Combination of humic biostimulants with a microbial inoculum improves lettuce productivity, nutrient uptake, and primary and secondary metabolism

Biostimulants of natural origin represent a growing ecological strategy to increase crops productivity, especially when applied in combination with microbial bioeffectors. We studied the effect of biostimulants such as Potassium Humates (KH) from Leonardite and Compost Tea (CT) from green compost on both productivity and nutritional status of lettuce plants, as well as on the primary and secondary metabolism of treated plants, when amended either alone or in combination with a commercial microbial inoculum (M+), mainly based on arbuscular mycorrhizal fungi (Micosat TabPlus)

Antibacterial and antioxidant properties of humic substances from composted agricultural biomasses

Background: Bioactive components isolated from composted agricultural biomasses have been receiving progressive attention, because they may improve the antibiotic susceptibility of drug resistant bacterial strains. Here, three different humic substances (HS) were isolated from composted artichoke (HS-CYN) and pepper (HS-PEP) wastes, and from coffee grounds (HS-COF), and characterized by infrared spectrometry, NMR spectroscopy, thermochemolysis–GC/MS, and high-performance size-exclusion chromatography. The antibacterial activity of HS was evaluated against some pathogenic bacterial strains, while their bioactivity was determined by a germination assay on basil (Red–Violet variety) seeds. Results: HS-CYN and HS-PEP exhibited the largest antioxidant activity and most significant antimicrobial capacity against some gram-positive bacterial strains, such as Staphylococcus aureus and Enterococcus faecalis. The same HS determined a significant increase of both root and epicotyls in seed germination experiments. The bioactivity of HS was related not only to their specific molecular composition but also to the conformational stability of their suprastructures. Specifically, the greatest bioactive and antimicrobial properties were related to the largest abundance of hydrophobic aromatic and phenolic components and to a more rigid conformational arrangement, that, in turn, appeared to be related to a small fragmentation degree of lignin structures. Conclusions: Our results showed that extraction of bioactive HS from green composts may be a sustainable and eco-compatible way to valorise agricultural byproducts. HS may be indeed exploited as substrates to produce novel materials not only to improve plant productivity but also for medical applications. Graphical Abstract: [Figure not available: see fulltext.

Fertilisation with compost mitigates salt stress in tomato by affecting plant metabolomics and nutritional profiles

Abstract Background Salinity is one of the major threats for crop growth and yield and its rate of expansion is expected to increase. We conducted a pot experiment to evaluate and compare the effect of a green compost addition and mineral fertilisation, on growth, nutrition and metabolites of tomato plants, exposed to increasing doses of NaCl. Results Although the development of stressed plants was lower than the corresponding controls, compost-treated plants performed better than mineral-amended plants watered with the same amount of salt. The different plant growth was related to an increased nutritional status. Namely, compost-treated plants showed a larger content of macro- and micronutrients, and a greater accumulation of osmoprotectants, such as soluble sugars and amino acids. Moreover, compost-treated plants showed a larger content of metabolites involved in modulating the response to salt stress, such as molecules related to energy transfer in plants and precursors of Reactive Oxygen Species scavenging compounds. Overall, the better performance of compost-added plants may be attributed to a greater availability of the organic forms of nutrients and to the positive bioactivity of compost-derived humic substances. Conclusions Compost application efficiently mitigated salt stress in tomato plants in respect to mineral fertilisation. This alleviating role was associated to the induction of a more efficient metabolic response that increased accumulation of metabolites involved in modulating the salinity stress. Therefore, fertilising with composted agricultural residue may represent a convenient alternative to mineral fertilisers to grow tomato plants in the presence of salt stress. Graphical Abstrac

Innovative nutraceutical and antibacterial proprieties of Humic extracts from composted vegetable wastes.

