Implications of polluted soil biostimulation and bioaugmentation with spent mushroom substrate (Agaricus bisporus) on the microbial community and polycyclic aromatic hydrocarbons biodegradation

Full utilization of Flammulina filiformis spent mushroom substrate for sustainable production of oil/water separation bacterial nanocellulose composite with high liquid flux and seperation efficiency

Bacterial nanocellulose (BNC) is a promising material for oily wastewater separation due to its hydrophilic and nanometer-scale porous structure. However, its application is constrained by high production costs. This study explores the utilization of underutilized Flammulina filiformis spent mushroom substrate (Ff-SMS) to produce BNC cost-effectively. Ff-SMS was pretreated with dilute sulfuric acid and cellulase to obtain hydrolysate and lignin residue. The hydrolysate was fermented using bacteria strains LDU-K and LDU-A to produce BNC. The lignin residue was modified to enhance hydrophilicity and cross-linked with BNC to create lignin-bacterial nanocellulose (LIG-BNC) composites for oil/water separation. The yields of BNC from white and yellow F. filiformis hydrolysates were increased significantly than from the nitrogen-free glucose synthesis medium. LIG-BNC demonstrated improved hydrophilicity and porosity, with water fluxes of 19,316 ± 170 L m-2 h-1 for diesel/water and 14,899 ± 168 L m-2 h-1 for vegetable oil/water mixtures, and separation efficiencies above 96.0 %. This study effectively converts Ff-SMS into value-added products and expands the application of BNC in environmental management.

Status and development of spent mushroom substrate recycling: A review

The edible mushroom industry is the sixth largest after grain, cotton, oil, vegetables and fruits, and the annual production of edible mushrooms in China exceeds 40 million tons. Edible mushroom cultivation produces a class of by-products consisting mainly of mycelium remnants and lignocellulosic waste, known as Spent Mushroom Substrate (SMS) or Spent Mushroom Compost (SMC). SMS/SMC is rich in nutrients and active ingredients and has an extremely high recycling potential. This review paper summarizes SMS recycling strategies from the perspectives of "environmental remediation" and "circular economy", and briefly discusses the legitimacy, possible challenges and future research of SMS recycling. It is hoped that this will assist researchers in related fields and promote the development of the SMS recycling industry, thereby contributing to sustainable environmental and economic development.Implications: The efficient management of SMS is important for many countries around the world, particularly major mushroom producing countries. Traditional disposal methods (incineration, burial, piling) can cause serious damage to the environment and waste resources. The correct disposal method can protect the natural environment and provide certain economic benefits. This study presents the main methods of SMS processing from both an "environmental remediation" and "circular economy" perspective. In general, this paper emphasizes the importance of SMS processing, introduces the current mainstream processing methods and briefly discusses the legality of their processing methods.

Sustainable agricultural practices influence s-metolachlor, foramsulfuron and thiencarbazone-methyl degradation and their metabolites formation

The effect of sustainable agricultural practices, such as mulching or the application of straw residues as an organic amendment, on the degradation, dissipation and persistence in the soil of S-metolachlor (SMOC), foramsulfuron (FORAM) and thiencarbazone-methyl (TCM) is still unclear. The objective here was to conduct a laboratory experiment to evaluate the impact of milled wheat straw (WS) simulating its individual use as mulch or applied as an organic amendment to two agricultural soils: unamended and WS-amended soils on the degradation kinetics of the herbicides SMOC, FORAM and TCM, and on the formation of their major metabolites at two incubation temperatures (14 °C and 24 °C). The degradation rate of SMOC on WS was 6.9-16.7 times faster than that observed for FORAM and TCM at both temperatures. The half-life (DT50) values were 1.1-10.6 times lower for FORAM than for SMOC and TCM in the unamended and WS-amended soils at 14 °C and 24 °C. The application of WS to soils increased the DT50 values from 1.1 to 11.2 times for all the herbicides at both incubation temperatures due to their higher adsorption and lower bioavailability. The herbicides recorded a faster degradation at 24 °C (1.2-3.9 times) than at 14 °C, according to Q10 values >1. SMOC metabolites were more persistent in WS-amended soils than in unamended ones, in agreement with the DT50 values recorded for the parent compound. The results indicate that the effect of the mulch applied to soils as an organic amendment was different depending on the herbicide and incubation temperature. The outcomes of this research can give key suggestions for reducing the effects of residual herbicides following sustainable agricultural practices by avoiding soil and groundwater contamination, which is one of the challenges involved in the application of chemical inputs.

The role of cattle manure-driven polysaccharide precursors in humus formation during composting of spent mushroom substrate

The study examined the impact of adding cattle manure to the composting process of Agaricus bisporus mushroom substrate on compost humification. A control group CK comprised entirely of Agaricus bisporus mushroom substrate, while the experimental group CD (70 percent Agaricus bisporus mushroom substrate and 30 percent cattle manure) comprised the two composting treatments that were established. The study determined that the addition of cow dung has promoted the formation of humus components. Particularly, humic substance (HS-C) and humic acid (HA) increased by 41.3 and 74.7%, respectively, and the ratio of humic acid to fulvic acid (HA/FA) also increased by 2.78. It showed that the addition of cow dung accelerated the synthesis and decomposition of precursors, such as polysaccharides, polyphenols, and reducing sugars. Thereby promoting the formation of humic acid. Network analysis revealed that adding cow dung promoted microbial interactions increased the complexity and stability of the bacterial and fungal symbiotic network, enhanced cooperation and reciprocity among microbes, and assisted in transforming fulvic acid (FA) components. Structural equation modeling (SEM) is a multivariate data analysis method for analyzing complex relationships among constructs and core indicators. SEM illustrated that introducing cattle manure into the composting process resulted in alterations to the correlation between physicochemical parameters and the microbial community, in addition to humus formation. Polysaccharides are the primary precursors for polymerization to form HA, which is an essential prerequisite for the conversion of fulvic acid to humic acid. Additionally, microbes affected the formation of humus, with bacteria substantially more influential than fungi. These findings provide new ideas for regulating the degree of humification in the composting process and have important practical implications for optimizing mushroom cultivation and composting techniques today.

Importance of soil ecoenzyme stoichiometry for efficient polycyclic aromatic hydrocarbon biodegradation

Efficient remediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs) is challenging. To determine whether soil ecoenzyme stoichiometry influences PAH degradation under biostimulation and bioaugmentation, this study initially characterized soil ecoenzyme stoichiometry via a PAH degradation experiment and subsequently designed a validation experiment to answer this question. The results showed that inoculation of PAH degradation consortia ZY-PHE plus vanillate efficiently degraded phenanthrene with a K value of 0.471 (depending on first-order kinetics), followed by treatment with ZY-PHE and control. Ecoenzyme stoichiometry data revealed that the EEAC:N, vector length and angle increased before day five and decreased during the degradation process. In contrast, EEAN:P decreased and then increased. These results indicated that the rapid PAH degradation period induced more C limitation and organic P mineralization. Correlation analysis indicated that the degradation rate K was negatively correlated with vector length, EEAC:P, and EEAN:P, suggesting that C limitation and relatively less efficient P mineralization could inhibit biodegradation. Therefore, incorporating liable carbon and acid phosphatase or soluble P promoted PAH degradation in soils with ZY-PHE. This study provides novel insights into the relationship between soil ecoenzyme stoichiometry and PAH degradation. It is suggested that soil ecoenzyme stoichiometry be evaluated before designing bioremeiation stragtegies for PAH contanminated soils.

