Caracterización y eficiencia agronómica de nuevos productos fertilizantes y bioestimulantes

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Agrícola y Bromatología. Fecha de Lectura: 20-10-202

Design of a hydroponic test to evaluate the biostimulant potential of new organic and organomineral products

Currently, the use of biostimulants is increasing due to the need for greater productivity in agriculture. The European Union presented a new fertilizer regulation, UE 2019/1009, appearing for the first time the concept of biostimulants. Its main objective is to improve the efficiency of plants in the absorption and assimilation of nutrients or their tolerance to biotic or abiotic stresses, regardless of the nutrient content of the product. The objective of this work consisted in the development of a methodology to test in a short-term experiment the efficiency of commercial products as potential biostimulants in a crop of Capsicum annuum L. in strictly hydroponic conditions. Plants were irrigated with the respective product at the recommended dose in water, without the addition of other nutritional sources for 15 days. At the end of the test, the weights of the root and aerial part, the humidity, the chlorophyll indexes, and nutritional leaf content, as well as the volume and morphology of the roots and plants were obtained to evaluate the biostimulant effects on the plant growth and development. The water consumption was also evaluated to analyze whether any of the products generates greater water savings. The study concluded that the nutritive solutions with biostimulants produced a greater increase in the weight of the plant and a lower percentage of leaf moisture, as well as higher values of leaf chlorophyll. On the other hand, it was humic, fulvic, and algae biostimulants that presented the best values in terms of water savings. The methodology developed could be set to test in the short term the biostimulant potential of new productsThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sector

Assessment of different spent mushroom substrates to bioremediate soils contaminated with petroleum hydrocarbons

Bioremediation techniques are being developed as substitutes for physical–chemical methodologies that are expensive and not sustainable. For example, using the agricultural waste spent mushroom substrate (SMS) which contains valuable microbiota for soil bioremediation. In this work, SMSs of four cultivated fungal species, Pleurotus eryngii, Lentinula edodes, Pleurotus ostreatus, and Agaricus bisporus were evaluated for the bioremediation of soils contaminated by petroleum hydrocarbons (TPHs). The bioremediation test was carried out by mixing the four different SMSs with the TPH-contaminated soil in comparison with an unamended soil control to assess its natural attenuation. To determine the most efficient bioremediation strategy, hydrolase, dehydrogenase, and ligninolytic activities, ergosterol content, and percentage of TPHs degradation (total and by chains) were determined at the end of the assay at 40 days. The application of SMS significantly improved the degradation of TPHs with respect to the control. The most effective spent mushroom substrate to degrade TPHs was A. bisporus, followed by L. edodes and P. ostreatus. Similar results were obtained for the removal of aliphatic and aromatic hydrocarbons. The results showed the effectiveness of SMS to remove aliphatic and aromatic hydrocarbons from C10 to C35. This work demonstrates an alternative to valorizing an abundant agricultural waste as SMS to bioremediate contaminated soil

An assessment of Pleurotus ostreatus to remove sulfonamides, and its role as a biofilter based on its own spent mushroom substrate

A double strategy based on the removal of sulfonamide antibiotics by Pleurotus ostreatus and adsorption on spent mushroom substrate was assessed to reclaim contaminated wastewater. P. ostreatus was firstly tested in a liquid medium fortified with five sulfonamides: sulfamethoxazole, sulfadiazine, sulfathiazole, sulfapyridine and sulfamethazine, to evaluate its capacity to remove them and to test for any adverse effects on fungal growth and for any reduction in residual antibiotic activity. P. ostreatus was effective in removing sulfonamides up to 83 to 91% of the applied doses over 14 days. The antibiotic activity of the sulfonamide residues was reduced by 50%. Sulfamethoxazole transformation products by laccase were identified, and the degradation pathway was proposed. In addition, P. ostreatus growth on a semi-solid medium of spent mushroom substrate and malt extract agar was used to develop a biofilter for the removal of sulfonamides from real wastewater. The biofilter was able to remove more than 90% of the sulfonamide concentrations over 24 h by combining adsorption and biodegradation mechanisms.This work was supported by the Ministry of Science and Innovation of Spain (Project AGL2016-78490-R

Mycoremediation of soils polluted with trichloroethylene: first evidence of pleurotus genus effectiveness

Trichloroethylene (TCE) is a proven carcinogenic chlorinated organic compound widely used as a solvent in industrial cleaning solutions; it is easily found in the soil, air, and water and is a hazardous environmental pollutant. Most studies have attempted to remove TCE from air and water using different anaerobic bacteria species. In addition, a few have used white-rot fungi, although there are hardly any in soil. The objective of the present work is to assess TCE removal efficiency using two species of the genus Pleurotus that have not been tested before: Pleurotus ostreatus and Pleurotus eryngii, growing on a sandy loam soil. These fungi presented different intra- and extracellular enzymatic systems (chytochrome P450 (CYP450), laccase, Mn peroxidase (MnP)) capable of aerobically degrading TCE to less harmful compounds. The potential toxicity of TCE to P. ostreatus and P. eryngii was firstly tested in a TCE-spiked liquid broth (70 mg L−1 and 140 mg L−1) for 14 days. Then, both fungi were assessed for their ability to degrade the pollutant in sandy loam soil spiked with 140 mg kg−1 of TCE. P. ostreatus and P. eryngii improved the natural dissipation of TCE from soil by 44%. Extracellular enzymes were poorly expressed, but mainly in the presence of the contaminant, in accordance with the hypothesis of the involvement of CYP450

