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.

Caratterizzazione di sostanze umiche ed estratti etanolici da compost verdi.Valutazione degli effetti antiossidanti e biostimolanti in piante di lattuga

Humic substances play a fundamental role in improving the physical, chemical and biological soil properties, and determining carbon sequestration in soil and stimulating plant growth. Therefore, they are increasingly used for both soil and plant treatments. In this work, humic and hydroethanolic (water:ethanol; 30:70, v:v) substances have been isolated from composted green soil improvers, aiming to identify new products capable to deliver benefits to plant and soil, and enhance the reuse of vegetable wastes resulting from the production process of artichoke, coffee, pepper and lemon (pastazzo). The compost and their extracts have been subjected to molecular characterisation through analytical techniques such as DRIFT spectroscopy, GC/MS pyrolysis, and solid-state 13C-CPMAS-NMR spectroscopy.These analyses have revealed pronounced differences between the composition of compost and their extracts, mostly attributable to the different vegetable materials used for the composting stage. In particular, the humic substances extracted from artichoke compost have shown the highest values of hydrophobicity and aromaticity. The studied products have been tested in order to evaluate their biological activity and identify any possible structure-activity relation. ABTS and Folin-Ciocalteu tests have revealed a positive correlation between the antioxidant activity and the total content of phenols, with higher significant values, for both parameters, found for the humic substances from artichoke compost and lemon pastazzo. The effect exerted by humic substances on roots elongation has been proved through the germination test which was conducted on Zea mays. This effect resulted particularly pronounced in the case of humic substances from artichoke compost and was attributed to the relatively high content of phenolic compounds. Based on these results, humic substances from artichoke compost, in association with potassium humate extracted from lignite, have been tested, by soil application, on lettuce plants, distributing them both individually and combined in different percentages. Phenological results (dry biomass and chlorophyll content) have indicated a particularly positive effect only when the materials have been used individually. The secondary metabolome analysis, conducted through mass spectrometry IT-TOF, has revealed that humic substances from artichoke determine a mild stress condition, inducing a modulation in the content of several flavonoids. Phytotoxicity tests have been conducted on Lepidium sativum seeds using hydroethanolic extracts from coffee, artichoke and lemon pastazzo. The results not only have permitted to exclude the phytotoxicity of these materials, but have also revealed an effect on roots elongation. Such a result was particularly evident for artichoke and lemon pastazzo compost extracts applications. These products have been also tested by foliar application. Although any significant result has been appreciated, in terms of dry biomass and chlorophyll content, it is noteworthy the detection of small variations in the primary metabolome, as revealed by liquid-state 1H-NMR spectroscopy. In fact, it was detected a treatment-depending variation for some carbohydrates, organic acids and amino acids. Concluding, our results demonstrate that the substances considered for this thesis are capable to determine a biological effect on plants, whose action and intensity varies depending on the molecular composition of the products for the treatment. In addition, the fact that some of the studied products promote plant growth permits to consider the materials deriving from the recycle of waste plant biomass as ecologically sustainable sources of biostimulants for agricultural crops

Draft genome sequence of the plant growth-promoting rhizobacterium Pseudomonas fluorescens Strain CREAC16 isolated from pea (Pisum sativum L.) rhizosphere

Herein, we report the draft genome sequence of Pseudomonas fluorescens strain CREA-C16, a plant growth-promoting rhizobacterium that was isolated from the rhizosphere of Pisum sativum L. plants. The genome sequence is ~6 Mb in size, with a G+C content of 60.1%, and includes 4,457 candidate protein-encoding genes

The secretory senescence in otorhinolaryngology: principles of treatment

Atrophy or hypofunction of the salivary gland because of aging, radio-therapy or disease causes hyposalivation and impairs the quality of life of patients by compromising mastication, swallowing and speech and by leading to a loss of taste. Moreover, hyposalivation exacerbates dental caries and induces periodontal disease, and oral candidiasis. Currently, no satisfactory therapies have been established to solve salivary hypofunction. Current treatment options for atrophy or hypofunction of the salivary glands in clinical practice are only symptomatic and include saliva substitutes and parasympathetic agonists, such as pilocarpine, to stimulate salivary flow. However, parasympathomimetics have systemic side effects, so different treatment options are necessary, and research has recently focused on this. The main strategies that have been proposed to restore salivary gland atrophy and hypofunction are gene therapy by gene activation/silencing during stem cell differentiation and by the use of viral vectors, such as adenoviruses; cell-based therapy with salivary gland cells, stem cells and non-salivary gland and/or non-epithelial cells to regenerate damaged salivary gland cells; replacement with tissue bioengineering in which organoids from pluripotent stem cells are used in the development of organ replacement regenerative therapy. Remarkable progression in this research field has been made in the last decade, but a definitive therapy for salivary gland hypofunction has not been developed due to intrinsic challenges that come with each approach. However, with research efforts in the future, a range of precision medicine therapies may become available individualized to each patient