Mycelium-Enhanced Bacterial Degradation of Organic Pollutants under Bioavailability Restrictions

Assembly and functional profile of rhizosphere microbial community during the Salix viminalis-AMF remediation of polycyclic aromatic hydrocarbon polluted soils

Arbuscular mycorrhizal fungi (AMF) are positive to the phytoremediation by improving plant biomass and soil properties. However, the role of AM plants to the remediation of polycyclic aromatic hydrocarbons (PAHs) is yet to be widely recognized, and the impact of AM plants to indigenous microbial communities during remediation remains unclear. In this work, a 90-day study was conducted to assess the effect of AMF-Salix viminalis on the removal of PAHs, and explore the impact to the microbial community composition, abundance, and function. Results showed that AMF-Salix viminalis effectively enhanced the removal of benzo[a]pyrene, and enriched more PAH-degrading bacteria, consisting of Actinobacteria, Chloroflexi, Sphingomonas, and Stenotrophobacter, as well as fungi including Basidiomycota, Pseudogymnoascus, and Tomentella. For gene function, AM willow enhanced the enrichment of genes involved in amino acid synthesis, aminoacyl-tRNA biosynthesis, and cysteine and methionine metabolism pathways. F. mosseae inoculation had a greater effect on alpha- and beta-diversity of microbial genes at 90 d. Additionally, AMF inoculation significantly increased the soil microbial biomass carbon and organic matter concentration. All together, the microbial community assembly and function shaped by AM willow promoted the dissipation of PAHs. Our results support the effectiveness of AM remediation and contribute to reveal the enhancing-remediation mechanism to PAHs using multi-omics data.

Enhancing bacterial biodegradation of n-hexane by utilizing the adsorption capacity of non-degrading fungi

Biodegradation of hydrophobic volatile organic compounds (VOCs) such as n-hexane is limited by their poor accessibility. Constructing fungal-bacterial degradation alliances is an effective approach, but the role of those fungi without the capability to degrade VOCs may have been overlooked. In this study, a non-n-hexane-degrading fungus, Fusarium keratoplasticum FK, was utilized to enhance n-hexane degradation by the bacterium Mycobacterium neworleansense WCJ. It was shown that strain WCJ removed 64.84% of n-hexane (at a concentration of 648.20 mg L-1) over 3 d, and 84.04% after introducing strain FK. Microbial growth kinetic studies revealed that the growth of strain WCJ was also promoted. Through a stepwise adsorption-degradation experiment combined with qPCR technology, it was found that the strain WCJ could utilize the n-hexane pre-adsorbed by strain FK, with an increase in copy number from 108.2662 to 108.7731. Therefore, the non-degrading fungi can improved the accessibility of n-hexane by providing n-hexane adsorbed by the mycelium to the degrading bacteria. In addition, the adsorption tests and characterization of the fungal samples before and after Soxhlet extraction indicated that the adsorption of n-hexane on strain FK conformed to Lagergren's pseudo-second-order kinetics and Freundlich adsorption isotherms, and was correlated with the presence of lipids and nonpolar groups. This study emphasizes the potential role of non-degrading fungi in bioremediation and proposes a viable strategy to enhance the bacterial degradation of hydrophobic VOCs.

Microbial interactions within beneficial consortia promote soil health

By ecologically interacting with various biotic and abiotic agents acting in soil ecosystems, highly diverse soil microorganisms establish complex and stable assemblages and survive in a community context in natural settings. Besides facilitating soil microbiome to maintain great levels of population homeostasis, such microbial interactions drive soil microbes to function as the major engine of terrestrial biogeochemical cycling. It is verified that the regulative effect of microbe-microbe interplay plays an instrumental role in microbial-mediated promotion of soil health, including bioremediation of soil pollutants and biocontrol of soil-borne phytopathogens, which is considered an environmentally friendly strategy for ensuring the healthy condition of soils. Specifically, in microbial consortia, it has been proven that microorganism-microorganism interactions are involved in enhancing the soil health-promoting effectiveness (i.e., efficacies of pollution reduction and disease inhibition) of the beneficial microbes, here defined as soil health-promoting agents. These microbial interactions can positively regulate the soil health-enhancing effect by supporting those soil health-promoting agents utilized in combination, as multi-strain soil health-promoting agents, to overcome three main obstacles: inadequate soil colonization, insufficient soil contaminant eradication and inefficient soil-borne pathogen suppression, all of which can restrict their probiotic functionality. Yet the mechanisms underlying such beneficial interaction-related adjustments and how to efficiently assemble soil health-enhancing consortia with the guidance of microbe-microbe communications remain incompletely understood. In this review, we focus on bacterial and fungal soil health-promoting agents to summarize current research progress on the utilization of multi-strain soil health-promoting agents in the control of soil pollution and soil-borne plant diseases. We discuss potential microbial interaction-relevant mechanisms deployed by the probiotic microorganisms to upgrade their functions in managing soil health. We emphasize the interplay-related factors that should be taken into account when building soil health-promoting consortia, and propose a workflow for assembling them by employing a reductionist synthetic community approach.

