Polyhydroxyalkanoates (PHAs) are microbially-produced, plastic-like polymers which are biodegraded by microbial PHA depolymerases. We used electrospray time-of-flight mass spectrometry (ESI-TOF-MS) to identify and quantify products from degradation of various PHAs by a PHA depolymerase from the soil bacterium, <i>Streptomyces </i>sp. 5A<i>.</i> The enzyme degraded polyhydroxybutyrate [P(3HB)], polyhydroxyvalerate [P(3HV)], and a copolymer of P(3HB) and P(3HV). The products included the monomers, dimers, and trimers of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV), with the monomers as the primary products. The enzyme degraded P(3HB) 8.7 times faster than P(3HV) and yielded 2.1 times more total products. Thus, P(3HB) was a preferred substrate, possibly because P(3HV) has a longer monomer carbon chain than P(3HB), creating greater steric hindrance and hydrophobicity in the active site of the enzyme. Time course trials of PHA degradation suggested that PHB depolymerase degraded trimers of 3HB and 3HV into their monomers and dimers and was subject to feedback inhibition by PHA degradation products.

Characterization of polyhydroxyalkanoate enzymatic degradation products by mass spectrometry

255th National Meeting (2018)

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