Are humic substances soil microbial residues or unique synthesized compounds? A perspective on their distinctiveness

Dou, Sen; Yan, Xiaoyuan; Song, Xiangyun; Cao, Rui; Wu, Meng; Li, Chenglin; Guan, Song

doi:10.1016/s1002-0160(20)60001-7

Cited by 91 publications

(42 citation statements)

References 53 publications

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“…Similar results were observed in the chemical fractionation of soil humus [ 5 ]. Therefore, the results of the present investigation are in line with the concepts and views propounded by traditional humification [ 3 , 4 ]. More particularly, TyrB enhances HS synthesis in coir pith biomass.…”

Section: Discussionsupporting

confidence: 89%

“…However, increasing evidence in support of the traditional view of humic substance synthesis [ 3 , 4 ] has also been reported. The traditional concept of the humification hypothesis is that the soil added plant residues undergo decomposition by the extracellular enzyme secreted by soil microorganisms.…”

Section: Discussionmentioning

confidence: 99%

“…In recent years, soil carbon flow modeling has played a vital role in predicting future carbon emission patterns in soil, assisted in the development of mitigation strategies to restrict soil CO 2 emission, and offered ways to increase soil carbon sequestration for improved soil productivity [ 2 ]. One of the most promising ways to reduce CO 2 emission from the soil and enhance soil productivity is to improve the HS synthesis in soil [ 3 ]. HS are formed by the oxidative polymerization of phenols in soil.…”

Section: Introductionmentioning

confidence: 99%

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Bacillus aryabhattai TFG5-mediated synthesis of humic substances from coir pith wastes

et al. 2021

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Background Humic substances (HS) form the largest proportion among all the constituents of soil organic matter and are a key component of the terrestrial ecosystem. HS plays a multifunctional role in the environment by controlling the biogeochemical carbon cycle, providing nutrients and bio-stimulants for plant growth, and interacting with inorganic and organic pollutants. The rate of formation of HS in soils determines its productivity and carbon sequestration capacity. Enhancement of HS synthesis in the soil through the microbial route not only increases CO2 sequestration but also mitigates the greenhouse gas emissions in the environment. Result In this study, we attempted to understand the mechanism of formation and enhancement of HS from coir pith wastes using the tyrosinase produced by Bacillus aryabhattai TFG5. The bacterium TFG5 isolated from the termite garden produced the tyrosinase (1.34 U mL−1) and laccase (2.1 U mL−1) at 48 h and 60 h of fermentation, respectively. The extracellular tyrosinase from B. aryabhattai TFG5 was designated as TyrB. Homology modeling of TyrB revealed a structure with a predicted molecular mass of 35.23 kDa and two copper ions in the active center with its conserved residues required for the tyrosinase activity. TyrB efficiently transformed and polymerized standard phenols, such as p-cresol, p-hydroxyl benzoic acid, Levo DOPA, and 2,6 DMP, besides transforming free phenols in coir pith wash water (CWW). Additionally, UV–Vis and FT-IR spectra of the degradation products of the coir pith treated with TyrB revealed the formation of HS within 3 days of incubation. Furthermore, the E472/664 ratio of the degradation products revealed a higher degree of condensation of the aromatic carbons and the presence of more aliphatic structures in the HS. Conclusion The results confirmed the influence of TyrB for the effective synthesis of HS from coir pith wastes. The results of the present study also confirm the recently accepted theory of humification proposed by the International Humic Substances Society.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bacillus aryabhattai TFG5-mediated synthesis of humic substances from coir pith wastes

et al. 2021

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“…Though the actual existence of HS and the justification of its extraction procedure have been debated recently (Kleber & Lehmann, 2019; Lehmann & Kleber, 2015; Schmidt et al., 2011), the alkaline extraction procedure and the subsequent fractionation are still the most effective method to explore and elucidate the vital and complex role of HS in terrestrial ecosystems (Dou et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