Enhancement of methane production from livestock manure with pre-treatments based in fungi of genus Pleurotus

Livestock manure, traditionally used just as fertilizer, can be energetically valued to produce biogas as an attractive alternative, since nowadays, energy production and its cost stands for a pressing problem around the world. Nevertheless, the presence of lignin in manure hinders the production of methane. This could be improved by pre-treating the manure with ligninolytic fungi, able to break lignin and therefore facilitate the hydrolysis step for the hydrolytic bacteria, yielding higher volumes of biomethane. Three strategies of incubation with living fungi of genus Pleurotus were evaluated to enhance methane production from livestock manure mixed with bedding material: short term (two weeks 2L container) and long term (two months 400 L container) and 24 h (2 L container) with a crude water extraction of Pleurotus extracellular enzymes. The positive effect of the fungal treatment was observed in the three strategies obtaining an increase in methane production with respect to the control manure of 7% at short term, 111% at long term and 173% (crude enzymatic extract). Consequently, the strategy of using crude enzyme extracts from Pleurotus to improve hydrolysis step as pre-treatment of manure should be considered as a novel, easy, cheap and promising tool to optimize methane productionThis research was funded by a contract with the company Kepler Ingeniería y Ecogestión SL managed by Foundation from University Autónoma of Madrid (FUAM) and with reference 01091

Synergistic effects of biochar and biostimulants on nutrient and toxic element uptake by pepper in contaminated soils

BACKGROUND: Nowadays a significant amount of land contaminated with toxic elements is being used for agriculture, posing a serious risk of crop contamination and toxicity. Several methodologies are being used to remediate soil contamination, including the use of amendments such as biochar. This work evaluated the effects of biochar combined with different fertirrigations (water, a conventional fertilizer solution, or a fertilizer solution with a commercial biostimulant derived from leonardite) on the availability of toxic elements and nutrients for pepper cultivated in a soil contaminated with As, Cd, Pb, and Zn. RESULTS: Irrigation with fertilizer solutions improved plant growth regardless of the biochar amendment. Biochar decreased the bioavailability of Cu and Pb in soil and the Cu content in pepper leaves. Combined with fertilization, biochar also decreased plant As and Pb content. Biochar combined with biostimulant decreased the bioavailable content of Cd in soil and its uptake by pepper plants. CONCLUSION: The use of biochar and biostimulant presented advantages for plant production in a non-suitable scenario of nutrient scarcity and contaminationWe thank the agronomic technicians Manuel Campos Macossay and Carlos Rodriguez Orta for the location of the soil and supply of materials. This article is the result of a research project ‘Compar ison of agronomic efficiency between Huma Gro® products and mineral conventional fertilizers’ funded by Bio Huma Netics Inc. (Gilbert, Arizona, USA). Bio Huma Netics Inc. did not participate in the experimental procedures or in the evaluation of the result

Bioremediation of petroleum hydrocarbons polluted soil by spent mushroom substrates: Microbiological structure and functionality

Spent mushroom substrate (SMS) holds valuable microbiota that can be useful in remediating polluted soils with hydrocarbons. However, the microorganisms behind the bioremediation process remain uncertain. In this work, a bioremediation assay of total petroleum hydrocarbons (TPHs) polluted soil by SMS application was performed to elucidate the microorganisms and consortia involved in biodegradation by a metabarcoding analysis. Untreated polluted soil was compared to seven bioremediation treatments by adding SMS of Agaricus bisporus, Pleurotus eryngii, Pleurotus ostreatus, and combinations. Soil microbial activity, TPH biodegradation, taxonomic classification, and predictive functional analysis were evaluated in the microbiopiles at 60 days. Different metagenomics approaches were performed to understand the impact of each SMS on native soil microbiota and TPHs biodegradation. All SMSs enhanced the degradation of aliphatic and aromatic hydrocarbons, being

Evaluation of the rhizosphere resistome of cultivated soils polluted with antibiotics from reclaimed wastewater

The use of reclaimed wastewater to irrigate crops is a valuable option due to water scarcity. However, the presence of antibiotics residues that are not removed in the tertiary treatments reaches crop soils when irrigated and it poses a serious concern for human health. Crops rhizosphere is considered a hotspot of antibiotic resistant genes (ARG) being in addition a link to plant phyllosphere and human microbiome. Understanding the structure of the soil microbiota is crucial before applying any bioremediation or biostimulation strategy. The aim of this work was firstly to confirm the presence of antibiotics residues in soil and fruits in two greenhouses at the south of Spain irrigated with reclaimed water. Secondly, to characterize the rhizosphere microbiome of three crops (Capsicum annuum, Cucumis melo and Solanum melongena) cultured in those greenhouses. Finally, a predictive functional analysis was done using PICRUSt2 to figure out the rhizosphere resistome. The presence of residues of antibiotics was confirmed both soil and fruits. Antibiotics absorbed by plants correlated with those on soil. The most abundant resistance gene was the multidrug in all the three crops tested. Compatibility of basidiomycete fungi (i.e., Pleurotus) with soil bacteria could be indicative of their possible use for restoration of agricultural soils polluted with antibioticsThis research was funded by the Ministry of Science and Innovation of Spain, Transformation and Resilience Recovery Plan Next Generation EU, grant number PDC2021-120744-I0