Life cycle assessment of n-caproic acid production via chain elongation from food waste: Comparison of shunting and staged technology.

n-Caproic acid is a widely used biochemical that can be produced from organic waste through chain elongation technology. This study aims to evaluate the environmental impacts of n-caproic acid production through chain elongation by two processes (i.e., shunting and staged technology). The Open-life cycle assessment (LCA) model was used to calculate the environmental impacts of both technologies based on experimental data. Results showed that the shunting technology had higher environmental impacts than the staged technology. Water and electricity made bigger contribution to the environmental impacts of both technologies. Reusing chain elongation effluent substituting for water and using electricity produced by wind power could reduce the environmental impacts of water and electricity effectively. Using ethanol from food waste had higher global warming potential than fossil ethanol, which suggested that a cradle-to-grave LCA is needed to be carried out for specific raw materials and chain elongation products in the future.

Optimization of organic solid waste composting process through iron-related additives: A systematic review.

Composting is an environmentally friendly method that facilitates the biodegradation of organic solid waste, ultimately transforming it into stable end-products suitable for various applications. The element iron (Fe) exhibits flexibility in form and valence. The typical Fe-related additives include zero-valent-iron, iron oxides, ferric and ferrous ion salts, which can be targeted to drive composting process through different mechanisms and are of keen interest to academics. Therefore, this review integrated relevant literature from recent years to provide more comprehensive overview about the influence and mechanisms of various Fe-related additives on composting process, including organic components conversion, humus formation and sequestration, changes in biological factors, stability and safety of composting end-products. Meanwhile, it was recommended that further research be conducted on the deep action mechanisms, biochemical pathways, budget balance analysis, products stability and application during organic solid waste composting with Fe-related additives. This review provided guidance for the subsequent targeted application of Fe-related additives in compost, thereby facilitating cost reduction and promoting circular economy objectives.

Origin, distribution and spatial characteristics of dissolved organic matter in the Heilongjiang River.

The Heilongjiang River Basin is a vast area with significant DOM sources and composition differences. The mechanism of DOM degradation under spatial variation remains unclear. This research investigated the degradation characteristics of DOM in different watersheds of the Heilongjiang River. DOM levels were higher in midstream waters, while DOM degradation rates were higher in midstream and downstream waters. The parallel factor analysis (PARAFAC) results showed that the upstream amino acid fraction was significantly depleted, the midstream was dominated by the degradation of DOM of terrestrial origin, and the downstream humic acid fraction was decreased considerably. Gene sequencing results indicated that the upstream, middle, and downstream water bodies' microbial community composition and structure differed significantly. The network analysis results revealed microorganisms in upstream water bodies mainly utilized amino acid-like substances and small molecule humic acids. Microorganisms in the middle and lower reaches of the water column were characterized by the utilization of humic acid-like fractions. In this study, we further screened the key driving microorganisms (e.g., Flavobacterium and Lacibacter) responsible for the difference in the DOM utilization function of upstream-to-midstream and midstream-to-downstream microorganisms in the Heilongjiang River. These findings will help identify the cycling process of DOM under spatial variation and predict the succession pattern of microbial communities.

Fe-N complex biochar as a superior partner of sodium sulfide for methyl orange decolorization by combination of adsorption and reduction.

To enhance the decolorization of methyl orange (MO), Fe-N complex biochar (Fe-N-BC) was developed as an accelerator in the sodium sulfide (Na2S) reduction system. The decolorization effect and mechanism of MO in the Fe-N-BC/Na2S composite system were studied. Surface pore analysis, Raman spectroscopy, FT-IR, XPS, and electrochemical analysis were used to characterize Fe-N-BC and unmodified biochar (BC). These results demonstrated that Fe-N-BC had better adsorption performance (specific surface area 463.46 m2 g-1) and electron transfer capacity than BC. By adding Fe-N-BC to the Na2S reduction system for MO, it was found that the decolorization of MO was greatly improved (increased by 93%). Besides, the effects of critical factors such as the initial concentration of Na2S, the dosage of Fe-N-BC, pH value, and temperature on the decolorization rate of MO were evaluated. Through the analysis of the action mechanism, the cooperation mode of Fe-N-BC and Na2S was to form an infinite cycle of adsorption-reduction-regeneration, so as to realize the rapid decolorization of MO. On the one hand, Fe-N-BC could adsorb MO and Na2S on its surface to increase the contact opportunity; on the other hand, it could act as a redox mediator to accelerate the electron transfer of the reduction reaction. In addition, the degradation of MO by Na2S was also an in-situ regeneration of Fe-N-BC. These findings may provide a feasible method to decolorize azo dyes quickly by cooperating with chemical reducing agents from a new perspective.

