Characterization of partially transesterified poly(beta-hydroxyalkanoate)susing matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometr y (MALDI-TOFMS) was used for the characterization of a partially transester ified poly(beta-hydroxyalkanoate),PHA, polymer produced by the bacterial st rain Alcaligenes eutrophus using saponified vegetable oils as the sole carb on sources. The transesterification was carried out separately under acidic and basic conditions to obtain PHA oligomers weighing less than 10 kDa, Th e intact oligomers were detected in their cationized [M + Na](+) and [M + K ](+) forms by MALDI-TOFMS, A composition analysis, using the MALDI-TOF spec tra, indicate that the oligomers obtained via acid catalysis were terminate d with a methyl 3-hydroxybutyrate end group, and those obtained by base cat alysis had a methyl crotonate (olefinic) termination. In addition to IIB (h ydroxy butyrate), the oligomers were found to contain a small percentage of HV (hydroxy valerate), This was independently confirmed using gas chromato graphy/mass spectrometry (GC/MS), In comparison, the analysis of a commerci al PHA polymer, transesterified under identical conditions, only showed the presence of HB, i.e. a pure PHB homopolymer. Copyright (C) 1999 John Whey & Sons, Ltd.