Frontiers of Chemical Science and Engineering最新文献

The engineering of microbial cell factories for the production of high-value chemicals from renewable resources presents several challenges, including the optimization of key enzymes, pathway fluxes and metabolic networks. Addressing these challenges involves the development of synthetic auxotrophs, a strategy that links cell growth with enzyme properties or biosynthetic pathways. This linkage allows for the improvement of enzyme properties by in vivo directed enzyme evolution, the enhancement of metabolic pathway fluxes under growth pressure, and remodeling of metabolic networks through directed strain evolution. The advantage of employing synthetic auxotrophs lies in the power of growth-coupled selection, which is not only high-throughput but also labor-saving, greatly simplifying the development of both strains and enzymes. Synthetic auxotrophs play a pivotal role in advancing microbial cell factories, offering benefits from enzyme optimization to the manipulation of metabolic networks within single microbes. Furthermore, this strategy extends to coculture systems, enabling collaboration within microbial communities. This review highlights the recently developed applications of synthetic auxotrophs as microbial cell factories, and discusses future perspectives, aiming to provide a practical guide for growth-coupled models to produce value-added chemicals as part of a sustainable biorefinery.

In the present study, a sustainable pretreatment methodology combining liquid hot water and deep eutectic solvent is proposed for the efficient fractionation of hemicellulose, cellulose, and lignin from sugarcane bagasse, thereby facilitating the comprehensive utilization of both C5 and C6 sugars. The application of this combined pretreatment strategy to sugarcane bagasse led to notable enhancements in enzymatic saccharification and subsequent fermentation. Experiment results demonstrate that liquid hot water-deep eutectic solvent pretreatment yielded 85.05 ± 0.66 g·L⁻¹ of total fermentable sugar (glucose: 60.96 ± 0.21 g·L⁻¹, xylose: 24.09 ± 0.87 g·L⁻¹) through enzymatic saccharification of sugarcane bagasse. Furthermore, fermentation of the pretreated sugarcane bagasse hydrolysate yielded 34.33 ± 3.15 g·L⁻¹ of bioethanol. These findings confirm the effectiveness of liquid hot water-deep eutectic solvent pretreatment in separating lignocellulosic components, thus presenting a sustainable and promising pretreatment method for maximizing the valuable utilization of biomass resources.

Engineered photosynthetic bacterium Rhodo-pseudomonas palustris is excellent at one-step CO₂ biomethanation and can use near-infrared light sources, overcoming the limitations of conventional photosynthetic systems. The current study constructed a biohybrid system that deposited CdS nanoparticles on R. palustris. This biohybrid system broadens the capture of sustainable solar energy, achieving a 155 nmol·mL⁻¹ biological CH₄ production under full visible light irradiation, 13.4-fold of that by the pure R. palustris. The transcriptome profiles revealed that gene expression related to photosynthetic electron transfer chain, nitrogenase, nanofilaments, and redox stress defense was activated. Accordingly, we attributed the much-enhanced CO₂ biomethanation in the biohybrid system to the remarkable increase in the intracellular reducing power and the stronger rigidity of the cells assisted by photoexcited electrons from CdS nanoparticles. Our discovery offers insight and a promising strategy for improving the current CO₂–CH₄ biomanufacturing system.

Genomic rearrangements play a crucial role in shaping biological phenotypic diversity and driving species evolution. Synthetic chromosome rearrangement and modification by LoxP-mediated evolution (SCRaMbLE) has been applied to explore large-scale genomic rearrangements, yet it has been observed that these rearrangements occur exclusively in genomic regions containing loxPsym sites. Here, we found that SCRaMbLE of synthetic yeast harboring synthetic chromosome V and X can generate a variety of synthetic segment insertions into wild-type chromosomes, ranging from 1 to 300 kb. Furthermore, it was revealed that the novel insertions impacted the transcriptional level of neighboring regions and affected the production of exemplar pathway of zeaxanthin. Collectively, our results improve the understanding of the ability of SCRaMbLE to generate complex structural variations in nonsynthetic regions and provide a potential model to explore genomic transposable events.

Photothermal catalytic oxidation emerges as a promising method for the removal of volatile organic compounds (VOCs). Herein, via sol-gel impregnation method, spinel CuMn₂O₄ was coated on attapulgite honeycombs with integrating biochar (BC) film as the second carrier, using chestnut shell as complexation agent. Various mass ratios of CuMn₂O₄ to chestnut shell was modulated to investigate the catalytic toluene degradation performance. Results indicated that the monolithic CuMn₂O₄/BC/honeycomb catalyst demonstrated superior photothermal catalytic toluene degradation with a low T₉₀ (temperature at 90% degradation) of 263 °C when the mass ratio of CuMn₂O₄ to biomass was 1:4. The addition of BC film substantially increased the honeycomb’s specific surface area and improved the photothermal conversion of spinel, leading to enhanced photothermal catalytic activity. This study presents a cost-effective strategy for eliminating industrial VOCs using clay-biomass based monolithic catalyst.