Lithium Carbonate Recovery from Cathode Scrap of Spent Lithium-Ion Battery: A Closed-Loop Process.

A closed-loop process to recover lithium carbonate from cathode scrap of lithium-ion battery (LIB) is developed. Lithium could be selectively leached into solution using formic acid while aluminum remained as the metallic form, and most of the other metals from the cathode scrap could be precipitated out. This phenomenon clearly demonstrates that formic acid can be used for lithium recovery from cathode scrap, as both leaching and separation reagent. By investigating the effects of different parameters including temperature, formic acid concentration, H2O2 amount, and solid to liquid ratio, the leaching rate of Li can reach 99.93% with minor Al loss into the solution. Subsequently, the leaching kinetics was evaluated and the controlling step as well as the apparent activation energy could be determined. After further separation of the remaining Ni, Co, and Mn from the leachate, Li2CO3 with the purity of 99.90% could be obtained. The final solution after lithium carbonate extraction can be further processed for sodium formate preparation, and Ni, Co, and Mn precipitates are ready for precursor preparation for cathode materials. As a result, the global recovery rates of Al, Li, Ni, Co, and Mn in this process were found to be 95.46%, 98.22%, 99.96%, 99.96%, and 99.95% respectively, achieving effective resources recycling from cathode scrap of spent LIB.

Insight into bacterial role attribution in dissolved organic matter humification during rice straw composting with microbial inoculation.

This study aims to investigate the effect of microbial role distribution in microbial carbon pumps on dissolved organic matter (DOM) humification during rice straw composting with microbial inoculation. Three composting groups were designed, named CK (control), B4 (with Bacillus subtilis, OR058594) and Z1 (with Aspergillus fumigatus, AF202956.1). As a result of inoculation, the composition of microbial communities was changed, so that the microorganisms that promoted DOM humification were concentrated in the responders in the microbial carbon pump. DOM was divided into three components in three composting treatments: C1, C2 and C3. After inoculation with Bacillus subtilis, the C2 component was significantly affected, while after inoculation with Aspergillus fumigatus, the C3 component was significantly affected. The results of physicochemical factors affecting the transformation of DOM fluorescence components indicated that C1, C2 and C3 were related to the abundance of the cellulose-degrading enzyme-encoding gene GH7 in CK and B4 composting. However, the C2 was susceptible to organic matter in Z1 composting. This study explored the distribution of microbial communities from a new perspective, which provided new information for analyzing DOM humification and treating agricultural straws to achieve clean conditions for environmental friendliness.

Greenhouse gas emission characteristics during kitchen waste composting with biochar and zeolite addition.

Aerobic kitchen waste composting can contribute to greenhouse gas (GHGs) emissions and global warming. This study investigated the effects of biochar and zeolite on GHGs emissions during composting. The findings demonstrated that biochar could reduce N2O and CH4 cumulative releases by 47.7 %and 47.9 %, respectively, and zeolite could reduce the cumulative release of CO2 by 28.4 %. Meanwhile, the biochar and zeolite addition could reduce the abundance of potential core microorganisms associated with GHGs emissions. In addition, biochar and zeolite reduced N2O emissions by regulating the abundance of nitrogen conversion functional genes. Biochar and zeolite were shown to reduce the impact of bacterial communities on GHGs emissions. In summary, this study revealed that biochar and zeolite can effectively reduce GHG emissions during composting by altering the compost microenvironment and regulating microbial community structure. Such findings are valuable for facilitating high-quality resource recovery of organic solid waste.

