EXPRESSION OF THE BACILLUS-SUBTILIS LEVANASE GENE IN ESCHERICHIA-COLI AND SACCHAROMYCES-CEREVISIAE

The gene coding for the inulin hydrolyzing enzyme levanase which was previously cloned from Bacillus subtilis was fused to the tac-promoter. Overexpression in Escherichia coli resulted in high amounts of intracellularly produced levanase (up to 20 U mg-1). After removal of the bacterial 5' sequences, the levanase gene was also cloned into a yeast expression vector based on the PGK-promoter. Clones containing the intact levanase gene including the bacterial signal sequence gave rise to synthesis of active levanase by Saccharomyces cerevisiae transformants. A considerable amount of levanase protein was found in the culture medium (around 0.5 U ml-1) indicating efficient secretion of B. subtilis levanase from yeast.