High poly(β-hydroxybutyrate) production by Pseudomonas fluorescens A2a5 from inexpensive substrates

A strain of poly(β-hydroxybutyrate) (PHB)-accumulating bacterium was isolated from the soil in Alaska of USA, identified as Pseudomonas fluorescens, and designated as strain A2a5. The organism grew at temperatures below 30 °C, and accumulated a large amount of granules in its cells when it was cultured in the sugarcane liquor medium. The purified sample from cells was determined as PHB by gas chromatographic and nuclear magnetic resonance analysis of polyesters. The cell density of the culture in shaking bottles reached OD600 = 155 with PHB concentration of 31 g l−1. In 5 l bioreactor, a maximum cell dry weight (CDW) of 32 g l−1 with a PHB concentration of 22 g l−1 was obtained, and the PHB content was up to 70% and productivity was 0.23 g l−1 h−1.