Enzymatic biodegradation of Poly(ε-Caprolactone) (PCL) by a thermostable cutinase from a mesophilic bacteria...

Cutinases are esterases that can be potentially used as biocatalysts for polycaprolactone (PCL) degradation. In order to develop an efficient enzyme for biodegradation and recycling of PCL, MmCut3, a novel cutinase derived from Mycobacterium marinum has been exploited. MmCut3 demonstrated activity on substrates such as p-Nitrophenyl acetate and butyrate (C2, C4), Triolein (C18), and Cutin (hydroxy C16, C18), with optimal performance at pH 6.5-8.5 and 45 °C. The enzyme exhibited remarkable thermal stability, retaining activity up to 90 °C due to reversible structural changes and dimerization. Its activity increased by 150 % in the presence of calcium ions and was inhibited by EDTA, indicating a metal-dependent mechanism. MmCut3 remained stable in organic solvents (10-60 %) and surfactants (1 and 10 mM). PCL biodegradation by MmCut3 primarily targeted amorphous regions, confirmed by FT-IR and DSC analysis. Turbidimetric studies revealed that calcium ions enhanced hydrolysis by increasing the enzyme affinity for binding to the polymer surface, consistent with the Langmuir model. Molecular docking identified key interactions with PCL diol, highlighting MmCut3 potential as a biocatalyst for plastic degradation and sustainable material production.