Core fungal species strengthen microbial cooperation in a food-waste composting process

Salinity causes differences in stratigraphic methane sources and sinks

Methane metabolism, driven by methanogenic and methanotrophic microorganisms, plays a pivotal role in the carbon cycle. As seawater intrusion and soil salinization rise due to global environmental shifts, understanding how salinity affects methane emissions, especially in deep strata, becomes imperative. Yet, insights into stratigraphic methane release under varying salinity conditions remain sparse. Here we investigate the effects of salinity on methane metabolism across terrestrial and coastal strata (15-40 m depth) through in situ and microcosm simulation studies. Coastal strata, exhibiting a salinity level five times greater than terrestrial strata, manifested a 12.05% decrease in total methane production, but a staggering 687.34% surge in methane oxidation, culminating in 146.31% diminished methane emissions. Salinity emerged as a significant factor shaping the methane-metabolizing microbial community's dynamics, impacting the methanogenic archaeal, methanotrophic archaeal, and methanotrophic bacterial communities by 16.53%, 27.25%, and 22.94%, respectively. Furthermore, microbial interactions influenced strata system methane metabolism. Metabolic pathway analyses suggested Atribacteria JS1's potential role in organic matter decomposition, facilitating methane production via Methanofastidiosales. This study thus offers a comprehensive lens to comprehend stratigraphic methane emission dynamics and the overarching factors modulating them.

The Potential of Co-Evolution and Interactions of Gut Bacteria-Phages in Bamboo-Eating Pandas: Insights from Dietary Preference-Based Metagenomic Analysis

Bacteria and phages are two of the most abundant biological entities in the gut microbiome, and diet and host phylogeny are two of the most critical factors influencing the gut microbiome. A stable gut bacterial community plays a pivotal role in the host's physiological development and immune health. A phage is a virus that directly infects bacteria, and phages' close associations and interactions with bacteria are essential for maintaining the stability of the gut bacterial community and the entire microbial ecosystem. Here, we utilized 99 published metagenomic datasets from 38 mammalian species to investigate the relationship (diversity and composition) and potential interactions between gut bacterial and phage communities and the impact of diet and phylogeny on these communities. Our results highlight the co-evolutionary potential of bacterial-phage interactions within the mammalian gut. We observed a higher alpha diversity in gut bacteria than in phages and identified positive correlations between bacterial and phage compositions. Furthermore, our study revealed the significant influence of diet and phylogeny on mammalian gut bacterial and phage communities. We discovered that the impact of dietary factors on these communities was more pronounced than that of phylogenetic factors at the order level. In contrast, phylogenetic characteristics had a more substantial influence at the family level. The similar omnivorous dietary preference and closer phylogenetic relationship (family Ursidae) may contribute to the similarity of gut bacterial and phage communities between captive giant panda populations (GPCD and GPYA) and omnivorous animals (OC; including Sun bear, brown bear, and Asian black bear). This study employed co-occurrence microbial network analysis to reveal the potential interaction patterns between bacteria and phages. Compared to other mammalian groups (carnivores, herbivores, and omnivores), the gut bacterial and phage communities of bamboo-eating species (giant pandas and red pandas) exhibited a higher level of interaction. Additionally, keystone species and modular analysis showed the potential role of phages in driving and maintaining the interaction patterns between bacteria and phages in captive giant pandas. In sum, gaining a comprehensive understanding of the interaction between the gut microbiota and phages in mammals is of great significance, which is of great value in promoting healthy and sustainable mammals and may provide valuable insights into the conservation of wildlife populations, especially endangered animal species.

Disparities and mechanisms of carbon and nitrogen conversion during food waste composting with different bulking agents

