Exploring the Diversity of Polyesterases from marine Bacteria

In recent years, marine bacteria have proven to be a prolific source of polyester degrading enzymes. Such polymer-active enzymes can effectively break down plastic polymers into their constituent components and thus contribute to mitigate environmental pollution. With this study, we aimed to expand the repertoire of available polyesterases with a focus on enzymes showing activity at high salt concentrations, low temperatures and elevated pressure. We have isolated polyesterases from marine bacteria which inhabit plastic-polluted coasts and deep-sea environments assuming that they may have evolved an enzyme repertoire enabling the degradation of plastics. To this end, we used sediment samples for growing enrichment cultures with various synthetic polymers as sole carbon sources. More than 20 marine organisms displaying polyesterase activities were isolated, their genomes sequenced, and potentially novel polyesterase encoding genes identified by using search algorithms based on Hidden-Markov-models. Selected candidate genes were then expressed in E. coli and tested for polyesterase activity on indicator plates. Subsequently, 8 enzymes were purified and activity assays confirmed the hydrolysis of a broad range of synthetic substrates (eg. BHET, MHET, Impranil® DLN-SD). Some of these enzymes exhibited a high tolerance towards different organic solvents (eg. Methanol, dimethyl sulfoxide) and showed high activity also at temperatures lower than 10 °C. Our study shows that marine bacteria can be source of novel polyesterases with biochemical properties useful for biotechnological applications.