Formation Of Humic Substances Research Articles

Insight into the effects of regulating denitrification on composting: Strategies to simultaneously reduce environmental pollution risk and promote aromatic humic substance formation

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 NO3−-N, NO2−-N and N2 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.

Hyperthermophilic pretreatment composting to produce high quality sludge compost with superior humification degree and nitrogen retention

Composting of sewage sludge is widely used for stabilization treatment to realize the reduction of moisture and pathogen as well as the formation of humic substances. However, the major limitators were protein hydrolysis and functional bacteria activity. This study aimed to verify the potential of hyperthermophilic pretreatment composting (HPC) with HP at 120 °C for 30 min to improve sludge stabilization and to explore the key mechanism for enhancing sludge humification and improving organic nitrogen (N) retention. This study conducted the lab-scale facility of HPC in contrast to the control composting (CC) without thermal pretreatment. Surprisingly, HPC was more efficient at sludge degradation and phytotoxicity removal, further, the end sludge compost of HPC achieved 123.3% increase of the humification degree (HAC/FAC) and 14.2 % growth of organic N retention. Chemical analyses of extracellular organic substance indicated HPC had the more drastic protein transformation and HA polymerization. Solid-state 13C NMR and electrochemical measurements of HA indicated HPC enhanced HA’s aromatic structural development with greater quinones regeneration and condensation. Further mechanism analyses highlighted the essential effects of HP on stimulating HA’s precursors formation and functional bacterial community evolution. HP destroyed sludge EPSs allowing a 37.5% increase of proteins solubilization and a 112.6% enhance of HA release into SMPs; during which the quinones in HA exposed and activated thus improving redox properties to accelerate protein consumption towards new quinones regeneration, aromatic amino acids biosynthesis and metabolism. HP helped to inactivate Pseudomonas but accumulate thermophilic bacteria that enhanced proteins utilization to produce proteinaceous HA’s precursors with less N mineralization, facilitating the final enrichment of Actinobacteria with positive effects on N retention and humic polymerization.

Fluorescence properties of humic substances transformed in ectohumus horizons of Podzols affected by alkaline fly‐ash

AbstractLignite burning is still the main source of energy in many countries, generating huge amounts of alkaline residues deposited in dumping sites, which affects the surrounding environment. There are only a few publications dealing with the effects on pH changes of surface horizons, but there are no reports on the impact on other soil properties. The aim of this paper was to characterize the changes occurring in the soil organic matter (SOM) of ectohumus horizons of Podzols located near the dumping site and at the control site. Conventional one‐dimensional, synchronous, and three‐dimensional fluorescence can provided a new information on differences in the structure of humic substances (HS), which are crucial constituents of SOM. Humic acid (HA) and fulvic acid (FA), originally present in the ectohumus horizon, indicated a lower degree of humification, and were characterized by a looser structure, than HS that were extracted from soils affected by fly‐ash. The neutralization of the soil reaction resulting from the deposition of fly‐ash favored the formation of higher humified HS, characterized by a higher concentration of aromatic rings in the core of the molecule and the presence of double conjugated bonds. The fluorescence technique could be applicable to monitor the chemical modification of soils in regions affected by ashes but also all factors changing soil pH. The conducted research has shown that fluorescence spectroscopy can be successfully used as a sensitive technique to characterize qualitatively structures of different organic substances present in terrestrial and aquatic systems.

