Microbial degradation of the artificial polyhydroxyalkanoate poly(2-hydroxybutyrate-co-3-hydroxybutyrate) with random...

This study aimed to examine whether microorganisms capable of degrading the artificial polyhydroxyalkanoate (PHA) copolymer poly(2-hydroxybutyrate-co-3-hydroxybutyrate) [P(2HB-co-3HB)], with random and block sequences, are present in natural environments. Previously isolated PHA-degrading soil bacteria were tested using 2HB-rich copolymers, P(2HB-ran-3HB) and P(2HB)-b-P(3HB), as a major carbon source. The assimilation of 2HB and 3HB fractions in these copolymers and the effect of monomer sequence on degradability were investigated.

Acidovorax sp. YM1609, Cupriavidus sp. T1, and Variovorax spp. A25i and A60i2 were tested in clear zone analysis to determine the depolymerization of the polymer and GC analysis to assess the assimilation of the monomer component following depolymerization. Strains YM1609, A25i, and A60i2 depolymerized emulsified P(2HB-ran-3HB) and assimilated both components. For emulsified P(2HB)-b-P(3HB), all the strains depolymerized and assimilated the 3HB component but hardly did the 2HB component within 2 weeks.

This study revealed that both P(2HB-ran-3HB) and P(2HB)-b-P(3HB) can be degraded to some extent by soil bacteria. 2HB components were more susceptible to degradation in random sequence than in the block sequence; in contrast, the opposite trend was rather applied for 3HB components.