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The sulfate reduction reaction releases malodorous gases (H 2 S) during composting, with potential pollution risks to the environment. In this study, chicken manure (CM) with high sulfur content and beef cattle manure (BM) with low sulfur content were used to investigate the effect of control (CK) and low moisture content (LW) on sulfur metabolism. The results showed that compared to CK composting, the cumulative H 2 S emission of CM and BM composting decreased by 27.27% and 21.08% under LW condition, respectively. Meanwhile, the abundance of core microorganisms related to sulfur components was reduced under LW condition. Furthermore, the KEGG sulfur pathway and network analysis suggested that LW composting weakened the sulfate reduction pathway, and reduced the number and abundance of functional microorganisms and genes. These results indicated that low moisture content had important effects on inhibiting the release of H 2 S during composting, which provided a scientific basis to control environmental pollution., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The aim of this study was to clarify the aromatic cleavage pathways and microbes involved in the adverse effect of nitrate on aromatic compounds humic substances during sludge composting. Results showed that the functional microbes involved in aromatic compounds humic substances precursors (catechol, tyrosine, tryptophan and phenylalanine) cleavage pathways significantly enriched after nitrate addition. Linear regression analysis showed that aromatic-ring cleavage functional microbes exhibited significant negative correlation with aromatic humic substances (p < 0.05). Furthermore, network analysis indicated that most of microbial communities prefer cooperative with aromatic-ring cleavage functional microbes. Structural equation model further revealed that composting microenvironment drove aromatic-ring cleavage functional microbes activities, resulting in the biodegradation of complex aromatic compounds. This study parsed the effect of a negative factor on aromatic compounds humic substances from an opposing perspective. Properly controlling nitrate concentration and aromatic-ring cleavage functional microbes involved in precursors cleavage was suggested to the practice of composting., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Denitrification during composting is a hidden danger that causes environmental pollution risk and aromatic humic substance damage, which needs to be better regulate urgently. In this study, two denitrification regulation methods, moisture and biochar amendment, were conducted during chicken manure composting. Denitrification performance data showed two regulation methods obviously reduced NO 3 - -N, NO 2 - -N and N 2 contents. Humic substance increased by 25.3 % and 29.1 % under two regulations. Microbiological analysis indicated that two regulation methods could decreasing denitrifying functional microbes with aroma degradation capability. Subsequently, denitrification gene narG, nirS, nosZ were significantly inhibited (p < 0.05) and the aromatic degradation metabolism pathways were down-regulated. Correlation analysis further revealed the important influence of interspecific interactions and non-biological characteristics on functional microbes. These results provided important scientific basis to denitrification regulation in the practice of composting, which achieved the purpose of simultaneously controlling environmental pollution risk and conducing end-product formation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The aim of this study was to evaluate nitrogen pollution risks from distinct materials composting with the discrepancy of component, including chicken manure, municipal solid and straw waste (CM, MSW, SW). Results showed total nitrogen maximum mean concentrations were observed in CM (39.57 g/kg). Pollution risks in CM were continuous, while MSW and SW mainly concentrated during heating phases. Microbial analysis confirmed that pollution risks from ammonification and nitrification were more prevalent in CM. The risks of pollution caused by nitrate reduction accompanied N 2 O were the most serious in MSW. The multifunctional nitrogen-related microbes Pseudomonas and Bacillus were affected by microenvironments and contributed to different pollution risks. Furthermore, PICRUSt analysis identified the "inferred" key genes (pmoC-amoC, nrfH, nifD etc.) related to nitrogen pollution risks. This study evaluated nitrogen pollution risks and proposed the future directions, providing theoretical basis and feasible optimization measures for the mitigation of nitrogen pollution during composting., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study revealed core bacterial metabolic mechanisms involved in carbon (C) and nitrogen (N) in composting with adding MnO 2 . Two tests (control group (CK), adding MnO 2 (M)) were performed. The results indicated that the MnO 2 accelerated the transformation of carbon and nitrogen in composting. Core bacteria involved in the C and N conversion were identified, the complementarity effects of core bacteria were stimulated in M composting. Additionally, the influence of core bacteria on the C and N conversion could be divided into two pathways in M composting. One was that core bacteria promoted C and N conversion by accelerating the flow of amino acids into the tricarboxylic acid cycle. Another was that the complementarity effects of core bacteria increased the overall bacterial diversity, which contributed to C and N conversion. These findings showed that the addition of MnO 2 to composting was a promising application to treat agricultural organic waste., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Nitrate can stimulate microbes to degrade aromatic compounds, whereas humic acid (HA) as a high molecular weight aromatic compound, its formation may be affected by elevated nitrate during composting. Therefore, this study is conducted to determine the effect of elevated nitrate on HA formation. Five tests were executed by adding different nitrate concentrations to chicken manure composting. Results demonstrate that the concentration of HA in treatment group is significantly decreased compared with control group (p < 0.05), especially in the highest nitrate concentration group. RDA indicates that the microbes associated with HA and environmental parameters are influenced by elevated nitrate. Furthermore, structural equation model reveals that elevated nitrate reduces HA formation by mediating microbes directly, or by affecting ammonia and pH as the indirect drivers to regulate microbial community structure., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Enriched phosphate-solubilizing bacteria (PSB) agent were acquired by domesticated cultivation, and inoculated into kitchen waste composting in different stages. The effect of different treatments on organic acids production, tricalcium phosphate (TCP) solubilization and their relationship with bacterial community were investigated during composting. Our results pointed out that inoculation affected pH, total acidity and the production of oxalic, lactic, citric, succinic, acetic and formic acids. We also found a strong advantage in the solubilization of TCP and phosphorus (P) availability for PSB inoculation especially in the cooling stage. Redundancy analysis and structural equation models demonstrated inoculation by different methods changed the correlation of the bacterial community composition with P fractions as well as organic acids, and strengthened the cooperative function related to P transformation among species during composting. Finally, we proposed a possible mechanism of P solubilization with enriched PSB inoculation, which was induced by bacterial community and organic acids production., (Copyright © 2017 Elsevier Ltd. All rights reserved.)