Biodegradation of polybutylene succinate by an extracellular esterase from Pseudomonas mendocina

An extracellular esterase (HP) with polybutylene succinate (PBS)-degrading ability was identified from Pseudomonas mendocina SA-1503. The HP also had the ability to degrade poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and polycaprolactone. This HP had optimal activity at pH 9.0 and 40 °C and remained stable at pH 8.0–9.0 and temperatures of 30–40 °C. Mn²⁺ promoted the enzyme activity. HP could hydrolyze all p-NP fatty acid ester substrates containing even numbers of carbon atoms from C2 to C18 and had the highest catalytic activity for the p-NP C6 substrate. After 60 h of HP-catalyzed degradation, PBS films experienced a weight loss of more than 60%. Butanedioic acid, 1,4-butanediol, and a series of oligomers were detected in the degradation products of PBS by HP. Further structural analysis of HP revealed that it could be classified as a microbial esterase of α/β hydrolase superfamily and contained a conserved catalytic triad structure (Ser-148, Asp-198, and His-228) with a relatively exposed active site.