Enzymatic and non-enzymatic removal of organic micropollutants with spent mushroom substrate of Agaricus bisporus

Water bodies are increasingly contaminated with a diversity of organic micropollutants (OMPs). This impacts the quality of ecosystems due to their recalcitrant nature. In this study, we assessed the removal of OMPs by spent mushroom substrate (SMS) of the white button mushroom (Agaricus bisporus) and by its aqueous tea extract. Removal of acesulfame K, antipyrine, bentazon, caffeine, carbamazepine, chloridazon, clofibric acid, and N, N-diethyl-meta-toluamide (DEET) by SMS and its tea was between 10 and 90% and 0-26%, respectively, in a 7-day period. Sorption to SMS particles was between 0 and 29%, which can thus not explain the removal difference between SMS and its tea, the latter lacking these particles. Carbamazepine was removed most efficiently by both SMS and its tea. Removal of OMPs (except caffeine) by SMS tea was not affected by heat treatment. By contrast, heat-treatment of SMS reduced OMP removal to < 10% except for carbamazepine with a removal of 90%. These results indicate that OMP removal by SMS and its tea is mediated by both enzymatic and non-enzymatic activities. The presence of copper, manganese, and iron (0.03, 0.88, and 0.33 µg L-1, respectively) as well as H2O2 (1.5 µM) in SMS tea indicated that the Fenton reaction represents (part of) the non-enzymatic activity. Indeed, the in vitro reconstituted Fenton reaction removed OMPs > 50% better than the teas. From these data it is concluded that spent mushroom substrate of the white button mushroom, which is widely available as a waste-stream, can be used to purify water from OMPs.

The role of biochar and green compost amendments in the adsorption, leaching, and degradation of sulfamethoxazole in basic soil

The fate of the antibiotic sulfamethoxazole in amended soils remains unclear, moreover in basic soils. This work aimed to assess the adsorption, leaching, and biodegradation of sulfamethoxazole in unamended and biochar from holm oak pruning (BC)- and green compost from urban pruning (CG)-amended basic soil. Adsorption properties of the organic amendments and soil were determined by adsorption isotherms of sulfamethoxazole. The leachability of this antibiotic from unamended (Soil) and BC- (Soil + BC) and GC- (Soil + GC) amended soil was determined by leaching columns using water as solvent up to 250 mL. Finally, Soil, Soil + BC, and Soil + GC were spiked with sulfamethoxazole and incubated for 42 days. The degradation rate and microbial activity were periodically monitored. Adsorption isotherms showed poor adsorption of sulfamethoxazole in unamended basic soil. BC and CG showed good adsorption capacity. Soil + BC and Soil + GC increased the sulfamethoxazole adsorption capacity of the soil. The low sulfamethoxazole adsorption of Soil produced quick and intense sulfamethoxazole leaching. Soil + BC reduced the sulfamethoxazole leaching, unlike to Soil + GC which enhanced it concerning Soil. The pH of adsorption isotherms and leachates indicate that the anion of sulfamethoxazole was the major specie in unamended and amended soil. CG enhanced the microbial activity of the soil and promoted the degradability of sulfamethoxazole. In contrast, the high adsorption and low biostimulation effect of BC in soil reduced the degradation of sulfamethoxazole. The half-life of sulfamethoxazole was 2.6, 6.9, and 11.9 days for Soil + GC, Soil, and Soil + BC, respectively. This work shows the benefits and risks of two organic amendments, BC and GC, for the environmental fate of sulfamethoxazole. The different nature of the organic carbon of the amendments was responsible for the different effects on the soil.

Establishing the extent of pesticide contamination in Irish agricultural soils

To establish meaningful and sustainable policy directives for sustainable pesticide use in agriculture, baseline knowledge of pesticide levels in soils is required. To address this, five pesticides and one metabolite widely used in Irish agriculture and five neonicotinoid compounds pesticides were screened from soils from 25 fields. These sites represented a diversity of soil and land use types. Prothioconazole was detected in 16 of the 18 sites where it had been recently applied, with the highest maximum concentration quantified of 46 μg/kg. However, a week after application only four fields had prothioconazole concentrations above the limit of quantification (LOQ). Fluroxypyr was applied in 11 sites but was not detected above LOQ. Glyphosate and AMPA were not detected. Interestingly, neonicotinoids were detected in 96% of all sampling sites, even though they were not reported as recently applied. Excluding neonicotinoids, 60% of sites were found to contain pesticide residues of compounds that were not previously applied, with boscalid and azoxystrobin detected in 15 of the 25 sites sampled. The total number of pesticides detected in Irish soils were significantly negatively correlated with clay fraction, while average pesticide concentrations were significantly positively correlated with log Kow values. 17 fields were found to have total pesticide concentrations in excess of 0.5 μg/kg, even when recently applied pesticides were removed from calculations. Theoretical consideration of quantified pesticides determined that azoxystrobin has high leaching risk, while boscalid, which was detected but not applied, has an accumulation risk. This information provides insight into the current level of pesticide contamination in Irish agricultural soil and contributes to the European-level effort to understand potential impacts of pesticide contamination in soil.

Mycoremediation with Agaricus bisporus and Pleurotus ostreatus growth substrates versus phytoremediation with Festuca rubra and Brassica sp. for the recovery of a Pb and γ-HCH contaminated soil

Mycoremediation with mushroom growth substrates can be used for the recovery of mixed contaminated soils due to the benefits derived from the physicochemical characteristics of the substrates, the activity of extracellular enzymes secreted by the fungi, and the presence of the fungal mycelia. The objective of this work was to assess the potential of Agaricus bisporus and Pleurotus ostreatus growth substrates (inoculated mushroom substrates vs. spent mushroom substrates) for the mycoremediation of soils co-contaminated with lead and lindane (γ-HCH). We compared the efficiency of these mycoremediation strategies with the phytoremediation with Brassica spp. Or Festuca rubra plants, in terms of both reduction in contaminant levels and enhancement of soil health. An enhanced soil health was achieved as a result of the application of mycoremediation treatments, compared to phytoremediation and control (untreated) treatments. The application of P. ostreatus inoculated substrate led to the most significant reduction in γ-HCH concentration (up to 88.9% compared to corresponding controls). In the presence of inoculated mushroom substrate, P. ostreatus fruiting bodies extracted more Pb than Brassica spp. Or F. rubra plants. Mycoremediation with P. ostreatus growth substrates appears a promising strategy for the recovery of the health of soils co-contaminated with Pb and γ-HCH.