Enhanced Fenton-like catalysis for pollutants removal via MOF-derived CoxFe3-xO4 membrane: Oxygen vacancy-mediated mechanism

Traditional batch configuration is not sustainable due to catalyst leaching and ineffective recovery. Herein, a novel membrane-based catalyst with oxygen vacancies is developed, which assembled metal-organic-framework cobalt ferrite nanocrystals (MOF-d Co_xFe_3-xO₄) on polyvinylidene fluoride membrane to activate peroxymonosulfate (PMS) for catalytic degradation of emerging pollutants. MOF-d Co_xFe_3-xO₄ are synthesized by one-step pyrolysis using Co/Fe bimetallic organic frameworks (Co_xFe_3-x bi-MOF) with tunable cobalt content as a template (x/3-x represented the molar ratio of Co and Fe in MOF). Intriguingly, MOF-d Co_1.75Fe_1.25O₄ membrane exhibits excellent PMS activation efficiency as indicated by 95.12% removal of the probe chemical (bisphenol A) at 0.5 mM PMS (∼100 L m^-2 h^-1 at the loading of 10 mg), which is significantly higher than the traditional Co_1.75Fe_1.25O₄ suspension system (34.16%). Experimental results show that the membrane has excellent anti-interference ability to anions and dissolved organic matter, and can effectively degrade a variety of emerging pollutants, and its performance is not inhibited by the change of solution pH (3-9) or the long-term (20 h) continuous flow operation. EPR and quenching experiments show that catalytic degradation is the result of the synergistic effect of radicals and non-radicals. The oxygen vacancy-mediated mechanism can explain the formation of active substances, and the formation of ¹O₂ plays an important role in the degradation of bisphenol A. This study provides a membrane-based strategy for effective and sustainable removal of emerging pollutants.

Removal of ibuprofen by sodium alginate-coated iron-carbon granules combined with the ultrasound and Fenton technologies: influencing factors and degradation intermediates

This study focuses on the preparation of sodium alginate-coated iron-carbon granules (FeCGs) and their capacity to remove ibuprofen (IBU) by combining Fenton and ultrasound technologies. The preferred preparation conditions are as follows: 2% (w/v) sodium alginate, 10% (w/v) iron fillings and biochar, and used CaCl2 as the cross-linking agent. 74.72% of IBU was removed by ultrasound/FeCG under 10 g/L FeCG and 250 W ultrasound power. Fenton/FeCG could remove 92.41% of IBU under 10 g/L FeCG and 2 mM H2O2. Under the above experimental conditions, ultrasound/FeCG has higher reaction speed (9.44 × 10-3 min-1) than Fenton/FeCG (4.95 × 10-3 min-1). However, Fenton/FeCG could remove more TOC than ultrasound/FeCG. During the reaction using the Fenton/FeCG system, 11 degradation intermediates were detected, but only 7 intermediates were produced by the ultrasound/FeCG system. A common single-chain product C5H10O3 formed by IBU degradation was detected in the reaction products during Fenton/FeCG reaction, which benzene ring structure was destroyed; however, the minimum molecular weight of the product detected using the ultrasound/FeCG system was that of C8H10O; the benzene ring structure of IBU is not destroyed. This study provides guidance in the preparation of sodium alginate-coated FeCGs, evaluating the applicability of Fenton/FeCG and ultrasound/FeCG, which was meaningful for organic pollution wastewater treatment.

