通过碳水化合物结合模块增强LCC-ICCG的PET降解效率

Enhancing PET degradation efficiency through fusing carbohydrate-binding modules in LCC-ICCG

摘要:

聚对苯二甲酸乙二醇酯(polyethylene terephthalate,PET)是全球产量最大的聚酯之一，但由于其废弃量大且难降解，环境污染严重。酶解法处理PET是目前的研究热点，碳水化合物结合模块(carbohydrate binding module,CBM)的加入可以增加酶与底物之间的亲和力，提高酶的降解能力。为了开发更高效的PET水解酶，本研究在PET降解酶LCC-ICCG中引入来源于不同家族具有不同底物亲和力的碳水化合物结合结构域(CBM)，并以高结晶度PET粉末和无定型PET膜为底物，对改造后酶的降解效率进行了表征，以探寻降解能力最优的酶。结果表明，融合B型CBM后降低了酶对PET的降解率和T_m值，而引入A、C型CBM后，酶对膜状底物的降解率得到了显著提高，PET的降解速率和T_m值也得到了提升，尤其是融合酶LCC-ICCG-CBM9-2对膜状PET底物的降解率对比原始酶LCC-ICCG提高了10倍以上。本研究的结果表明，通过引入A、C两型CBM的方式，可以提高LCC-ICCG对膜状PET降解率和热稳定性，改善其活性低的问题，从而更有效地降解PET。本研究可为塑料降解提供技术支持，有利于推进环保事业。

Abstract:

Polyethylene terephthalate (PET) is a largely-produced polymer worldwide. However, its extensive waste generation and resistance to degradation pose significant environmental concerns. Consequently, there is considerable interest in researching enzymatic degradation of PET. Relevant studies have shown that the addition of a carbohydrate binding module (CBM) can increase the affinity between the enzyme and the substrate, enhancing the enzyme’s degradation ability. In order to develop more efficient PET hydrolytic enzymes, this study introduced carbohydrate binding domains (CBMs) from different families with different substrate affinities into the PET-degrading enzyme LCC-ICCG. High crystallinity PET powder and amorphous PET film were used as substrates to characterize the degradation efficiency of the modified enzymes, aiming to explore the enzyme with the optimal degradation ability. The results showed that the fusion of type B CBM reduced the degradation rate and T_m value of the enzyme towards PET, while the introduction of type A and type C CBMs significantly improved the degradation rate of the enzyme towards the film-like substrate. The degradation rate and T_m value of PET were also enhanced, especially with the fusion enzyme LCC-ICCG-CBM9-2, which showed an over 10-fold increase in the degradation rate compared to the original enzyme LCC-ICCG. Therefore, this study demonstrates that by introducing type A and type C CBMs, the degradation rate and thermal stability of LCC-ICCG towards film-like PET can be improved, addressing the issue of its low activity and enabling more effective PET degradation. This research provides support for plastic degradation technology and contributes to environmental conservation efforts.