プラスチックを食べる酵素で、何十億トンもの埋立廃棄物をなくせる可能性(Plastic-eating Enzyme Could Eliminate Billions of Tons of Landfill Waste)

2022-04-27 テキサス大学オースチン校(UT Austin)

<関連情報>

• https://news.utexas.edu/2022/04/27/plastic-eating-enzyme-could-eliminate-billions-of-tons-of-landfill-waste/
• https://www.nature.com/articles/s41586-022-04599-z

機械学習を援用したPET解重合用ヒドロラーゼの創製 Machine learning-aided engineering of hydrolases for PET depolymerization

Hongyuan Lu,Daniel J. Diaz,Natalie J. Czarnecki,Congzhi Zhu,Wantae Kim,Raghav Shroff,Daniel J. Acosta,Bradley R. Alexander,Hannah O. Cole,Yan Zhang,Nathaniel A. Lynd,Andrew D. Ellington & Hal S. Alper
Nature  Published: 27 April 2022
DOI:https://doi.org/10.1038/s41586-022-04599-z

Abstract

Plastic waste poses an ecological challenge^1,2,3 and enzymatic degradation offers one, potentially green and scalable, route for polyesters waste recycling⁴. Poly(ethylene terephthalate) (PET) accounts for 12% of global solid waste⁵, and a circular carbon economy for PET is theoretically attainable through rapid enzymatic depolymerization followed by repolymerization or conversion/valorization into other products^6,7,8,9,10. Application of PET hydrolases, however, has been hampered by their lack of robustness to pH and temperature ranges, slow reaction rates and inability to directly use untreated postconsumer plastics¹¹. Here, we use a structure-based, machine learning algorithm to engineer a robust and active PET hydrolase. Our mutant and scaffold combination (FAST-PETase: functional, active, stable and tolerant PETase) contains five mutations compared to wild-type PETase (N233K/R224Q/S121E from prediction and D186H/R280A from scaffold) and shows superior PET-hydrolytic activity relative to both wild-type and engineered alternatives¹² between 30 and 50 °C and a range of pH levels. We demonstrate that untreated, postconsumer-PET from 51 different thermoformed products can all be almost completely degraded by FAST-PETase in 1 week. FAST-PETase can also depolymerize untreated, amorphous portions of a commercial water bottle and an entire thermally pretreated water bottle at 50 ºC. Finally, we demonstrate a closed-loop PET recycling process by using FAST-PETase and resynthesizing PET from the recovered monomers. Collectively, our results demonstrate a viable route for enzymatic plastic recycling at the industrial scale.