The low C/N ratio, high moisture content, and low porosity of food waste require the addition of bulking agents for adjustment during the composting process. However, the effect and mechanism of different bulking agents on the reduction of carbon and nitrogen losses are unclear. Therefore, this study conducted experiments to evaluate and clarify the differences in carbon and nitrogen transformation between sawdust, rice husk and wheat bran in food waste composting. The results showed that the addition of bulking agents promoted the conversion of carbon and nitrogen into total organic carbon (TOC) and total organic nitrogen (TON) rather than CO2 and NH3. The carbon and nitrogen losses were reduced by 16.00-25.71% and 11.56-29.54%, respectively. Notably, the Sawdust group exhibited the highest carbon retention, whereas the Wheat_bran group demonstrated superior nitrogen retention. The succession of bacterial communities showed that sawdust enhanced the cellulolysis and xylanolysis functions while wheat bran promoted nitrogen fixation. Correlation analysis was further employed to speculate on potential interactions among carbon and nitrogen components. The incorporation of sawdust and rice husk improved humification partly due to the addition of lignocellulose and the accumulation of total dissolved nitrogen (DTN) in the substrate, respectively. In the process of ammonia assimilation, the addition of wheat bran promoted the accumulation of dissolved organic carbon (DOC), contributing to the synthesis of TON to a degree. These findings offer cost-effective strategies for conserving carbon and nitrogen from loss in food waste composting by selecting suitable bulking agents, ultimately producing high-quality fertilizer.

Innovating Household Food Waste Management: A User-Centric Approach with AHP-TRIZ Integration

Food waste management remains a paramount issue in the field of social innovation. While government-led public recycling measures are important, the untapped role of residents in food waste management at the household level also demands attention. This study aims to propose the design of a smart system that leverages sensors, mobile terminals, and cloud data services to facilitate food waste reduction. Unlike conventional solutions that rely on mechanical and biological technologies, the proposed system adopts a user-centric approach. By integrating the analytical hierarchy process and the theory of inventive problem solving, this study delves into users' actual needs and explores intelligent solutions that are alternatives to traditional approaches to address conflicts in the problem solving phase. The study identifies five main criteria for user demands and highlights user-preferred subcriteria. It determines two physical conflicts and two technical conflicts and explores corresponding information and communications technology (ICT)-related solutions. The tangible outcomes encompass a semi-automated recycling product, a mobile application, and a data centre, which are all designed to help residents navigate the challenges regarding food waste resource utilisation. This study provides an approach that considers users' genuine demands, empowering them to actively engage in and become practitioners of household food waste reduction. The findings serve as valuable references for similar smart home management systems, providing insights to guide future developments.

Affinity difference determines the assembly and interaction mode of anammox community reconstructed by siderophores

Anammox community is the core of anammox process. The constancy of the anammox community determines the stability of the anammox process and the ability of withstand environmental impact. Community stability is influenced by the assembly and interaction mode of the community. This study aimed to explore the assembly, interaction mode, and stability of anammox community influenced by two siderophores (enterobactin and putrebactin) specific for Ca. Brocadia and Ca. Kuenenia as produced in our previous research. Siderophores improved the stability of the anammox community, among which vulnerability dropped by 30.02 % and 72.53 % respectively. Enterobactin and putrebactin altered the succession speed and assembly pattern of communities, with a respective increase of 9.77 % and 80.87 % in the deterministic process of anammox community assembly, respectively. Enterobactin and putrebactin reduced the dependence of Ca. Brocadia and Ca. Kuenenia on companion bacteria by 60 items and 27 items respectively. The affinity of different siderophore-Fe with bacterial membrane receptors caused variations in community reconstruction, with Ca. Brocadia and Ca. Kuenenia exhibiting the highest affinity with enterobactin-Fe (-11.4 kcal/mol) and putrebactin-Fe (-9.0 kcal/mol), respectively. This study demonstrated how siderophores can enhance the stability of anammox process by regulating assembly and interaction mode of anammox community, while also revealing the underlying molecular mechanisms.

Integrated fixed-film activated sludge systems in continuous-flow and batch mode acclimated from low to high aniline concentrations: Performance, mechanism and metabolic pathways

Integrated fixed-film activated sludge (IFAS) system has considerable advantages in treating aniline wastewater economically and efficiently. However, the response mechanism of IFAS to aniline needs further study. Herein, IFAS in continuous-flow (CF-IFAS) and batch mode (B-IFAS) were set up to investigate it. The removal efficiency of aniline exceeded 99% under different stress intensities. At low stress intensity (aniline ≈ 200 mg/L), the total nitrogen removal efficiency of B-IFAS was approximately 37.76% higher than CF-IFAS. When the stress intensity increased (aniline ≥ 400 mg/L), both were over 82%. CF-IFAS was restrained by denitrification while nitrification in B-IFAS. The legacy effect of perturbation of B-IFAS made microflora quickly reach new stability. The closer interspecific relationship in B-IFAS and more key species: Leucobacter, Rhodococcus, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Ellin6067 and norank_f_NS9_marine_group. Metabolic and Cell growth and death were the most abundant metabolic pathways, resulting both systems the excellent pollutant removal and stability under high stress intensity.

