Cultivation conditions for the extracellular production of a hybrid beta-1,3-glucanase (EC 3.2.1.39) from Bacillus were established using a recombinant Escherichia coli BL21 (DE3) pET-bgl-hisactophillin-sec. Maximal beta-1,3-glucanase production of 510 U ml(-1) after 28 h, was obtained using an optimized medium which had an initial lactose level of 7 and 24 g l(-1) yeast extract and 5 g l(-1) NaCl. Lactose was a potent inducer of beta-1,3-glucanase. It is a cheap and easily available substrate for large-scale cultivations. In addition, the kinetics of extracellular production of beta-glucanase depended on salt concentration (NaCl). Batch fermentation in a 3-1 laboratory fermentor using the optimized medium allowed the production of 495 U ml(-1) beta-glucanase after only 15 h. Final enzyme activity in the optimized medium can be increased up to 3.5 times (510 U ml(-1)) compared with the concentration obtained with the starting medium (150 U ml(-1)). (C) 2003 Elsevier Science Ltd. All rights reserved.