Enhanced turnover of phenolic precursors by Gloeophyllum trabeum pretreatment promotes humic substance formation during co-composting of pig manure and wheat straw

The present work aimed to explore the effect of Gloeophyllum trabeum pretreatment on phenol dynamics, humic substance (HS) formation and bacterial community succession during co-composting of wheat straw (WS) and pig manure (PM). The results showed that the phenol production was significantly improved during WS pretreatment with G. trabeum. Moreover, the phenol conversion during composting was significantly promoted after G. trabeum pretreatment of WS. Compared with raw WS, the composting process was accelerated by 13 days and HS content was increased by 15.7% during co-composting of pretreated WS and PM. Furthermore, G. trabeum pretreatment increased the relative content of aromatic functional groups in HS by enhancing the correlations between phenolic compounds and chemical structure of HS. The influence of phenol on bacterial community shift was strengthened by G. trabeum pretreatment, resulting in increased relative abundance of laccase-producing bacteria. Our findings provide a new way to promote the humification process by enhancing phenolic precursors turnover with functional microorganisms.

Tyrosinase and laccase-producing Bacillus aryabhattai TFG5 and its role in the polymerization of phenols

BackgroundTyrosinases and laccases are oxidoreductase enzymes that are used widely in the food, feed, textile, and biofuel industries. The rapidly growing industrial demand for bacterial oxido-reductases has encouraged research on this enzyme worldwide. These enzymes also play a key role in the formation of humic substances (HS) that are involved in controlling the biogeochemical carbon cycle, providing nutrients and bio-stimulants for plant growth, and interacting with inorganic and organic pollutants besides increasing carbon sequestration and mitigating greenhouse gas emission in the environment. The present study aimed to screen and characterize extracellular tyrosinase and laccase-producing soil bacteria that could be utilized in the polymerization of phenols.ResultsTwenty isolates from different soil samples collected from forest ecosystems were characterized through ARDRA using restriction digestion with AluI, HpaII, and HaeIII restriction enzymes. The results of Hierarchical Cluster Analysis (HCA) revealed a 60 % similarity coefficient among 13 out of 20 isolates, of which, the isolate TFG5 exhibited only 10 % similarity when compared to all the other isolates. The isolate TFG5 exhibited both tyrosinase (1.34 U.mL− 1) and laccase (2.01 U.mL− 1) activity and was identified as Bacillus aryabhattai. The increased polymerization activity was observed when B. aryabhattai TFG5 was treated with phenols. The monomers such as catechol, p-Hydroxy benzoic acid, ferulic acid, and salicylic acid were polymerized efficiently, as evidenced by their FT-IR spectra depicting increased functional groups compared to the standard mushroom tyrosinase.ConclusionsThe polymerization ability of B. aryabhattai TFG5 could be applied to phenol-rich wastewater treatment for efficient precipitation of phenols. Furthermore, tyrosinases can be used for enhancing the synthesis of HS in soil.

Efficient decomposition of lignocellulose and improved composting performances driven by thermally activated persulfate based on metagenomics analysis

In this study, fresh dairy manure and bagasse pith were used as raw materials to study the effect of potassium persulfate in the aerobic composting process. The influence of sulfate radical anion (SO4−·) generated by thermally activated persulfate on physicochemical parameters, lignocellulose degradation, humic substance (HS) formation, microbial community succession, and carbohydrate-active enzymes (CAZymes) composition were assessed during composting. Experimental results showed that the degradation rates of cellulose, hemicellulose and lignin in the treatment group with potassium persulfate (PS) (61.47%, 74.63%, 73.1%) were higher than that in blank control group (CK) (59.98%, 71.47%, 70.89%), respectively. Additionally, persulfate additive promoted dynamic variation of dissolved organic matter (DOM) and accelerated the formation of HS. Furthermore, metagenomics analysis revealed that persulfate changed the structure of the microbial community, and the relative abundances of Actinobacteria and Proteobacteria increased by 17.64% and 34.09% in PS, whereas 12.09% and 29.96% in CK. Glycoside hydrolases (GHs) and auxiliary activities (AAs) families were crucial to degrade lignocellulose, and their abundances were more in PS. Redundancy analysis (RDA) manifested that Actinobacteria and Proteobacteria were closely associated with lignocellulosic degradation. In brief, persulfate could accelerate the degradation of organic components, promote the formation of HS, optimize the structure of microbial community, and improve the compost quality.

