Dissanayake Lakshika, Jayakody Lahiru N
School of Biological Sciences, Southern Illinois University, Carbondale, IL, United States.
Fermentation Science Institute, Southern Illinois University, Carbondale, IL, United States.
Front Bioeng Biotechnol. 2021 May 28;9:656465. doi: 10.3389/fbioe.2021.656465. eCollection 2021.
Polyethylene terephthalate (PET) is globally the largest produced aromatic polyester with an annual production exceeding 50 million metric tons. PET can be mechanically and chemically recycled; however, the extra costs in chemical recycling are not justified when converting PET back to the original polymer, which leads to less than 30% of PET produced annually to be recycled. Hence, waste PET massively contributes to plastic pollution and damaging the terrestrial and aquatic ecosystems. The global energy and environmental concerns with PET highlight a clear need for technologies in PET "upcycling," the creation of higher-value products from reclaimed PET. Several microbes that degrade PET and corresponding PET hydrolase enzymes have been successfully identified. The characterization and engineering of these enzymes to selectively depolymerize PET into original monomers such as terephthalic acid and ethylene glycol have been successful. Synthetic microbiology and metabolic engineering approaches enable the development of efficient microbial cell factories to convert PET-derived monomers into value-added products. In this mini-review, we present the recent progress of engineering microbes to produce higher-value chemical building blocks from waste PET using a wholly biological and a hybrid chemocatalytic-biological strategy. We also highlight the potent metabolic pathways to bio-upcycle PET into high-value biotransformed molecules. The new synthetic microbes will help establish the circular materials economy, alleviate the adverse energy and environmental impacts of PET, and provide market incentives for PET reclamation.
聚对苯二甲酸乙二酯（PET）是全球产量最大的芳香族聚酯，年产量超过5000万吨。PET可以进行机械回收和化学回收；然而，将PET转化回原始聚合物时，化学回收的额外成本并不合理，这导致每年生产的PET中只有不到30%被回收利用。因此，废弃PET大量造成塑料污染，破坏陆地和水生生态系统。全球对PET的能源和环境担忧凸显了对PET“升级回收”技术的迫切需求，即从回收的PET中制造高价值产品。已经成功鉴定出几种能降解PET的微生物和相应的PET水解酶。对这些酶进行表征和工程改造，以选择性地将PET解聚为对苯二甲酸和乙二醇等原始单体，已经取得成功。合成微生物学和代谢工程方法能够开发高效的微生物细胞工厂，将PET衍生的单体转化为增值产品。在这篇小型综述中，我们介绍了利用完全生物策略和化学催化-生物混合策略，工程改造微生物以从废弃PET中生产高价值化学结构单元的最新进展。我们还强调了将PET生物升级回收为高价值生物转化分子的有效代谢途径。新型合成微生物将有助于建立循环材料经济，减轻PET对能源和环境的不利影响，并为PET回收提供市场激励。