Changes in vineyard soil parameters after repeated application of organic-inorganic amendments based on spent mushroom substrate

The changes of physicochemical and biochemical parameters of a silty loam (S1) and sandy loam (S2) vineyard soils added with spent mushroom substrate (SMS) or SMS composted with ophite (OF) as rock dust (SMS + OF) were studied. Two doses of SMS or SMS + OF (25 and 100 Mg ha^-1) were applied for two consecutive years (2020-2021) and changes of soil physicochemical parameters, and dehydrogenase activity (DHA), respiration (RES), microbial biomass (BIO), and the phospholipid fatty acids (PLFAs) profile were assayed on a temporal basis. The results showed an increase in soil organic carbon (OC) content, total and mineralised N, P, and K, especially when the highest SMS dose was applied to soils. Repeated application caused OC content over time up to 2.3 times higher than initial content in the silty loam soil. This increase was not observed in sandy soil, possibly due to a higher bioavailability of OC, as indicated by the evolution of extractable humic acid/fulvic acid pools. In both soils, all biochemical parameters increased after amendment, being favoured both by the OC and by the presence of OF. Significant positive correlations were found between DHA, RES and BIO, and OC content especially in the first part and then levelled off after the second dose application. Total bacterial or fungal PLFAs patterns reflected the variation of BIO by SMS application. The higher growth of fungi vs. bacterial community in amended soils was recorded after the first SMS application, although the opposite effect occurred after the second application, with similar results in both soils. The findings indicate that the application of SMS or SMS + OF in vineyard soils could be an appropriate agronomic management practice for maintaining soil sustainability, although doses and application times of these amendments should first be evaluated depending on soil texture.

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 soils.

Microbial diversity drives pyrene dissipation in soil

Soil microbial diversity is an essential driver of multiple ecosystem functions and services. However, the role and mechanisms of microbial diversity in the dissipation of persistent organic pollutants in soil are largely unexplored. Here, a gradient of soil microbial diversity was constructed artificially by a dilution-to-extinction approach to assess the role of soil microbial diversity in the dissipation of pyrene, a high molecular weight polycyclic aromatic hydrocarbon (PAH), in a 42-day microcosm experiment. The results showed that pyrene dissipation (98.1%) and the abundances of pyrene degradation genes (the pyrene dioxygenase gene nidA and the gram-positive PAH-ring hydroxylating dioxygenase gene PAH-RHDα GP) were highest in soils with high microbial diversity. Random-forest machine learning was combined with linear regression analysis to identify a range of keystone taxa (order level) associated with pyrene dissipation, including Sphingobacteriales, Vampirovibrionales, Blastocatellales, Myxococcales, Micrococcales and Rhodobacterales. The diversity of these keystone taxa was significantly and positively correlated with the abundance of pyrene degradation genes and the removal rate of pyrene. According to (partial) Mantel tests, keystone taxa diversity was the dominant factor determining pyrene dissipation compared with total microbial diversity. Moreover, co-occurrence network analysis revealed that diverse keystone taxa may drive pyrene dissipation via more positive interactions between keystone species and with other species in soil. Taken together, these findings provide new insights on the regulation of keystone taxa diversity to promote the dissipation of PAH in soil.

Recent advances and future directions on the valorization of spent mushroom substrate (SMS): A review

Commercial mushrooms are cultivated on lignocellulose wastes, such as corncob, saw dust, straw and wood chips. Following the rapidly increasing global mushroom production, the efficient recycling and utilization of the by-product, known as spent mushroom substrate (SMS) has garnered much attention due to the serious pollution issues caused. Embracing the concept of 'circular economy', the SMSs have demonstrated immense potential in wide range of applications, including recycling as the substrate for new cultivation cycle of mushroom, biofertilizer and soil amendment, animal feed, renewable energy production and pollution bioremediation. The review provided an overview and recent advances focusing on these applications, analyzed the possible challenges and proposed future directions for sustainable development of global mushroom industry.

Ascomycetes versus Spent Mushroom Substrate in Mycoremediation of Dredged Sediments Contaminated by Total Petroleum Hydrocarbons: The Involvement of the Bacterial Metabolism

Two mycoremediation approaches for the depletion of the total petroleum hydrocarbons in dredged sediments were compared: co-composting with spent mushroom substrate (SMS) from Pleurotus ostreatus and bioaugmentation with Lambertella sp. MUT 5852, an ascomycetes autochthonous to the sediment, capable of utilizing diesel oil its sole carbon source. After 28 days of incubation, 99% depletion was observed in presence of Lambertella sp. MUT 5852. No total petroleum hydrocarbon depletion was observed in sediment co-composting with the SMS after 60 days of incubation. 16S rDNA metabarcoding of the bacterial community was performed to evaluate the potential synergism between fungi and bacteria in the bioremediation process. The functional metagenomic prediction approach indicated that the biodiversity of the bacterial genera potentially involved in the degradation of TPH was higher in sediment bioaugmented with Lambertella sp. MUT 5852, which resulted in being mandatory for TPH depletion. Mechanisms of co-substrate inhibition of the hydrocarburoclastic bacterial species, due to the bioavailable organic matter of the SMS, are suggested to be involved in the observed kinetics of TPH depletion, failing in the case of SMS and successful in the case of Lambertella sp. MUT 5852.

Effect of Organic Residues on Pesticide Behavior in Soils: A Review of Laboratory Research

The management of large volumes of organic residues generated in different livestock, urban, agricultural and industrial activities is a topic of environmental and social interest. The high organic matter content of these residues means that their application as soil organic amendments in agriculture is considered one of the more sustainable options, as it could solve the problem of the accumulation of uncontrolled wastes while improving soil quality and avoiding its irreversible degradation. However, the behavior of pesticides applied to increase crop yields could be modified in the presence of these amendments in the soil. This review article addresses how the adsorption–desorption, dissipation and leaching of pesticides in soils is affected by different organic residues usually applied as organic amendments. Based on the results reported from laboratory studies, the influence on these processes has been evaluated of multiple factors related to organic residues (e.g., origin, nature, composition, rates, and incubation time of the amended soils), pesticides (e.g., with different use, structure, characteristics, and application method), and soils with different physicochemical properties. Future perspectives on this topic are also included for highlighting the need to extend these laboratory studies to field and modelling scale to better assess and predict pesticide fate in amended soil scenarios.

