现代生物技术推动塑料中聚对苯二甲酸乙二酯绿色降解的研究进展

Research progress of modern biotechnology-promoted green degradation of polyethylene terephthalate in plastics

聚对苯二甲酸乙二酯(PET)因其耐用、可塑性强、安全性好等特点而广泛应用于食品包装和服装产业等领域,同时由于疏水性强、结晶度高等原因难以被微生物或酶降解利用,造成PET废弃物的不断积累,带来严重的环境和社会问题。部分高质量的PET净片可以再用到食品包装中,但绝大多数废弃PET通过常规的机械回收方法被降级利用,不能做到绿色高效回收。因此,解决“白色污染”,探索安全高效的生物降解方法成为急需攻克的重大研究课题。本文以石油基塑料的现状为背景,以PET的生物降解为切入点,综述了PET的生物降解研究现状,以宏基因组学、蛋白质组学为基础,重点总结了微生物和新酶基因的挖掘方法,并通过结构分析,以追溯不同来源的PET降解酶特性,利用定向改造和智能计算策略提高酶特性以及PET的降解效率。在改造降解酶的同时,探索对PET原材料的可降解性改良,提出了“双向改造”的思想。塑料降解酶新酶挖掘与工程改造、多酶催化体系开发以及塑料的可持续性能的改良等领域将成为塑料绿色降解的主流趋势,其为探索PET高效生物降解提供了新思路。

Polyethylene terephthalate(PET) has been widely used in the food packaging and clothing industries due to its good durability, high plasticity, and safety. However, PET is difficult to be degraded by microorganisms or enzymes due to its high hydrophobicity and high crystallinity, which has led to severe environmental and social problems globally. Some of the high-quality PET can be reused in food packaging, but the majority of waste PET is downgraded through conventional mechanical recycling ways and cannot be recycled in a green and efficient manner. The proportion of recycled plastics that relies on recycling and green degradation is decreasing year by year, and only a small percentage of plastic can be recycled, accounting for 17.6% of annual plastic use. Thus, exploring a safe and efficient biodegradation for plastic to solve “white pollution” has become a major research issue that needs to be pursued urgently. Herein, this paper reviews the current status of research on PET biodegradation, focusing on the mining methods of microbes and genes encoding novel enzyme based on macrogenomics and proteomics. The characteristics and mechanism of plasticdegrading enzymes from different sources were elucidated through an analysis of the crystal structures. Importantly, the activity and degradation efficiency of the plastic-degrading enzymes were improved by directed evolution and smartcomputing strategy. This provides insights into the structural modification of plastic-degrading enzymes and introduces some frontier research fields. The idea of “two-direction modification” is proposed to improve the degradability for PET raw materials using modifying degradation enzymes. Furthermore, new enzymes mining and modification for plastic degradation, the development of multi-enzyme catalytic system and the improvement of sustainable performance of plastic will significantly stimulate the new ideas for exploring efficient biodegradation of PET in the future.