Waste Willow-Bark from Salicylate Extraction Successfully Reused as an Amendment for Sewage Sludge Composting

Due to the fact that compost is a valuable fertilizer that serves principally as a source of macronutrients, composting is one of the preferred methods of management of organic waste, including municipal sewage sludge. However, due to its high moisture content and low C/N ratio, sewage sludge cannot be composted alone. This study investigated the usefulness of waste willow-bark (WWB) (after salicylate extraction) as an amendment for municipal sewage-sludge composting in a two-stage system: an aerated bioreactor and a periodically turned windrow. Both organic matter (OM) removal and humification progress were monitored. It was found that the prepared feedstock (70% sewage sludge, 25% WWB, and 5% wood chips, w/w) enabled proper temperature profiles to be obtained, with a maximum temperature of 72.3 °C. The rate constant of OM degradation in the bioreactor was 0.25 d−1, almost 4-fold higher than that in the windrows. During composting, the concentrations of humic substances (HS), humic acids (HA), and the fulvic fraction (FF) changed. HS, HA, and FF formation proceeded according to 1. order kinetics, and their respective rates were 1.33 mg C/(g OM d), 1.03 mg C/(g OM d), and 0.76 mg C/(g OM d). However, in mature compost, FF predominated (ca. 70%) in HS. These results indicate that waste willow-bark, a product of salicylate extraction, can be successfully reused as an amendment during municipal sewage sludge composting. Both waste willow-bark reuse and sewage sludge composting are compatible with a circular economy.

Specified Dosages of Biochar Application Not Impact Native Organic Carbon but Promote a Positive Effect on Native Humic Acid in Humicryepts Soil

Biochar is considered to have potential use in carbon (C) sequestration and has been widely used in soil amendment. Humic substances (HSs), assigned as the stable organic C, have obvious agronomic benefits. However, the response mechanisms of these carbonaceous substances to biochar are unclear in biochar-amended soils. In a two-year experiment, the δ13C technique was employed to trace the fate of the biochar-derived C in HSs and evaluate the effects of four treatments, including no biochar control (CK) and biochar addition at dosages of 6 t ha−1 (BC6), 12 t ha−1 (BC12), and 24 t ha−1 soil (BC24), on soil organic carbon (SOC) and HSs. Compared to CK, biochar application significantly improved total SOC contents and the C pool index, whereas the C labile index declined. Humic acid (HA) and humin were distinctly enhanced in bulk soil. Moreover, the aliphaticity was intensified in the chemical composition of HA. In particular, native HA contents substantially increased by 16.30–55.95%. Biochar-applied C of 4.08–6.43% was finitely involved in HA formation over the two years, which resulted in a genetic relationship between soil HA and biochar to some extent. The low dosages of biochar at 6 t ha−1, 12 t ha−1 and 24 t ha−1 did not obviously affect native SOC contents. Moreover, BC24 had less of an effect on HA formation compared to BC6 and BC12, but had the highest SOC. These results demonstrate that biochar application can improve SOC stocks, reduce C instability and promote HSs formation, and they suggest that determining and keeping an optimum dosage of biochar application can represent an effective strategy (i.e., not only sequestrate C, but also improve soil quality), which is beneficial to sustainability in the ecological environment and agriculture.

Enhanced abiotic integrated polyphenol-Maillard humification by Mg/Fe layered double hydroxide (LDH): Role of Fe(III)-polyphenol complexation

