Poly-β-hydroxybutyrate production in eight strains of the genus Acinetobacter

Since poly-β-hydroxybutyrate (PHB) inclusions have been reported in only a few strains of Acinetobacter grown on β-hydroxybutyrate, it was of interest to study comparatively the production of this lipid reserve in eight different acinetobacters. Three lines of evidence for PHB production were used: spectrophotometric analysis, infrared analysis, and electron microscopy. The spectrophotometric method showed that all eight strains produce PHB in stationary phase, the amounts ranging from 0.55 to 10.7 fmol/cell. PHB production was maximum after 1 h of growth in batch culture, with the amounts declining by 2 h and returning to near stationary phase cell levels in 4 h. Infrared spectra of purified PHB from the eight strains matched the spectrum of a commercial sample of PHB. In electron micrographs, the PHB reserves were visible as small electron-transparent bodies delineated by ultramembranes. PHB production in four strains (bath cultures) varied in response to exogenous glucose or xylose, with maximum production occurring over a range of 8–17 mM monosaccharide. Glucose was transported into cells by all strains in amounts that ranged from 0.5 to 1.6 fmol/cell, and 0.1–2.2% of that glucose was converted into PHB. Glucose transport was inhibited by cyanide. Key words: poly-β-hydroxybutyrate, acinetobacters.