Recalcitrant plastic waste has caused serious global ecological problems. There is an urgent need to develop environmentally friendly and efficient methods for degrading the highly stable carbon skeleton structure of plastics. To that end, we used a quantum mechanical calculation to thoroughly investigate the oxidative scission of the carbon-carbon (C–C) backbone in polyethylene (PE). Here, we studied the reaction path of C–C bond oxidation via hydroxyl radical in PE. The flexible force constants and fuzzy bond orders of the C–C bonds were calculated in the presence of one or more carbocations in the same PE carbon chain. By comparison, the strength of the C–C bond decreased when carbocation density increased. However, the higher the density of carbocations, the higher the total energy of the molecule and the more difficult it was to be generated. The results revealed that PE oxidized to alcohol and other products, such as carboxylic acid, aldehyde and ketone, etc. Moreover, the presence of carbocations was seen to promote the cleavage of C–C backbones in the absence of oxygen.

Medium- and long-chain triacylglycerol (MLCT), as a novel functional lipid, is valuable due to its special nutritional properties. Its low content in natural resources and inefficient synthesis during preparation have limited its practical applications. In this study, we developed an effective Pickering emulsion interfacial catalysis system (PE system) for the enzymatic synthesis of MLCT by trans-esterification. Lipase NS 40086 served simultaneously as a catalyst and a solid emulsifier to stabilize the Pickering emulsion. Benefitting from the sufficient oil–water interface, the obtained PE system exhibited outstanding catalytic efficiency, achieving 77.5% of MLCT content within 30 min, 26% higher than that of a water-free system. The K_m value (0.259 mM) and activation energy (14.45 kJ mol⁻¹) were 6.8-fold and 1.6-fold lower than those of the water-free system, respectively. The kinetic parameters as well as the molecular dynamics simulation and the tunnel analysis implied that the oil–water interface enhanced the binding between substrate and lipase and thus boosted catalytic efficiency. The conformational changes in the lipase were further explored by FT-IR. This method could give a novel strategy for enhancing lipase activity and the design of efficient catalytic systems to produce added-value lipids. This work will open a new methodology for the enzymatic synthesis of structured lipids.

Branched‐chain fatty acids (BCFAs) exhibit enhanced oxidative stability, lower melting points, and reduced viscosity compared to straight‐chain fatty acids (StCFAs), making them valuable for biological systems and industrial applications. Previous studies have shown that metazoan fatty acid synthase (mFAS) can produce BCFAs through the incorporation of branched starter units and branched extender substrates such as methylmalonyl‐CoA (metmal‐CoA). However, the mechanistic and kinetic underpinnings of BCFA biosynthesis in metazoans remain poorly understood. Here, we address this by characterizing the kinetic parameters of mFAS‐catalyzed BCFA synthesis using NADPH consumption assays and analyzing the synthesized products via GC–MS. These experiments revealed a lower turnover number of mFAS with metmal‐CoA and a shift toward medium‐chain fatty acids compared to the native StCFA biosynthesis with malonyl‐CoA. The ketoacyl synthase (KS) kinetic measurements revealed low elongation rates, indicating that the KS domain dictates the substrate specificity and speed of BCFA production. To gain a better understanding of the reaction mechanism, we performed molecular dynamic simulations, which revealed key KS: substrate interactions by conserved threonine residues. These insights support a refined decarboxylative condensation mechanism and illuminate how substrate specificity arises within mFAS. These findings offer a foundation for future protein engineering and inhibitor design strategies.

Different plasticizers have obvious differences in plasticizing properties. As one of the important indicators for evaluating plasticization performance, the substitution factor (SF) has great significance for product cost accounting. In this research, a genetic algorithm with “variable mutation probability” was developed to screen the key molecular descriptors of plasticizers that are highly correlated with the SF, and a SF prediction model was established based on these filtered molecular descriptors. The results show that the improved genetic algorithm greatly improved the prediction accuracy in different regression models. The coefficient of determination (R²) for the test set and the cross-validation both reached 0.92, which is at least 0.15 higher than the R² of the unimproved genetic algorithm. From the results of the selected descriptors, most of the descriptors focused on describing the branching of the molecule, which is consistent with the view that the branching chain plays an important role in the plasticization process. As the first study to establish the relationship between plasticizer SF and plasticizer molecular structure, this work provides a basis for subsequent plasticizer performance and evaluation system modeling.

The efficient expression and excellent thermal stability of Candida antarctica lipase B (CALB) are crucial for its industrial production. In this study, through genetic engineering and rational design, while preserving the superior catalytic properties of CALB, we optimized the induction pathway using glycerol as the sole carbon source; moreover, the thermal stability sites of CALB were predicted and optimized. The results revealed that the level of CALB expression in this expression system reached 2.27 g/L under the condition of a 5 L fermenter. The Tm value of the CALB-Q231F increased by 10 °C. Moreover, after thermal inactivation at 80 °C for 1 h, the retention rate of esterification enzymatic activity over 24 h was 2.99 times that of wild-type (WT) CALB, whereas the retention rate of hydrolytic enzymatic activity was 2.23 times that of WT CALB. In this study, a non-methanol-induced Pichia pastoris expression system was successfully designed and constructed; a non-methanol-induced CALB-producing strain, X33-pGAPZ(Mα) A-CalB-Q231F, with high thermal stability and a high expression level was obtained, which can be used for the development of industrial enzymes.