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.