Diversity and structure of phenanthrene degrading bacterial communities associated with fungal bioremediation in petroleum contaminated soil

Fungal bioremediation is a promising technique for the cleanup of sites contaminated with polycyclic aromatic hydrocarbons (PAHs). However, due to limited understanding of the composition and dynamics of the native PAH-degrading microorganisms in contaminated sites, its application has been difficult. In the present study, DNA stable-isotope probing was performed to identify indigenous phenanthrene (PHE)-degrading bacteria and determine their diversity during the fungal bioremediation process. The results showed a total of 14 operational taxonomic units (OTUs) enriched in the heavy DNA fractions, which were related to seven genera (Sphingomonas, Sphingobacterium, Acidovorax, Massilia, Flavobacterium, Cupriavidus, Aeromicrobium, and unclassified Chitinophagaceae). Along with enhanced efficiency of PHE removal, the number and diversity of indigenous PHE-degrading bacteria in soil bioaugmented with fungi were significantly increased. Furthermore, based on the results of linear model analysis, we found that PHE degraders affiliated with the genus Sphingomonas were significantly enriched during fungal bioremediation. Moreover, fungal bioaugmentation promoted indigenous functional Proteobacteria involved in PAH degradation through co-metabolism, suggesting that PAH biodegradation was attributable to cooperative metabolism by fungi and indigenous bacteria. Our findings provide new insights into the diversity of PHE-degrading communities and support a more comprehensive view of the fungal bioremediation process.

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.

Bacillus cereus liquid fertilizer was produced from Agaricus bisporus industrial wastewater

During the Agaricus bisporus canning processes, a large number of water-soluble elements were dissolved into the processing hot water. This study was conducted to use the industrial wastewater of A. bisporus to prepare agricultural microbial fertilizer. In the work, the influence of 6 different liquid fermentation factors on the total biomass of living Bacillus cereus was evaluated with the one-factor-at-a-time method and the Plackett-Burman design. The total biomass of living B. cereus was most influenced by fermentation temperature, shaking speed, and inoculation volume, which were identified as the most critical independent variables for the B. cereus biomass. The approximate ranges of optimal fermentation conditions for the three key factors were identified by the path of steepest ascent. The center point of these factors were 24 ℃ of temperature, 250 rpm of shaking speed and 12 % inoculum amount, respectively. The Box-Behnken design was applied to derive a statistical model for optimizing the three fermentation factors for B. cereus biomass. After further optimizations based on statistical predictions, the optimum fermentation parameters for B. cereus cultured in the A. bisporus industrial wastewater were fermentation temperature of 24.8 °C, shaking speed of 234 rpm, inoculum dose of 12.2 % (v:v, %), industrial wastewater concentration of 4%, initial pH values of 6.5, loading liquid of 60 mL/250 mL, and culture time of 24 h. Culturing with the optimal fermentation conditions resulted in the biomass of B. cereus of 1.35 ± 0.02 × 10⁹ Obj/mL (N = 3), which was consistent with the predicted values (1.32 × 10⁹ Obj/mL) predicted by the corresponding regression models (p < 0.05), and more, was also far higher than that of the standard of agricultural bacterial fertilizers in People's Republic of China. Further, the results of field trial indicated that the of B. cereus liquid fertilizer can remarkably enhance the yield of Brassica chinensis L. It is practicable to make use of the industrial wastewater of A. bisporus to prepare the microbial fertilizer.

Enhancing Salix viminalis L.-mediated phytoremediation of polycyclic aromatic hydrocarbon-contaminated soil by inoculation with Crucibulum laeve (white-rot fungus)

Although plant-white-rot fungi (WRF) remediation is considered efficient in improving polycyclic aromatic hydrocarbon (PAH)-contaminated soil, the prospects for using it remain poorly known. Therefore, we evaluated whether the WRF Crucibulum laeve could improve the phytoremediation of PAH-contaminated soil by Salix viminalis L. A 60-day pot experiment was conducted to investigate the effects of C. laeve inoculation (using two inoculation treatments and a non-inoculated control) on the phytoremediation potential, growth, and antioxidant metabolism of S. viminalis cultivated in PAH-contaminated soil. The S. viminalis-C. laeve association synergistically caused the highest PAH removal rate. Under the S. viminalis-C. laeve treatment, 80% of the biological concentration and translocation factors for all tissues of S. viminalis were > 1, whereas only 20% of these factors were > 1 when S. viminalis was used alone. C. laeve inoculation remarkably enhanced phytoremediation by promoting S. viminalis-based phytoextraction of PAHs from soils. Furthermore, although C. laeve inoculation altered the antioxidant metabolism of S. viminalis by inducing oxidative stress, thereby inhibiting plant growth, the plant's hardiness enabled it to survive and grow normally for 60 days after treatment. Therefore, phytoremediation using S. viminalis inoculated with C. laeve can be considered a feasible approach for the phytoremediation of PAH-contaminated soil.

Effects of spent mushroom substrate on the dissipation of polycyclic aromatic hydrocarbons in agricultural soil

Spent mushroom substrate (SMS) is an agricultural waste with a high potential for polycyclic aromatic hydrocarbons (PAH) removal in aged contaminated soils. In this study, fresh and air-dried Pleurotus ostreatus, Pleurotus eryngii, and Auricularia auricular SMSs were used to remove PAHs in agricultural soil under 60-day incubation. The potential of SMS in PAH dissipation was studied by detecting the dissipation rate and the soil physicochemical index, enzyme activity, PAH-degradation bacterial biomass, and microbial diversity. Results showed that SMS significantly enhanced the dissipation of PAHs and fresh SMS had a better effect than air-dried SMS. The highest dissipation rate of 16 PAHs was 34.5%, which was observed in soil amended with fresh P. eryngii SMS, and the PAH dissipation rates with low and high molecular weights were 41.3% and 19.4%, respectively. By comparison, fresh P. eryngii SMS presented high nutrient contents, which promoted the development of PAH-degrading bacteria and changed the soil bacterial community involved in degradation, thereby promoting the PAH dissipation. The lignin-degrading enzymes in fresh SMS were abundant, and the laccase and manganese peroxidase activities in the treatment of fresh P. eryngii SMS was higher than those in other treatments. Fresh P. eryngii SMS improved the relative abundance of Microbacterium, Rhizobium, and Pseudomonas in soil, which were all related to PAH degradation. Consequently, adding fresh P. eryngii SMS was an effective method for remediating aged PAH-contaminated agricultural soils.

Impact of digestate and its fractions on mineralization of 14C-phenanthrene in aged soil

The impact of whole digestate (WD) and its fractions (solid [SD] and liquid [LD]) on ¹⁴C-phenanthrene mineralization in soil over 90 d contact time was investigated. The ¹⁴C-phenanthrene spiked soil was aged for 1, 30, 60 and 90 d. Analysis of water-soluble nitrogen, phosphorus, total (organic and inorganic) carbon, and quantitative bacterial count were conducted at each time point to assess their impact on mineralization of ¹⁴C-phenanthrene in soils. Indigenous catabolic activity (total extents, maximum rates and lag phases) of ¹⁴C-phenanthrene mineralization were measured using respirometric soil slurry assay. The soil amended with WD outperformed the SD and LD fractions as well as showed a shorter lag phase, higher rate and extent of mineralization throughout the study. The digestates improved (P < 0.05) the microbial population and nutritive content of the soil. However, findings showed that spiking soil with phenanthrene generally reduced the growth of microbial populations from 1 to 90 d and gave a lower nutritive content in comparison with the non-spiked soil. Also, soil fertility and bacteria count were major factors driving ¹⁴C-phenanthrene mineralization. Particularly, the non-phenanthrene degraders positively influenced the cumulative mineralization of ¹⁴C-phenanthrene after 60 d incubation. Therefore, the digestates (residue from anaerobic digestion) especially WD, which enhanced ¹⁴C-phenanthrene mineralization of the soil without minimal basal salts medium nor additional degraders should be further exploited for sustainable bioremediation of PAHs contaminated soil.

