High Production of Thermostable Beta-galactosidase of Bacillus stearothemophilus in mesophiles

Recent advances in recombinant DNA techniques have provided a tool for breeding of microorganisms of hyper production. Enzyme production by cloned microorganism has some advantages. They are ⅰ) Enzymes can be produced by a microorganism easily cultured ⅱ) Hyper production. ⅲ) In some cases, such as thermophilic enzyme gene is cloned in a mesophilic bacteria, the enzyme purification procedure can be simplified. One example, production of thermophilic ${\beta}$-galactosidase in B. subtilis will be presented. Bacillus stearothermophilus IAM 11001 produced three ${\beta}$-galactosidases, ${\beta}$-galactosidase I, II and III (${\beta}$-gal-I, II and III). By connecting restriction fragments of the chromosomal DNA to plasmid vector, followed by transformation of Escherichia coli, two ${\beta}$-galactosidase genes (bgaA and bgaB) located close to each other on the chromosome were cloned.