their technique derives 25 grammes of concentrate from a litre of artemisinic acid. A previous attempt, reported by a European team last year, made only 1.6 grammes per litre.
The artemisinic acid can then be converted to artemisin by a simple chemical process using oxygen as a catalyst.
"Because all intellectual property rights have been provided free of charge, this technology has the potential to increase provision of first-line antimalarial treatments to the developing world at a reduced average annual price," the researchers said.
In 2010 there were more than 200 million cases of malaria, and at least 655,000 deaths, according to the UN's World Health Organisation.