RR2 dye adsorption to Hymenaea courbaril L. bark activated carbon associated with biofilm

This study addressed the removal performance of RR2 from aqueous solutions in adsorption columns experiments by comparing the potential of activated carbon alone (ACA) and microbially inoculated (MIAC), prepared from barks of a largely available tree in Brazilian Cerrado biome, Hymenaea courbaril L. or "Jatobá," presenting the kinetics, isotherms, breakthrough curves, and dissolved organic carbon removal. ACA presented strong interaction to RR2 dye, evidenced at the first 20 min when absorbance already attained 66.4%. The removal percentage gradually increased with time and the equilibrium occurred around 91.7% within 120 min. Langmuir model best fitted the isotherm data, indicating a maximum adsorption capacity of 4.068 mg g^-1 for the amount of 0.5 g of adsorbent. The Langmuir's model parameters K_L, R_L, and R² corresponded to 0.0234 L mg^-1, 0.4159, and 0.9663, respectively, indicating a favorable adsorption process (0 < R_L < 1). The experiments in adsorption columns revealed maximum adsorption capacities of 14.38 and 11.43 mg g^-1 for MIAC and ACA, respectively, where the microbial activity favorably retarded the adsorption breakpoint in approximately 20 min and enhanced the RR2 consumption in 25.8%. Effectiveness of DOC removal attained above 90% for both ACA and MIAC, reducing the content from 86.1 to 7.84 mg L^-1 and 4.82 mg L^-1, respectively.

Simultaneous determination of dissolved phenanthrene and its metabolites by derivative synchronous fluorescence spectrometry with double scans method in aqueous solution

A simple and sensitive derivative synchronous fluorescence spectrometry with double scans (DS-DSFS) method was developed for simultaneous determination of dissolved Phenanthrene (Phe) and its metabolites 1-hydroxy-2-naphthoic acid (1H2NA) and salicylic acid (SA) in aqueous solution. The value of 69 nm was selected as the optimal Δλ conditions for Phe and 1H2NA, and the Δλ value of 55 nm was selected for SA. The overlapping fluorescence emission spectra of Phe, 1H2NA and SA were resolved by DS-DSFS. The signals detected at wavelength of 296 nm for Phe, 352 nm for 1H2NA and 307 nm for SA vary linearly when the concentrations in the range of 4.0-1.0 × 10³ μg L^-1, 4.0-1.2 × 10³ μg L^-1 and 4.0-8.0 × 10² μg L^-1, respectively. The detection limits were 0.08, 0.07 and 0.88 μg L^-1 for Phe, 1H2NA and SA, with the relatively standard deviations less than 5.0%. The established method was successfully applied in the determination of Phe and the metabolites during the biodegradation of dissolved Phe in the lab. It was evidenced that the method has potential for the in situ investigation of PAH biodegradation.

Simultaneous enhancement of nonylphenol biodegradation and short-chain fatty acids production in waste activated sludge under acidogenic conditions

Nonylphenol (NP) biodegradation in waste activated sludge (WAS) under anaerobic conditions is usually slow, and no information on NP biodegradation under acidogenic conditions is currently available. In this study, the simultaneous enhancement of NP biodegradation and short-chain fatty acids (SCFAs) accumulation in a WAS fermentation system under acidogenic conditions was accomplished by controlling pH 10 and adding sodium lauryl sulfate (SLS). The biodegradation efficiency of NP was found to be 55.5% within 8 d under acidogenic conditions, much higher than that in the control (24.6%). Meanwhile, the concentration of SCFAs under the same conditions for NP biodegradation was increased from 2234 mg COD/L (control) to 4691 mg COD/L (at pH 10 with SLS). Mechanism study revealed that the abundances of both NP-degrading microorganisms and acidogenic bacteria increased under acidogenic conditions. Altering the enzymatic activity and the quantity of functional genes in the acidogenic fermentation system were beneficial to NP biodegradation and SCFAs accumulation. Furthermore, organic substrates available for uptake by NP-degrading and acidogenic bacteria, i.e. NP, protein and carbohydrate, were released from WAS under acidogenic conditions. More importantly, intermediate substrates involved in acidogenic fermentation were advantageous to the cometabolic biodegradation of NP.

Linking initial soil bacterial diversity and polycyclic aromatic hydrocarbons (PAHs) degradation potential

The aim of this study was to understand the role of indigenous soil microbial communities on the biodegradation of polycyclic aromatic hydrocarbons (PAHs) and to determine whether PAHs degradation potential in soils may be evaluated by analysis of bacterial diversity and potential metabolisms using a metagenomics approach. Five different soils were artificially contaminated with seven selected PAHs and the most abundant bacterial taxa were assessed by sequencing the 16S rRNA gene, and linking them to PAH biodegradation efficiencies. A PICRUSt approach was then led to estimate the degradation potentials by metagenomics inference. Although the role of bacteria in PAHs degradation is not directly established here, the presence of a large number of bacteria belonging to the Betaproteobacteria class correlated to a higher degradation of LMW PAHs. A link with specific bacterial taxa was more difficult to establish concerning HMW PAHs, which seemed to require more complex mechanisms as shown by PICRUSt.