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Synthetic biology seeks to reprogram microbial cells for efficient production of value-added compounds from low-cost renewable substrates. A great challenge of chemicals biosynthesis is the competition between cell metabolism and target product synthesis for limited cellular resource. Dynamic regulation provides an effective strategy for fine-tuning metabolic flux to maximize chemicals production. In this work, we created a tunable growth phase-dependent autonomous bifunctional genetic switch (GABS) by coupling growth phase responsive promoters and degrons to dynamically redirect the carbon flux for metabolic state switching from cell growth mode to production mode, and achieved high-level GABA production from low-value glycerol in Corynebacterium glutamicum. A ribosome binding sites (RBS)-library-based pathway optimization strategy was firstly developed to reconstruct and optimize the glycerol utilization pathway in C. glutamicum , and the resulting strain CgGly2 displayed excellent glycerol utilization ability. Then, the initial GABA-producing strain was constructed by deleting the GABA degradation pathway and introducing an exogenous GABA synthetic pathway, which led to 5.26 g/L of GABA production from glycerol. In order to resolve the conflicts of carbon flux between cell growth and GABA production, we used the GABS to reconstruct the GABA synthetic metabolic network, in which the competitive modules of GABA biosynthesis, including the tricarboxylic acid (TCA) cycle module and the arginine biosynthesis module, were dynamically down-regulated while the synthetic modules were dynamically up-regulated after sufficient biomass accumulation. Finally, the resulting strain G7-1 accumulated 45.6 g/L of GABA with a yield of 0.4 g/g glycerol, which was the highest titer of GABA ever reported from low-value glycerol. Therefore, these results provide a promising technology to dynamically balance the metabolic flux for the efficient production of other high value-added chemicals from a low-value substrate in C. glutamicum. • A RBS-library-based pathway optimization strategy was designed to reconstruct glycerol utilization pathway in C. glutamicum. • A tunable growth phase-dependent autonomous bifunctional switch was designed to dynamically orchestrate the carbon flux. • Growth-coupled regulation network was rebuilt using GABS to achieve a desirable metabolic state switching. • The engineered strain showed the highest titer and yield of GABA production from glycerol ever reported. [ABSTRACT FROM AUTHOR]

This paper studies the impacts of renewable energy support policies on energy prices, fossil fuel supply and thus carbon emissions from fossil fuels. Such supports are climate friendly if the renewables are already competitive against fossil fuels. But if the renewables are not yet competitive, the climate change impacts are often ambiguous and are sensitive to capacity constraints of renewables production and to the fossil fuel market structure. If the renewables do not have capacity constraints, then the subsidies are subject to the Green Paradox under perfect competition, but might be climate friendly under monopoly. Supports for capacity constrained renewables under perfect competition lead to more current fossil fuel supply but delay fossil fuel exhaustion time, and these effects are reversed under monopoly. Our results highlight the importance of considering the long-term effects on fossil fuel supply as well as capacity constraints and market power in designing renewable energy policies and evaluating their carbon footprints. [ABSTRACT FROM AUTHOR]

This paper shows how policies aimed at insuring health risks and those intended to improve the environment are (and should be) deeply intertwined. In the model economy inspired by recent Chinese experience, pollution raises the likelihood of future, poor health prompting households to save more so as to self-insure against anticipated medical expenses. Increased household saving generates more capital while capital use by firms generates more pollution. Along the transition, such a “pollution-growth nexus” may be attractive from a capital-accumulation perspective; however, rising pollution, via the health channel, hurts welfare. Both insurance and environmental policies affect capital accumulation and can have additional dynamic benefits. The availability of private health insurance to top up pay-as-you-go coverage of medical bills along with a Pigouvian tax on emissions and a profit tax can replicate the first best. [ABSTRACT FROM AUTHOR]

We compare the short- and long-run effects of environmental reform and harmonization under autarky and free trade. When trade is driven by environmental distortions rather than real relative advantages, harmonization of environmental policies, even if achieved by lowering standards in one country, can improve short-run aggregate welfare. With the possibility of multiple steady states, harmonization can improve long-run welfare, especially when the environment is fragile. Further, long-run considerations favor upward harmonization even when it is equivalent to downward harmonization in the short run. For a country trapped in a low (or bad) steady state, environmental reform may not move it to a high (or good) steady state under autarky. However, under trade, harmonization of policies may enable this country to reach the high steady state. Conversely, reforms that increase the relative differences in distortions may, under trade, cause economies to move to a low steady state. [Copyright &y& Elsevier]

