Biodegradation Of Organic Pollutants Research Articles

Biochar imparted constructed wetlands (CWs) for enhanced biodegradation of organic and inorganic pollutants along with its limitation.

The remediation of polluted soil and water stands as a paramount task in safeguarding environmental sustainability and ensuring a dependable water source. Biochar, celebrated for its capacity to enhance soil quality, stimulate plant growth, and adsorb a wide spectrum of contaminants, including organic and inorganic pollutants, within constructed wetlands, emerges as a promising solution. This review article is dedicated to examining the effects of biochar amendments on the efficiency of wastewater purification within constructed wetlands. This comprehensive review entails an extensive investigation of biochar's feedstock selection, production processes, characterization methods, and its application within constructed wetlands. It also encompasses an exploration of the design criteria necessary for the integration of biochar into constructed wetland systems. Moreover, a comprehensive analysis of recent research findings pertains to the role of biochar-based wetlands in the removal of both organic and inorganic pollutants. The principal objectives of this review are to provide novel and thorough perspectives on the conceptualization and implementation of biochar-based constructed wetlands for the treatment of organic and inorganic pollutants. Additionally, it seeks to identify potential directions for future research and application while addressing prevailing gaps in knowledge and limitations. Furthermore, the study delves into the potential limitations and risks associated with employing biochar in environmental remediation. Nevertheless, it is crucial to highlight that there is a significant paucity of data regarding the influence of biochar on the efficiency of wastewater treatment in constructed wetlands, with particular regard to its impact on the removal of both organic and inorganic pollutants.

Electrode potential regulates extracellular polymer secretion enhanced tetracycline removal

Bacteria colonized on solid electrode developing electroactive biofilm (EAB) has been shown to promote the contaminants biodegradation. Regulating electrode potential can improve the stability of extracellular electron transfer (EET), but how the electrode potential regulating the extracellular polymer secretion and the tetracycline (TC) removal has not been fully studied. Here, EAB cultured at 0 V was used to study the degradation mechanism of TC at different electrode potentials. Results showed that −0.1 V was the optimized electrode potential for TC biodegradation compared with 0.1 V, 0 V and −0.3 V, which was 28 % higher than that without electric field. Stimulation of electric field can retain proper extracellular polymer (EPS) to relieve the poison of TC, while excessive extracellular polysaccharide (PS) at 0 V have hindered the contact between microorganisms and TC, thus limited electron transfer and reduced the TC biodegradation efficiency. Excessively negative potential (−0.3 V) will restrict the electron transfer which was not conducive to the biodegradation of organic pollutants. Microbial community analysis revealed that TC addition have refreshed the EAB structure, Dokdonella and Norank_f_Rikenellaceae replaced Geobacter as the dominant species in EAB to promote TC biodegradation. The variation of metabolic pathway was suggested that the up-regulation of pyruvate metabolism and ubiquinone synthesis at −0.1 V have promoted the TC removal. This study has provided theoretical support for the electrode potential regulating the extracellular polymer secretion and promoting the pollution bioremediation.

Role of biochar pyrolysis temperature on intracellular and extracellular biodegradation of biochar-adsorbed organic compounds

