scholarly journals Contribution of Microbial Residues Obtained from Lignin and Cellulose on Humus Formation

2019 ◽  
Vol 11 (17) ◽  
pp. 4777 ◽  
Author(s):  
Shuai Wang ◽  
Nan Wang ◽  
Junping Xu ◽  
Xi Zhang ◽  
Sen Dou
Keyword(s):  
Aromatic Compounds ◽  
Oxidative Degradation ◽  
Molecular Structures ◽  
Lower Degree ◽  
Humus Formation ◽  
Fluid Medium ◽  
Degree Of Oxidation ◽  
Degree Of Condensation ◽  
Microbial Residue ◽  
Microbial Residues

The contribution of microbial residues formed on lignin and cellulose to the formation of humus (HS) was investigated. The microbial residues formed by Aspergillus niger (A. niger) in the cultures of cellulose and lignin in a fluid medium were structurally characterized by elemental analysis, differential thermal analysis (DTA), FTIR spectroscopy and CP/MAS 13C NMR spectroscopy. Compared to cellulose itself, the microbial residue from cellulose contains more aromatic compounds and N-containing compounds and fewer carbohydrates and carboxylic compounds. A. niger improved the thermal stability and aromaticity of the cellulose. However, compared with that on lignin, more N-containing compounds, carbohydrates and carboxylic acid derivatives and less aromatic material were found in the microbial residue from lignin. Regardless of whether the carbon source was cellulose or lignin, A. niger utilized the N in the fluid medium to synthesize its own cells, and eventually, they could transfer the N into the microbial residue; in addition, the O-alkyl species dominated over the alkyl and aromatic compounds in the microbial residue. Although the molecular structures of the components of the microbial residue from lignin tended to be simpler, they were more alkylated, more hydrophobic and less aliphatic than those from cellulose. During culture with A. niger, the cellulose underwent degradation and then a polymerization, which led to an increased degree of condensation but a lower degree of oxidation, providing essential precursor substances for HSs formation. However, lignin underwent oxidative degradation. The microbial residue from lignin had a lower degree of condensation and a higher degree of oxidation.

The fate of peroxyl radicals in aqueous solution

1997 ◽  
Vol 35 (4) ◽  
pp. 9-15 ◽  
Author(s):  
Clemens von Sonntag ◽  
Peter Dowideit ◽  
Fang Xingwang ◽  
Ralf Mertens ◽  
Pan Xianming ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Aromatic Compounds ◽  
Advanced Oxidation Processes ◽  
Room Temperature ◽  
Oxidative Degradation ◽  
High Reactivity ◽  
Peroxyl Radicals ◽  
Oh Radical ◽  
Oxidation Processes ◽  
Water And Wastewater

The reactions of peroxyl radicals occupy a central role in oxidative degradation. Under the term Advanced Oxidation Processes in drinking-water and wastewater processing, procedures are summarized that are based on the formation and high reactivity of the OH radical. These react with organic matter (DOC). With O2, the resulting carbon-centered radicals O2 give rise to the corresponding peroxyl radicals. This reaction is irreversible in most cases. An exception is hydroxycyclohexadienyl radicals which are formed from aromatic compounds, where reversibility is observed even at room temperature. Peroxyl radicals with strongly electron-donating substituents eliminate O2.−, those with an OH-group in a-position HO2.. Otherwise organic peroxyl radicals decay bimolecularly. The tetroxides formed in the first step are very short-lived intermediates and decay by various pathways, leading to molecular products (alcohols, ketones, esters and acids, depending on the precursor), or to oxyl radicals, which either fragment by scission of a neighbouring C-C bond or, when they carry an a-hydrogen, undergo a (water-assisted) 1,2-H-shift.

scholarly journals The foliar endophytePhialocephala scopiformisDAOMC 229536 secretes enzymes supporting growth on wood as sole carbon source