Abiotic humification can be facilitated by iron-containing minerals or oxides, but most studies have focused on well-crystallized and stable iron phases, the catalytic effect of which is generally unremarkable. In the present study, we report an enhanced abiotic integrated polyphenol-Maillard humification reaction catalysed by Mg/Fe-layered double hydroxide (Mg/Fe-LDH) with high surface reactivity. The results demonstrated that Mg/Fe-LDH could effectively promote the humification reaction at a lower dosage compared with Fe2O3. As an iron-chelating ligand, catechol rapidly induced iron dissolution from Mg/Fe-LDH through the formation of an Fe(III)-catechol complex, which strengthened the catalytic effect of Fe(III). The photochemical behaviour of Fe(III)-catechol complex and its impact on the Fe(III)-catalysed humification process were investigated. Under light irradiation, environmentally persistent free radicals (EPFRs) originated from the Fe(III)-catechol complex were formed and stabilized in the presence of Mg/Fe-LDH particles, which inhibited the oxidation of catechol and the humification process. Hence, the formation of humic substances (HS) catalysed by Mg/Fe-LDH was more efficient under darkness. Iron redox cycling and generation of reactive oxygen species (ROS), HO• and O2•-, were also involved. According to transformation products (TPs) analysis, ortho-aminophenol was proposed to be a key product in the humification reaction. Self-coupling of catechol radical and ortho-aminophenol radical, ring cleavage were likely to occur in the Fe(III)-catalysed humification process. Higher relative abundance of CHO products was observed in the presence of Mg/Fe-LDH by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), suggesting that iron is effective on promoting C–C bonds formation. The above results provide more comprehensive insights into Fe(III)-catalysed humification and a guidance to improve the efficiency of HS formation and carbon sequestration in organic wastes utilization.

Biochar reinforced the populations of cbbL-containing autotrophic microbes and humic substance formation via sequestrating CO2 in composting process

The quality of compost is drastically reduced due to the loss of carbon, which negatively impacts the environment. Carbon emission reduction and carbon dioxide (CO2) fixation have attracted much attention in composting research. In this study, the relationship between CO2 emission, humic substances (HS) formation and cbbL-containing autotrophic microbes (CCAM) was analyzed by adding biochar during cow manure composting. The results showed that biochar can facilitate the degradation of organic matter (OM) and formation of HS, as well as reinforce the diversity and abundance of CCAM community, thereby promoting CO2 fixation and reducing carbon loss during composting. High-throughput sequencing analysis revealed significant increase in Actinobacteriota and Proteobacteria abundance by 30.97 % and 10.48 %, respectively, thus increasing carbon fixation by 32.07 %. Additionally, Alpha diversity index increased significantly during thermophilic phase, while Shannon index increased by 143.12 % and Sobs index increased by 51.62 %. Redundancy analysis (RDA) indicated that CO2 was positively correlated with C/N, temperature, HS and dissolved organic matter (DOM), while the abundance of Paeniclostridium, Corynebacterium, Bifidobacterium, Clostridium, Turicibacter and Romboutsia were positively correlated with temperature, CO2, C/N and E2/E4 (p < 0.01).

Thickening and Storage of Sewage Sludge Contribute to the Degradation of LAS and EOX and the Humification of Organic Matter

Land application of sewage sludge on agricultural soils can be sustainable only if pollutant contents and organic matter quality meet the requirements imposed by minimization of environmental risks. This study investigated the degradation of linear alkylbenzene sulfonates (LAS) and extractable organic halogens (EOX) and the formation of humic substances (HS) during the thickening and storage phases of sewage sludge treatment. Changes in spectroscopic properties (UV-Vis, FT-IR, and excitation-emission matrix (EEM) fluorescence) of HS were also evaluated to assess the occurrence of biological activities during these curing phases of sewage sludge (SS). Humic acids (HA), fulvic acids (FA), EOX, and LAS were extracted from sewage sludge sampled from four municipal wastewater treatment plants of different size and treatment sequence, before and after 90 days of aerobic or anaerobic storage. During storage, the loss of organic C in the SS ranged from almost null to 31%. No significant changes of FA were registered, whereas HA increased in almost all samples, up to 30%. The amount of humic substances synthesized during storage correlated with the percentage of C lost. Spectroscopic changes of FA and HA showed an increase in their aromaticity, with a corresponding decrease in the aliphatic contribution. These changes show the improved agronomical quality of SS. LAS decreased during storage up to 30%, surprisingly more under anaerobic than aerobic conditions, whereas EOX decreased significantly in all samples, even up to 81%. In conclusion, although storage may be normally considered not influencing the quality of SS, their organic matter quality improved and contamination decreased during 90 days of storage, whatever the conditions of oxygen availability applied.

