Green Chemical Engineering最新文献

Waste plastics are serious environmental threats due to their low degradability and low recycling rate. Rapid and efficient waste plastics recycling technologies are urgently demanded for a sustainable future. Herein, we report a rapid, closed-loop, and streamlined process to convert polyesters such as poly(ethylene terephthalate) (PET) back to its purified monomers. Using trifluoromethanesulfonic acid or metal triflates as the recyclable catalyst, polyesters such as PET can be completely depolymerized by simple carboxylic acids within 1 h. By coupling this acidolysis with a subsequent hydrogenolysis process, the consumed carboxylic acid was recovered and the closed-loop of PET depolymerization could be established. All catalysts and depolymerization agents are fully recycled while only PET and hydrogen are consumed.

Non-methane hydrocarbons (NMHCs) are a common type of volatile organic compounds (VOCs) pollutant in the petrochemical industry and have attracted widespread attention because of their adverse health effects and environmental impacts. In this paper, we report a new porous slurry formed with zeolitic imidazolate framework-8 (ZIF-8) and iso-hexadecane to capture the low-concentration and multi-component NMHCs (mainly ethane (C₂H₆), propane (C₃H₈), and n-butane (n-C₄H₁₀)) from the oil field exhaust. The sorption capacity of C₂H₆ in the slurry is significantly higher than that of nitrogen (N₂) and methane (CH₄). Moreover, the slurry demonstrated a clear advantage for C₂H₆ over N₂ and CH₄ in competitive adsorption through the pressure-drop curves. In the NMHCs capture experiments, the C₃H₈ and n-C₄H₁₀ concentrations after purification can be reduced to below 100 ppm, while the C₂H₆ concentration can reach approximately 180 ppm. More encouragingly, in the breakthrough tests, the slurry exhibits a perfect kinetic separation selectivity for multi-component NMHCs. Furthermore, to avoid structural collapse of ZIF-8 material during long-term use in acidic and wet environments, a certain amount of 2-methylimidazole was retained in the slurry as a protective agent in the material synthesis process. In this way, the ZIF-8 materials in the slurry can retain the stable characteristic structure in an aqueous and acidic environment and keep the capture capacity for NMHCs without degradation. We believe the porous ZIF-8/iso-hexadecane slurry is a promising capture agent for low-concentration and multi-component NMHCs with strong purification capacity and stability.

In the chemical synthesis of L-syn-p-methylsulfoxide phenylserine ethyl ester (D-ethyl ester), l-tartaric acid or enzymatic resolution is employed to resolve the racemate, and thus obtain the target compound, and the remaining isomer can be recycled to obtain the raw material. In this study, high-purity L-syn-p-methylsulfoxide phenylserine (L-syn-MPS) was obtained. The kinetics of the d-threonine aldolase enzymatic hydrolysis reaction reveals that D-syn-p-sulfoxylphenylserine resolves well in [BMIM][BF₄] ionic solvents. The D/L-syn-MPS racemate was resolved using a two-phase ionic solvent [BMIM][NTf₂] to afford L-syn-MPS (ee (enantiomeric excess) > 99%) and a white solid in 41.7% yield. Therefore, this system is suitable for the separation of insoluble aldehydes and successfully avoids the condensation of hydroxyl aldehydes to form D-anti-MPS.

The genomic scale metabolic networks of the microorganisms can be constructed based on their genome sequences, functional annotations, and biochemical reactions, reflecting almost all of the metabolic functions. Mathematical simulations of metabolic fluxes could make these functions be visualized, thereby providing guidance for rational engineering design and experimental operations. This review summarized recently developed flux simulation algorithms of microbial systems. For the single microbial systems, the optimal planning algorithm has low complexity because there is no interaction between microorganisms, and it can quickly simulate the stable metabolic states through the pseudo-steady hypothesis. Besides, the experimental conditions of single microbial systems are easier to reach or close to the optimal states of simulation, compared with polymicrobial systems. The polymicrobial culture systems could outcompete the single microbial systems as they could relieve metabolic pressure through metabolic division, resource exchange, and complex substrate co-utilization. Besides, they provide varieties of intracellular production environments, which render them the potential to achieve efficient bioproduct synthesis. However, due to the quasi-steady hypothesis that restricts the simulation of the dynamic processes of microbial interactions and the algorithm complexity, there are few researches on simulation algorithms of polymicrobial metabolic fluxes. Therefore, this review also analyzed and combed the microbial interactions based on the commonly used hypothesis of maximizing growth rates, and studied the strategies of coupling interactions with optimal planning simulations for metabolism. Finally, this review provided new insights into the genomic scale metabolic flux simulations of polymicrobial systems.

