Quantitative Evaluation of Noncovalent Interactions between 3,4-Dimethyl‑1H‑pyrazole and Dissolved Humic Substances by NMR Spectroscopy

Nitrification inhibitors (NI) represent a valid chemical strategy to retard nitrogen oxidation in soil and limit nitrate leaching or nitrogen oxide emission. We hypothesized that humic substances can complex NI, thus affecting their activity, mobility, and persistence in soil. Therefore, we focused on 3,4-dimethylpyrazole phosphate (DMPP) by placing it in contact with increasing concentrations of model fulvic (FA) and humic (HA) acids. The complex formation was assessed through advanced and composite NMR techniques (chemical shift drift, line-broadening effect, relaxation times, saturation transfer difference (STD), and diffusion ordered spectroscopy (DOSY)). Our results showed that both humic substances interacted with DMPP, with HA exhibiting a significantly greater affinity than FA. STD emphasized the pivotal role of the aromatic signal, for HA-DMPP association, and both alkyl methyl groups, for FA-DMPP association. The fractions of complexed DMPP were determined on the basis of self-diffusion coefficients, which were then exploited to calculate both the humo-complex affinity constants and the free Gibbs energy (Kd and ΔG for HA were 0.5169 M and −1636 kJ mol−1 , respectively). We concluded that DMPP-based NI efficiency may be altered by soil organic matter, characterized by a pronounced hydrophobic nature. This is relevant to improve nitrogen management and lower its environmental impact

Valorization of lignins from energy crops and agro-industrial byproducts as antioxidant and antibacterial materials

BACKGROUND: Developing eco-friendly antioxidant and antimicrobial substances originating from biomass residues has recently attracted considerable interest. In this study, two lignosulfonates and various oxidized water-soluble lignins were investigated for their antioxidant properties, as assessed by ABTS, DPPH and Folin–Ciocalteu methods, and their antimicrobial activity against some bacterial strains responsible for human pathologies. RESULTS: The lignosulfonates showed the largest antiradical/antimicrobial capacity, whereas the other substrates were less effective. The observed antioxidant/antibacterial properties were positively correlated with lignin aromatic/phenolic content. The positive correlation between antiradical and antimicrobial activities suggests that lignin scavenging capacity was also involved in its antibacterial activity. A greater antimicrobial performance was generally observed against Gram-positive bacterial strains, and it was attributed to the intrinsic larger susceptibility of Gram-positive bacteria to lignin phenols. A significant though lesser inhibitory activity was also found against Escherichia coli. CONCLUSION: Our results confirmed the dependence of lignin antioxidant/antibacterial power on its extraction method and chemical structure, as well as on the type of bacterial strains. Identifying the relationship between lignin molecular composition and its antioxidant/antibacterial features represents an advance on the potential future use of renewable and eco-compatible lignin materials in nutraceutical, pharmaceutical and cosmetic sectors. © 2021 Society of Chemical Industry

Waste to Wealth Approach: Improved Antimicrobial Properties in Bioactive Hydrogels through Humic Substance-Gelatin Chemical Conjugation

: Exploring opportunities for biowaste valorization, herein, humic substances (HS) were combined with gelatin, a hydrophilic biocompatible and bioavailable polymer, to obtain 3D hydrogels. Hybrid gels (Gel HS) were prepared at different HS contents, exploiting physical or chemical cross-linking, through 1-ethyl-(3-3-dimethylaminopropyl)carbodiimide (EDC) chemistry, between HS and gelatin. Physicochemical features were assessed through rheological measurements, X-ray diffraction, attenuated total reflectance (ATR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM). ATR and NMR spectroscopies suggested the formation of an amide bond between HS and Gel via EDC chemistry. In addition, antioxidant and antimicrobial features toward both Gram(-) and Gram(+) strains were evaluated. HS confers great antioxidant and widespread antibiotic performance to the whole gel. Furthermore, the chemical cross-linking affects the viscoelastic behavior, crystalline structures, water uptake, and functional performance and produces a marked improvement of biocide action