SPECTROSCOPIC TECHNIQUES COMBINED WITH CHEMOMETRICS TO STUDY ORGANIC MATTER IN TROPICAL SOILS WITH DIFFERENT DEGREES OF PEDOGENETIC EVOLUTION

Understanding of the organomineral interactions in soil can elucidate the humic substances (HS) formation and the humification process. This study aimed to structurally characterize the humic acids (HA) formed in tropical soils with different pedogenesis degrees. The HA fraction was extracted from soil samples in the superficial horizons of an Inceptisol and a Mollisol in Rio de Janeiro state. The HA was characterized using spectroscopic techniques following by chemometric analyses: principal component analysis, descriptive analysis, and multivariate curve resolution. The results show that HA extracted from superficial horizon of Inceptisol and Mollisol are structurally different. The Inceptisol HA has a lower E4/E6 ratio than the Mollisol HA. The chemical groups show that most -CH groups belong to -CH2 and -CH3 and hydroxyls (-OH) for the Inceptisol HA, whereas the Mollisol HA predominantly contains aromatic C=C groups. The Inceptisol HA is mainly composed of CAlkyl-H,R and -C=O structures, whereas the Mollisol HA contains a higher quantity of CAlkyl-O,N, CAlkyl-O and CAromatic-H,R groups. The Inceptisol HA has a higher aliphatic content and hydrophobicity than the Mollisol HA. In Inceptisol, organic carbon stabilization can be facilitated by hydrophobic interactions, whereas in Mollisol, different interaction sites can stabilize proteinaceous compounds.

COMPOSITION, PROPERTIES AND RECYCLING OF VEGETATIVE POPLAR AFTER REMOVAL OF EXTRAC-TIVES. REPORT 3. OBTAINING BIOIOGICAL PRODUCTS BASED ON FUNGI OF THE GENUS TRIGHODERMA

The purpose of this work was to assess the suitability of solid and liquid waste generated during processing of the vegetative part of poplar as substrates for biochemical processing in order to obtain biologics for various purposes. For the study, we used post-extraction residues, as well as a cubic liquid formed after distilling essential oils and extracting alcohol-soluble substances from the vegetative part of the balsamic poplar (Populus balzamifera L.). Siberian strains of fungi of the genus Trichoderma used as a biodestructor.&#x0D; Studies have shown that the vegetative part of poplar and its individual elements are an available substrate for the growth of mycelial fungi. The high yield of spores (4.5×109 spor/g) and the formation of humic substances (11%) used as plant growth stimulators during solid-phase cultivation of the MG-97 strain of Trichoderma fungi gives grounds to use the vegetative part of poplar as a technological raw material for obtaining a biological product of the "Trichodermin" type or soil humification. Depending on the purpose of the preparations, the duration of cultivation can vary: for obtaining agricultural biologics up to 15 days, more – for soil humification. The inclusion of a cubic liquid at the stage of substrate humidification allows to obtain a biological product with a higher spore titer (5×109 spor/g), makes it possible to close the water consumption cycle and make the technology of processing the vegetative part of poplar waste-free.

