Development of a New 1,2,4-butanetriol Biosynthesis Pathway in an Engineered Homoserine-producing Strain of Escherichia coli

1,2,4-butanetriol (BT) is a compound of high interest with applications in pharmaceutical and materials. In this work, we designed a novel biosynthetic pathway for BT from glucose via a nonessential amino acid homoserine. This non-natural pathway used an engineered phosphoserine transaminase (SerC_R42W/R77W) to achieve the deamination of homoserine to 4-hydroxy-2-oxobutanoic acid (HOBA). Three consecutive enzymes including a lactate dehydrogenase, a 4-hydroxybutyrate CoA-transferase and a bifunctional aldehyde/alcohol dehydrogenase are used to catalyze HOBA to BT. To enhance the carbon flux to homoserine, a homoserine-producing Escherichia coli was developed by improving the overexpression of two relevant key genes metL and lysC (V339A). The simultaneous overexpression of the genes encoding these enzymes for the homoserine-derived BT pathway enabled production of 19.6 mg/L BT from glucose in the homoserine-producing E. coli.

A High-efficiency Cathode Using Co₃O₄ and Carbon Paper by Electrodeposition for Rechargeable Lithium-oxygen Batteries

The conductivity, microstructure, low cost, eco-friendliness, simple and controllable preparation are key points of the preparation and application of cathode materials for lithium-oxygen batteries. Considering the above-mentioned important factors comprehensively, the Co₃O₄@CP electrode with a three-dimensional structure was prepared by directly growing Co₃O₄ on the surface of carbon paper (CP) using a simple and controllable electrodeposition method. The obtained Co₃O₄ depositing layer has a nanosheet microstructure and can provide abundant catalytic active sites for the oxygen evolution and reduction reactions. The network architecture of electronic transmission is constructed by CP in the cathode, promoting the efficiency of the electrode reaction. It’s worth noting that the binder-free and conductive additive-free cathode is beneficial to reduce side reactions. The lithium-oxygen battery assembled with the obtained Co₃O₄@CP electrode showed satisfactory electrochemical performance. The cell assembled with the obtained Co₃O₄@CP electrode provided a discharge specific capacity of 10954.7 mA·h·g⁻¹ at a current density of 200 mA·g⁻¹, and the voltage profiles of the cell were good under 100 mA·g⁻¹ at a limited capacity of 500 mA·h g⁻¹ based on the mass of Co₃O₄. Therefore, the Co₃O₄@CP composite material is a promising candidate with good application prospects as a cathode material for lithium-oxygen batteries.

Foreword to Resumption

Recent Progress in Modification and Preparations of the Promising Biodegradable Plastics: Polylactide and Poly(butylene adipate-co-terephthalate)

The acquisition of high-performance biodegradable plastics is of great significance in addressing the problem of environmental pollution of plastics. Polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are the most promising biodegradable polymers and have excellent functional properties. However, low elongation at break and impact strength of PLA and low tensile modulus and flexural strength of PBAT hinder their application. A large number of studies focus on improving the performance of PLA and PBAT and broadening their applications. In terms of polymer modification, this paper summarized recent progresses in both chemical and physical modification methods for PLA and PBAT, respectively. The properties of PLA can be improved by co-polymerization, grafting, cross-linking and blending. The properties of PBAT can be improved mainly through blending with other degradable polymers, natural macromolecules and inorganic materials. This review can provide the reference and ideas for the modification of biomass-based biodegradable plastics like PLA and fossil-based biodegradable plastics like PBAT.

Coiled Coils as Versatile Modules for Mammalian Cell Regulation

Synthetic biology is a rapidly growing field that allows us to better understand biological processes at the molecular level, and enables therapeutic interventions and biotechnological applications. One of the most powerful tools in synthetic biology is the small, customizable, and modular protein–protein interaction domains, which is used to regulate a wide variety of processes within mammalian cells. Here we review designed coiled coil dimers that represent a set of heterodimerization domains with many advantages. These dimers have been useful for directing the localization of selected proteins within cells, enhancing chemical or light-regulated transcription, creating fast proteolysis-based responsive systems and protein secretion, genome editing, and cell–cell interaction motifs. Additionally, we will discuss how these building blocks are used in diverse applications, such as CAR T cell regulation and genome editing. Finally, we will look at the potential for future advances in synthetic biology using these building modules.

