Expression of fungal thermotolerant endo-1,4-β-glucanase in transgenic barley seeds during germination

The malting quality of two barley cultivars, Kymppi and Golden Promise, was modified to better meet the requirements of the brewing process. The egl1 gene, coding for fungal thermotolerant endo-1,4-β-glucanase (EGI, cellulase), was transferred to the cultivars using particle bombardment, and transgenic plants were regenerated on bialaphos selection. Integration of the egl1 gene was confirmed by Southern blot hybridization. The transgenic seeds were screened for the expression of the heterologous EGI. Under the high-pI α-amylase promoter, the egl1 gene was expressed during germination. The heterologous enzyme was thermotolerant at 65 °C for 2 h, thus being suitable for mashing conditions. The amount of heterologous EGI produced by the seeds (ca. 0.025% of soluble seed protein), has been shown to be sufficient to reduce wort viscosity by decreasing the soluble β-glucan content. A decrease in the soluble β-glucan content in the wort improves the filtration rate of beer.