Bioassimilation of atactic poly[(R,S)-3-hydroxybutyrate] oligomers by selected bacterial strains

Water-soluble a-PHB oligomers (from dimer to dodecamer) were synthesized by anionic oligomerization of (R,S)-beta-butyrolactone and characterized by e lectrospray ionization tandem mass spectrometry (ESI-MSn). The oligomers we re analogous to the degradation products remaining after enzymatic hydrolys is of synthetic high molecular weight atactic poly[(R,S)-3-hydroxybutyrate] by extracellular PHB depolymerases. Selected bacterial strains were used t o test bioassimilability of a-PHB oligomers. It was found that not only two PHB-degrading bacteria (Alcaligenes faecalis T1 and Comamonas sp.) but als o a non-PHB-degrading bacterium (Ralstonia eutropha H16) could grow on a-PH B oligomers as sole source of carbon and energy. Utilization of a-PHB oligo mers by the three bacterial strains (total oligomer consumption and molecul ar weight distribution changes) was investigated by ESI-MS. Total oligomer consumption (tested after 30 h of bacterial growth) followed the same trend as the observed bacterial growth (A. faecalis > Comamonas sp. > R. eutroph a). Mineralization of a-PHB oligomers demonstrates total biodegradability o f synthetic high molecular weight atactic poly[(R,S)-3-hydroxybutyrate].