ABSTRACT

Recently, the thermostability of β-amylase in barley (Hordeum vulgare L.) has been studied. These studies indicate that the barley varieties are mainly divided into three groups based on differences in their β-amylase thermostability and the thermostability has a close relationship to the apparent attenuation limit which is a major malting quality parameter for the determination of the fermentability. This fact suggests that the β- amylase thermostability is a useful marker for the selection of barley with high fermentability. For the efficient breeding to improve the fermentability in malting barley using MAS (marker-assisted selection), DNA markers with β-amylase thermostability have been developed. On the other hand, improvement in the β-amylase thermostability using genetic engineering has been attempted. A Seven fold - mutant thermostable β-amylase gene has been constructed, and transgenic barley plants containing its expression vectors under the control of the β-amylase or hordein promoter region have been produced. These experiments show that thermostable β-amylase was synthesized in transgenic barley grains.