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Soil contamination constitutes a significant threat to the health of soil ecosystems in terms of complexity, toxicity, and recalcitrance. Among all contaminants, aliphatic petroleum hydrocarbons (APH) are of particular concern due to their abundance and persistence in the environment and the need of remediation technologies to ensure their removal in an environmentally, socially, and economically sustainable way. Soil remediation technologies presently available on the market to tackle soil contamination by petroleum hydrocarbons (PH) include landfilling, physical treatments (e.g., thermal desorption), chemical treatments (e.g., oxidation), and conventional bioremediation. The first two solutions are costly and energy-intensive approaches. Conversely, bioremediation of on-site excavated soil arranged in biopiles is a more sustainable procedure. Biopiles are engineered heaps able to stimulate microbial activity and enhance biodegradation, thus ensuring the removal of organic pollutants. This soil remediation technology is currently the most environmentally friendly solution available on the market, as it is less energy-intensive and has no detrimental impact on biological soil functions. However, its major limitation is its low removal efficiency, especially for long-chain hydrocarbons (LCH), compared to thermal desorption. Nevertheless, the use of fungi for remediation of environmental contaminants retains the benefits of bioremediation treatments, including low economic, social, and environmental costs, while attaining removal efficiencies similar to thermal desorption. Mycoremediation is a widely studied technology at lab scale, but there are few experiences at pilot scale. Several factors may reduce the overall efficiency of on-site mycoremediation biopiles (mycopiles), and the efficiency detected in the bench scale. These factors include the bioavailability of hydrocarbons, the selection of fungal species and bulking agents and their application rate, the interaction between the inoculated fungi and the indigenous microbiota, soil properties and nutrients, and other environmental factors (e.g., humidity, oxygen, and temperature). The identification of these factors at an early stage of biotreatability experiments would allow the application of this on-site technology to be refined and fine-tuned. This review brings together all mycoremediation work applied to aliphatic petroleum hydrocarbons (APH) and identifies the key factors in making mycoremediation effective. It also includes technological advances that reduce the effect of these factors, such as the structure of mycopiles, the application of surfactants, and the control of environmental factors. [ABSTRACT FROM AUTHOR]

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 A. bisporus the most effective, promoting an efficient consortium constituted by the bacterial families Alcanivoraceae, Alcaligenaceae, and Dietziaceae along with the fungal genera Scedosporium and Aspergillus. The predictive 16 S rRNA gene study partially explained the decontamination efficacy by observing changes in the taxonomic structure of bacteria and fungi, and changes in the potential profiles of estimated degradative genes across the different treatments. This work provides new insights into TPHs bioremediation. [Display omitted] • SMS of P. ostreatus , P eryngii, and A. bisporus promoted the degradation of TPHs. • bisporus SMS was the most effective for TPHs biodegradation, including heavy fractions. • TPHs polluted soil amended with fungal SMS led to shifts in microbial structure. • A.bisporus SMS enhanced hydrocarbonoclastic consortium of Alcanivoraceae and Scedosporium. [ABSTRACT FROM AUTHOR]

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 contamination. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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 antibiotics. [ABSTRACT FROM AUTHOR]

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 production. [Display omitted] • Short and long-term pre-treatments of manure with Pleurotus were assessed. • Manure storage in deep closed container enhanced biogas production. • Manure with crude water extracts from Pleurotus yielded significant higher biogas. • Crude enzyme extracts from Pleurotus, a novel, easy, cheap, promising pre-treatment. [ABSTRACT FROM AUTHOR]

Tetracyclines are one of the most widely used class of veterinary and human antibiotics. The conventional treatment of wastewater based on activated sludge is not effective to remove antibiotics and their residues are still biologically active, which represents a problem in terms of bacterial resistance. The main objective of this work is to assess ability of stevensite and two biochars to adsorb three tetracycline antibiotics from water. Batch adsorption experiments were carried out to test the ability of these materials to adsorb tetracyclines. Then desorption experiments were performed to determine the adsorption strength on stevensite. In order to elucidate the adsorption mechanism of tetracyclines on stevensite, cation exchange analysis and spectroscopic analyses by IR and XRD were performed. The adsorption of tetracyclines on stevensite was tested on continuous system with water artificially contaminated. Finally, the designed filter was validated with tetracyclines spiked wastewater. The two biochars and stevensite were able to adsorb between 60 and 100% of the tetracyclines present in the batch system. Stevensite was the material with the highest tetracyclines removal capacity (around 100% at low concentrations of tetracyclines). Biochars showed less affinity for tetracyclines adsorption (70%). Tetracyclines desorption from stevensite reached values lower than 10% for low tetracyclines concentrations. The IR spectroscopy suggested that cation exchange is the main mechanism of tetracyclines adsorption on clay and also proved the role of amide and amine groups in this adsorption. The cation exchange mechanism was confirmed by displacement of Ca and Mg from stevensite. A continuous wastewater flow through a system composed by stevensite leaved this system with no tetracyclines, indicating water purification by tetracyclines adsorption in clay. [ABSTRACT FROM AUTHOR]