Immobilizing organic pollutants by adsorption of biochar in farmland soil is a cost-effective remediation method for contaminated soil. As the adsorption capacity of biochar is limited, biodegradation of biochar-adsorbed organic pollutants was a potential way to regenerate biochars and maintain the adsorption performance of biochars to lower the cost. It could be affected by the biochar pyrolysis temperature, but was not evaluated yet. In this study, biodegradation of adsorbed phenanthrene on a series of biochars with pyrolysis temperatures from 150 to 700 °C by Sphingobium yanoikuyae B1 was investigated using batch experiments of biodegradation kinetics at 30 °C, to explore the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds. It was observed that 37.5–47.9% of adsorbed phenanthrene on moderate temperature-pyrolyzed biochars produced at 400 and 500 °C were biodegraded, less than that on high temperature-pyrolyzed biochars produced at ≥600 °C (48.8–60.8%) and low temperature-pyrolyzed biochars produced at ≤300 °C (63.4–92.5%). Phenanthrene adsorbed largely on the low temperature-pyrolyzed biochars by partition mechanism and thus is easily desorbed to water for a dominated intracellular biodegradation. On the high temperature-pyrolyzed biochars, phenanthrene is adsorbed largely by pore-filling mechanism and thus less desorbed to water for intracellular biodegradation. However, high temperature-pyrolyzed biochars can promote microbes to produce siderophore, H2O2 and thus release extracellular •OH for a dominated degradation of adsorbed phenanthrene by Fenton-like reaction. With the increase of biochar pyrolysis temperature, desorption and consequently the intracellular biodegradation of adsorbed phenanthrene on biochars decreased, while the secretion of siderophore and H2O2 by microbes on biochars increased to produce more extracellular •OH for degradation by Fenton-like reaction. The results could provide deep insights into the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds, and optimize the selection of biochar with higher adsorption performance and easier regeneration for soil remediation.

PVA-TiO2 Nanocomposite Hydrogel as Immobilization Carrier for Gas-to-Liquid Wastewater Treatment

This study investigates the development of polyvinyl alcohol (PVA) gel matrices for biomass immobilization in wastewater treatment. The PVA hydrogels were prepared through a freezing–thawing (F-T) cross-linking process and reinforced with high surface area nanoparticles to improve their mechanical stability and porosity. The PVA/nanocomposite hydrogels were prepared using two different nanoparticle materials: iron oxide (Fe3O2) and titanium oxide (TiO2). The effects of the metal oxide nanoparticle type and content on the pore structure, hydrogel bonding, and mechanical and viscoelastic properties of the cross-linked hydrogel composites were investigated. The most durable PVA/nanoparticles matrix was then tested in the bioreactor for the biological treatment of wastewater. Morphological analysis showed that the reinforcement of PVA gel with Fe2O3 and TiO2 nanoparticles resulted in a compact nanocomposite hydrogel with regular pore distribution. The FTIR analysis highlighted the formation of bonds between nanoparticles and hydrogel, which caused more interaction within the polymeric matrix. Furthermore, the mechanical strength and Young’s modulus of the hydrogel composites were found to depend on the type and content of the nanoparticles. The most remarkable improvement in the mechanical strength of the PVA/nanoparticles composites was obtained by incorporating 0.1 wt% TiO2 and 1.0 wt% Fe2O3 nanoparticles. However, TiO2 showed more influence on the mechanical strength, with more than 900% improvement in Young’s modulus for TiO2-reinforced PVA hydrogel. Furthermore, incorporating TiO2 nanoparticles enhanced hydrogel stability but did not affect the biodegradation of organic pollutants in wastewater. These results suggest that the PVA-TiO2 hydrogel has the potential to be used as an effective carrier for biomass immobilization and wastewater treatment.

Multifaceted application of modified biochar for water and wastewater treatment

AbstractBiochar, a carbon‐rich material produced through the pyrolysis of biomass, has been shown to have the potential to remove contaminants from water and wastewater. However, due to the weak adsorption capacity and narrow adsorption range of pure biochar, it is modified, either chemically or physically, in order to optimize its applications in water and wastewater treatment. This study summarizes the recent advancements in the application of modified biochar for water and wastewater treatment. Modification of biochar increases its surface area and porous structure, which makes it an effective adsorbent to immobilize a range of contaminants, such as heavy metals, dyes, and organic contaminants. It can also be used as a catalyst in the biodegradation of organic pollutants as it can provide a substrate for microbial growth and metabolism, enhancing pollutant degradation. This study also summarizes various biochar modifications such as gas, acid, alkali, metal, organic compounds, and oxidizing agents. Among the metal‐modified biochar, Iron‐modified biochar has shown the highest tetracycline (TC) removal efficiency (90.7%) and nitrate adsorption capacity (32.33 mg g−1). N‐doped biochars were found to be the most effective biochars for removing heavy metals such as Cd2+ or Cu2+ and aromatic compounds as they can increase the adsorption of raw biochar by up to 70%. Increasing the number of functional groups on the surface of the biochar by using organic compounds like acrylonitrile and chitosan showed a two to three‐fold increase in the adsorption capacity of pollutants such as Cd2+ and Hg2+. According to this review, modified biochar technology is a cost‐effective and environmentally friendly wastewater treatment method.