Bioremediation of Historically Chlorimuron-Ethyl-Contaminated Soil by Co-Culture Chlorimuron-Ethyl-Degrading Bacteria Combined with the Spent Mushroom Substrate

In this study, a novel chlorimuron-ethyl-degrading Pleurotus eryngiu-SMS-CB was successfully constructed for remediation of soil historically contaminated with chlorimuron-ethyl. The P. eryngiu-SMS-CB was prepared using efficient chlorimuron-ethyl-degrading cocultured bacteria, Rhodococcus sp. D310-1 and Enterobacter sp. D310-5, with spent mushroom substrate (SMS, a type of agricultural waste containing laccase) of Pleurotus eryngiu as a carrier. The chlorimuron-ethyl degradation efficiency in historically chlorimuron-ethyl-contaminated soil reached 93.1% at the end of 80 days of treatment with the P. eryngiu-SMS-CB. Although the P. eryngiu-SMS-CB altered the microbial community structure at the beginning of the 80 days, the bacterial population slowly recovered after 180 days; thus, the P. eryngiu-SMS-CB does not have an excessive effect on the long-term microbial community structure of the soil. Pot experiments indicated that contaminated soil remediation with P. eryngiu-SMS-CB reduced the toxic effects of chlorimuron-ethyl on wheat. This paper is the first to attempt to use chlorimuron-ethyl-degrading bacterial strains adhering to P. eryngiu-SMS to remediate historically chlorimuron-ethyl-contaminated soil, and the microbial community structure and P. eryngiu-SMS-CB activity in chlorimuron-ethyl-contaminated soil were traced in situ to evaluate the long-term effects of this remediation.

Biodegradation of aged polycyclic aromatic hydrocarbons in agricultural soil by Paracoccus sp. LXC combined with humic acid and spent mushroom substrate

Paracoccus sp. LXC combined with humic acid (HA) and spent mushroom substrate (SMS) obtained from Auricularia auricular and Sarcomyxa edulis was tested for the remediation of agricultural soil contaminated with aged polycyclic aromatic hydrocarbons (PAHs). The biomass and diversity of bacteria and fungi and the soil enzyme activity were analyzed. PAH removal and dissipation kinetics were examined. The highest degradation rate of PAHs was 56.5% when soil was amended with Paracoccus sp. LXC combined with HA and unsterilized SMS from A. auricular. The half-life of PAHs decreased from 2323.3 days in natural attenuation to 66.6-277.2 days in amended treatments. Soil treated with Paracoccus sp. LXC combined with HA and SMS from A. auricular acquired high contents of organic matter and nutrients. HA and SMS aided the growth of PAH-degrading bacteria and promoted the diversity of bacteria but not of fungi. The degradation rate of PAHs was mainly correlated positively with soil laccase activity. Low- and middle-molecular-weight PAHs were significantly removed by Paracoccus sp. LXC, HA and SMS. High-molecular-weight PAHs were removed by SMS but not by Paracoccus sp. LXC. Biodegradation by Paracoccus sp. LXC combined with HA and SMS is a promising choice for remediating aged PAH-contaminated agricultural soils.

Mycoremediation of PCBs by Pleurotus ostreatus: Possibilities and Prospects

With the rising awareness on environmental issues and the increasing risks through industrial development, clean up remediation measures have become the need of the hour. Bioremediation has become increasingly popular owing to its environmentally friendly approaches and cost effectiveness. Polychlorinated biphenyls (PCBs) are an alarming threat to human welfare as well as the environment. They top the list of hazardous xenobiotics. The multiple effects these compounds render to the niche is not unassessed. Bioremediation does appear promising, with myco remediation having a clear edge over bacterial remediation. In the following review, the inputs of white-rot fungi in PCB remediation are examined and the lacunae in the practical application of this versatile technology highlighted. The unique abilities of Pleurotus ostreatus and its deliverables with respect to removal of PCBs are presented. The need for improvising P. ostreatus-mediated remediation is emphasized.

Extraction of PAHS from an aged creosote-polluted soil by cyclodextrins and rhamnolipids. Side effects on removal and availability of potentially toxic elements

This study evaluated the effect of several cyclodextrins (CDs) and a rhamnolipid (RL) on the removal of polycyclic aromatic hydrocarbons (PAHs) from a co-contaminated soil which had received historically creosote and inorganic wood preservatives for almost 100 years, and the effect of such extractions on the potentially toxic elements (PTEs). The influence on such processes of an electrolyte (0.01 M Ca(NO₃)₂) was also studied. Up to 15.4% of the ∑16 PAHs were extracted using RL in the absence of the electrolyte as washing solution, but decreases until reaching 0.60% in the presence of Ca²⁺ due to RL precipitation and partial inactivation. Only up to 2% of the ∑16 PAHs was extracted with CDs (4-ring PAHs in higher concentrations), but the electrolyte had no effect on extraction. In relation to PTEs, CDs proved to be inefficient for their extraction, and even RL in the presence of the background electrolyte. But in the absence of electrolyte PTEs extraction by RL increased. Apart from that, the availability of Ni, Cr, and As, those more associated to Fe and Al soil surfaces, increased after extraction with RLs in the presence of Ca²⁺ (about 100% for Cr and Ni and 200% for As). Under these conditions Fe and Al availability increased two- and ten-fold, respectively, indicating that Fe-Al soil surfaces were altered. Therefore, the ionic strength and the cations present in the soil solution of soils have to be considered when RLs are used as extractants for remediation purposes.

A comparative study to evaluate natural attenuation, mycoaugmentation, phytoremediation, and microbial-assisted phytoremediation strategies for the bioremediation of an aged PAH-polluted soil

Biological treatments are considered an environmentally option to clean-up polluted soil with polycyclic aromatic hydrocarbons (PAHs). A pot experiment was conducted to comparatively evaluate four different strategies, including natural attenuation (NA), mycoaugmentation (M) by using Crucibulum leave, phytoremediation (P) using maize plants, and microbial-assisted phytoremediation (MAP) for the bioremediation of an aged PAH-polluted soil at 180 days. The P treatment had higher affinity degrading 2-3 and 4 ring compounds than NA and M treatments, respectively. However, M and P treatments were more efficient in regards to naphthalene, indeno[l,2,3-c,d]pyrene and benzo[g,h,i]perylene degradation respect to NA. However, 4, 5-6 rings undergo a strong decline during the microbe-assisted phytoremediation, being the treatment which determined the highest rates of PAHs degradation. Sixteen PAH compounds, except fluorene and dibenzo[a,h]anthracene, were found in maize roots, whereas the naphthalene, phenanthrene, anthracene, fluoranthene, and pyrene were accumulated in the shoots, in both P and MAP treatments. However, higher PAH content in maize biomass was achieved during the MAP treatment respect to P treatment. The bioconversion and translocation factors were less than 1, indicating that phystabilization/phytodegradation processes occurred rather than phytoextraction. The microbial biomass, activity and ergosterol content were significantly boosted in the MAP treatment respect to the other treatments at 180 days. Ours results demonstrated that maize-C. laeve association was the most profitable technique for the treatment of an aged PAH-polluted soil when compared to other bioremediation approaches.

