ENHANCED BIOSURFACTANT PRODUCTION BY A BACILLUS-LICHENIFORMIS MUTANT

A Bacillus licheniformis mutant derived by random mutagenesis with N-m ethyl-N'-nitro-N-nitrosoguanidine treatment producing high levels of t he lipopeptide biosurfactants was selected by an ion-pair plate assay. The mutant, designated B. licheniformis KGL11, is capable of producin g lipopeptide biosurfactants at concentrations lip to 391 mg l(-1) whi ch is twelve rimes more than the parent strain. HPLC analysis, infrare d spectroscopy analysis, and surface tension measurement indicated tha t the biosurfactants produced by the mutant were identical to those pr oduced by the wildtype strain. The biosurfactants exhibited a low surf ace tension of 26.5 dyne cm(-1) and a low critical micelle concentrati on of 10 mg l(-1). Similar to the wildtype strain, the mutant produced biosurfactants at the mid-exponential phase and subsequently deactiva ted biosurfactants at the onset of the stationary phase; nevertheless, the deactivated biosurfactants was re-excreted into the culture upon further incubation. (C) 1998 Elsevier Science Inc.