Biodegradation of furfuryl alcohol by indigenous Bacillus species of industrial effluent-contaminated sites: estimation, biokinetics and toxicity assessment of bio-transformed metabolites.

Furfuryl alcohol (FA) and other furanic compounds have garnered considerable attention in the quest for sustainable alternatives. FA-based resins have been used in various sectors that entail the release of FA into the environment. Hence, to ensure sustainability in this scenario, devising a dependable approach to its degradation is imperative. Given the crucial role of bacterial strains in the biodegradation of various organic pollutants, this study investigates the microbial degradation of FA, using bacterial strains isolated from sites that are constantly exposed to industrial waste. Three potential isolates were identified as B. paramycoides, B. cereus, and B. tequilensis by 16S rRNA gene sequencing. At a concentration of 300µg/ml, these isolates demonstrated efficient FA degradation; 60-70% (at 300µg/ml FA) and 50-60%, (at 500µg/ml FA). Fourier-transform infrared (FTIR) spectroscopy and High-Performance Liquid Chromatography (HPLC) analysis further supported the result that the bacterial isolates consumed FA as the carbon source. Liquid chromatography-mass spectrometry (LC-MS) facilitates the detection of the major metabolic intermediate product in which FA gets transformed. The prominent peaks at 113 and 119m/z obtained in the MS spectra of the degraded FA samples indicated the possibility of the conversion of FA into furoic acid or levulinic acid. The phytotoxicity bioassay findings revealed the non-toxic nature of the bio-transformed products as compared to pure FA. This investigation presents the initial documentation of the FA degradative potential of Bacillus strains, thereby augmenting the understanding of the prospective implementation of Bacillus species in industrial waste treatment projects.

The variations of native plasmids greatly affect the cell surface hydrophobicity of sphingomonads.

Microbial cell surface hydrophobicity (CSH) reflects nonspecific adhesion ability and affects various physiological processes, such as biofilm formation and pollutant biodegradation. Understanding the regulation mechanisms of CSH will contribute to illuminating microbial adaptation strategies and provide guidance for controlling CSH artificially to benefit humans. Sphingomonads, a common bacterial group with great xenobiotic-degrading ability, generally show higher CSH than typical Gram-negative bacteria, which plays a positive role in organic pollutant capture and cell colonization. This study verified that the variations of two native plasmids involved in synthesizing outer membrane proteins and polysaccharides greatly affected the CSH of sphingomonads. It is feasible to control their CSH by changing the plasmid copy number and sequences. Additionally, considering that plasmids are likely to evolve faster than chromosomes, the CSH of sphingomonads may evolve quickly to respond to environmental changes. Our results provide valuable insights into the CSH regulation and evolution of sphingomonads.

Immobilization of laccase on magnetic PEGDA–CS inverse opal hydrogel for enhancement of bisphenol A degradation in aqueous solution

Endocrine disruptors such as bisphenol A (BPA) adversely affect the environment and human health. Laccases are used for the efficient biodegradation of various persistent organic pollutants in an environmentally safe manner. However, the direct application of free laccases is generally hindered by short enzyme lifetimes, non-reusability, and the high cost of a single use. In this study, laccases were immobilized on a novel magnetic three-dimensional poly(ethylene glycol) diacrylate (PEGDA)–chitosan (CS) inverse opal hydrogel (LAC@MPEGDA@CS@IOH). The immobilized laccase showed significant improvement in the BPA degradation performance and superior storage stability compared with the free laccase. 91.1% of 100 mg/L BPA was removed by the LAC@MPEGDA@CS@IOH in 3 hr, whereas only 50.6% of BPA was removed by the same amount of the free laccase. Compared with the laccase, the outstanding BPA degradation efficiency of the LAC@MPEGDA@CS@IOH was maintained over a wider range of pH values and temperatures. Moreover, its relative activity of was maintained at 70.4% after 10 cycles, and the system performed well in actual water matrices. This efficient method for preparing immobilized laccases is simple and green, and it can be used to further develop ecofriendly biocatalysts to remove organic pollutants from wastewater.