Impact of the Fenton-like treatment on the microbial community of a diesel-contaminated soil

Fenton-like treatment (FLT) is an ISCO technique relying on the iron-induced H₂O₂ activation in the presence of additives aimed at increasing the oxidant lifetime and maximizing iron solubility under natural soil pH conditions. The efficacy of FLT in the clean-up of hydrocarbon-contaminated soils is well established at the field-scale. However, a better assessment of the impact of the FLT on density, diversity and activity of the indigenous soil microbiota, might provide further insights into an optimal combination between FLT and in-situ bioremediation (ISB). The aim of this work was to assess the impacts of FLT on the microbial community of a diesel-contaminated soil collected nearby a gasoline station. Different FLT conditions were tested by varying either the H₂O₂ concentrations (2 and 6%) or the oxidant application mode (single or double dosage). The impact of these treatments on the indigenous microbial community was assessed immediately after the Fenton-like treatment and after 30, 60 and 90 d and compared with enhanced natural attenuation (ENA). After FLT, a dramatic decrease in bacterial density, diversity and functionality was evident. Although in microcosms with double dosing at 2% H₂O₂ a delayed recovery of the indigenous microbiota was observed as compared to those subjected to single oxidant dose, after 60 d incubation the respiration rate increased from 0.036 to 0.256 μg CCO₂ g^-1soil h^-1. Irrespective of the oxidant dose, best degradation results after 90 d incubation (around 80%) were observed with combined FLT, relying on double oxidant addition, and bioremediation.

Purification of polluted water with spent mushroom (Agaricus bisporus) substrate: from agricultural waste to biosorbent of phenanthrene, Cd and Pb

The present research was aimed to (i) report the recycling of spent A. bisporus substrate (SAS) to remove heavy metals (Cd and Pb) and phenanthrene (Phe) from polluted water and (ii) assess the possibility to use the treated water for irrigation. Batch experiments were carried out to assess, firstly, the effect of interaction time between pollutants with SAS and, secondly, the pH of the polluted water. Then a biofilter was designed by using pressurized glass columns. Chemical parameters such as pH, electrical conductivity and content of Pb, Cd, Phe, nutrients (NPK) and Cl^- were determined. Equilibrium for contaminants was quickly reached (1-2 h). The pH of the polluted water was the key factor for pollutants' adsorption. The polluted water's pH was increased after biofilter interaction. Phe was not detected in any fraction. Pb and Cd sorption rates were higher than 99%. The pollutant concentrations were within the permitted range to be used for agriculture purposes. Purified water showed significant concentrations of NPK, indicating its potential use as fertilizer. The SAS shows potential to be used as Phe, Pb and Cd biosorbent and the resulting treated water can be used for irrigation according to pollutant contents and agronomical evaluation.

Anti-inflammatory effect of aqueous extracts of spent Pleurotus ostreatus substrates in mouse ears treated with 12-O-tetradecanoylphorbol-13-acetate

Aims:

To evaluate the application of spent Pleurotus ostreatus substrates, enriched or not with medicinal herbs, as a source of anti-inflammatory compounds.

Subjects and Methods:

P. ostreatus was cultivated on five different substrates: Barley straw (BS) and BS combined 80:20 with medicinal herbs (Chenopodium ambrosioides L. [BS/CA], Rosmarinus officinalis L. [BS/RO], Litsea glaucescens Kunth [BS/LG], and Tagetes lucida Cav. [BS/TL]). The anti-inflammatory activity of aqueous extracts of spent mushroom substrates (SMSs) (4 mg/ear) was studied using an acute inflammation model in the mouse ear induced with 2.5 μg/ear 12-O-tetradecanoylphorbol13-acetate (TPA).

Results:

Groups treated with BS/CA, BS/RO, and BS/LG aqueous extracts exhibited the best anti-inflammatory activity (94.0% ± 5.5%, 92.9% ± 0.6%, and 90.4% ± 5.0% inhibition of auricular edema [IAO], respectively), and these effects were significantly different (P < 0.05) from that of the positive control indomethacin (0.5 mg/ear). BS/TL and BS were also able to reduce TPA-induced inflammation but to a lesser extent (70.0% ± 6.7% and 43.5% ± 6.6% IAO, respectively).

Conclusions:

Spent P. ostreatus substrate of BS possesses a slight anti-inflammatory effect. The addition of CA L. to mushroom substrate showed a slightly synergistic effect while RO L. had an additive effect. In addition, LG Kunth and TL Cav. enhanced the anti-inflammatory effect of SMS. However, to determine whether there is a synergistic or additive effect, it is necessary to determine the anti-inflammatory effect of each medicinal herb.

The use of spent mushroom compost to enhance the ability of Atriplex halimus to phytoremediate contaminated mine soils

The mushroom cultivation industry produces a huge amount of spent mushroom compost (SMC), a wide world agricultural organic waste which causes serious environmental problems. However, this cheap organic waste could be useful in the remediation of contaminated soils. The aim of this work was to assess the potential of SMC in combination with the native shrub Atriplex halimus, to phytoremediate two mine soils contaminated with Cd, Pb and Cu. Firstly, to minimize metal availability in the soil, the optimal doses of SMC were determined. Secondly, a phytoremediation assay in greenhouse conditions was carried out to test the effects of A. halimus in combination with SMC at different doses. The results showed the ability of SMC to reduce soil acidity, the mobility of the metals and the enhancement of A. halimus growth. SMC promoted metal immobilization in the root of A. halimus and decreased the translocation from the roots to the shoots. The combination of SMC amendment and A. halimus produced phytostabilization of the metals in the mine soils assayed. In conclusion, SMC represents an adequate organic solid waste which in combination with A. halimus can reduce the adverse impact caused by the high mobility of metals in acid mine soils.

