Brewery boon: gene to tweak yeast behaviour
New Delhi, June 26: Scientists here have identified a plant gene that they say could be used to change the behaviour of yeast and increase ethanol production, a potential gift to industrial breweries worldwide.
The scientists at the National Institute of Plant Genome Research (NIPGR) have shown that the gene from a mustard family weed when inserted into yeast boosts a process called flocculation used by breweries and wine-making industries.
"The genetically-engineered yeast cells can increase ethanol production up to four times the amount available from natural yeast," said Jitendra Thakur, a staff scientist at the NIPGR who led the research described as the first to use a plant gene to alter the properties of yeast.
People have used yeast for centuries to process food and alcoholic beverages. It is the world's most industrially-exploited organism, primarily used as a tool for fermentation. But once the fermentation process is complete, the yeast cells need to be removed from the ethanol-containing broth.
Breweries usually rely on flocculation - a property of yeast cells to tightly cluster into clumps - to remove yeast from the suspension. "Yeast makes the suspension look translucent or milky and leads to a sweet, off-flavour taste. So it is important to remove the yeast to obtain clear ethanol," Thakur said.
Conventional techniques of removing yeast depend on filters, chemical-induced flocculation, or centrifugation in which the solution is rotated at high speeds to push the yeast cells to form pellets. Some breweries also use yeast genetically engineered to raise the activity of genes that drive flocculation process.
"But these processes are time-consuming, expensive, or reduce ethanol output," said Thakur.
Thakur and his colleagues P. Dahiya and D. Bhat who worked with laborabory yeast strains have shown that the gene called AtMed15 acts on multiple yeast genes that drive flocculation - leading to robust flocculation and an increase in ethanol production. Their findings have been published in the journal Scientific Reports.
The early or premature flocculation of yeast cells hampers complete fermentation and results in loss of some key flavours of beverages. "The use of the AtMed15 gene will not only yield more ethanol, it will also preserve some flavours lost when ethanol is made through conventional techniques," Thakur said.
The NIPGR feat has impressed other scientists, but some point out that the technology has yet to be demonstrated on industrial strains of yeast.
"This appears promising, but the next step would be to establish the economics of applying this technique at the industrial scale," said Neel Sarovar Bhavesh, a group leader at the International Centre for Genetic Engineering and Biotechnology, New Delhi, who was not associated with the project.