Revealing mechanism of phenol-amine reaction to form humus in compost based on high-resolution liquid chromatography mass spectrometry and spectroscopy.

Humus is the stable form of carbon storage in straw compost. The phenol-amine reaction is a pathway for humus formation in straw compost. In this study, two reaction systems, GP group (pyrogallol and glycine) and GCP group (catechol, pyrogallol, and glycine), were constructed in a simulated composting environment and revealed the molecular binding mechanism of the phenol-amine reaction through spectroscopy and mass spectrometry. The results showed that phenolic self-polymerization was faster than phenol-amine reaction. Therefore, the aromatization degree of GP was 27.14 % higher than that of GCP. The phenol-amine reaction first produced fulvic acid, and then formed humus units rich in active functional group structures (i.e., phenolic hydroxyl and carboxyl groups). These units further captured small molecule compounds to form humic acid eventually. This study would provide theoretical support for exploring the humus formation process and the promotion of straw humification by adding phenol or amino acids to compost.

Malonic acid shapes bacterial community dynamics in compost to promote carbon sequestration and humic substance synthesis.

The incorporation of malonic acid (MA) into compost as a regulator of the tricarboxylic acid (TCA) cycle has the potential to increase carbon sequestration. However, the influence of MA on the transformation of the microbial community during the composting process remains unclear. In this investigation, MA was introduced at different stages of chicken manure (CM) composting to characterize the bacterial community within the compost using high-throughput sequencing. We assess the extent of increased carbon sequestration by comparing the concentration of total organic carbon (TOC). At the same time, this study examines whether increased carbon sequestration contributes to humus formation, which was elucidated by evaluating the content and composition of humus. Our results show that the addition of MA significantly improved carbon sequestration within the compost, reducing the carbon loss rate (C loss (%)) from 64.70% to 52.94%, while increasing HS content and stability. High throughput sequencing and Random Forest (RF) analysis show that the introduction of MA leads to a reduction in the diversity of the bacterial communities, but enhanced the ability of bacterial communities to synthesize humus. Furthermore, the addition of MA favors the proliferation of Firmicutes. Also, the hub of operational taxonomic units (OTUs) within the community co-occurrence network shifts from Proteobacteria to Firmicutes. Remarkably, our study finds a significant decrease in negative correlations between bacteria, potentially mitigating substrate consumption due to negative interactions such as competition. This phenomenon contributes to the improved retention of TOC in the compost. This research provides new insights into the mechanisms by which MA regulates bacterial communities in compost, and provides a valuable theoretical basis for the adoption of this innovative composting strategy.

Regulation of extracellular polymers based on quorum sensing in wastewater biological treatment from mechanisms to applications: A critical review.

Extracellular polymeric substances (EPS) regulated by quorum sensing (QS) could directly mediate adhesion between microorganisms and form tight microbial aggregates. Besides, EPS have redox properties, which can facilitate electron transfer for promoting electroactive bacteria. Currently, the applications research on improving wastewater biological treatment performance based on QS regulated EPS have been widely reported, but reviews on the level of QS regulated EPS to enhance EPS function in microbial systems are still lacking. This work proposes the potential mechanisms of EPS synthesis by QS regulation from the viewpoint of material metabolism and energy metabolism, and summarizes the effects of QS on EPS synthesis. By synthesizing the role of QS in EPS regulation, we further point out the applications of QS-regulated EPS in wastewater biological treatment, which involve a series of aspects such as strengthening microbial colonization, mitigating membrane biofouling, improving the shock resistance of microbial metabolic systems, and strengthening the electron transfer capacity of microbial metabolic systems. According to this comprehensive review, future research on QS-regulated EPS should focus on the exploration of the micro-mechanisms, and economic regulation strategies for QS-regulated EPS should be developed, while the stability of QS-regulated EPS in long-term production experimental research should be further demonstrated.

Comprehensive carbon footprint analysis of wastewater treatment: A case study of modified cyclic activated sludge technology for low carbon source urban wastewater treatment.

