Microbial Degradation of Polyhydroxyalkanoates with Different Chemical Compositions and Their Biodegradability

The study addresses degradation of polyhydroxyalkanoates (PHA) with different chemical compositions—the polymer of 3-hydroxybutyric acid [P(3HB)] and copolymers of P(3HB) with 3-hydroxyvalerate [P(3HB/3HV)], 4-hydroxybutyrate [P(3HB/4HB)], and 3-hydroxyhexanoate [P(3HB/3HHx)] (10–12 mol%)—in the agro-transformed field soil of the temperate zone. Based on their degradation rates at 21 and 28 °C, polymers can be ranked as follows: P(3HB/4HB) > P(3HB/3HHx) > P(3HB/3HV) > P(3HB). The microbial community on the surface of the polymers differs from the microbial community of the soil with PHA specimens in the composition and percentages of species. Thirty-five isolates of bacteria of 16 genera were identified as PHA degraders by the clear zone technique, and each of the PHA had both specific and common degraders. P(3HB) was degraded by bacteria of the genera Mitsuaria, Chitinophaga, and Acidovorax, which were not among the degraders of the three other PHA types. Roseateles depolymerans, Streptomyces gardneri, and Cupriavidus sp. were specific degraders of P(3HB/4HB). Roseomonas massiliae and Delftia acidovorans degraded P(3HB/3HV), and Pseudoxanthomonas sp., Pseudomonas fluorescens, Ensifer adhaerens, and Bacillus pumilus were specific P(3HB/3HHx) degraders. All four PHA types were degraded by Streptomyces.