Study of processes influencing bioavailability of pesticides in wood-soil systems: Effect of different factors

Lignocellulosic wastes and by-products containing lignin are now available in large amounts from forestry and industrial activities, and could be promising organic materials for the biosorption of pesticides by soils in order to reduce point-source pollution. Adding these materials to soil requires understanding the process of pesticide sorption-desorption by wood-soils, as sorption capacity could increase, with changes in pesticide bioavailability and final fate. The objective of this work was to study the effect that pine and oak wood added to soils had on the sorption/desorption of the pesticides linuron, alachlor, and metalaxyl. Experiments were conducted with two sandy loam and sandy clay soils each amended with two wood doses (5% and 50%) after different incubation times (0, 5 and 12 months). A low wood dose (5%) had no significant impact on the sorption (K_f) of alachlor, but K_f increased for linuron (up to 5.4-1.7 times) and metalaxyl (up to 4.4 and 8.6 times) in all wood-soil systems. The results were not significantly different after different incubation times. The desorption results indicated that wood decreases the sorption irreversibility of alachlor, and increases that of linuron and metalaxyl, with a varying effect of the wood-soil incubation time. The addition of a high wood dose to soil (50%) was more significant for increasing the sorption of all the pesticides, and the sorbed amounts remaining after desorption (>49% for linuron, >33% for alachlor and >6% for metalaxyl), although there was no apparent discrimination between the two types of woods. The role of the nature of the organic carbón (K_oc values) for sorption was evidenced for alachlor and metalaxyl, but not for linuron. These outcomes are of interest for extending wood application to soil as a barrier for avoiding environmental risk by point-source pollution due to the use and management of pesticides in farming systems.

Comparison of the effectiveness of soil heating prior or during in situ chemical oxidation (ISCO) of aged PAH-contaminated soils

Thermal treatments prior or during chemical oxidation of aged polycyclic aromatic hydrocarbon (PAH)-contaminated soils have already shown their ability to increase oxidation effectiveness. However, they were never compared on the same soil. Furthermore, oxygenated polycyclic aromatic hydrocarbons (O-PACs), by-products of PAH oxidation which may be more toxic and mobile than the parent PAHs, were very little monitored. In this study, two aged PAH-contaminated soils were heated prior (60 or 90 °C under Ar for 1 week) or during oxidation (60 °C for 1 week) with permanganate and persulfate, and 11 O-PACs were monitored in addition to the 16 US Environmental Protection Agency (US EPA) PAHs. Oxidant doses were based on the stoichiometric oxidant demand of the extractable organic fraction of soils by using organic solvents, which is more representative of the actual contamination than only the 16 US EPA PAHs. Higher temperatures actually resulted in more pollutant degradation. Two treatments were about three times more effective than the others: soil heating to 60 °C during persulfate oxidation and soil preheating to 90 °C followed by permanganate oxidation. The results of this study showed that persulfate effectiveness was largely due to its thermal activation, whereas permanganate was more sensitive to PAH availability than persulfate. The technical feasibility of these two treatments will soon be field-tested in the unsaturated zone of one of the studied aged PAH-contaminated soils.

Bacterial mineralization of phenanthrene on thermally activated palygorskite: A 14C radiotracer study

Clay-bacterial interaction can significantly influence the biodegradation of organic contaminants in the environment. A moderate heat treatment of palygorskite could alter the physicochemical properties of the clay mineral and thus support the growth and function of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria. By using ¹⁴C-labelled phenanthrene and a model bacterium Burkholderia sartisoli, we studied the mineralization of phenanthrene on the surface of a moderately heat-treated (up to 400°C) palygorskite. The heat treatment at 400°C induced a reduction of binding sites (e.g., by the elimination of organic matter and/or channel shrinkage) in the palygorskite and thus imparted a weaker sequestration of phenanthrene on its surface and within the pores. As a result, a supplement with the thermally modified palygorskite (400°C) significantly increased (20-30%; p<0.05) the biomineralization of total phenanthrene in a simulated soil slurry system. These results are highly promising to develop a clay mineral based technology for the bioremediation of PAH contaminants in water and soil environments.

Combination of Fenton processes and biotreatment for wastewater treatment and soil remediation

There is a continuously increasing worldwide concern for the development of wastewater and contaminated soil treatment technologies. Fenton processes and biological treatments have long been used as common technologies for treating wastewater and polluted soil but they still need to be modified because of some defects (high costs of Fenton process and long remediation time of biotreatments). This work first briefly introduced the Fenton technology and biotreatment, and then discussed the main considerations in the construction of a combined system. This review shows a critical overview of recent researches combining Fenton processes (as pre-treatment or post-treatment) with bioremediation for treatment of wastewater or polluted soil. We concluded that the combined treatment can be regarded as a novel and competitive technology. Furthermore, the outlook for potential applications of this combination in different polluted soil and wastewater, as well as the mechanism of combination was also discussed.

Impact of Spent Mushroom Substrates on the Fate of Pesticides in Soil, and Their Use for Preventing and/or Controlling Soil and Water Contamination: A Review

Intensive crop production involves a high consumption of pesticides. This is a cause of major environmental concern because the presence of pesticides in water is becoming increasingly common. Physicochemical methods based on soil modification with organic residues have been developed to enhance the immobilization and/or degradation of pesticides in agricultural soils, which may control both the diffuse and the point pollution of soils and waters. This review summarizes the influence of spent mushroom substrate (SMS) on the environmental fate of pesticides when both are simultaneously applied in agriculture. The processes of adsorption, leaching and dissipation of these compounds in SMS-amended soils were evaluated at laboratory and field scale. Relationships were established between the experimental parameters obtained and the properties of the soils, the SMS, and the pesticides in order to determine the effect that the application of SMS in agricultural soils has on the environmental impact of pesticides. Accordingly, this review highlights the use of SMS as a strategy for the prevention and/or control of soil and water contamination by pesticides to strike a balance between agricultural development and the use of these compounds.

Treatment of petroleum drill cuttings using bioaugmentation and biostimulation supplemented with phytoremediation

This study sought to compare the effectiveness of bioaugmentation and biostimulation, as well as the combination of both techniques, supplemented with phytoremediation, in the decontamination of petroleum drill cuttings. Drill cuttings with relatively low concentration of total petroleum hydrocarbons (TPH) and metals were mixed with soil in the ratio 5:1 and treated with three different combinations of the bioremediation options. Option A entailed bioaugmentation supplemented with phytoremediation. Option B had the combination of biostimulation and bioaugmentation supplemented with phytoremediation. While biostimulation supplemented with phytoremediation was deployed in option C. Option O containing the drill cuttings-soil mixture without treatment served as untreated control. Fertilizer application, tillage and watering were used for biostimulation treatment, while spent mushroom substrate (Pleurotus ostreatus) and elephant grass (Pennisetum purpureum) were employed for bioaugmentation and phytoremediation treatment, respectively. The drill cuttings-soil mixtures were monitored for TPH, organic carbon, total nitrogen, pH, metal concentrations, and fungal counts, over time. After 56 days of treatment, there was a decline in the initial TPH concentration of 4,114 mg kg(-1) by 5.5%, 68.3%, 75.6% and 48% in options O, A, B and C, respectively. Generally, higher TPH loss resulted from the phytoremediation treatment stage. The treated options also showed slight reductions in metal concentrations ranging from 0% to 16% of the initial low concentrations. The results highlight the effectiveness of bioaugmentation supplemented with phytoremediation. The combination of bioaugmentation and biostimulation supplemented with phytoremediation, however, may prove better in decontaminating petroleum drill cuttings to environmentally benign levels.