Phosphorus species in sequentially extracted soil organic matter fractions

The majority of organic P (Porg) in soil is considered to be part of soil organic matter (SOM) associations, but its chemical nature is largely ‘unresolved’. In this study, we investigated the Porg composition in different SOM fractions of a Gleysol soil using the Humeomics sequential chemical fractionation (SCF) procedure combined with nuclear magnetic resonance (NMR) spectroscopy. In summary, SCF procedure with subsequent NaOH-EDTA extraction of the soil residue extracted a total of 1769 mg P/kgsoil compared to 1682 mg P/kgsoil of a single-step NaOH-EDTA extraction. Approximately 38 % of the extracted Porg was present in the form of the unresolved Porg pool, which was represented by one or two underlying broad signals in the phosphomonoester region of solution 31P NMR spectra. The SCF revealed that phosphomonoesters were recovered in each fraction: 47 % of the unresolved phosphomonoesters were associated with the SOM fraction released by breaking ester bonds (40 %) and ether bonds (7 %), whereas about 30 % of this unresolved Porg pool appeared in the SOM fraction closely associated with the soil mineral phase. Furthermore, the extractability of inositol phosphates (IP) was increased from 312 mg P/kgsoil to 534 mg P/kgsoil (factor 1.7) using the SCF procedure compared to a single-step NaOH-EDTA extraction. Previous studies have reported the presence of IP in molecular size fractions greater than 10 kDa. Our findings on the removal of IP with the fractionation of the SOM could explain the presence of IP in these large associations. We demonstrate that major pools of Porg are closely associated with SOM structures, comprising a diverse array of chemical species and bonding types. These results forward our understanding of Porg stabilisation, P transformation, and P cycling in terrestrial ecosystems towards an association point of view.ISSN:0016-7061ISSN:1872-625

Prokaryotic Diversity of the Composting Thermophilic Phase: The Case of Ground Coffee Compost

Waste biomass coming from a local coffee company, which supplied burnt ground coffee after an incorrect roasting process, was employed as a starting material in the composting plant of the Experimental Station of the University of Naples Federico II at Castel Volturno (CE). The direct molecular characterization of compost using 13C-NMR spectra, which was acquired through cross-polarization magic-angle spinning, showed a hydrophobicity index of 2.7% and an alkyl/hydroxyalkyl index of 0.7%. Compost samples that were collected during the early “active thermophilic phase” (when the composting temperature was 63 °C) were analyzed for the prokaryotic community composition and activities. Two complementary approaches, i.e., genomic and predictive metabolic analysis of the 16S rRNA V3–V4 amplicon and culture-dependent analysis, were combined to identify the main microbial factors that characterized the composting process. The whole microbial community was dominated by Firmicutes. The predictive analysis of the metabolic functionality of the community highlighted the potential degradation of peptidoglycan and the ability of metal chelation, with both functions being extremely useful for the revitalization and fertilization of agricultural soils. Finally, three biotechnologically relevant Firmicutes members, i.e., Geobacillus thermodenitrificans subsp. calidus, Aeribacillus pallidus, and Ureibacillus terrenus (strains CAF1, CAF2, and CAF5, respectively) were isolated from the “active thermophilic phase” of the coffee composting. All strains were thermophiles growing at the optimal temperature of 60 °C. Our findings contribute to the current knowledge on thermophilic composting microbiology and valorize burnt ground coffee as waste material with biotechnological potentialities

Compost-derived thermophilic microorganisms producing glycoside hydrolase activities as new potential biocatalysts for sustainable processes

Abstract Background The management of the organic waste recycling process determines the interest in the thermophiles microorganisms involved in composting. Although many microbial enzymes have been isolated and studied for their industrial and commercial uses, there is still a continuous search for microorganisms which could synthesize industrially feasible enzymes, especially when the microbial diversity of cow dung itself makes a potential source of biotechnological enzymes. Results The composting process studied at the Experimental Station of the University of Naples Federico II (Castel Volturno, Caserta, Italy) was characterized by fresh saw dust 40%, bovine manure 58%, and 2% mature compost as raw organic substrates, and its thermophilic phase exceeded a temperature of 55 °C for at least 5 days, thus achieving sanitation. Six microbial strains were isolated and designated as follow: CV1-1, CV1-2, CV2-1, CV2-2, CV2-3 and CV2-4. Based on 16S rRNA gene sequence, HRMAS–NMR spectroscopy, and biochemical investigations, they were ascribed to the genera Geobacillus and Bacillus. All the microbial isolates were qualitatively screened on plates for the presence of hydrolytic activities, and they were quantitatively screened in liquid for glycoside hydrolase enzymes in the extracellular, cell-bound, and cytosolic fractions. Based on these results, strains CV2-1 and CV2-3 were also quantitatively screened for the presence of cellulase and pectinase activities, and pH and temperature optimum plus thermostability of cellulase from CV2-1 were analyzed. Conclusions The isolation and the identification of these thermophilic microorganisms such as Geobacillus toebii, Geobacillus galactosidasius, Bacillus composti, Bacillus thermophilus and Aeribacillus composti have allowed the study of the biodiversity of compost, with emphasis on their primary metabolome through an innovative and underutilized technique, that is HRMAS–NMR, also highlighting it as a novel approach to bacterial cell analysis. Subsequently, this study has permitted the identification of enzymatic activities able to degrade cellulose and other polymeric substrates, such as the one investigated from strain CV2-1, which could be interesting from an industrial and a biotechnological point of view, furthermore, increasing the knowledge for potential applicability in different industrial fields as an efficient and environmentally friendly technique. Graphical Abstrac