To reduce pollution and carbon emissions, a quantitative evaluation of the carbon footprint of the wastewater treatment processes is crucial. However, micro carbon element flow analysis is rarely focused considering treatment efficiency of different technology. In this research, a comprehensive carbon footprint analysis is established under the micro carbon element flow analysis and macro carbon footprint analysis based on life cycle assessment (LCA). Three wastewater treatment processes (i.e., anaerobic anoxic oxic, A2O; cyclic activated sludge technology, CAST; modified cyclic activated sludge technology, M-CAST) for low carbon source urban wastewater are selected. The micro key element flow analysis illustrated that carbon source mainly flows to the assimilation function to promote microorganism growth. The carbon footprint analysis illustrated that M-CAST as the optimal wastewater treatment process had the lowest global warming potential (GWP). The key to reduce carbon emissions is to limit electricity consumption in wastewater treatment processes. Under the comprehensive carbon footprint analysis, M-CAST has the lowest environmental impact with low carbon emissions. The sensitivity analysis results revealed that biotreatment section variables considerably reduced the environmental impact on the LCA and the GWP, followed by the sludge disposal section. With this research, the optimization scheme can guide wastewater treatment plants to optimize relevant treatment sections and reduce pollution and carbon emissions.

A new strategy for accelerating recovery of anaerobic granular sludge after low-temperature shock: In situ regulation of quorum sensing microorganisms embedded in polyvinyl alcohol sodium alginate.

Low-temperature could inhibit the performance of anaerobic granular sludge (AnGS). Quorum sensing (QS), as a communication mode between microorganisms, can effectively regulate AnGS. In this study, a kind of embedded particles (PVA/SA@Serratia) based on signal molecule secreting bacteria was prepared by microbial immobilization technology based on polyvinyl alcohol and sodium alginate to accelerate the recovery of AnGS system after low temperature. Low-temperature shock experiment verified the positive effect of PVA/SA@Serratia on restoring the COD removal rate and methanogenesis capacity of AnGS. Further analysis by metagenomics analysis showed that PVA/SA@Serratia stimulated higher QS activity and promoted the secretion of extracellular polymeric substance (EPS) in AnGS. The rapid construction of EPS protective layer effectively accelerated the establishment of a robust microbial community structure. PVA/SA@Serratia also enhanced multiple methanogenic pathways, including direct interspecies electron transfer. In conclusion, this study demonstrated that PVA/SA@Serratia could effectively strengthen AnGS after low-temperature shock.

The role of microbiota during chicken manure and pig manure co-composting.

Co-composting is an excellent and effective technology for treating livestock manure in which microorganisms play a crucial function. Therefore, this study aimed at investigating the changes of microbial interactions during co-composting. Six different addition ratios of chicken and pig manure were used in composting experiment. The results showed that the co-composting system using 60% chicken manure and 40% pig manure significantly altered the microbial diversity and community structure. In addition, the complexity and tightness of its microbial community network structure reached the maximum, as did the strength of its cooperative and competitive microbial interactions. The higher microbial abundance and microbial interaction have the potential to promote the decomposition and transformation of compost components. Therefore, this study preliminarily revealed the changes of microbial community in co-composting, which provided a theoretical basis for optimizing microbial community interaction in composting systems by mixing different ratios of materials in practice.

Effect of ferrous ions combined with zeolite on humification degree during food waste composting.

The research aims to clarify role of ferrous sulfate (FeSO4) combined with zeolite (Z) on humification degree based on investigation of concentration and structural stability of humic acid (HA) during food waste composting. Four treatments were set up, namely CK (control), Fe (5 %), Z (5 %) and Fe + Z (2.5 %+2.5 %). Results demonstrated that concentration and polymerization degree of HA were 53.4 % and 97.3 % higher in composting amended with Fe + Z than in the control, respectively. Meanwhile, formation of aromatic functional groups and recalcitrant fluorescent components (HAC3) was significantly promoted, indicating that Fe + Z treatment enhanced HA structure stability. The bacterial networks became tighter, and the proportion of core bacteria in dominant modules increased at Fe + Z treatment. Additionally, key factors affecting HAC3 and product quality were identified by structural equation models, which verified potential mechanism of humification enhancement. Overall, this study provided theoretical support for improving humification degree and product quality.