Synergistic effects of bacterial consortium and thermal energy on treatment of sewage by waste stabilisation pond

The low rates of biodegradation of organic pollutants in wastewater have been attributed to the daily fluctuation of temperatures, which affects microbial metabolism and activities in reactors. This work aimed to develop a method to degrade sewage pollutants using a synergistic effect of bacterial consortium and thermal energy, while a grey concrete pond served as the control. The results demonstrated that the temperature profile of ICCP showed that all through the experiment, the temperature was above 25 °C, which is a suitable temperature for mesophilic bacterial growth. A properly-stabilised effluent was achieved by the ICCP with a low biodegradation index between 0.11 and 0.14. The values of BOD (95%) and COD (74%) removal efficiencies were obtained at a 10-day retention time in ICCP, which is in accordance with standard of the United State Environmental protection Agency. Moreover, a comparison between a control and ICCP revealed that the latter emits heat energy 30% higher than the first. The temperature of 30 °C (dark) and 30.8 °C (light) produced a BOD removal > 90%. Therefore, this method could be considered to bridge the gap in daily fluctuation of temperature for enhanced biodegradation.•Designing of a thermal coated concrete pond to investigate their thermal performance during the dark and light condition•Bioremediation test for selection of mixed bacteria strain of high degradation potential used as inoculum•A detention time of 10 days under natural sunlight used for investigation for concentration balance of organic pollutant

Fe-Based Nanomaterials and Plant Growth Promoting Rhizobacteria Synergistically Degrade Polychlorinated Biphenyls by Producing Extracellular Reactive Oxygen Species.

Plant growth promoting rhizobacteria (PGPR) produce extracellular reactive oxygen species (ROS) to protect plants from external stresses. Fe-based nanomaterials can potentially interact with PGPR and synergistically degrade organic pollutants, yet they have received no study. Here, we studied how the interaction between a typical PGPR (Pseudomonas chlororaphis, JD37) and Fe-based nanomaterials facilitated the degradation of 2,4,4'-trichlorobiphenyl (PCB28), by comparing the zerovalent iron of 20 nm (nZVI20), 100 nm (nZVI100), and 5 μm; iron oxide nanomaterials (α-Fe2O3, γ-Fe2O3, and Fe3O4) of ca. 20 nm; and ferrous and ferric salts. Although all Fe materials (0.1 g L-1) alone could not degrade aqueous PCB28 (0.1 mg L-1) under dark or aerobic conditions, nZVI20, nZVI100, α-Fe2O3, and Fe2+ promoted PCB28 degradation by JD37, with the half-life of PCB28 shortened from 16.5 h by JD37 alone to 8.1 h with nZVI100 cotreatment. Mechanistically, the nanomaterials stimulated JD37 to secrete phenazine-1-carboxylic acid and accelerated the NADH/NAD+ conversion, promoting O2*- generation; JD37 increased Fe(II) dissolution from the nanomaterials, facilitating *OH generation; and the ROS gradually degraded PCB28 into benzoic acid through dihydroxy substitution, oxidation to quinone, and Michael addition. These findings provide a new strategy of nanoenabled biodegradation of organic pollutants by applying Fe-based nanomaterials and PGPR.

Defluorination of fluorophenols by a nonheme iron(IV)-oxo species: observation of a new intermediate along the reaction.

