Advance in Study on Beta-amylase Thermostability in Malting Barley

β-amylase was a starch-decomposing enzyme closely related to diastatic power during barley malting, influencing the economy of malt industry. It's thermostability affected the enzyme activity during malting. There was great difference in β-amylase thermostability of barley genotypes from the different areas, and three types may be classified according to the capacity of thermostability with a clear cultivar geographic distribution. The genetic research showed that β-amylase thermostability was (co-dominated) by structural gene locus and adjacent multiple alleles, and modified by some minor genes. The different β-amylases in thermostability were formed with the change of amino acids on the protein sequence. Three allele genes, namely Sd1, Sd2 and Sd3, encoding three β-amylase forms, have been identified respectively. β-amylase thermostability affected wort fermentability, and there was an obvious difference in wort fermentability among the barley cultivars with different alleles controlling thermostability. It was indicated that β-amylase thermostability could be enhanced through transferring the constructed mutant genes of β-amylase thermostability. The significance of investigation on genotypic and environmental variation in β-amylase thermostability was also discussed in the paper.