ABSTRACT
Several methods have been established to accomplish plasmid transformation of Bacillus subtilis. The protoplast transformation method is highly efficient, but it takes several days before acquiring transformed cells after laborious procedures. A new alkali cation method that is applicable to wild strains of B. subtilis is proposed. The simplified alkali cation transformation method includes the following steps: cell harvesting, alkali cation treatment, plasmid addition, addition of polyethylene glycol (PEG) 6000, PEG dilution and washing and gene expression. Lipopeptides represent a unique class of bioactive microbial secondary metabolites, and many of them show attractive therapeutical and biotechnological properties. Surfactin was isolated as an inhibitor of fibrin clotting and is known to lyse erythrocytes and it is a potent surface-active reagent and antibiotic. Purification of the antifungal substance was carried out as follows by modifying the methods developed for purification of fengycin or plipastatin.