Plastics shape the black soldier fly larvae gut microbiome and select for biodegrading functions

Abstract Background In the last few years, considerable attention has been focused on the plastic-degrading capability of insects and their gut microbiota in order to develop novel, effective, and green strategies for plastic waste management. Although many analyses based on 16S rRNA gene sequencing are available, an in-depth analysis of the insect gut microbiome to identify genes with plastic-degrading potential is still lacking. Results In the present work, we aim to fill this gap using Black Soldier Fly (BSF) as insect model. BSF larvae have proven capability to efficiently bioconvert a wide variety of organic wastes but, surprisingly, have never been considered for plastic degradation. BSF larvae were reared on two widely used plastic polymers and shotgun metagenomics was exploited to evaluate if and how plastic-containing diets affect composition and functions of the gut microbial community. The high-definition picture of the BSF gut microbiome gave access for the first time to the genomes of culturable and unculturable microorganisms in the gut of insects reared on plastics and revealed that (i) plastics significantly shaped bacterial composition at species and strain level, and (ii) functions that trigger the degradation of the polymer chains, i.e., DyP-type peroxidases, multicopper oxidases, and alkane monooxygenases, were highly enriched in the metagenomes upon exposure to plastics, consistently with the evidences obtained by scanning electron microscopy and 1H nuclear magnetic resonance analyses on plastics. Conclusions In addition to highlighting that the astonishing plasticity of the microbiota composition of BSF larvae is associated with functional shifts in the insect microbiome, the present work sets the stage for exploiting BSF larvae as “bioincubators” to isolate microbial strains and enzymes for the development of innovative plastic biodegradation strategies. However, most importantly, the larvae constitute a source of enzymes to be evolved and valorized by pioneering synthetic biology approaches. Video Abstrac

Hydrochar obtained with by-products from the sugarcane industry: Molecular features and effects of extracts on maize seed germination

Sugarcane bagasse, vinasse and a mixture of sugarcane bagasse and vinasse were hydrothermally carbonized (HTC), with and without the addition of phosphoric acid, in order to propose new applications of sucroenergetic industry by-products on soil. Detailed information on the composition and properties of hydrochars has been obtained through elemental composition, thermogravimetric analysis, nuclear magnetic resonance and, ther- mochemolysis GC-MS. The soluble acidic fraction from the hydrochar samples were applied to maize seeds to evaluate the agronomic potential as biostimulants and relate the molecular features with maize seed germina- tion. The HTC treatment converted polysaccharide-based biomasses into hydrochars with hydrophobic charac- teristics (C-Aryl and C-Akyl). Furthermore, the addition of phosphoric acid further increased the overall hydrophobicity and shifted the thermal degradation of the hydrochars to higher temperatures. Biomass influ - enced the hydrochars that formed, in which the molecular features of sugarcane bagasse determined the for- mation of more polar hydrochar, due to the preservation of lignin and phenolic components. Meanwhile, the HTC of vinasse resulted in a more hydrophobic product with an enrichment of condensed and recalcitrant organic fractions. The germination assay showed that polar structures of bagasse may play a role in improving the maize seeds germination rate (increase of ~11%), while the hydrophobic domains showed negative effects. The re- sponses obtained in germination seems to be related to the molecular characteristics that organic extracts can present in solution