Impact of bacterial activity on turnover of insoluble hydrophobic substrates (phenanthrene and pyrene)-Model simulations for prediction of bioremediation success

Many attempts for bioremediation of polycyclic aromatic hydrocarbon (PAH) contaminated sites failed in the past, but the reasons for this failure are not well understood. Here we apply and improve a model for integrated assessment of mass transfer, biodegradation and residual concentrations for predicting the success of remediation actions. First, we provide growth parameters for Mycobacterium rutilum and Mycobacterium pallens growing on phenanthrene (PHE) or pyrene (PYR) degraded the PAH completely at all investigated concentrations. Maximum metabolic rates vmax and growth rates μ were similar for the substrates PHE and PYR and for both strains. The investigated Mycobacterium species were not superior in PHE degradation to strains investigated earlier with this method. Real-world degradation scenario simulations including diffusive flux to the microbial cells indicate: that (i) bioaugmentation only has a small, short-lived effect; (ii) Increasing sorption shifts the remaining PAH to the adsorbed/sequestered PAH pool; (iii) mobilizing by solvents or surfactants resulted in a significant decrease of the sequestered PAH, and (iv) co-metabolization e.g. by compost addition can contribute significantly to the reduction of PAH, because active biomass is maintained at a high level by the compost. The model therefore is a valuable contribution to the assessment of potential remediation action at PAH-polluted sites.

Application of compost for effective bioremediation of organic contaminants and pollutants in soil

Soils contaminated with hazardous chemicals worldwide are awaiting remediation activities; bioremediation is often considered as a cost-effective remediation approach. Potential bioapproaches are biostimulation, e.g. by addition of nutrients, fertiliser and organic substrates, and bioaugmentation by addition of compound-degrading microbes or of organic amendments containing active microorganisms, e.g. activated sludge or compost. In most contaminated soils, the abundance of the intrinsic metabolic potential is too low to be improved by biostimulation alone, since the physical and chemical conditions in these soils are not conducive to biodegradation. In the last few decades, compost or farmyard manure addition as well as composting with various organic supplements have been found to be very efficient for soil bioremediation. In the present minireview, we provide an overview of the composting and compost addition approaches as 'stimulants' of natural attenuation. Laboratory degradation experiments are often biased either by not considering the abiotic factors or by focusing solely on the elimination of the chemicals without taking the biotic factors and processes into account. Therefore, we first systemise the concepts of composting and compost addition, then summarise the relevant physical, chemical and biotic factors and mechanisms for improved contaminant degradation triggered by compost addition. These factors and mechanisms are of particular interest, since they are more relevant and easier to determine than the composition of the degrading community, which is also addressed in this review. Due to the mostly empirical knowledge and the nonstandardised biowaste or compost materials, the field use of these approaches is highly challenging, but also promising. Based on the huge metabolic diversity of microorganisms developing during the composting processes, a highly complex metabolic diversity is established as a 'metabolic memory' within developing and mature compost materials. Compost addition can thus be considered as a 'super-bioaugmentation' with a complex natural mixture of degrading microorganisms, combined with a 'biostimulation' by nutrient containing readily to hardly degradable organic substrates. It also improves the abiotic soil conditions, thus enhancing microbial activity in general. Finally, this minireview also aims at guiding potential users towards full exploitation of the potentials of this approach.

The potential of organic substrates based on mushroom substrate and straw to dissipate fungicides contained in effluents from the fruit-packaging industry - Is there a role for Pleurotus ostreatus?

Citrus fruit-packaging plants (FPP) produce large wastewater volumes with high loads of fungicides like ortho-phenylphenol (OPP) and imazalil (IMZ). No methods are in place for the treatment of those effluents and biobeds appear as a viable alternative. We employed a column study to investigate the potential of spent mushroom substrate (SMS) of Pleurotus ostreatus, either alone or in mixture with straw and soil plus a mixture of straw /soil to retain and dissipate IMZ and OPP. The role of P. ostreatus on fungicides dissipation was also investigated by studying in parallel the performance of fresh mushroom substrate of P. ostreatus (FMS) and measuring lignolytic enzymatic activity in the leachates. All substrates effectively reduced the leaching of OPP and IMZ which corresponded to 0.014-1.1% and 0.120-0.420% of their initial amounts respectively. Mass balance analysis revealed that FMS and SMS/Straw/Soil (50/25/25 by vol) offered the most efficient removal of OPP and IMZ from wastewaters respectively. Regardless of the substrate, OPP was restricted in the top 0-20cm of the columns and was bioavailable (extractable with water), compared to IMZ which was less bioavailable (extractable with acetonitrile) but diffused at deeper layers (20-50, 50-80cm) in the SMS- and Straw/Soil-columns. PLFAs showed that fungal abundance was significantly lower in the top layer of all substrates from where the highest pesticide amounts were recovered suggesting an inhibitory effect of fungicides on total fungi in the substrates tested. Our data suggest that biobeds packed with SMS-rich substrates could ensure the efficient removal of IMZ and OPP from wastewaters of citrus FPP.

Application of spent mushroom (Lentinula edodes) substrate and acclimated sewage sludge on the bioremediation of polycyclic aromatic hydrocarbon polluted soil

A novel technology for remediation and improvement of soil was provided along with a new approach for waste recycling.

Bioremediation of multi-polluted soil by spent mushroom (Agaricus bisporus) substrate: Polycyclic aromatic hydrocarbons degradation and Pb availability

This study investigates the effect of three spent Agaricus bisporus substrate (SAS) application methods on bioremediation of soil multi-polluted with Pb and PAH from close to a shooting range with respect natural attenuation (SM). The remediation treatments involve (i) use of sterilized SAS to biostimulate the inherent soil microbiota (SSAS) and two bioaugmentation possibilities (ii) its use without previous treatment to inoculate A. bisporus and inherent microbiota (SAS) or (iii) SAS sterilization and further A. bisporus re-inoculation (Abisp). The efficiency of each bioremediation microcosm was evaluated by: fungal activity, heterotrophic and PAH-degrading bacterial population, PAH removal, Pb mobility and soil eco-toxicity. Biostimulation of the native soil microbiology (SSAS) achieved similar levels of PAH biodegradation as SM and poor soil detoxification. Bioaugmented microcosms produced higher PAH removal and eco-toxicity reduction via different routes. SAS increased the PAH-degrading bacterial population, but lowered fungal activity. Abisp was a good inoculum carrier for A. bisporus exhibiting high levels of ligninolytic activity, the total and PAH-degrading bacteria population increased with incubation time. The three SAS applications produced slight Pb mobilization (<0.3%). SAS sterilization and further A. bisporus re-inoculation (Abisp) proved the best application method to remove PAH, mainly BaP, and detoxify the multi-polluted soil.