AbstractThebg/M gene DNA coding for a thermostable beta‐1.3,1.4‐glucanase ofBacillus maceransE138 was isolated by direct shot‐gun cloning intoEscherichia coliusing plasmid pBR322 as a vector. By deletion analysis thebg/M coding region was located within a 1.0 kb region of the clonedBacillusDNA fragment. InE. coli, plasmid pBGLM12/2 containing theB. macerans bg/M gene gave rise to a beta‐glucanase expression 40 times higher than that of theB. maceransgene donor. The molecular weight of beta‐glucanase, isolated either fromE. colicells or from the culture filtrate ofB. macerans, was in the range of 24 kD. The enzymes purified fromE. colior from the culture filtrate ofB. macerans, had a halflife of about 40 min at 65 °C. This indicated an increased temperature stability of theB. maceransenzyme in comparison to otherBacillus‐bet