High-valent iron(IV)-oxo intermediates are versatile oxidants in the biotransformation of various substrates by metalloenzymes and catalyze essential reactions for human health but also in the biodegradation of toxic organic pollutants in the environment. Herein, we report a biomimetic system that efficiently reacts with fluorophenols through defluorination reactions and trap and characterize various short-lived intermediates along the reaction mechanism. We present the synthesis and characterization of a nonheme iron(IV)-oxo species and study its reactivity patterns with a series of trihalophenols (X = F, Cl, Br). A combined experimental and computational study reveals that the oxidative dehalogenation of 2,4,6-trifluorophenol is initiated with an H-atom abstraction from the phenolic group by the iron(IV)-oxo species resulting in the formation of a phenolate radical and an iron(III)-hydroxo species. This iron(III)-hydroxo species forms an adduct with the oxidized substrate with lmax at 558 nm which subsequently decays to give quinones as products.

The versatility of <i>Penicillium</i> species to degrade organic pollutants and its use for wastewater treatment

The removal of xenobiotics from industrial wastewater is of great interest to avoid environmental contamination. <italic>Penicillium</italic> species have been shown to be able to adapt its metabolism to many different circumstances and these fungi can use different xenobiotics as a carbon source. In this review, the ability of <italic>Penicillium</italic> to degrade different xenobiotic compounds is discussed. This review describes not only the biodegradation processes but also addresses the toxicity of the degradation products as well as the potential application of these processes in wastewater treatment. <italic>Penicillium</italic> strains have proven to be versatile and capable of being used for the biodegradation of different organic pollutants (phenols, azo dyes, hydrocarbons, pharmaceutical compounds, etc.) and show high potential to be used for wastewater treatment. From this review, it is concluded that beyond the degradation and optimization processes; pilot scale studies and toxicity must be carried out.

Bacterial Laccases as Biocatalysts for the Remediation of Environmental Toxic Pollutants: A Green and Eco-Friendly Approach—A Review

Biological treatment methods for the biodegradation of anthropogenic toxic pollutants are eco-friendly in nature and are powered by a variety of microbial enzymes. Green chemistry and enzymes play a crucial role in catalyzing the biodegradation of organic and inorganic pollutants including azo dyes; polyaromatic hydrocarbons; lead; organic cyanides; aromatic amines; mono-, di-, and polyphenols; polymers; and mercury. Laccases form a prospective group of multifunctional oxidoreductase enzymes with great potential for oxidizing different categories of organic and inorganic pollutants and their diversified functions, such as pigment formation, lignin degradation, and detoxification of industrial wastes including xenobiotics mainly from the pharmaceutical, paper textile, and petrochemical industries. Therefore, it is very important to study laccases as green and environmentally friendly alternatives for the degradation of xenobiotics. This review article will cover comprehensive information about the functions and properties of bacterial laccases for a deep understanding of their scope and applications for effective bioremediation of recalcitrant xenobiotics.

HEAVY METAL ANALYSIS AND ANTIBIOTIC SENSITIVITY OF BACTERIA FROM WASTE DUMPSITES IN BENIN CITY

In this research work, there was analysis of the levels of heavy metals and antibioticsensitivity of bacteria present from waste dumpsites in Benin City, Edo state. Themethodology of this research involved the collection of samples in triplicates from randomdumpsites. The sites were Ekosodin, Oluku and Uselu all within Benin City metropolis. Also,standard pour plating method with dilution to 10-3 was done to isolate organisms present in the soil samples. Analysis of heavy metals level was done using flame Atomic AbsorptionSpectrophotometer. The results showed the concentration of heavy metal in all the samplesbetween 0.463 - 1.392, 0.030 – 0.070, 1.681 - 2.851, 0.685 – 1.386 and 0.342 – 0.422 allin ppm for Lead, Cadmium, Iron, Zinc and Copper respectively. The total heterotrophicbacterial count of all the samples ranged from 1.1×104 cfu/g to 3.4×104cfu/g. The bacterialisolated include Bacillussubtilis, Arthrobacter sp., Pseudomona saeruginosa, Escherichiacoli, and Proteus sp. The isolates exhibited resistance to a wide range of antibiotics namelyTarivid, Gentamycin and Ciprofloxacin, and sensitivity to Amoxicillin, Rocephin, Augmentinand Ampiclox. The organisms with antibiotic and heavy metal resistance isolated andidentified in this study have potential application in bioremediation of environments polluted with metals and may also help to overcome the inhibition that heavy metals exert on the biodegradation of organic pollutants.