Metabolic engineering seeks to rewire the metabolic network of cells for the efficient production of value-added compounds from renewable substrates. However, it remains challenging to evaluate and identify strains with the desired phenotype from the vast rational or random mutagenesis library. One effective approach to resolve this bottleneck is to design an efficient high-throughput screening (HTS) method to rapidly detect and analyze target candidates. L-cysteine is an important sulfur-containing amino acid and has been widely used in agriculture, pharmaceuticals, cosmetics, and food additive industries. However, HTS methods that enable monitoring of L-cysteine levels and screening of the enzyme variants and strains to confer superior L-cysteine biosynthesis remain unavailable, greatly limiting the development of efficient microbial cell factories for L-cysteine production at the industrial scale. Here, we took advantage of the L-cysteine-responsive transcriptional regulator CcdR to develop a genetically encoded biosensor for engineering and screening the L-cysteine overproducer. The in vivo L-cysteine-responsive assays and in vitro electrophoretic mobility shift assay (EMSA) and DNase I footprint analysis indicated that CcdR is a transcriptional activator that specifically interacts with L-cysteine and binds to its regulatory region to induce the expression of target genes. To improve the response performance of the L-cysteine biosensor, multilevel optimization strategies were performed, including regulator engineering by semi-rational design and systematic optimization of the genetic elements by modulating the promoter and RBS combination. As a result, the dynamic range and sensitivity of the biosensor were significantly improved. Using this the excellent L-cysteine biosensor, a HTS platform was established by coupling with fluorescence-activated cell sorting (FACS) and was successfully applied to achieve direct evolution of the key enzyme in the L-cysteine biosynthetic pathway to increase its catalytic performance and to screen the high L-cysteine-producing strains from the random mutagenesis library. These results presented a paradigm of design and optimization of biosensors to dynamically detect metabolite concentrations and provided a promising tool enabling HTS and metabolic regulation to construct L-cysteine hyperproducing strains to satisfy industrial demand. • The regulation mechanism of a L-cysteine-responsive transcriptional factor CcdR was firstly investigated. • The dynamic range and sensitivity of the L-cysteine biosensor were significantly improved using regulator engineering. • A biosensor-based high-throughput screening (HTS) platform was constructed by coupling with FACS. • The biosensor-based HTS platform was applied in direction evolution of the key enzyme CysE to increase its activity. • The developed HTS platform allowed us to identify the efficient L-cysteine-producing strains from a large-scale mutagenesis library. [ABSTRACT FROM AUTHOR]

The use of anti-pollution facemasks (APFs) in defense against particulate matter (PM) pollution is subject to debate as air pollution and wildfire events intensify. Inward leakage due to imperfect fitting and the Peltzman effect of people spending more time outdoors when wearing masks have led to mixed evidence regarding the effectiveness of APFs, which in turn has contributed to conflicting public messages about APFs with potentially large public health costs. We conduct a large-scale randomized field study on individuals' daily outdoor time and mask wearing behaviors and the associated health outcomes during an entire winter heating season in a provincial capital city in Northeastern China. We find that APFs used in everyday life achieved an overall efficiency of 80% in reducing respiratory or cardiovascular disease related doctor visits. Mask wearing, due to its discomfort, reduced outdoor time. However, the added protection provided by masks against PM led respondents to spend more time outdoors on smog days, and this relative Peltzman effect wiped out about 12% of APFs' health benefits. Taken together, APFs' health benefits far exceed their financial costs. These findings call for affirmatory but careful messaging to the public about using APFs as personal protection against PM pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon fibers modified with ionic liquid was prepared as SPME fiber. • Simultaneous determination method of phytohormones by LC–MS/MS was developed. • Phytohormones were determined during different development stages in strawberries. • Level Changes and roles of phytohormones in strawberries were studied. In the present document, we report a novel miniaturized dispersive solid-phase extraction based on carbon fibers functionalized with ionic liquid for the determination of multiple-phytohormones and investigation on temporal distribution of phytohormones during the development in strawberry. 1-(3-Aminopropyl)-3-methylimidazolium bromide was modified on the carbon fibers by using covalent functionalization to prepare ionic liquid-carbon fibers (IL-CFs). It contains the structural feature suitable for the simultaneous extraction of a variety of phytohormones. The main experimental parameters were optimized, and the method was used to determine phytohormones during fruit development in strawberries. The limits of detection and quantification of the proposed method were found to be in the range of 0.00330−0.283 ng mL−1 and 0.0110−0.944 ng mL−1, respectively. All the relative recoveries were in the range of 81.7–121.4% with RSD ≤ 10.0 % (n = 3). This report highlighted the level changes of multiple-phytohormones during different developmental stages in strawberries. The level of cytokinins and ABA increased as strawberry fruits ripened, while IAA content steadily decreased. Meanwhile GA 7 level was relatively stable in all stages, and SA level exhibited fluctuations. [ABSTRACT FROM AUTHOR]

The invasion and metastasis of tumor cells are the hallmarks of malignant diseases and the greatest obstacle to overcome. Heparanase-mediated degradation of heparan sulfate (HS) is the critical process for tumor angiogenesis and metastasis, therefore, heparanase become an attractive target for cancer research. Herein, we reported a native fucosylated glycosaminoglycan (nHG) extracted from sea cucumber Holothuria fuscopunctata and a depolymerized nHG (dHG) and its contained oligosaccharides (hs17, hs14, hs11, hs8 and hs5), acting as heparanase inhibitors. nHG and its derivatives have the ability to bind with heparanase directly, leading to significant inhibition of heparanase activity. Moreover, their apparent binding affinity to heparanase was comparable to their inhibitory effect, which was elevated along with the increase of chain length, similar to the effect of heparins. In addition, oligosaccharides inhibited the migration and invasion of 4T1 mammary carcinoma cells and human umbilical vein endothelial cells (HUVECs) and also suppressed tube formation in Matrigel matrix and angiogenesis in the chick chorioallantoic membrane (CAM) assay. In the metastatic mouse model, oligosaccharides exhibited practical antimetastatic effects on 4T1 mammary carcinoma cells. According to the reported anticoagulant activity and the low bleeding tendency of dHG and its oligosaccharides, the use of the oligosaccharides may lead to better effects on tumor patients with thrombosis tendency. [Display omitted] • Fucosylated GAG and its derivatives are discovered as heparanase inhibitors. • Oligosaccharides originated from FG inhibit cell migration and invasion in vitro. • The oligosaccharides inhibit tube formation and angiogenesis. • The oligosaccharides suppress tumor cell metastasis in mice. [ABSTRACT FROM AUTHOR]