Search

Additional file 1. Table S1. List of the main products released by the thermochemolysis from humic substances from artichoke (HS-CYN), coffee grounds (HS-COF) and pepper (HS-PEP). Fig. S1. Total ion chromatograms of thermochemolysis products of humic substances from artichoke (HS-CYN), coffee grounds (HS-COF) and pepper (HS-PEP).

Additional file1: Figure S1 DGGE fingerprints of bacterial 16S rRNA gene fragments from total community DNA. Figure S2 Fungal DGGE fingerprints of ITS fragments.

Aims Plant growth-promoting bacteria of the genus Bacillus are known to solubilize phosphates and enhance plant growth in many plant species. We explored the effects of the inoculation with a commercial isolate Bacillus amyloliquefaciens on the growth and metabolic processes of maize plants in pot soils treated with triple superphosphate, rock phosphate, and either cow- or horse-manure composts, as P-fertilizers. Methods The metabolic profiles of maize leaves in the different treatments were determined by both Gas Chromatography–Mass Spectrometry and Nuclear Magnetic Resonance spectroscopy. Principle Components Analysis (PCA) based on data matrix from both techniques revealed a relationship between treatments and specific plant metabolites. Results Inoculated plants showed larger P and N contents and a more differentiated metabolome when treated with the two composts than with inorganic fertilizers. B. amyloliquefaciens in combination with composts significantly increased glucose, fructose, alanine and GABA metabolites in maize leaves, thus suggesting an improved photosynthetic activity due to enhanced P and N uptake. Both composts sustained plant growth and the phosphate solubilizing activity of B. amyloliquefaciens, while differences in P and N contents in plant leaves were attributed to the different content in compost of lignin residues and alkyl moieties, and consequent impact on microbial growth. Conclusions The combination of B. amyloliquefaciens inoculation with composted organic P-fertilizers rich in available metabolic carbon appears as an efficient alternative to mineral fertilizers to enhance nutrients uptake and foster growth mechanisms in maize plants.

Additional file 1. Additional tables.

In this study, lignin from three biomasses (miscanthus, giant reed and a pre-treated giant reed) has been isolated by two different methodologies and thoroughly characterized to produce humic-like substances, which were shown to positively affect plant growth and physiology. The techniques employed concerned the use of either sulfuric acid (SAL) or hydrogen peroxide at alkaline pH (Ox). Low yields were obtained by the Ox-method (less than 30% of Klason lignin), whereas the amount of materials coming from the SAL-extractive method was even greater than the Klason lignin, maybe due to condensation reaction between lignin and plant cell wall carbohydrates. An aqueous solubility test at pH 7 showed that a large depolymerization was obtained with the Ox-method, due to oxidation of isolated lignin material. This was also supported by elemental analyses, which showed that Ox samples had large oxygen content. Conversely, the lignin materials obtained with the SAL method were less than 6% water-soluble, thereby indicating lower depolymerization fragmentation. Thermal analyses and both infrared and nuclear magnetic resonance (NMR) spectroscopies confirmed the effectiveness of the two methods in separating cellulose from lignin. Size exclusion chromatography conducted on the Ox lignins from the three substrates, revealed nominal molecular sizes lower than 3000 Da for all substrates. Gas-chromatography Mass Spectrometry (GC-MS) analyses conducted on Ox-lignins extracted from raw miscanthus and giant reed biomasses, revealed a predominant abundance of guaiacyl-type molecule, though the small presence of sugars was also noted. Finally, different concentrations of aqueous solutions of lignins isolated by the Ox method from miscanthus and giant reed raw biomass were tested on the early stage of maize seedlings growth, in order to verify whether thse humic-like fragments displayed a plant biostimulation. Germination was not effected by any concentration of both lignin substrates, while root and shoot length were significantly enhanced at specific concentrations. These results are in accordance with some literature that indicated the bioativity of humic matter on plant growth parameters. These results suggest that water-soluble lignin fragments isolated from the lignocellulosic biomasses of this study exert hormone-like effects inasmuch as humic matter from soils of recycled biomasses. The employement of lignin residues from biorefineries in enhancing productivity of lignocellulosic biomasses in particular and agricultural crops in general appears to become an important contribution to the sustaiability of biorefineries.

Long-term exposure to air pollution has been associated with the development of some inflammatory processes related to skin. The goal of modern medicine is the development of new products with antiflammatory action deriving from natural sources to improve environmental and economic sustainability. In this study, two different humic acids (HA) were isolated from from lignite (HA-LIG) and composted artichoke wastes (HA-CYN) and characterized by infrared spectrometry, NMR spectroscopy, thermochemolysis-GC/MS, and high-performance size-exclusion chromatography (HPSEC), while their antiflammatory activity was evaluated on HaCaT cells. Spectroscopic results showing the predominance of apolar aliphatic and aromatic components in HA-LIG, whereas HA-CYN revealed a presence of polysaccharides and polyphenolic lignin residues. The HA application on human keratinocyte pre-treated with Urban Dust revealed a general increase of viability suggesting a protective effect of humic matter due to the content of aromatic, phenolic and lignin components. Conversely, the gene expression of IL-6 and IL-1β cytokines indicated a significant decrease after application of HA-LIG, thus exhibiting a greater antiflammatory power than HA-CYN. The specific combination of HA protective hydrophobic components, viable conformational arrangements, and content of bioactive molecules, suggests an innovative applicability of humic matter in dermatology as skin protectors from environmental irritants and as antiflammatory agents.

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.

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.

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

Lignin is a by-product of biorefineries and paper mills and is usually discarded or burnt. However, it may represent a source of novel fertilising products, able to support the sustainable intensification of agricultural productions. The aim of this review is to explore the literature regarding the effect of lignin application towards plant growth and nutrient use efficiency. First, we reviewed the biostimulant role of lignin, which was reported to positively perturbing plant hormonal balances or improving the efficiency of photosynthesis and respiration. Also, when added to soils, lignin was shown to enhance nitrogen uptake, as well as the development of beneficial soil microorganisms. Then, we summarised the research related to the chemical modifications of lignin structure devised to boost its bioactivity, an approach opening possibilities to tailor the effects of lignin addition on plant development. We further examined the literature about the use of lignin and its derivatives as starting substrates to produce sustainable materials (chelates, coatings, micro- and nano-materials) for the slow release of plant nutrients. Encouraging results emerged from the summarised articles, suggesting that lignin may replace the currently used synthetic polymers exploited to chelate or entrapping nutrients. We additionally hereby highlighted the role of lignin chemical nature in affecting its biological and release properties, hence pointing out the relevance of thoroughly studying its structure at a molecular level by the most advanced analytical tools. Finally, we suggested the need for researchers to combine their skills and expertise, in order to develop more efficient lignin-inspired fertilisers.