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Enzymatic Self-Biodegradation of Poly(l-lactic acid) Films by Embedded Heat-Treated and Immobilized Proteinase K

Biomacromolecules 2020 128 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
QiuYuan Huang, Masatoshi Hiyama, Taizo Kabe, Satoshi Kimura, Tadahisa Iwata

Summary

Polylactic acid plastic films containing embedded enzyme proteinase K successfully biodegraded from the inside out, losing 78% of their weight in four days. Immobilizing the enzyme improved its heat stability during manufacturing, offering a new concept for self-biodegrading plastics that could reduce microplastic accumulation in the environment.

Non-biodegradable microplastics have become a global problem. We propose a new enzyme-embedded biodegradable plastic that can be self-biodegraded anytime and anywhere. Proteinase K from Tritirachium album was embedded in poly(l-lactic acid) (PLLA). The PLLA solution-cast film with embedded proteinase K showed weight loss of 78% after 96 h incubation. In addition, PLLA extruded films embedding immobilized proteinase K encapsulated in polyacrylamide were produced at 200 °C and embedded-enzyme degradation was monitored. Immobilized proteinase K embedded in the extruded film maintained its degradation activity and degraded the PLLA film from inside to make small holes and cavities, suggesting that immobilization is a powerful technique to prepare thermoforms with embedded enzymes. The rate of embedded-enzyme degradation was accelerated by dividing the film into smaller pieces, which can be regarded as a model experiment for biodegradation of microplastics. Various biodegradable plastics with specific embedded enzymes will contribute to solve global environmental problems.

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