Nitric oxide synthase-guided genome mining identifies a cytochrome P450 enzyme for olefin nitration in bacterial specialized metabolism.

The biological signaling molecule nitric oxide (NO) has recently emerged as a metabolic precursor for the creation of microbial natural products with diversified structures and biological activities. Within the biosynthetic gene clusters (BGCs) of these compounds, genes associated with NO production pathways have been pinpointed. In this study, we employ a nitric oxide synthase (NOS)-guided genome mining strategy for the targeted discovery of NO-derived bacterial natural products and NO-utilizing biocatalysts. We show that a conserved NOS-containing BGC, distributed across several actinobacterial genomes, is responsible for the biosynthesis of lajollamycin, a unique nitro-tetraene-containing antibiotic whose biosynthetic mechanism remains elusive. Through a combination of in vivo and in vitro studies, we unveil the first cytochrome P450 enzyme capable of catalyzing olefin nitration in natural product biosynthesis. These results not only expand the current knowledge about biosynthetic nitration processes but also offer an efficient way for targeted identification of NO-utilizing metabolic pathways and novel nitrating biocatalysts.

Targeted genome mining for microbial antitumor agents acting through DNA intercalation.

Microbial natural products have been one of the most important sources for drug development. In the current postgenomic era, sequence-driven approaches for natural product discovery are becoming increasingly popular. Here, we develop an effective genome mining strategy for the targeted discovery of microbial metabolites with antitumor activities. Our method employs uvrA-like genes as genetic markers, which have been identified in the biosynthetic gene clusters (BGCs) of several chemotherapeutic drugs of microbial origin and confer self-resistance to the corresponding producers. Through systematic genomic analysis of gifted actinobacteria genera, identification of uvrA-like gene-containing BGCs, and targeted isolation of products from a BGC prioritized for metabolic analysis, we identified a new tetracycline-type DNA intercalator timmycins. Our results thus provide a new genome mining strategy for the efficient discovery of antitumor agents acting through DNA intercalation.

Greenhouse gas emissions from U.S. crude oil pipeline accidents: 1968 to 2020.

Crude oil pipelines are considered as the lifelines of energy industry. However, accidents of the pipelines can lead to severe public health and environmental concerns, in which greenhouse gas (GHG) emissions, primarily methane, are frequently overlooked. While previous studies examined fugitive emissions in normal operation of crude oil pipelines, emissions resulting from accidents were typically managed separately and were therefore not included in the emission account of oil systems. To bridge this knowledge gap, we employed a bottom-up approach to conducted the first-ever inventory of GHG emissions resulting from crude oil pipeline accidents in the United States at the state level from 1968 to 2020, and leveraged Monte Carlo simulation to estimate the associated uncertainties. Our results reveal that GHG emissions from accidents in gathering pipelines (~720,000 tCO2e) exceed those from transmission pipelines (~290,000 tCO2e), although significantly more accidents have occurred in transmission pipelines (6883 cases) than gathering pipelines (773 cases). Texas accounted for over 40% of total accident-related GHG emissions nationwide. Our study contributes to enhanced accuracy of the GHG account associated with crude oil transport and implementing the data-driven climate mitigation strategies.

Heterologous Reconstitution of Toxoflavin Biosynthesis Reveals Key Pathway Intermediates and a Cofactor-Independent Oxidase.

Bacterial azapteridine-containing phytotoxin toxoflavin is a causal agent of rice grain rot. Here, we heterologously reconstitute Bukholderia toxoflavin biosynthesis in Escherichia coli and identify key pathway intermediates, including the hitherto unknown ribityl-dedimethyl-toxoflavin. Furthermore, we characterized a cofactorless oxidase that converts ribityl-dedimethyl-toxoflavin to ribose and dedimethyl-toxoflavin, the latter of which then undergoes stepwise methylations to form toxoflavin. These findings provide new insights into the biosynthetic pathways of toxoflavin and related triazine metabolites.

Substance flow analysis of arsenic and its discharge reduction in the steelworks.