Waterborne Polyurethane Dispersion Synthesized from CO₂ Based Poly (Ethylene Carbonate) Diol with High Performance

CO₂-based aliphatic polycarbonates (APCs) are not widely commercialized due to the poor performance and high cost, compared to the traditional synthetic materials. In this paper, poly(ethylene carbonate) diol (PECD) was synthesized from CO₂ and ethylene oxide (EO), and the comprehensive properties were characterized. Furthermore, the preparation and properties of waterborne polyurethane dispersion (WPU) derived from PECD were studied. The result showed that PECD had high reactivity, narrow molecular weight distribution index and excellent thermal stability. The obtained WPU exhibited superior tensile performance, adhesion properties and surface hardness. Due to the low cost of EO and CO₂, PECD is expected to be widely used in the preparation of polyurethanes.

Established Hepatic Stellate Cell Lines in Hepatology Research

Hepatic stellate cells comprise a minor cell population in the liver that plays a key role in the pathogenesis of hepatic fibrosis. In chronic liver damage, they undergo a transition from a quiescent to a highly proliferative phenotype with the capacity to synthesize large quantities of extracellular matrix compounds such as collagens. Because of their pivotal role in liver disease pathogenesis, this hepatic cell population has become into the focus of liver research for many years. However, the isolation of these cells is time consuming and requires trained laboratory personnel. In addition, working with primary cells requires the following of ethical and legal standards that need to be approved by the respective authorities. Therefore, continuous growing hepatic stellate cells have become very popular in research laboratories because they are widely available, easy to handle, allow a continuous supply of materials, and further allow reduction of lab animal use in biomedical research. This communication provides some general information about immortalized hepatic stellate cell lines from mouse, rats and humans.

Ultra-thin Solid Electrolyte in Lithium-ion Batteries

Safety concern of lithium-ion battery, attributed to using volatile and flammable liquid electrolytes, could be addressed by using solid electrolytes. Solid electrolytes including inorganic solid electrolytes, polymer solid electrolytes and organic/inorganic composite electrolytes have the common drawbacks in low ion-conductivity. Much efforts have been devoted to increase the specific ion conductivity, especially for inorganic solid electrolyte whose intrinsic conductivity are close to liquid electrolyte. However, most solid-state electrolyte membranes in lithium-ion batteries are thick, resulting in long ion-conduction pathway, low energy density and high cost. In this review, the advantages and disadvantages of different kinds of solid electrolytes were analyzed, and the promising strategies of ultra-thin solid electrolyte preparation are summarized and prospected. Applying organic-inorganic composite, continuous phase enhancement and in situ integration have been devoted to reduce thickness of electrolyte membrane and improve battery performance. On the basis of the technical requirement of lithium-ion batteries, this review aims to provide a guidance in terms of rational design and synthesis of ultra-thin solid electrolytes for further research that addresses the safety issues and improves cycling performance of batteries.

Thermoanaerobacter Species: The Promising Candidates for Lignocellulosic Biofuel Production

Thermoanaerobacter species, which have broad substrate range and high operating temperature, can directly utilize lignocellulosic materials for biofuels production. Compared with the mesophilic process, thermophilic process shows greater prospects in consolidated bioprocessing (CBP) due to its relatively higher efficiency of lignocellulose degradation and lower risk of microbial contamination. Additionally, thermophilic conditions can reduce cooling costs, and further facilitate downstream product recovery. This review comprehensively summarizes the advances of Thermoanaerobacter species in lignocellulosic biorefinery, including their performance on substrates utilization, and genetic modification or other strategies for enhanced biofuels production. Furthermore, bottlenecks of sugar co-fermentation, metabolic engineering, and bioprocessing are also discussed.

Reduced Climate Impacts of Dairy Sludge Management by Introducing Hydrothermal Carbonization

Dairies which produce cheese and milk products can, however, produce large volumes of wastewater that require treatment, usually via activated sludge treatment. Disposal of the resulting activated sludge to land is viewed favorably as the sludge is rich in phosphorus (P) and nitrogen (N) and enables nutrient recycling. Nonetheless, sludge management can significantly influence the greenhouse gas (GHG) emissions to the atmosphere. This manuscript has modelled the GHG emissions arising from two sludge management strategies currently adopted by Danish dairies whereby: (i) sludge is stored and later applied to fields; or (ii) sludge is treated by anaerobic digestion (AD), stored, and the digestate will later be applied to fields. This is compared to (iii) an alternative sludge management strategy with treatment by Hydrothermal Carbonization (HTC). HTC is a technologically simple sludge treatment that could lower the cost for dewatering dairy sludge, forming a biochar-like material known as hydrochar. The produced hydrochar can be applied to the land for the purpose of carbon sequestration, P and N recycling. Our calculations indicate that GHG balances of HTC sludge management can result in a net carbon sequestration of 63 kg CO_2eq per ton sludge, as opposed to net emissions of 420 and 156 kg CO_2eq per ton sludge for strategies (i) and (ii), therefore offering significant reductions GHG emissions for the dairy sector.