Poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid) and poly(4-hydroxybutyric acid) have been synthesized from gamma-butyrolactone using a Hydrogenophaga pseudoflava strain without subsequent degradation. The efficient synthesis of the poly(4-hydroxybutyric acid) homopolymer was made possible through a three-stage cultivation process in which the polymer does not degrade during prolonged incubation. On the other hand, poly(3-hydroxybutyric acid) in cells was completely degraded within 30 hours of cultivation after transfer to a carbon-free mineral medium that contains additional ammonium sulfate.
Sulfate-reducing bacteria (SRB) present in the sediments of Lake Ciso in Spain degrade poly-beta-hydroxyalkanoates (PHA) and use the carbon and electrons formed by this degradation for the reduction of sulfates. The amount of sulfide formed depends on the amount of PHA present in the sediments and if the breaking down of PHA is reduced by adding sodium molybdate, the amount of sulfide formed also decreases.
Results demonstrate occurrence of poly(hydroxyalkanoate) (PHA) containing hydroxyvalerate repeating units in stratified photosynthetic microbial mats. Data reveal that PHA constitute a 0.5 to 6% of the organic carbon content of the mats, exhibit little seasonal variation in the PHA levels, and show a diel pattern in PHA.