2018 ◽  
Author(s):  
Jennifer M. Bhatnagar ◽  
Grzegorz Sabat ◽  
Daniel Cullen
Keyword(s):  
Carbon Source ◽  
Aromatic Compounds ◽  
Glycoside Hydrolase ◽  
Pinus Contorta ◽  
Sole Carbon Source ◽  
Oxidative Degradation ◽  
Cellobiose Dehydrogenase ◽  
Lytic Polysaccharide Monooxygenases ◽  
Polysaccharide Monooxygenases ◽  
Conifer Needle

AbstractThe conifer needle endophyte,Phialocephala scopiformis, was cultivated in media containing groundPinus contortawood as sole carbon source. After five and seven days growth, concentrated extracellular fluids were subjected to LC-MS/MS analyses. A total of 590 proteins were identified of which 99 were assigned to glycoside hydrolase families within the Carbohydrate Active Enzyme (CAzyme) system. Multiple isozymes of exo-and endo-acting cellulases were among the most abundant proteins, and oxidative degradation of cellulose was supported by the presence of lytic polysaccharide monooxygenases, glucooligosaccharide oxidase and cellobiose dehydrogenase. Oxidoreductases were also plentiful and included GMC oxidoreductases, alcohol dehydrogenases, laccases, copper radical oxidases, tyrosinases and catalase. The expression and diversity of extracellular oxidoreductases indicates a capacity to metabolize alcohols and aromatic compounds.

scholarly journals Composition and light absorption of N-containing aromatic compounds in organic aerosols from laboratory biomass burning

2019 ◽  
Vol 19 (5) ◽  
pp. 2899-2915 ◽  
Author(s):  
Mingjie Xie ◽  
Xi Chen ◽  
Michael D. Hays ◽  
Amara L. Holder
Keyword(s):  
Experimental Data ◽  
Biomass Burning ◽  
Light Absorption ◽  
Aromatic Compounds ◽  
Chemical Properties ◽  
Molecular Structures ◽  
Forest Understory ◽  
Prescribed Fires ◽  
Volatile Organic ◽  
And Chemical Properties

Abstract. This study seeks to understand the compositional details of N-containing aromatic compounds (NACs) emitted during biomass burning (BB) and their contribution to light-absorbing organic carbon (OC), also termed brown carbon (BrC). Three laboratory BB experiments were conducted with two United States pine forest understory fuels typical of those consumed during prescribed fires. During the experiments, submicron aerosol particles were collected on filter media and subsequently extracted with methanol and examined for their optical and chemical properties. Significant correlations (p<0.05) were observed between BrC absorption and elemental carbon (EC)∕OC ratios for individual burns data. However, the pooled experimental data indicated that EC∕OC alone cannot explain the BB BrC absorption. Fourteen NAC formulas were identified in the BB samples, most of which were also observed in simulated secondary organic aerosol (SOA) from photooxidation of aromatic volatile organic compounds (VOCs) with NOx. However, the molecular structures associated with the identical NAC formula from BB and SOA are different. In this work, the identified NACs from BB are featured by methoxy and cyanate groups and are predominately generated during the flaming phase. The mass concentrations of identified NACs were quantified using authentic and surrogate standards, and their contributions to bulk light absorption of solvent-extractable OC were also calculated. The contributions of identified NACs to organic matter (OM) and BrC absorption were significantly higher in flaming-phase samples than those in smoldering-phase samples, and they correlated with the EC∕OC ratio (p<0.05) for both individual burns and pooled experimental data, indicating that the formation of NACs from BB largely depends on burn conditions. The average contributions of identified NACs to overall BrC absorption at 365 nm ranged from 0.087±0.024 % to 1.22±0.54 %, which is 3–10 times higher than their mass contributions to OM (0.023±0.0089 % to 0.18±0.067 %), so the NACs with light absorption identified in this work from BB are likely strong BrC chromophores. Further studies are warranted to identify more light-absorbing compounds to explain the unknown fraction (>98 %) of BB BrC absorption.

