Polyethylene terephthalate (PET) is a synthetic aromatic polyester composed of ethylene glycol and terephthalic acid(TPA). Because of its versatile properties PET is used in many products such as textile fibers or beverage bottles. The widespread use of synthetic polyesters such as PET contributes to growing amounts of postconsumer plastic wastes. The related environmental pollution problems require efficient recycling processes. The biocatalytic degradation of PET offers a less energy consuming and environmentally friendly method than convention recycling process. Hydrolytic activity against PET has been shown for lipases, carboxylesterases and cutinases.

The type and ionic strength of buffers can influence the enzymatic activity in aqueous reaction systems. Here, Schmidt et al. studied Tris and other buffers effect on the hydrolysis of PET films by TfCut2 and LCC. When the hydrolysis of PET films was performed at different concentrations of TfCut2 and LCC in Tris-HCl, MOPS and sodium phosphate buffers(0.2 M, pH=8.0). The maximum initial hydrolysis rates were reached with lower LCC concentrations compared to TfCut2 in all three buffers. LCC showed the highest activity in Tri-HCl buffer with a 2.1-fold higher rate than TfCut2. And the effect of buffer concentrations on the hydrolysis of PET films by TfCut2 and LCC was also studied. The activity of TfCut2 and LCC depended on the concentration of the buffers. The activity of TfCut2 in MOPS buffer was low in the range from 0.1 to 1 M. In 1 M Tris buffer, its activity decreased by 80% compared to 0.1 M Tris buffer. In contrast, the hydrolysis rate was about 10-fold higher at 1 M sodium phosphate compared to 0.1 M. LCC showed a different response to changing buffer concentrations. While the hydrolysis rates were unaffected within 0.1–1 M of the phosphate buffer, in 1 M Tris and MOPS buffers its activity decreased by more than 90% compared to 0.1 M.

In summary, the activity of the polyester hydrolases LCC and TfCut2 against PET fifilms was shown to strongly depend on the type and concentration of the buffer according to Schmidt et al. studies. A buffer of high molarity and strength was required to stabilize the pH during the reaction. The hydrolytic activity of both enzymes was inhibited at higher concentrations of MOPS and Tris.

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