Impacts of red mud on lignin depolymerization and humic substance formation mediated by laccase-producing bacterial community during composting

The aim of this study was to investigate the impacts of red mud on lignin degradation, humic substance formation and laccase-producing bacterial community in composting to better improve composting performances. The results indicated that the organic matter contents of final compost products in the treatment group with red mud (T) decreased by 25.74%, which was more than the control group without red mud (CK) (12.09%). The final lignin degradation ratio and humic substance concentration of the T were 18.67% and 22.80% higher than that of the CK, respectively. The final C/N values of compost in the CK and T were 11.32 and 10.66, respectively, which were both less than 15, suggesting that compost reached maturity. Redundancy analysis showed that temperature was the main factors driving the variation of laccase-producing bacterial community. Pearson analysis suggested that Pseudomonas, Phenylobacterium, and Caulobacter were the most significantly correlated with lignin degradation and humification in the T.

Transformations of phenolic compounds in meadow soils

The aim of the research has been to determine the role of phenolic compounds in the processes of transformations of organic matter in meadow soils, leading to the formation of humic substances. The research has been performed based on the plant material and soil sampled from Europe’s unique complex of permanent grasslands irrigated continuously for 150 years applying the slope-and-flooding system, the Czerskie Meadows. Phenolic compounds were isolated from the plant material samples (hay, sward and roots) and soils (horizon A, AE and Bsv) and from the fraction of humic and fulvic acids. It was found that the contents of phenolic compounds decrease in the following order: hay > sward > roots > A horizon soil > AE horizon soil > Bsv horizon soil > A horizon fulvic acids > AE horizon fulvic acids > Bsv horizon fulvic acids > A horizon fulvic acids > AE horizon fulvic acids > Bsv horizon fulvic acids. A significantly higher share of cinnamyl than vanillyl and syringyl compounds in the extracts of fulvic acids and slightly higher in the hydrolysates of humic acids confirms the effect of the chemical composition of the plant material undergoing decomposition on the properties of the emerging humic substances.

Alkali lignin and sodium lignosulfonate additives promote the formation of humic substances during paper mill sludge composting

Alkali lignin (AL) and sodium lignosulfonate (SLS) are by-products of the papermaking industry and could influence composting processes due to their rich aromatic structures. In this study, the roles of AL and SLS additives in the formation of humic substances (HS) during paper mill sludge composting were investigated. Results showed that HS content and degree of polymerization of the final products in AL (44.42 mg·g−1 and 0.70, respectively) and SLS (45.87 mg·g−1 and 1.14, respectively) treatments were appreciably higher than those of the control sample (34.36 mg·g−1 and 0.67). Excitation-emission matrix-parallel factor coupled with two-dimensional FT-IR correlation spectroscopy analysis suggested that AL and SLS additives could speed the transformation of quinone-like substances by increasing the amounts of low molecular weight lignin depolymerized products, which led to higher HS concentrations. This work provided a way of promoting HS formation and the comprehensive utilization of papermaking wastes.

Influence of malonic acid and manganese dioxide on humic substance formation and inhibition of CO2 release during composting

The aim of thisstudy was to explore the effects of malonic acid (MA), manganese dioxide (MnO2), malonic acid combined with manganese dioxide (MA + MnO2) additionon reducing CO2 emission and promoting humic substance (HS) formation during composting. The result showed that the addition of MA and MnO2 were an efficient way to reduce CO2 emission. Meanwhile, the CO2 emissions in the MA + MnO2 treatment was 36.8% less than that of the CK, and the amount of humic acid (HA) produced in the MnO2 treatment was 38.7% higher than that of the CK. Structural equation models demonstrated that the addition of exogenoussubstance promoted the conversion of amino acids and reducing sugars to HA. The addition of exogenous substances was the main reason for influencing the concentration of HA. In general, this research provided theoretical supports for the addition of exogenous substances to promote HA formation during composting.

