The three new barley enzymes can yield up to 30 percent more sugar than enzymes found in conventional barley lines, said the scientists from the US Department of Agriculture's Agricultural Research Service (USDA ARS).
The enzymes are said to perform exceptionally well at temperatures of 70 degrees Celsius, or 160 degrees Fahrenheit, and because they produce more sugar, they result in more fermentable product for brewing beer.
Before brewing can begin, barley kernels must be 'malted', explained the ARS. Malting begins with steeping the kernels in water until the seeds begin to sprout, or germinate. This process helps cue production of enzymes that are crucial for turning starch into sugar. In nature, the young seed needs this sugar for energy to grow. In malting, brewers need it for fermentation.
But this manipulated growth spurt must be carefully controlled. About the time rootlets can be seen sprouting from the seeds, the kernels are blown dry in a 120 degrees Fahrenheit kiln to halt any further maturing in the seed. Soon after, the barley kernels are thrust into the heat again, where they are roasted at temperatures of 175 degrees Fahrenheit or more, depending on the degree of malting - light or dark - desired.
So while heat is needed to complete the malting process, too much heat is destructive.
"Two of barley's starch-degrading enzymes are heat-sensitive. One of those is the second-most-important enzyme for converting starches into fermentable sugars,"said Cynthia Henson, a plant physiologist in ARS's Cereal Crops Research Unit at Madison, Wisconsin.
For example, at high temperatures, alpha-glucosidase - one of the most important barley enzymes for turning starches into fermentable sugars during beer-making - has less than 5 percent of the activity it normally would, said the ARS.
In order to find enzymes that could best withstand the heat imposed by malting, Henson and her team assessed other plants in nature for their thermostability. They found sugar beet to have the most impressive heat tolerance, and so built a new barley enzyme with sugar beet as a model, endowing their barley enzyme with a pivotal amino acid that gives sugar beet its thermal edge.
However, the new enzymes, which have been patented, were not developed for breeding into current barley plants. The researchers are instead using them as a search tool to scan barley plants for accessions already possessing the desirable enzymes.
With a vast range of genetic diversity to sift through, the researchers said they hope to find barley plants containing the new enzymes within the next few years.