Accelerated Polyethylene Terephthalate (PET) Enzymatic Degradation by Room Temperature Alkali Pre‐treatment for Reduced Polymer Crystallinity

Abstract

Polyethylene terephthalate (PET) is the most widely employed plastic for single‐use applications. The use of enzymes isolated from microorganisms, such as PETase with the capacity to hydrolyze PET into its monomers, represents a promising method for its sustainable recycling. However, the accessibility of the enzyme to the hydrolysable bonds is an important challenge that needs to be addressed for effective biodegradation of postconsumer PET. Here, we combined an alkali pre‐treatment (25 °C) with PETase incubation (30 °C) with post‐consumed PET bottles. The pre‐treatment modifies the surface of the plastic and decreases its crystallinity enabling the access of the enzyme to the hydrolysable chemical bonds. When the alkali pre‐treatment is incorporated into the enzymatic process the degradation yields increase more than one order of magnitude reaching values comparable to those obtained during heating/cooling cycles. Our results show energetic advantages over other reported pre‐treatments and open new avenues for sustainable PET recycling.

Effect of chloride salts and microwaves on polyethylene terephthalate (PET) hydrolysis by iron chloride/acetic acid Lewis/Brønsted acidic deep eutectic solvent

“…This suggests that the less crystalline polymer on the surface of the flakes was hydrolyzed and converted to Na 2 TA . 21,34 The surface of the PET flakes was much smoother after this treatment (Fig. 2b).…”

“…increased amorphous fraction) of the polymer at the surface. 21,34 A mild post-reaction treatment maintaining all the recovered solid fractions (TA, oligomers and unreacted PET) in contact with 20 mL of NaOH 0.5 M for 12 h at room temperature under magnetic stirring was found to improve the conversion up to 54%. This suggests that the less crystalline polymer on the surface of the akes was hydrolyzed and converted to Na 2 TA.…”

“…In most cases, harsh conditions are necessary (T > 160 °C, many hours, sometimes high pressure) although exceptions can be found in recent studies. [19][20][21][22] On the industrial side, many processes are used, 23 including the pyrolysis of unsorted or sorted waste plastics and solvolysis, demonstrating widespread interest in the depolymerization process.…”

“…In most cases, harsh conditions are necessary ( T > 160 °C, many hours, sometimes high pressure) although exceptions can be found in recent studies. 19–22…”

Computation‐Based Design of Salt Bridges in PETase for Enhanced Thermostability and Performance for PET Degradation

“…However, due to its chemical inertness and hydrophobic surface, [3] it is difficult be decompose PET. Therefore, a large amount of PET waste has been accumulated in landfills and flowed into the ocean after being used, posing a serious threat to the ecosystem and biodiversity [4] . The efficient degradation, recycling, and reuse of PET waste are an urgent reality.…”