To reduce the dependency on petroleum-based products and emission of greenhouse gas, renewable biofuels and chemicals play an important role to meet the unmatched energy demands of the rapidly growing population. However, most biofuel and chemical products do not reach the commercialization stage, mainly hindered by incomparable economics to petroproducts. Techno-economic assessment (TEA) is a useful tool to estimate economic performance, and identify bottlenecks for the development of biofuel and chemical production technology, meanwhile, life cycle assessment (LCA) is applied to assess sustainability by reducing the environmental impact of biofuel and chemical production. This present review covers TEA and LCA research progress in the manufacturing of biofuels and biochemical, and discusses the impacts of TEA and LCA results on the development and optimization of biofuel and chemical production. In addition, challenges associated with TEA and LCA of biofuel and biochemical production were briefly overviewed, and potential approaches that may overcome such challenges were discussed enabling viable and sustainable biomanufacturing of fuels and chemicals. Future integrated TEA and LCA studies could significantly promote the economic and sustainable development of the biomanufacturing process.

N-acetylglucosamine (GlcNAc) is an amino monosaccharide that has a variety of bioactivities and is widely used in pharmaceutical and food industries. Production of GlcNAc by chitin hydrolysis is limited by the supply of raw materials and encounters the risk of shellfish protein contamination. For efficient biosynthesis of GlcNAc, one challenge is to balance the carbon distribution between growth and production. Here, we applied the strategy of synergistic carbon utilization, in which glycerol supports cell growth and provides the acetyl group of GlcNAc while glucose serves as the precursor to glucosamine. The efficiency of GlcNAc production was stepwise improved by blocking the product re-uptake and degradation, strengthening the biosynthetic pathway and synergistically utilizing two carbon sources. With these efforts, the final strain produced 41.5 g/L GlcNAc with a yield of 0.49 g/g of total carbon sources. In addition, we also explored the feasibility of using acetate as a cheap carbon source to partly replace glycerol. This study provides a promising alternative strategy for sustainable and efficient production of GlcNAc.

Ectoine is a natural macromolecule protector and synthesized by some extremophiles. It provides protections against radiation-mediated oxidative damages and is widely used as a bioactive ingredient in pharmaceutics and cosmetics. To meet its growing commercial demands, we engineered Escherichia coli strains for the high-yield production of ectoine. The ectABC gene cluster from the native ectoine producer Halomonas elongata was introduced into different Escherichia coli (E. Coil) strains via plasmids and 0.8 g L^-1 of ectoine was produced in flask cultures by engineered E. coli BL21 (DE3). Subsequently, we designed the ribosome-binding sites of the gene cluster to fine-tune the expressions of genes ectA, ectB, and ectC, which increased the ectoine yield to 1.6 g L^-1. After further combinatorial overexpression of Corynebacterium glutamicum aspartate kinase mutant (G1A, C932T) and the H. elongate aspartate-semialdehyde dehydrogenase to increase the supply of the precursor, the titer of ectoine reached to 5.5 g L^-1 in flask cultures. Finally, the engineered strain produced 60.7 g L^-1 ectoine in fed-batch cultures with a conversion rate of 0.25 g/g glucose.

Nanocellulose has various outstanding properties and great potential for replacing petrochemical products. The utilization of lignocellulose to produce nanocellulose is of great significance to the sustainable development of the economy and society. However, the direct extraction of nanocellulose from lignocellulose by chemical method is challenged by toxic chemicals utilization, energy and time consumption, and waste water generation. Therefore, this paper addressed the conversion of lignocellulosic biomass into bacterial nanocellulose (BNC) by the biological method. Moreover, this article highlights the recent advances in potentials and challenges of lignocellulosic biomass for BNC production through the bioconversion process, including biomass pretreatment, enzymatic hydrolysis, glucose and xylose fermentation, GA accumulation, and inhibitor tolerant. The development in metabolic and evolutionary engineering to enhance the production capacity of BNC-producing strain is also discussed. It is expected to provide guidance on the effective bioproduction of nanocellulose from lignocellulosic biomass.