Microwave assisted oxidative degradation of starch - estimation of degree of oxidation of the modified biopolymer

2007 ◽  
Author(s):  
Marcin Lukasiewicz ◽  
Szczepan Bednarz ◽  
Anna Ptaszek ◽  
Iwona Gerlich ◽  
Agata Bednarz ◽  
...  
Keyword(s):  
Oxidative Degradation ◽  
Microwave Assisted ◽  
Degree Of Oxidation

Simulation of 13C N.M.R. Spectra of Nitrogen-Containing Aromatic Compounds

1995 ◽  
Vol 48 (7) ◽  
pp. 1267 ◽  
Author(s):  
M Jalaliheravi ◽  
M Moosavi
Keyword(s):  
Standard Deviation ◽  
Linear Regression ◽  
Aromatic Compounds ◽  
Chemical Shifts ◽  
Structural Parameters ◽  
Semiempirical Method ◽  
Molecular Structures ◽  
Stepwise Multiple Linear Regression ◽  
Methyl Derivatives ◽  
Geometric Descriptors

The 13C n.m.r. spectra of a series of nitrogen-containing aromatic compounds have been simulated by using parametric techniques. The observed chemical shifts were related to numerically encoded structural parameters, called descriptors. The electronic and geometric descriptors were calculated after optimization of the molecular structures by using the MNDO semiempirical method. Subsequently, the method of stepwise, multiple linear regression was used to calculate coefficients relating the descriptors to the observed chemical shifts. This study involves 32 compounds such as pyridine, pyrimidine, triazine, pyridazine, and their methyl derivatives. Plotting of experimental against calculated chemical shifts for 23 carbon centres in the prediction set of five compounds shows a standard deviation of 1.41 ppm and a correlation coefficient of 0.999.

QSPR Study on Gross Heat of Combustion of Nitro Aromatic Compounds Based on Genetic Algorithm

2013 ◽  
Vol 750-752 ◽  
pp. 2248-2251
Author(s):  
Rui Wang ◽  
Hong Yin Cao ◽  
Quan Sheng Kang ◽  
Zhen Ming Li
Keyword(s):  
Genetic Algorithm ◽  
Aromatic Compounds ◽  
Correlation Coefficients ◽  
Molecular Structures ◽  
Heat Of Combustion ◽  
Qspr Model ◽  
Optimal Subset ◽  
Leave One Out ◽  
Prediction Capability ◽  
Nitro Aromatic

A novel QSPR model was proposed as to predict the gross heat of combustion of 32 nitro aromatic compounds. Genetic algorithm (GA) was applied to select the optimal subset of the molecular structures descriptors most related to gross heat of combustion. The multiple linear regression (MLR) was taken to build a prediction model of gross heat of combustion for the 32 compounds. The correlation coefficients (R2) together with correlation coefficient of the leave-one-out cross validation (Q2CV) of the model is 0.997 and 0.995, respectively. The new model is highly statistically significant, and the robustness as well as internal prediction capability of which is satisfactory. This study can provide a new way for predicting the gross heat of combustion of nitro aromatic compounds for engineering.

Effect of temperature on microbial residue dynamics in a temperate farmland soil

2021 ◽  
pp. 1-4
Author(s):  
Wei Zhang ◽  
Shuhan Dong ◽  
Ming Nie ◽  
Chao Liang ◽  
Xiaochen Zhang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Direct Effect ◽  
Decomposition Rate ◽  
Effect Of Temperature ◽  
Farmland Soil ◽  
Temperate Soil ◽  
Microbial Residue ◽  
Microbial Residues

Microorganisms mediate soil organic carbon (SOC) turnover, and microbial residues contribute a significant portion to SOC storage in temperate agroecosystems. However, little is known about the direct effect of temperature on microbial residues associated with SOC sequestration/decomposition. We assessed microbial residue dynamics in a 28 d incubation conducted at four temperatures (5, 15, 25, and 35 °C). Microbial residues did not change with time from 5 to 25 °C. However, at 35 °C, fungal residues decomposed significantly with time, and the decomposition rate was higher than SOC. Considering the important contribution of fungal residues to stable-C pool, our findings indicated warming may be detrimental to C stability in this temperate soil.

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