Genetic Engineering of Yeast: Construction of Strains that Degrade β-Glucans with the Aid of a Barley Gene. Karl Kristian Thomsen, Elizabeth A. Jackson, and Klaus Brenner, Department of Physiology, Carlsberg Laboratory, DK-2500 Valby, Copenhagen, Denmark. J. Am. Soc. Brew. Chem. 46:0031, 1988.

A cDNA gene encoding the mature form of a barley (1?3,1?4)-β-glucanase, fused in frame with a DNA fragment coding for an α-amylase signal peptide was inserted in replicating yeast plasmids behind the promoter region of the alcohol dehydrogenase I gene from Saccharomyces cerevisiae. Yeast cells carrying such plasmids synthesize (1?3,1?4)-β-glucanase, and the enzyme is exported to the culture medium. Small-scale fermentation experiments with β-glucanase-producing S. cerevisiae have shown that the amount of β-glucanase released to the culture medium is sufficient to degrade up to 500 mg/L of β-glucan during a seven-day fermentation period at 10° C. The β-glucanase expression unit (promoter, β-glucanase cDNA gene, and terminator) was inserted in an integrating vector to transfer the barley β-glucanase gene into the genome of brewing yeast strains. After transformation of yeast to G418 resistance, β-glucanase activity was detected in the culture medium.

Keywords: β-Glucanase, Barley, Brewing, Genetic engineering