EFFICIENT PRODUCTION OF THERMOSTABLE CLOSTRIDIUM-THERMOSULFUROGENES BETA-AMYLASE BY BACILLUS-BREVIS

The Bacillus brevis host-vector system was used for production of the thermostable Clostridium thermosulfurogenes beta-amylase. The promoter and translation initiation regions of the cell wall protein gene operon (cwp) of B. brevis were used to express the beta-amylase gene in B. brevis 47. B. brevis 47K, a previously isolated mutant that secreted human alpha-amylase efficiently was shown to be also a good host for the beta-amylase production. When the Clostridium signal peptide was used to direct secretion, 0.3 g of the beta-amylase with a correct NH2-terminus was secreted per liter of medium. When the signal peptide of a B. brevis cell wall protein was used, a very large amount (1.6 g/l) of the enzyme was secreted, which is about 60 times larger than that secreted by C. thermosulfurogenes, but the NH2-terminus of the secreted enzyme was heterogeneous. Both enzymes secreted by B. brevis showed almost the same specific activity, thermostability, and ability to bind and to digest raw starch, as those of the C. thermosulfurogenes enzyme.