Characterization of the amino acids of antifungal peptides from B. subtilis by cold on-column injection capillary GC/MS

Recent studies have shown that the cell-free culture liquor of Bacillys sublitis inhibits the growth of the peach brown rot fungus, Monilinia fructicola. Bacillus sublitis and other related bacilli are known to produce a variety of peptide antibiotics, including cyclic peptides of the Iturin family. Fractionation of the culture liquor yeilded two major components which were shown to be cyclic peptides of the Iturin type. Specific capilliary GC/MS methodology was developed for the characterization of the amino acids, including β-amino aliphatic acids, resulting from the hydrolyses of these cyclic antifungal peptides. After cold on-column injection, the N- pentafluoropropionyl- D,L-amino acid n- propyl esters were separated on a fused silica Chirasil-Val III ™ column and characterized by mass spectrometry on a Hewlett Packard 5985B GC/MS system equipped with an open-split interface. MS data used to characterize the long-chain aliphatic β-amino acids in the peptides are discussed.