Effects of acid/alkali pretreatments on lignocellulosic biomass mono-digestion and its co-digestion with waste activated sludge

The present study investigated the effects of acid/alkali pretreatments on wheat straw mono-digestion and its co-digestion with waste activated sludge (WAS). The effects of pretreatment conditions on different anaerobic digestion (AD) stages (hydrolysis, acidogenesis, acetogenesis and methanogenesis) were discussed. At first, this study analyzed the impacts of acid/alkali pretreatments on wheat straw morphology, lignocellulosic components and evaluated these impacts on subsequent AD process by SEM, XRD, FT-IR and 3D-EEM analysis. The results of AD process showed that both acid and alkali pretreatments can enhance the hydrolytic performance of substrates. W12 (0.01 mol/L NaOH pretreated wheat straw mono-digestion) obtained the highest cumulative specific methane yield (CSMY) of 227.4 mL/g·VS. However, due to the formation of humic substances in liquid fraction, 0.1 mol/L NaOH pretreated wheat straw (W13) presented inhibition in converting propionic acid into acetic acid process. Co-digestion with sludge can relieve this inhibition and obtain the highest CSMY of 221.4 mL/g·VS. This study also exhibited the effects of pretreatments on microbial community and diversity: the inhibition of acetogens in AD process was revealed. Eventually, this study summarizes the positive and negative effects of acid/alkali pretreatments on the different digestive stages, aiming to provide references for future research and engineering implementation.

Formation of humic substances in the reaction of D-glucose with p-toluidine in anhydrous ethanol

The aim of the study was to investigate the processes of formation and structural group composition of the products formed during the reaction of D-glucose with p-toluidine in anhydrous ethanol using electronic and vibrational spectroscopy methods. The evolution of the profiles of the electronic spectra of working solutions shows the formation of a chromophore system: clear peaks at 380 and 440 nm are already present at a reaction time of 60 min. The appearance of an additional maximum at 520 nm (90, 120 min) likely corresponds to the formation of chromophores in condensed structures, as confirmed by a decrease in the values of the E 4 /Е 6 indices over time. The dynamics of the transformation of structural elements is also clearly seen in the analysis of IR spectra: as the reactions proceed, the CH aliphatic component of the structure decreases, while the aromatisation and functionalisation of products by chromophore groups increases. For products obtained between 90 and 120 min, a clear band at 1656 cm -1 , attributed to stretching vibrations of multiple bonds in conjugated C=C – C=O systems and azomethine fragments, indicates the of condensation reactions. In the spectra of insoluble solid products fractionated by water, the intensity of the bands at 1656 and 1190 cm -1 is significantly reduced; this is possibly due to the transfer of some of the coloured low molecular weight products to the aqueous phase. A comparison of the IR Fourier transform spectra of the final solid products with the spectra of natural and synthetic humic-like substances indicates their similar structural group composition. The intensity of the bands at 1620, 1508 and 815 cm -1 indicates a significant contribution of the aromatic component to the structure of the products of water-insoluble fractions; the water-soluble fractions mainly include aliphatic oxygen-containing structures resulting from the oxidative destruction of the initial carbohydrate. The synthesised products seem promising as convenient plant growth regulators with controlled release of the active substance.

Roles of non-ionic surfactant sucrose ester on the conversion of organic matters and bacterial community structure during composting

The purpose of this study was to investigate the effect of sucrose ester (SE) addition on the physico-chemical parameters, organic matter (OM) biodegradation and related bacterial communities structure in dairy manure and cassava residuals co-composting. The biodegradation rates of OM, dissolved organic matters (DOM) and lignocellulose in SE (16.34%, 44.11% and 26.73%) group were higher than those in CK (14.71%, 39.11% and 19.90%). In addition, the content of humic substances (HS) (36.34%) in SE was obviously higher than that in CK (17.68%). The relative abundance of bacterial community in SE changed, in which the abundance of Firmicutes and Actinobacteria increased, while the amount of Blastomonas decreased. Redundancy analysis indicated Bacillus and Acinetobacter were positively correlated with the temperature and OM, whereas Azomonas and Luteimonas showed a positive relation with pH. In conclusion, the amendment of SE accelerated the degradation and conversion of organic matters, enhanced the formation of HS and improved the quality of compost.