Adding siderophores: A new strategy to reduce greenhouse gas emissions in composting

Microbial community is the primary driver causing the greenhouse gas emissions in composting. Thus, regulating the microbial communities is a strategy to reduce them. Here, two different siderophores (enterobactin and putrebactin) were added, which could bind and translocate iron by specific microbes, to regulate the composting communities. The results showed that adding enterobactin enriched Acinetobacter and Bacillus with specific receptors by 6.84-fold and 6.78-fold. It promoted carbohydrate degradation and amino acid metabolism. This resulted in a 1.28-fold increase in humic acid content, as well as a 14.02% and 18.27% decrease in CO₂ and CH₄ emissions, respectively. Meanwhile, adding putrebactin boosted the microbial diversity by 1.21-fold and enhanced potential microbial interactions by 1.76-fold. The attenuated denitrification process led to a 1.51-fold increase in the total nitrogen content and a 27.47% reduction in N₂O emissions. Overall, adding siderophores is an efficient strategy to reduce greenhouse gas emissions and promote the compost quality.

High oil content inhibits humification in food waste composting by affecting microbial community succession and organic matter degradation

Composting is an effective technology to realize resource utilization of food waste in rural China. However, high oil content in food waste limits composting humification. This study investigated the effects of blended plant oil addition at different proportions (0, 10, 20, and 30%) on the humification of food waste composting. Oil addition at 10%-20% enhanced lignocellulose degradation by 16.6%-20.8% and promoted humus formation. In contrast, the high proportion of oil (30%) decreased the pH, increased the electrical conductivity, and reduced the seed germination index to 64.9%. High-throughput sequencing showed that high oil inhibited the growth and reproduction of bacteria (Bacillus, Fodinicurvataceae, and Methylococcaceae) and fungi (Aspergillus), attenuated their interaction, thus, reducing the conversion of organic matter, such as lignocellulose, fat, and total sugar, to humus, consequently leading to negative impacts on composting humification. The results can guide composting parameter optimization and improve effective management of rural food waste.

Co-composting of faecal sludge and carbon-rich wastes in the earthworm's synergistic cooperation system: Performance, global warming potential and key microbiome

Composting is an effective alternative for recycling faecal sludge into organic fertilisers. A microflora-earthworm (Eisenia fetida) synergistic cooperation system was constructed to enhance the composting efficiency of faecal sludge. The impact of earthworms and carbon-rich wastes (rice straw (RS) and sawdust (S)) on compost properties, greenhouse gas emissions, and key microbial species of composting were evaluated. The addition of RS or S promoted earthworm growth and reproduction. The earthworm-based system reduced the volatile solid of the final substrate by 13.19-16.24 % and faecal Escherichia coli concentrations by 1.89-3.66 log10 cfu/g dry mass compared with the earthworm-free system. The earthworm-based system increased electrical conductivity by 0.322-1.402 mS/cm and reduced C/N by 56.16-64.73 %. The NH₄⁺:NO₃^- ratio of the final faecal sludge and carbon-rich waste was <0.16. The seed germination index was higher than 80 %. These results indicate that earthworms contribute to faecal sludge maturation. Earthworm addition reduced CO₂ production. The simultaneous addition of earthworms and RS system (FRS2) resulted in the lowest global warming potential (GWP). The microbial diversity increased significantly over time in the RS-only system, whereas it initially increased and later decreased in the FRS2 system. Cluster analysis revealed that earthworms had a more significant impact on the microbial community than the addition of carbon-rich waste. Co-occurrence networks for earthworm-based systems were simple than those for earthworm-free systems, but the major bacterial genera were more complicated. Highly abundant key species (norank_f_Chitinophagaceae and norank_f_Gemmatimonadaceae) are closely related. Microbes may be more cooperative than competitive, facilitating the conversion of carbon and nitrogen in earthworm-based systems. This work has demonstrated that using earthworms is an effective approach for promoting the efficiency of faecal sludge composting and reducing GWP.