Exploring the nitrogen fixing strategy of bacterial communities in nitrogen cycling by adding calcium superphosphate at various periods during composting.

Chicken manure, as an organic solid waste with a high nitrogen content, generates large amounts of ammonia during composting, which leads to pollution of the surrounding environment, and causes a reduction in the quality of the compost product. Nitrogen is transformed through the nitrogen cycle and bacterial communities are the main contributors to the transformation of the nitrogen cycle. The microbial composition changes dramatically at different stages during composting. Therefore, calcium superphosphate (SSP) was added to compost as a nitrogen-fixing agent to elucidate the strategy and function of the bacterial community involved in the nitrogen cycle. The results showed that the addition of SSP at the initial, high temperature and cooling stages increased the inorganic nitrogen (NH4+-N, NO3--N) content by 51.99 %, 202.72 % and 173.37 % compared to CK, respectively. In addition, nitrogen cycle functional genes (gdh, nifH, pmoA-amoA, hao, nxrA, nirK, napA, nosZ, narG) abundance were determined by real-time qPCR. The nitrogen cycle genetic results showed that SSP addition at high temperature phase resulted in a 62.43 % down-regulation of ammonification genes, while nitrogen fixation and nitrification genes were enhanced. Random forests revealed a shift in the participation strategy of bacterial communities (e.g., Mycobacterium, Izemoplasmatales, Paracoccus, Ruminococcus) within the nitrogen cycle, leading to altered importance rankings despite involvement in different nitrogen cycle pathways. Moreover, Regression analysis and structural equation modelling revealed that SSP addition at high temperature stage stimulated the bacterial community engaged in nitrogen fixation and nitrification, resulting in increased nitrogen accumulation as NO3--N during composting. This paper offers the potential to yield novel scientific insights into the impact of microbially mediated nitrogen transformation processes and reduce gaseous pollution.

Immunology and immunotherapy in gastric cancer.

Gastric cancer is the fifth leading cause of cancer-related deaths worldwide. As the diagnosis of early gastric cancer is difficult, most patients are at a late stage of cancer progression when diagnosed. The current therapeutic approaches based on surgical or endoscopic resection and chemotherapy indeed improve patients' outcomes. Immunotherapy based on immune checkpoint inhibitors has opened a new era for cancer treatment, and the immune system of the host is reshaped to combat tumor cells and the strategy differs according to the patient's immune system. Thus, an in-depth understanding of the roles of various immune cells in the progression of gastric cancer is beneficial to application for immunotherapy and the discovery of new therapeutic targets. This review describes the functions of different immune cells in gastric cancer development, mainly focusing on T cells, B cells, macrophages, natural killer cells, dendritic cells, neutrophils as well as chemokines or cytokines secreted by tumor cells. And this review also discusses the latest advances in immune-related therapeutic approaches such as immune checkpoint inhibitors, CAR-T or vaccine, to reveal potential and promising strategies for gastric cancer treatment.

Micro-aeration and leachate recirculation for the acceleration of landfill stabilization: Enhanced hydrolytic acidification by facultative bacteria.

The long duration of landfill stabilization is one of the challenges faced by municipalities. In this paper, a combination of micro-aeration and leachate recirculation is used to achieve rapid degradation of organic matter in landfill waste. The results showed that the content of volatile fatty acids (VFAs) in the hydrolysis phase increased significantly and could enter the methanogenic phase quickly. Until the end of the landfill, the removal rates of chemical oxygen demand (COD), total phosphorus (TP) and ammonia nitrogen (NH4+-N) by micro-aeration and leachate recirculation reached 80.17 %, 48.30 % and 48.56 %, respectively, and the organic matter degradation rate reached 50 %. Micro-aeration and leachate recirculation enhanced the abundance of facultative hydrolytic bacteria such as Rummeliibacillus and Bacillus and the oxygen tolerance of Methanobrevibacter and Methanoculleus. Micro-aeration and leachate recirculation improved the organic matter degradation efficiency of landfill waste by promoting the growth of functional microorganisms.

