Biosurfactants from Bacillus licheniformis: structural analysis and characterization

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Abstract
The surface-active compounds of the strain Bacillus licheniformis were isolated and their structure was elucidated. The high surface-active capacity of the crude extract was basically due to traces of long-chain saturated fatty acids, especially of palmitic and stearic acids, to a mixture of small amounts of hydrocarbons with chain lengths of 20 and 22 carbons, and mainly to appreciable amounts of four slightly different lipopeptides. The lipopeptides were found to be a mixture of four closely related compounds. The lipophilic part consisting of i-, n-C14 or i-, ai-C15 β-OH fatty acids was linked to the hydrophilic peptide moiety, which contained seven amino acids (Glu, Asp, Val, three Leu and Ile) by a lactone linkage. Fifteen milligrams per litre of the purified lipopeptide product decreased the surface tension of water from 72 mN m−1 to 27 mN m−1, characterizing the product as a powerful surface-active agent that compares favourably to other (bio)surfactants. Antibiotic activity was demonstrated against bacteria and yeasts.