Epoxidation of propylene to propylene oxide (PO) with hydrogen peroxide (HPPO) is an environmentally friendly and cost-efficient process in which titanosilicates are used as catalysts. Ti-MWW is a potential industrial catalyst for this process, which involves the addition of HPPO to PO. The silanol groups generated during secondary crystallization unavoidably result in ring-opening of PO and inefficient decomposition of HPPO, which diminish the PO selectivity and the lifespan of Ti-MWW. To address this issue, we conducted post-treatment modifications of the structured Bf-Ti-MWW catalyst with potassium fluoride aqueous solutions. By quenching the silanol groups with potassium fluoride and implanting electron-withdrawing fluoride groups into the Ti-MWW framework, both the catalytic activity and HPPO utilization efficiency were increased. Moreover, the ring opening reaction of PO was prohibited. In a continuous fixed-bed liquid-phase propylene epoxidation reaction, the KF-treated structured Ti-MWW catalyst displayed an exceptionally long lifespan of 2700 h, with a PO yield of 590 g·kg⁻¹·h⁻¹.

Carbon dioxide fixation presents a potential solution for mitigating the greenhouse gas issue. During carbon dioxide fixation, C1 compound reduction requires a high energy supply. Thermodynamic calculations suggest that the energy source for cofactor regeneration plays a vital role in the effective enzymatic C1 reduction. Hydrogenase utilizes renewable hydrogen to achieve the regeneration and supply cofactor nicotinamide adenine dinucleotide (NADH), providing a driving force for the reduction reaction to reduce the thermodynamic barrier of the reaction cascade, and making the forward reduction pathway thermodynamically feasible. Based on the regeneration of cofactor NADH by hydrogenase, and coupled with formaldehyde dehydrogenase and formolase, a favorable thermodynamic mode of the C1 reduction pathway for reducing formate to dihydroxyacetone (DHA) was designed and constructed. This resulted in accumulation of 373.19 µmol·L⁻¹ DHA after 2 h, and conversion reaching 7.47%. These results indicate that enzymatic utilization of hydrogen as the electron donor to regenerate NADH is of great significance to the sustainable and green development of bio-manufacturing because of its high economic efficiency, no by-products, and environment-friendly operation. Moreover, formolase efficiently and selectively fixed the intermediate formaldehyde (FALD) to DHA, thermodynamically pulled formate to efficiently reduce to DHA, and finally stored the low-grade renewable energy into chemical energy with high energy density.

Increasing global water shortages are accelerating the pace of membrane manufacturing, which generates many environmentally harmful solvents. Such challenges need a radical rethink of developing innovative membranes that can address freshwater production without generating environmentally harmful solvents. This work utilized the synthesized ultra-long hydroxyapatite (UHA) by the solvothermal method using the green solvent oleic acid in preparing UHA-based forward osmosis membranes. The membranes were developed using different loading ratios of graphene oxide (GO) by vacuum-assisted filtration technique. The prepared GO/UHA membranes were identified using X-ray diffraction, scanning electron microscope, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Water contact angle and pore size distribution were determined for the obtained GO/UHA membranes. The obtained hierarchical porous structure in the prepared membranes with interconnected channels results in a stable water flux with reverse salt flux. The best water flux rate of 42 ± 2 L·m⁻²·h⁻¹ was achieved using the 50 mg GO/UHA membrane, which is 3.3 times higher than the pristine membrane, and a reverse salt flux of 67 g·m⁻²·h⁻¹. The obtained results showed a promising capability of a new generation of sustainable inorganic-based membranes that can be utilized in freshwater generation by energy-efficient techniques such as forward osmosis.

Under optimal process conditions, pyrolysis of polyolefins can yield ca. 90 wt % of liquid product, i.e., combination of light oil fraction and heavier wax. In this work, the experimental findings reported in a selected group of publications concerning the non-catalytic pyrolysis of polyolefins were collected, reviewed, and compared with the ones obtained in a continuously operated bench-scale pyrolysis reactor. Optimized process parameters were used for the pyrolysis of waste and virgin counterparts of high-density polyethylene, low-density polyethylene, polypropylene and a defined mixture of those (i.e., 25:25:50 wt %, respectively). To mitigate temperature drops and enhance heat transfer, an increased feed intake is employed to create a hot melt plastic pool. With 1.5 g·min⁻¹ feed intake, 1.1 L·min⁻¹ nitrogen flow rate, and a moderate pyrolysis temperature of 450 °C, the formation of light hydrocarbons was favored, while wax formation was limited for polypropylene-rich mixtures. Pyrolysis of virgin plastics yielded more liquid (maximum 73.3 wt %) than that of waste plastics (maximum 66 wt %). Blending polyethylenes with polypropylene favored the production of liquids and increased the formation of gasoline-range hydrocarbons. Gas products were mainly composed of C₃ hydrocarbons, and no hydrogen production was detected due to moderate pyrolysis temperature.

Sodium-ion batteries (SIBs) have garnered significant interest in energy storage due to their similar working mechanism to lithium ion batteries and abundant reserves of sodium resource. Exploring facile synthesis of a carbon-based anode materials with capable electrochemical performance is key to promoting the practical application of SIBs. In this work, a combination of petroleum pitch and recyclable sodium chloride is selected as the carbon source and template to obtain hard carbon (HC) anode for SIBs. Carbonization times and temperatures are optimized by assessing the sodium ion storage behavior of different HC materials. The optimized HC exhibits a remarkable capacity of over 430 mA·hg⁻¹ after undergoing full activation through 500 cycles at a density of current of 0.1 A·g⁻¹. Furthermore, it demonstrates an initial discharge capacity of 276 mAh·g⁻¹ at a density of current of 0.5 A·g⁻¹. Meanwhile, the optimized HC shows a good capacity retention (170 mAh·g⁻¹ after 750 cycles) and a remarkable rate ability (166 mAh·g⁻¹ at 2 A·g⁻¹). The enhanced capacity is attributed to the suitable degree of graphitization and surface area, which improve the sodium ion transport and storage.