Resistance of &lt;i&gt;Rhodococcus ruber&lt;/i&gt; biofilms to CuO nanoparticles depending on exopolymer matrix composition

Background. The widespread use of copper oxide nanoparticles (CuO NPs) increases their release into the environment, which leads to accumulation in trophic chains. Bacterial biofilms are more resistant to physico-chemical factors compared to planktonic cells due to an exopolymer matrix (EPM) consisting of polysaccharides, proteins, lipids and nucleic acids. Rhodococcus actinobacteria are promising for environmental biotechnology due to biodegradation of petroleum products, pesticides and other organic pollutants, as well as bioaccumulation of heavy metals. The aim. To investigate effects of CuO NPs on the viability of Rhodococcus ruber IEGM 231 cells in biofilms and the dynamics of EPM components. Methods. R. ruber biofilms were grown on microscopy cover glass with CuO NPs and EPM components were studied using confocal laser scanning microscopy (CLSM) by differentiating staining with LIVE/DEAD to determine the number of living and dead cells, Nile Red for lipids, FITC for proteins and Calcofluor White for betapolysaccharides. Results. It was found that R. ruber biofilms grown in a mineral medium with1.0 vol.% n-hexadecane are more resistant to CuO NPs compared to biofilms growing in a rich culture medium (meat-peptone broth). This was due to more intensive EPM formation, which plays a major role in protecting cells from the bactericidal action of nanometals. A weak stimulating effect of a low (0.001 g/l) concentration of CuO NPs on biofilm formation was registered. Dynamics and localization of main EPM components were monitored during prolonged (24–72 h) biofilm cultivation with CuO NPs. When exposed to high (0.01–0.1 g/l) concentrations of CuO NPs, a consistently high lipid content and an increase in concentrations of polysaccharides and proteins were revealed. Conclusion. Understanding the complex interaction mechanisms of nanometals and biofilms will contribute to the development of effective biocatalysts based on immobilized bacterial cells. Also, the obtained data can be used to combat unwanted biofilms with the help of metal nanoparticles.

Improving mass transfer rates in microbial cell immobilization system for environmental applications: Synergistic interaction of cells on crude oil biodegradation

Among the various techniques used to clean up polluted environments, bioremediation is the most cost-effective and eco-friendly option. The diversity of microbial communities in a consortium can significantly affect the biodegradability of hazardous organic pollutants, particularly for in situ bioremediation processes. This is largely attributed to interactions between members of a consortium. In this study, the effect of internal diffusion limitations in substrate model biodegradation was firstly examined by immobilized bacterial cells at different particle sizes produced by the electrospray technique. According to the obtained results, for particles with large size, the effectiveness factors (η) were about 0.58–0.67, and the resistance to diffusive on the biodegradation rate was significant, while with decreasing the particle size, η increases and approaches about 1. After selection of suitable bead size, heavy crude oil biodegradation was investigated using a consortium consisting of three oil-degrading bacterial strains at different treatment systems. The removal rate in the suspended co-culture system stands at minimum value of 38% with all three strains which is an indicator of negative interactions among consortium members. Independent immobilization of microorganisms minimizes the competition and antagonistic interactions between strains and leads to more crude oil removal, so that, the biodegradation rate reached 60%.

Bacterial colonization dynamics of different microplastic types in an anoxic salt marsh sediment and impact of adsorbed polychlorinated biphenyls on the plastisphere

