Researchers in Singapore have brewed up a beer containing probiotic bacteria that can improve gut health and boost the immune system.

Food researcher Alcine Chan, 23, experimented for almost a year with a recipe of malt, alcohol, hops and a strain of probiotic bacteria, until she got the formula just right.

"The hops are the main ingredient that kills probiotics, so we had to find a way for the probiotics to overcome the hops," Chan said, demonstrating the pre-fermentation process in a laboratory at the National University of Singapore (NUS).

The popularity of beer promises huge market potential for the process, she said, adding that she hoped it would reach as many consumers as possible.

Chan, who perfected the beer recipe as a project for the senior year of her degree, said she drew inspiration from the probiotic yoghurt and dairy drinks she consumes every day.

The pale, bubbly drink tastes slightly sweet and has 3.5 percent alcohol content, just under the 4 percent to 6 percent of regular beers. Every 100 ml (3.4 oz) of the drink, or roughly just over a mouthful, contains 1 billion probiotic organisms.