Although certain emission standards have been implemented to reduce the air pollution from the steel industry, heavy metal pollution associated with steel production in China has not been well addressed yet. Arsenic is a metalloid element, commonly present in various compounds in many minerals. When it presents in steelworks, it not only affects the quality of steel products, but also causes environmental consequences such as soil degradation, water contamination, air pollution and associated biodiversity loss and public health risks. At present, most of the studies on arsenic were limited to its removal in a certain process, while there has not been a thorough analysis of the flow path of arsenic in steelworks that can facilitate a more efficient removal from its lifecycle. To achieve this, we established a model to depict arsenic flows in steelworks for the first time using adapted substance flow analysis. Then, we further analyzed arsenic flows in the steelworks using a case study in China. Finally, input-output analysis was applied to study the arsenic flow network and explore the reduction potential of arsenic-containing wastes in steelworks. The results show that: 1) the arsenic in the steelworks comes from inputs of iron ore concentrate (55.31 %), coal (12.71 %) and steel scrap (18.67 %), while the outputs were hot rolled coil (65.93 %) and slag (33.03 %). 2) The input, circulation, and final product content of arsenic are 96.120, 32.510, and 66.946 g/t-CS, respectively, and the recycling rate of arsenic was 48.28 %, in the steelworks. 3) The total arsenic discharge from the steelworks is 34.826 g/t-CS. 97.33 % of arsenic is discharged in the form of solid waste. 4) The reduction potential of arsenic in wastes is 14.31 % in the steelworks by adopting low-arsenic raw materials and removing arsenic from processes.

Assessment of different methods in analyzing motor vehicle emission factors.

To explore the emission characteristics of vehicle's pollutants is of great significance to prevent and control the diffusion of pollutants. Limited by geographic location and economic condition, the model- and guideline-based studies on vehicle's emission factor have become more concerned measures than the actual measurement. By analyzing the actual operating conditions of motor vehicles, this study obtains the emission factors of typical pollutants from different motor vehicles by adopting international vehicle emission (IVE) model and guideline method, respectively. Furthermore, the resulting emission factors by the above methods were compared and analyzed with on-road method. The results show that: (1) the emission factors of vehicle pollutants change regularly with velocity, emission standard, and accumulated mileage. Taking CO as an example, its emission factor shows a downward trend with the increase of velocity and emission standard and an upward trend with the increase of accumulated mileage; (2) compared with the actual measurement, the vehicle emission factor obtained by the guideline method has a large error, while the IVE model is close to the actual.

The changes in spatial layout of steel industry in China and associated pollutant emissions: A case of SO2.

The spatial layout of the steel industry has an impact on the regional atmospheric environment. In this study, the steel industry evolution model and the driving force analysis model were combined to analyze the evolution of spatial layout of the steel industry in China and the driving factors of this evolution. In addition, the WRF-SMOKE-CMAQ model was used to analyze the spatial dynamics of SO2 emissions from the steel industry. Our analysis presents the evolution of the steel industry in China in four stages: policy-determining, resource-oriented, economic promotion and market-oriented stage. The change in the spatial layout of the Chinese steel industry resulted in a continuously decreasing trend of pollutants in temporal characteristics and a decreasing share of emissions in North China and a continuous growth in East China in spatial characteristics. Our simulation shows that, by 2025, the pollutant SO2 emission concentration will migrate to the southeast, subject to market-oriented factors.

Molecular basis of enzymatic nitrogen-nitrogen formation by a family of zinc-binding cupin enzymes.

Molecules with a nitrogen-nitrogen (N-N) bond in their structures exhibit various biological activities and other unique properties. A few microbial proteins are recently emerging as dedicated N-N bond forming enzymes in natural product biosynthesis. However, the details of these biochemical processes remain largely unknown. Here, through in vitro biochemical characterization and computational studies, we report the molecular basis of hydrazine bond formation by a family of di-domain enzymes. These enzymes are widespread in bacteria and sometimes naturally exist as two standalone enzymes. We reveal that the methionyl-tRNA synthase-like domain/protein catalyzes ATP-dependent condensation of two amino acids substrates to form a highly unstable ester intermediate, which is subsequently captured by the zinc-binding cupin domain/protein and undergoes redox-neutral intramolecular rearrangement to give the N-N bond containing product. These results provide important mechanistic insights into enzymatic N-N bond formation and should facilitate future development of novel N-N forming biocatalyst.

Enzymatic Tailoring in Luzopeptin Biosynthesis Involves Cytochrome†P450-Mediated Carbon-Nitrogen Bond Desaturation for Hydrazone Formation.