Compost is commonly used as an organic fertilizer to recover and preserve the chemical and physical properties of agricultural soils. Effectively, the use of recycled biomasses, residues and by-products, such as compost, is an effective way to improve the environmental and economic sustainability of agroecosystems and agri-food value chains. The use of green compost is increasingly acknowledged in the EU policies as one of the most sustainable approaches to implement the circular economy in agricultural sector due to an economic and environmental re-evaluation of agricultural biomass. Following the raising attention on compost as valuable organic resource for crop productivity, in the recent years the research activity was addressed on the innovative utilization of specific compost fractions such as humic substances and compost teas for crop biostimulation, acting as bio-effectors on biochemical activities, physiological processes and plant microbial interactions The research described in this thesis, is focused on the application of compost as renewable resource for the production of these potential bioactive materials such as humic substances (HS) and compost teas (CTs) as biostimulant to promote the biosynthesis of nutraceutical products in aromatic crop represented by common basil plant. These organic materials were obtained from different composted agricultural biomasses: artichoke, coffee and pepper. Compost teas and humic substances isolated from the different on-farm composts were characterized in details for their chemical properties and molecular composition. Experiments using HS and CTs obtained from artichoke, coffee and pepper composted biomasses highlighted a relationship with the capacity to increase the development of Basil plants with positive effects on phenological parameters such as fresh and dry biomasses and chlorophyll content. Moreover, the plant treatments with compost extracts promoted the synthesis of metabolites with antioxidant proprieties and antibacterial activity against some common human pathogens. In line with the most advanced research approaches, the results indicated the occurrence of structural-activity relationships based on a combination of physical and chemical features of applied organic fractions as triggering factors for biostimulant properties. The data of molecular characterization suggested the prevalent role of hydrophobic conformation and aromatic components, lignin derivatives and peptidic cluster in the modulation of analysed metabolic pathways. The application of metabolomics and lipidomic approaches have shown an increase in the biosynthesis of secondary metabolites with nutraceutical properties such as hydroxycinnamic acids (caffeic, ferulic, trans-cinnamic and p-cumaric) naringenin, resveratrol and coenzyme Q-10, thus confirming the effect of compost derivatives on plant metabolism. The organic materials influenced the production of primary metabolic intermediates such as erythrosis-4-phosphate and phosphoenolpyruvate that activate the production of metabolites involved in the biochemical pathway of schikimic acid. Moreover, the treatment of Basil plants with humic materials such as HS-artichoke improved the yield, antimicrobial and antioxidant properties of Essential oils (EOs) extracted from Basil leaves by steam distillation with a clear dose-response effect on the production of most bioactive chemical components like eucalyptol, methyl-chavicol, eugenol, methyl-Eugenol, trans-α-Bergamotene, geranyl acetate. Finally, medical applications of the HS and CTs extracted from different composted biomasses were carried out using in vitro assays on epithelial adenocarcinoma epithelial colon cancer cells (CaCo-2) and immortalized cells of cervical tumor (HeLa). The results of the determination of cytotoxic activity showed the significant inhibition in the proliferation of these tumorigenic cell lines, thus further supporting the reliable utilization and exploitation of natural compost extracts in pharmaceutical, nutraceutical and cosmetic field

Evaluation of Sustainable Recycled Products to Increase the Production of Nutraceutical and Antibacterial Molecules in Basil Plants by a Combined Metabolomic Approach

Background: An important goal of modern medicine is the development of products deriving from natural sources to improve environmental sustainability. In this study, humic substances (HS) and compost teas (CTs) extracted from artichoke (ART) and coffee grounds (COF) as recycled biomasses were employed on Ocimum basilicum plants to optimize the yield of specific metabolites with nutraceutical and antibacterial features by applying sustainable strategies. Methods: The molecular characteristics of compost derivates were elucidated by Nuclear Magnetic Resonance spectroscopy to investigate the structure-activity relationship between organic extracts and their bioactive potential. Additionally, combined untargeted and targeted metabolomics workflows were applied to plants treated with different concentrations of compost extracts. Results: The substances HS-ART and CT-COF improved both antioxidant activity (TEAC values between 39 and 55 μmol g-1) and the antimicrobial efficacy (MIC value between 3.7 and 1.3 μg mL-1) of basil metabolites. The metabolomic approach identified about 149 metabolites related to the applied treatments. Targeted metabolite quantification further highlighted the eliciting effect of HS-ART and CT-COF on the synthesis of aromatic amino acids and phenolic compounds for nutraceutical application. Conclusions: The combination of molecular characterization, biological assays, and an advanced metabolomic approach, provided innovative insight into the valorization of recycled biomass to increase the availability of natural compounds employed in the medical field

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

Humic substances from composted fennel residues control the inflammation induced by Helicobacter pylori infection in AGS cells.

Helicobacter pylori (H. pylori) is a common human pathogen causing inflammation. Recent studies have suggested a sophisticated interplay between mitochondria, innate immunity and inflammatory response, thus proposing mitochondrial disfunction as the hallmark of severe inflammatory disorders. In this study, humic substances isolated from composted fennel residues (HS-FEN) were tested as potential therapeutical strategy to restore the mitochondrial physiology and control the inflammation associated with H. pylori infection. The molecular features of HS-FEN were characterized by infrared spectrometry, thermochemolysis-GC/MS, NMR spectroscopy, and high-performance size-exclusion chromatography (HPSEC), which revealed the presence of aromatic polyphenolic components arranged in a rather stable conformation. In vitro results showed antioxidant and anti-inflammatory properties of HS-FEN, that was found to increase the expression level of OPA-1 and SOD-2 genes and in AGS cells stimulated with H. pylori culture filtrate (Hpcf) and concomitantly decrease the expression level of Drp-1 gene and IL-12, IL-17 and G-CSF proteins. The hydrophobic features of HS, their conformational arrangement and large content of bioactive molecules may explain the beneficial effects of HS-FEN, that may potentially become an interesting source of anti-inflammatory agents capable to counteract or prevent the H. pylori-related inflammatory disorders