Differences in organic nitrogen transformation during chicken manure composting with the addition of different disaccharides.

The effect of different carbon sources on nitrogen (N) transformation and N loss through nitrogenous gas volatilization during composting of manure is not clear. Disaccharides had moderate degradation stability compared to monosaccharides and polysaccharides. Therefore, we investigated the effect of adding sucrose (nonreducing sugar) and maltose (reducing sugar) as carbon sources on volatile N loss and hydrolysable organic nitrogen (HON) transformation. HON is composed of bioavailable organic nitrogen (BON) and hydrolysable unknown nitrogen (HUN). Three laboratory-scale experimental groups were conducted with control (CK), 5 % sucrose (SS), and 5 % maltose (MS) addition. Our findings indicated that, while excluding leaching and surface runoff, adding sucrose and maltose decreased the N loss through gas volatilization by 15.78 % and 9.77 %, respectively. The addition of maltose significantly increased the BON content (P < 0.05), which was 6.35 % higher than in CK. The addition of sucrose led to an increase in HUN content (P < 0.05), which was 22.89 % higher than that in CK. In addition, the core microbial communities associated with HON changed after the addition of disaccharides. The transformation of the HON fractions was facilitated by the succession of microbial communities. Ultimately, variation partition analysis (VPA) and structural equation modeling (SEM) verified that the core microbial communities were the major contributors to promoting HON transformation. In summary, adding disaccharides could promote the different transformations of organic nitrogen (ON) and reduce the volatilization of nitrogenous gases by changing the succession of the core microbial communities during composting. This study provided theoretical and technical support for reducing volatile N loss and promoting ON fraction sequestration during composting. Furthermore, the effect of carbon source addition on the nitrogen cycle was also explored.

The important role of tricarboxylic acid cycle metabolism pathways and core bacterial communities in carbon sequestration during chicken manure composting.

As a kind of livestock manure, chicken manure (CM) was rich in organic matter and microorganisms. However, a large amount of foul gas discharged by its random stacking not only threatened the environment, but also caused harm to human health. In view of the serious carbon loss and the unclear action mechanism of microbial community on carbon metabolism during CM composting, the effect of adding regulators on the sequestration of organic carbon was explored. Therefore, the purpose of this study was to explore the regulation mechanism of adding tricarboxylic acid cycle (TCA cycle) regulators on the core carbon metabolism pathway during CM composting. The results showed that the adenosine triphosphate (ATP) and malonic acid (MA) slowed down organic carbon degradation, resulting in lower carbon loss rate, which were 64.99% (CK), 62.35% (MA), and 61.26% (ATP) in each treatment. By comparing the abundance and structure of the carbon-related bacterial communities in different treatments, it was found that adding ATP and MA not only reduced the bacterial community abundance, but also tended to be similar in bacterial community composition. Moreover, the microbial specificity related to carbon metabolism pathway was enhanced, while the related gene expression and gene abundance were weakened. The regulation of TCA cycle metabolism pathway was confirmed to be the main way to improve organic carbon content. These findings revealed the positive effects of ATP and MA on carbon fixation from the perspective of gene metabolism.

Effect of Maillard reaction on the formation of humic acid during thermophilic phase of aerobic fermentation.

This study aimed to explore the main pathway of humic acid (HA) formation during the thermophilic phase (TP) of aerobic fermentation, clarify the contribution of Maillard reaction. These experiments were carried out on cow dung, chicken manure and rice straw. Results indicated that the maximum temperature reached 60.2℃ during TP led to a sharp decrease in microbial abundance, while the production of HA increased. The network analysis indicated that microorganisms did not participate in the formation of HA and may be dominated by abiotic pathways. In addition, proteins and sugars were consumed at the highest rate during TP, and the trends were similar to HA formation. These findings suggested that the formation of HA has relationship to Maillard reaction, because TP provided suitable reaction conditions for Maillard reaction. Therefore, these results elucidated the contribution of Maillard reaction in HA formation during TP, and provided theoretical support for directional humification.

Microhabitat drive microbial anabolism to promote carbon sequestration during composting.

Transforming organic waste into stable carbon by composting is an eco-friendly way. However, the complex environment, huge microbial community and complicated metabolic of composting have limited the directional transformation of organic carbon, which is also not conducive to the fixation of organic carbon. Therefore, this review is based on the formation of humus, a stable by-product of composting, to expound how to promote carbon fixation by increasing the yield of humus. Firstly, we have clarified the transformation regularity of organic matter during composting. Meanwhile, the microhabitat factors affecting microbial catabolism and anabolism were deeply analyzed, in order to provide a theoretical basis for the micro habitat regulation of directional transformation of organic matter during composting. Given that, a method to adjust the directional humification and stabilization of organic carbon has been proposed. Hoping the rapid reduction and efficient stabilization of organic waste can be realized according to this method.

Humus formation driven by ammonia-oxidizing bacteria during mixed materials composting.

The aim of this study was to identify the effects of ammonia-oxidizing bacteria (AOB) inoculation on humus formation. Both nitrogen conversion and humus formation were considered as the main processes, because NH4+-N-like compounds not only substrates of nitrification, but also precursors of humus. During composting, the inoculation of AOB indeed increased humus concentration by fixing NH3 emission as NH4+-N, but it has also promoted nitrogen transformation. While the main reason was the changed bacteria community structure caused by inoculating AOB. Moreover, the relationship between bacteria and nitrogen transformation and humus formation has become closer. And bacteria were more likely to synthesize humus. Therefore, it is conjectured that AOB inoculation could not only provide NH4+-N for humus formation, but also enhance the anabolism of microorganisms. This suppose has been confirmed by structural equation model in this study. Therefore, AOB inoculation has a driving effect on promoting humus formation.

Combination of Lewis Basic Selenium Catalysis and Redox Selenium Chemistry: Synthesis of Trifluoromethylthiolated Tertiary Alcohols with Alkenes.

A new and efficient method for diaryl selenide catalyzed vicinal CF3S hydroxylation of 1,1-multisubstitued alkenes has been developed. Various trifluoromethylthiolated tertiary alcohols could be readily synthesized under mild conditions. This method is also effective for the intramolecular cyclization of alkenes tethered by carboxylic acid, hydroxy, sulfamide, or ester groups and is associated with the introduction of a CF3S group. Mechanistic studies have revealed that the pathway involves a redox cycle between Se(II) and Se(IV) and Lewis basic selenium catalysis.

Diaryl Selenide Catalyzed Vicinal Trifluoromethylthioamination of Alkenes.

An efficient approach to vicinal trifluoromethylthioamination of alkenes with a broad substrate scope catalyzed by electron-rich diaryl selenide has been developed. This intermolecular amination strategy was successfully applied to SCF3-esterification of alkenes using weak acids as nucleophiles.