Luzopeptins and related decadepsipeptides are bisintercalator nonribosomal peptides featuring rare acyl-substituted tetrahydropyridazine-3-carboxylic acid (Thp) subunits that are critical to their biological activities. Herein, we reconstitute the biosynthetic tailoring pathway in luzopeptin A biosynthesis through in vivo genetic and in vitro biochemical approaches. Significantly, we revealed a multitasking cytochrome P450 enzyme that catalyzes four consecutive oxidations including the highly unusual carbon-nitrogen bond desaturation, forming the hydrazone-bearing 4-OH-Thp residues. Moreover, we identified a membrane-bound acyltransferase that likely mediates the subsequent O-acetylation extracellularly, as a potential self-protective strategy for the producer strain. Further genome mining of novel decadepsipeptides and an associated P450 enzyme have provided mechanistic insights into the P450-mediated carbon-nitrogen bond desaturation. Our results not only reveal the molecular basis of pharmacophore formation in bisintercalator decadepsipeptides, but also expand the catalytic versatility of P450 family enzymes.

A plant-by-plant strategy for high-ambition coal power phaseout in China.

More than half of current coal power capacity is in China. A key strategy for meeting China's 2060 carbon neutrality goal and the global 1.5 °C climate goal is to rapidly shift away from unabated coal use. Here we detail how to structure a high-ambition coal phaseout in China while balancing multiple national needs. We evaluate the 1037 currently operating coal plants based on comprehensive technical, economic and environmental criteria and develop a metric for prioritizing plants for early retirement. We find that 18% of plants consistently score poorly across all three criteria and are thus low-hanging fruits for rapid retirement. We develop plant-by-plant phaseout strategies for each province by combining our retirement algorithm with an integrated assessment model. With rapid retirement of the low-hanging fruits, other existing plants can operate with a 20- or 30-year minimum lifetime and gradually reduced utilization to achieve the 1.5 °C or well-below 2 °C climate goals, respectively, with complete phaseout by 2045 and 2055.

Spatiotemporal analysis of anthropogenic phosphorus fluxes in China.

Anthropogenic phosphorus supports food systems while have caused water pollution and posed challenges to the ecosystems. The increasing socioeconomic interactions between regions and systems have added more complexities to manage the sustainability of effective phosphorus use that requires joint analyses of multiple regions or multiple systems of phosphorus flow. This study builds a framework to systematically model the phosphorus fluxes in China based on material flow analysis. This model consists of phosphorus industrial system, agricultural planting system, rural residential system, urban residential system, large-scale livestock breeding system and household livestock breeding system. This study further explored the temporal and spatial characteristics of phosphorus fluxes in terms of phosphorus utilization efficiency and water load during 1995-2015. The results showed that the total amount of phosphorus input in China had increased nearly 1.78 times during 1995-2015, of which about 85% is used for fertilizer production. The phosphorus utilization rates of urban residential and large-scale livestock breeding systems remained low with a declining trend, dropping to 5%. The phosphorus water load peaked and declined during the study period. Among them, the phosphorus water load in large-scale and household livestock breeding systems accounted for more than 60% of the total. In spatial dimension, Southwest China is the region with the largest input of phosphorus, about 375.33 × 104 t, while Northeast China is the region with the largest phosphorus water load, about 28.06 × 104 t.

Technologies-based potential analysis on saving energy and water of China's iron and steel industry.

Water and energy conservation are indispensable commitments to achieve the sustainable development of the iron and steel industry. Hereby, this study established an evaluation framework to model the water and energy consumption in the iron and steel industry. This framework quantitatively assessed the energy and water saving with adoption of conventional and emerging technologies. Thirty mainstream technologies, among which 21 focused on energy saving and the remaining 9 focused on water saving, were selected for analysis. Five scenarios were developed to examine systematic water- and energy-saving potentials, including benchmark (BM) scenario, constrained product (CP) scenario, business as usual (BAU) scenario, and benefit/cost-driven (BD) scenario and strengthened policy (SP) scenario. The results show that the energy-saving potentials of BAU, BD and SP scenarios are 1.75 PJ, 1.21 PJ and 1.65 PJ, respectively. The water-saving potentials of BAU, BD and SP scenarios are 4.83 billion m3, 5.71 billion m3 and 9.15 billion m3, respectively. The specific energy consumption and water consumption decreased to 15.01-15.59 GJ/t and 54.13-58.77 m3/t, respectively. This study suggested to implement encouraging policies in prompt popularity rate of technologies, and promote energy-saving and water-saving technologies to achieve sustainable development of iron and steel industry.

