GAS-CHROMATOGRAPHY MASS-SPECTROMETRIC ANALYSIS AND ITS APPLICATION TOA SCREENING-PROCEDURE FOR NOVEL BACTERIAL POLYHYDROXYALKANOIC ACIDS CONTAINING LONG-CHAIN SATURATED AND UNSATURATED MONOMERS

The structures of polyhydroxyalkanoic acids (PHA) containing long chai n saturated and unsaturated monomers have been determined by gas chrom atography-mass spectrometric (GC-MS) analysis, Trimethylsilyl (TMSi) d erivatives of 3-hydroxyalkanoic acid methyl esters of PHA have been id entified by comparing their retention times to those of chemically or biologically synthesized standards. From the mass spectra of the TMSi derivatives, the characteristic fragment of m/e 175 which was due to c leavage alpha to the derivatized hydroxyl group revealed a 3-hydroxyl functional group, and the molecular ion-related fragments of m/e [M-15 ], m/e [M-31] and m/e [M-73] clearly reflected their chain length. Dif ferences in position of the unsaturated functional group caused a shif t in the base peak and changes in the fragmentation pattern. Structura l determination of a bacterial PHA by TMSi derivatization followed by GC-MS analysis can be routinely applied to a simple and rapid identifi cation of isolated strains which can accumulate a PHA containing long chain saturated and unsaturated monomers. The Pseudomonas strains whic h could accumulate this functional PHA were isolated on the basis of G C-MS analysis, and the contents and compositions of PHA synthesized by the strains isolated were also determined.