Adsorption-desorption behaviors of ciprofloxacin onto aged polystyrene fragments in aquatic environments.

As two emerging pollutants of great concern, microplastics (MPs) and antibiotics inevitably cooccur in various aquatic environments and interact with each other, impacting the fate and ecological risks. Aging obviously complicates their interaction and deserves further study. Therefore, the adsorption-desorption behaviors of ciprofloxacin (CIP) onto polystyrene (PS) fragments with various aging extent were investigated, and the key physiochemical properties influencing the interaction and the interaction mechanisms were clarified by redundancy analysis, FTIR and XPS spectra. The physicochemical properties of PS MPs were significantly changed with aging time, and the morphological and chemical changes seemed to occur asynchronously. The adsorption of CIP onto the pristine PS MPs relied on physisorption, especially the ion-involving electrostatic and cation-π interaction. Due to the hydrogen bonding formed by the C-OH, CO, and O-CO groups of PS and CIP, the adsorption capacities of the aged PS MPs were greatly increased. The desorption efficiency of CIP from MPs in the gastric fluid was closely related to the solution ionic strengths, C-OH and CO groups of MPs, while that in the intestinal fluid was associated with O-CO groups of MPs. The different impact factors could be well described by the differences in the chemical components and pHs of the simulated gastric and intestinal fluids. This study gives a comprehensive understanding of the adsorption-desorption behaviors of antibiotics onto MPs at a molecular level and indicates that MPs could act as Trojan horses to transport antibiotics into aquatic organisms.

Enhanced landfill process based on leachate recirculation and micro-aeration: A comprehensive technical, environmental, and economic assessment.

The landfill is still the primary waste treatment method in developing countries. Due to the long stability time and long-term occupation of a large amount of land, the landfill poses a significant threat to the ecological environment and affects the process of urbanization. This study conducted a landfill simulation reactor (LSR) experiment to achieve rapid landfill stabilization through micro-aeration and leachate recirculation. More than 60 % of the degradable organic carbon in the enhanced process (LSR-IV contains 24 % of the retained carbon) can be relatively quickly converted to a gaseous state, which is nearly half higher than the degradation efficiency of the traditional process (LSR-I contains 59.3 % of the retained carbon). A comprehensive environmental assessment is developed for the enhanced process, and better environmental benefits are obtained from the whole landfill process. Compared with conventional treatment process, the enhanced process is applied to the actual landfill to analyze the economic cost. In terms of the total cost, the enhanced process cost (60.1 CNY) is about 44 % lower than the conventional landfill process cost (107.6 CNY). The enhanced process saves nearly half of the time cost and reduces the cost of land acquisition. This study can provide a reference for governmental and municipal administrations to carry out the technological transformation of traditional landfills from the aspects of technology, economy and environment.

Eight-year tillage in black soil, effects on soil aggregates, and carbon and nitrogen stock.

The effects of different tillage management practices on the soil aggregates, soil carbon stock (STCS), and soil nitrogen stock (STNS) are key issues in agricultural research. We conducted an 8-year field experiment to evaluate the effects of different tillage methods: stubble cleaning and ridging (CK), no-tillage with stubble retention (NT), plow tillage (PT), and width lines (WL) on soil aggregates, STCS, and STNS in the black soil corn continuous cropping area of Northeast China. Different tillage methods predominantly affected the soil aggregates in the 2-0.25 mm and 0.25-0.053 mm size classes. The PT methods increased the proportion of macroaggregates and improved the quality of the soil aggregates. PT methods significantly increased the soil organic carbon content at the 0-30 cm layer by changing the number of soil macroaggregates. The PT practices are better strategies for enhancing soil carbon sinks, and the WL method increased the total amount of N in the soil pool. Our results suggest that the PT and WL methods are the best strategies for improving the quality of soil aggregates and preventing/reducing depletion of soil C and N in a black soil area of Northeast China.