Scale, distribution and variations of global greenhouse gas emissions driven by U.S. households.

The U.S. household consumption, a key engine for the global economy, has significant carbon footprints across the world. Understanding how the U.S. household consumption on specific goods or services drives global greenhouse gas (GHG) emissions is important to guide consumption-side strategies for climate mitigation. Here we examined global GHG emissions driven by the U.S. household consumption from 1995 to 2014 using an environmentally extended multi-regional input-output model and detailed U.S. consumer expenditure survey data. The results show that the annual carbon footprint of the U.S. households ranged from 17.7 to 20.6 tCO2eq/capita with an expanding proportion occurring overseas. Housing and transportation contributed 53-66% of the domestic carbon footprint. Overseas carbon footprint shows an overall increasing trajectory, from 16.4% of the total carbon footprint in 1995 to the peak of 20.4% in 2006. These findings provide valuable insights on the scale, distribution, and variations of the global GHG emissions driven by the U.S. household consumption for developing consumption-side strategies in the U.S. for climate mitigation.

Comprehensive evaluation on energy-water saving effects in iron and steel industry.

The production of iron and steel is energy-intensive that motivated the emergence of various energy-saving technologies to reduce energy consumption. However, the effects of water-saving brought by these energy-saving technologies are rarely examined which can lead to misevaluation of their economic feasibility. In this regard, material flow analysis (MFA) was used in this study to establish the water-energy nexus and examine the potential of water-saving and energy-saving effects in the condition of applying various mixes of the 16 technologies (Ministry of Industry and Information Technology, 2015-2016) in iron and steel industry. Meanwhile, this study classified the selected 16 energy-saving technologies into three groups: direct water-saving technology, indirect water-saving technology, and water consumption technology. The low-temperature steel rolling technology is the only water-consuming energy-saving technology in this study; its indirect specific water computation reaches 0.06 m3/t. The remaining 15 energy-saving technologies have the potential of saving water indirectly, with averaged indirect specific water-saving amounting to 0.28 m3/t. This study also built an evaluation scheme of cost-benefit analysis for energy-saving technologies. With consideration of benefits brought by water saving, eleven technologies have the potential to achieve economic feasibility compared to nine in which mere energy-saving effects being considered. The results show that if the studied 16 technologies are implemented simultaneously, the comprehensive specific energy consumption will be reduced by 4.28 MJ, and the specific fresh water consumption will be reduced by 0.68 m3. Meanwhile, this research found that the cost of most energy-saving technologies will be decreased by an average of 5.52 CNY/GJ, despite the cost of low-temperature steel rolling technology increased by 0.68 CNY/GJ. This study evaluated the cost-effectiveness of energy-saving technologies taking the benefits of water conservation into consideration. It could provide references for decision-makers to develop commercialization strategies on energy saving technologies in the steel industry.

Environmental status of livestock and poultry sectors in China under current transformation stage.

Intensive animal husbandry had aroused great environmental concerns in many developed countries. However, some developing countries are still undergoing the environmental pollution from livestock and poultry sectors. Driven by the large demand, China has experienced a remarkable increase in dairy and meat production, especially in the transformation stage from conventional household breeding to large-scale industrial breeding. At the same time, a large amount of manure from the livestock and poultry sector is released into waterbodies and soil, causing eutrophication and soil degradation. This condition will be reinforced in the large-scale cultivation where the amount of manure exceeds the soil nutrient capacity, if not treated or utilized properly. Our research aims to analyze whether the transformation of raising scale would be beneficial to the environment as well as present the latest status of livestock and poultry sectors in China. The estimation of the pollutants generated and discharged from livestock and poultry sector in China will facilitate the legislation of manure management. This paper analyzes the pollutants generated from the manure of the five principal commercial animals in different farming practices. The results show that the fattening pigs contribute almost half of the pollutants released from manure. Moreover, the beef cattle exert the largest environmental impact for unitary production, about 2-3 times of pork and 5-20 times of chicken. The animals raised with large-scale feedlots practice generate fewer pollutants than those raised in households. The shift towards industrial production of livestock and poultry is easier to manage from the environmental perspective, but adequate large-scale cultivation is encouraged. Regulation control, manure treatment and financial subsidies for the manure treatment and utilization are recommended to achieve the ecological agriculture in China.