Humic substances and distribution in Mollisols affected by six‐year organic amendments

et al. 2020

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Organic amendments under crop rotation influence soil organic matter (SOM) content, while the distribution and structural changes of humic substances have not been thoroughly examined. Three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC) and fluorescence regional integration (FRI), and projection procedure regression (PPR) were used to comprehensively evaluate the structural characteristics and distribution of fulvic acids (FA). The fertilization regimes were: CNoF-SNoF (corn and soybean without fertilizer), CCF-SNoF (corn with chemical fertilizer and soybean without fertilizer), CCR-SNoF (corn and soybean stovers with chemical fertilizer and soybean without fertilizer), CCF-SCF (corn and soybean with chemical fertilizer), and CCF-SFM (corn with chemical fertilizer and soybean with dairy manure). Six-year organic amendments mainly increased SOM, FA and humic acids (HA) contents, and the ratio of HA to FA (HA/FA), the ratio of percent fluorescence response in the ultraviolet to visible region (P V,n /P III,n) and projection values in topsoil. Six-year stover return enhanced labile fractions of SOM in 20-30 cm soil depth, while dairy manure application increased labile fractions of SOM in 0-10 cm and 20-30 cm soil depths. The organic amendments had higher Fmax of component C1 (bioavailable aliphatic compounds) and component C2 (high molecular structure

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“…As such, knowledge of the characteristics and properties of organic amendments is essential when selecting the most suitable organic amendments in sustainable agricultural practices (Spaccini et al, 2019). Dou et al (2020) shows that OM isolated using alkaline extraction, particularly humic acids (HA), can be an effective approach to study the functionality of SOM in terrestrial ecosystems. Sodium hydroxide (NaOH) and sodium pyrophosphate (Na 4 P 2 O 7 , PyroP) have been commonly used for extracting SOM (Stevenson, 1994).…”

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confidence: 99%

Validation and comparisons of NaOH and Na₄P₂O₇ extraction methods for the characterization of organic amendments

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Gillespie

et al. 2021

Soil Science Soc of Amer J

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The objectives of this study are to compare the chemical properties of organic matter (OM) in alkaline extracts of turkey litter compost, source-separated organic compost and biosolid pellets, and to validate the use of humic acids (HA) for analyzing the functionality, i.e., the ability to complex with nutrients, of OM. The humic fractions, including humic acids (HA), fulvic acids (FA) and alkaline non-dissolved fraction (humin), were isolated either with NaOH or Na 4 P 2 O 7 (PyroP) and the chemical properties were analyzed by solid-state 13 C NMR spectroscopy. The study showed that the proportions of each functional group of the combination of HA, FA and humin were essentially identical to that of their HCl-treated original materials, except for a lower recovery of O-alkyl groups. Although the yield of HA extracted with PyroP was lower than that with NaOH, their spectral characteristics were not significantly different. The functionality of the OM, assuming a correlation with the sum of the proportions of carboxyl and phenolic groups, was higher in both HA and FA than that in humin. Based on the proportion and functionality of the HA in the OM, we conclude that the use of HA extracted with either NaOH or PyroP is valid for studies of OM functionality. The study also shows that the functionality and stability of OM are highly source dependent. We predict that amendments of the more humified turkey litter compost would have higher potential to increase SOM levels and retain nutrients compared to the source-separated organic compost and biosolid pellets.

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Are humic substances soil microbial residues or unique synthesized compounds? A perspective on their distinctiveness

Cited by 91 publications

References 53 publications

Bacillus aryabhattai TFG5-mediated synthesis of humic substances from coir pith wastes

Bacillus aryabhattai TFG5-mediated synthesis of humic substances from coir pith wastes

Humic substances and distribution in Mollisols affected by six‐year organic amendments

Validation and comparisons of NaOH and Na₄P₂O₇ extraction methods for the characterization of organic amendments

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Are humic substances soil microbial residues or unique synthesized compounds? A perspective on their distinctiveness

Cited by 91 publications

References 53 publications

Bacillus aryabhattai TFG5-mediated synthesis of humic substances from coir pith wastes

Bacillus aryabhattai TFG5-mediated synthesis of humic substances from coir pith wastes

Humic substances and distribution in Mollisols affected by six‐year organic amendments

Validation and comparisons of NaOH and Na4P2O7 extraction methods for the characterization of organic amendments

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Validation and comparisons of NaOH and Na₄P₂O₇ extraction methods for the characterization of organic amendments