Cutinase Adsorption to Polyester Surfaces Modulates Dissolved Oligomer Speciation during Enzymatic Depolymerization

Area of Science:

• Biotechnology
• Polymer Science
• Environmental Science

Background:

• Surface-active enzymes like cutinases initiate polyester plastic depolymerization via adsorption.
• The impact of enzyme adsorption on the chemical composition of dissolved degradation products is not well understood.

Purpose of the Study:

• To investigate how the adsorption of cutinase from *Humicola insolens* (HiC) to polyester surfaces affects dissolved oligomer speciation during poly(butylene succinate) (PBS) and poly(butylene sebacate-co-terephthalate) (PBSeT) depolymerization.

Main Methods:

• Utilized inverse and conventional Michaelis-Menten kinetics to quantify enzyme attack site densities (Γ_attack) and catalytic turnover rates (k_cat).
• Employed liquid chromatography coupled with mass spectrometry (LC-MS) to analyze the composition of dissolved oligomers.

Main Results:

• HiC showed similar attack site densities for PBS and PBSeT, but a significantly higher catalytic turnover rate for PBS (40.8 ± 8.4 s^-1) compared to PBSeT (0.13 ± 0.02 s^-1).
• Accumulation of larger oligomers was observed when enzyme-to-plastic ratios were below the determined attack site densities.

Conclusions:

• Relative levels of free enzyme significantly influence the composition of dissolved products during enzymatic plastic depolymerization.
• Understanding enzyme adsorption dynamics is crucial for optimizing enzymatic strategies for plastic degradation.