Design and construction of chemical-biological module clusters for degradation and assimilation of poly(ethylene terephthalate) waste.

The rising accumulation of poly(ethylene terephthalate) (PET) waste presents an urgent ecological challenge, necessitating an efficient and economical treatment technology. Here, we developed chemical-biological module clusters that perform chemical pretreatment, enzymatic degradation, and microbial assimilation for the large-scale treatment of PET waste. This module cluster included (i) a chemical pretreatment that involves incorporating polycaprolactone (PCL) at a weight ratio of 2% (PET:PCL = 98:2) into PET via mechanical blending, which effectively reduces the crystallinity and enhances degradation; (ii) enzymatic degradation using Thermobifida fusca cutinase variant (4Mz), that achieves complete degradation of pretreated PET at 300 g/L PET, with an enzymatic loading of 1 mg protein per gram of PET; and (iii) microbial assimilation, where Rhodococcus jostii RHA1 metabolizes the degradation products, assimilating each monomer at a rate above 90%. A comparative life cycle assessment demonstrated that the carbon emissions from our module clusters (0.25 kg CO2-eq/kg PET) are lower than those from other established approaches. This study pioneers a closed-loop system that seamlessly incorporates pretreatment, degradation, and assimilation processes, thus mitigating the environmental impacts of PET waste and propelling the development of a circular PET economy.

Directional-path modification strategy enhances PET hydrolase catalysis of plastic degradation.

Poly (ethylene terephthalate) (PET) is a widely used type of general plastic that produces a significant amount of waste due to its non-degradable properties. We propose a novel directional-path modification (DPM) strategy, involving positive charge amino acid introduction and binding groove remodeling, and apply it to Thermobifida fusca cutinase to enhance PET degradation. The highest value of PET degradation (90%) was achieved in variant 4Mz (H184S/Q92G/F209I/I213K), exhibiting values almost 30-fold that of the wild-type. We employed molecular docking, molecular dynamics simulations, and QM/MM MD for the degradation process of PET, accompanied by acylation and deacylation. We found that the distance of nucleophilic attack was reduced from about 4.6 Å in the wild type to 3.8 Å in 4Mz, and the free energy barrier of 4Mz dropped from 14.3 kcal/mol to 7.1 kcal/mol at the acylation which was the rate-limiting step. Subsequently, the high efficiency and universality of the DPM strategy were successfully demonstrated in LCC, Est119, and BhrPETase enhancing the degradation activity of PET. Finally, the highest degradation rate of the pretreated commercial plastic bottles had reached to 73%. The present study provides insight into the molecular binding mechanism of PET into the PET hydrolases structure and proposes a novel DPM strategy that will be useful for the engineering of more efficient enzymes for PET degradation.

[Facial nerve function index evaluation on deviation of the mouth in intractable facial palsy treated with sticking needle and traction method on three points of the mouth].

OBJECTIVE: To probe into the effective acupuncture technique for deviation of the mouth in intractable facial palsy. METHODS: One hundred and one cases of intractable facial palsy were randomly divided into an observation group (48 cases) and a control group (53 cases). Cuanzhu (BL 2), Sibai (ST 2), Jiache (ST 6) and Qianzheng (Extra) on the affected side were punctured in two groups. Additionally, three acupoints of the mouth were supplemented, named Dicang (ST 4), Kouheliao (LI 19) and Jiachengjiang (Extra) were added, and the sticking needle and traction method was adopted on them in observation group. the routine needling technique was applied in control group. The treatment was given once a day and 10-day treatment made one session. The changes in facial nerve function index (FNFI) were observed in 2 sessions of treatment. RESULTS: After treatment, FNFI in two groups increased significantly (both P < 0.01), but the improvement in observation group was better than that in control group (P < 0.01). In observation group, the basic recovery rate of FNFI was 87.5% (42/48), which was higher than that (67.9%, 36/53) in control group (P < 0.05). CONCLUSION: The sticking needle and traction method o three points is the quite effective approach in the treatment of deviation of the mouth in intractable facial palsy.