• The proposed methodology could be used to test the biostimulant potential of new products. • The methodology consists of a short-term hydroponic assay coupled with a battery of analysis. • The composition and origin of biostimulant determined the physiological effect on pepper plants. 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 products. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to the environmental issues that conventional fertilization is causing, biostimulants are proposed as environmentally friendly alternative for crop nutrition in agriculture. The aim of this study was to determine the effects of new Micro Carbon Technology (MCT®) fertilizers with biostimulant activity based on humic acids biologically digested from leonardite on pepper plant growth in three different soils with different textures. The assays were performed under controlled conditions in a growth chamber and in commercial greenhouses in Spain. The effects on soil were analyzed after the addition of the fertilizers by microbial respiration and enzymatic activities (hydrolase, dehydrogenase and urease). For the plant assays, biometric parameters (fresh weight and fruit hardness) and foliar analysis (chlorophyll indices and nutrients) were evaluated. Under controlled conditions, the use of these biostimulants resulted in a greater soil microbial activity in a 24 h interval with increased soil enzymatic activity. In plants, a positive correlation was found between fertilizers with biostimulant activity and Dualex indices of leaves and content of macronutrients Ca and Mg. In commercial greenhouses, the fertilizers with biostimulant activity strongly depended on the soil texture. In conclusion, these products have real potential to replace conventional fertilizers in commercial production fields. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effects of new Micro Carbon Technology (MCT®) fertilizers based on humic acids biologically digested on the growth and development of pepper plants. In this work, the biostimulant effect of MCT® fertilizers was compared to conventional mineral fertilizers. In order to evaluate MCT® fertilizers, a previous chemical characterization (infrared spectroscopy, liquid chromatography and mass spectrometry) of seven MCT® fertilizers was performed. Two fertilization tests of pepper plants were carried out in hydroponic conditions, where the fertilization and the age of the plants were studied in order to evaluate the specific effects on roots and leaves. Plant weight and foliar analysis (chlorophyll indices and nutrients) have been determined. Transmission electron microscopy was used to visualize the morphological differences in the root and leaf cells. Comparison between conventional and MCT® based fertilizers showed that, with the MCT® fertilizers, the plant is exposed to the presence of free amino acids (Glycine and Alanine), polyphenols and humic substances. Although no significant differences were found in plant mass production, the plants fertilized with MCT® products presented better nutritional status than plants treated with conventional fertilization in terms of nutrient content in leaves. Important morphological differences in root cells were found. A large central vacuole that represented the 68–83% of the total root cell area was shown if the MCT® products were used, suggesting significant changes of membrane permeability in terms of water adsorption and consequently nutrient storage. The morphological differences observed in the root cells were more noticeable in adult plants. [ABSTRACT FROM AUTHOR]

The presence of antibiotics in crops is mainly caused by their irrigation with reclaimed wastewater and by the use of organic amendments of animal origin. During this work, the fate of sulfonamide antibiotics in tomato crop has been assessed in two commercial greenhouses located in Almería (Spain) irrigated with reclaimed wastewater. Samplings were made annually for two years. Sulfonamides in several parts of the plant (roots, leaves and fruits) as well as reclaimed wastewater, amendments and soils were analyzed by UHPLC-MS/MS. The results showed that sulfonamides accumulated in soils (sulfamethoxazole between 2 and 14 µg kg−1; sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine and sulfadimethoxine in concentrations below 1 µg kg−1) were in the reclaimed wastewater at concentrations in the ng L−1 range. Their distribution in plants depended on the sulfonamide. The sulfonamides detected in tomato were sulfadiazine, sulfapyridine, sulfamethazole, sulfamethoxazole and sulfadimethoxine. Sulfamethoxazole was the antibiotic with highest concentration in tomato fruit, exceeding 30 µg kg−1. All sulfonamides were below the Acceptable Daily Intake, however, further studies and legislation are needed to assure food safety. [ABSTRACT FROM AUTHOR]