Plastic debris dispersed into the environment provide a substrate for microbial colonization, constituting a new human-made ecosystem called “plastisphere”, and altering the microbial species distribution in aquatic, coastal and benthic ecosystems. The study aims at exploring the interaction among microplastics (MPs) made of different polymers, a persistent organic contaminant (polychlorinated biphenyls, PCBs), and the environmental microbial communities, in an anoxic marine sediment. Plastic pellets were incubated in the field in a salt marsh anoxic sediment, to observe the stages of plastisphere formation, by quantitative PCR and 16S rRNA gene sequencing, and PCB dechlorination activity on the MPs surface. Microbes from the sediment rapidly colonized the different microplastics types, with PVC recruiting a peculiar community enriched in sulfate-reducing bacteria. The composition of the plastisphere varied along the 1-year incubation possibly in response either to warmer temperatures in spring-summer or to microhabitat's changes due to the progressive plastic surface weathering. Even if PCB contaminated MPs were able to recruit potentially dehalogenating taxa, actual dechlorination was not detectable after 1 year. This suggests that the concentration of potentially dehalorespiring bacteria in the natural environment could be too low for the onset of the dechlorination process on MP-sorbed contaminants. Our study, which is among very few available longitudinally exploring the plastisphere composition in an anoxic sediment context, is the first exploring the fate and possible biodegradation of persistent organic pollutants sorbed on MPs reaching the seafloor.

Organic Pollutant Biodegradation by an Immobilized Mixed Bacterial Culture

Pollution of organic compounds in rivers is generally contributed by wastewater discharge from human activities e.g. untreated black- &amp; greywater, livestock farming, and industry. Without proper control of this waste generation, the river ecosystem will suffer if just rely on its self-purification and dilution by natural runoff to reduce the downstream effect. This research aimed to treat organic wastewater with an immobilized mixed bacterial culture. Immobilization was carried out using calcium alginate in a form of macrocapsule/beads, allowing the degrader microbe to be entrapped in its matrix thus preventing it from washout from the system. 3% (w/v) sodium alginate was mixed with 5 mg (dry) mixed culture and dropwise on 4% (w/v) calcium chloride solution. The results showed that immobilized microbes were still able to grow despite being entangled in a calcium alginate matrix with an initial growth of 6.1 x 105 to 7.4 x 107 colonies/grams and reduced COD content up to 68.3%. Degrader microbe immobilization offers considerable advantages compared to free/ suspended cell system due to the influence of river water flow.

Functional bacterial consortium responses to biochar and implications for BDE-47 transformation: Performance, metabolism, community assembly and microbial interaction

The influence of biochar on the biodegradation of persistent organic pollutants (POPs) has been extensively studied. However, the underlying mechanisms behind the response of functional microbial consortia to biochar remain poorly understood. Herein, we systematically explored the effect of biochar on 2,2′,4,4′-tetrabrominated ether (BDE-47) biodegradation, and investigated the interaction and assembly mechanism of the functional bacterial consortium QY2. The results revealed that the biodegradation efficiency of QY2 for BDE-47 increased from 53.85% to 94.11% after the addition of biochar. Fluorescence excitation-emission matrix and electrochemical analysis showed that biochar-attached biofilms were rich in redox-active extracellular polymeric substances (EPS, 3.03-fold higher than free cell), whose strong interaction with biochar facilitated the electron transfer of the biofilm, thus enhancing the debromination degradation of BDE-47. Meanwhile, the assembly model and molecular ecological networks analysis indicated that bacterial community assembly in biofilms was more driven by deterministic processes (environmental selection >75.00%) upon biochar stimulation and exhibited closer interspecific cooperative interactions, leading to higher biodiversity and broader habitat niche breadth for QY2 in response to BDE-47 disturbance. Potential degraders (Methylobacterium, Sphingomonas, Microbacterium) and electrochemical bacteria (Ochrobactrum) were selectively enriched, whose role as keystone bacteria may be participated in biofilm formation and redox-active EPS secretion (r > 0.5, P < 0.05). These findings deepen the understanding of the mechanisms by which biochar promotes microbial degradation of PBDEs and provided a theoretical basis for better regulation of functional bacterial communities during environmental remediation.

Efficient biodegradation of straw and persistent organic pollutants by a novel strategy using recombinant Trichoderma reesei

Efficient biodegradation of lignocellulosic biomass needs a battery of enzymes targeting cellulose, hemicellulose, and lignin. In this study, recombinant Trichoderma reesei ZJ-09 with Pycnoporus sanguineus laccase gene was used to degrade rice straw by in situ production of laccase, xylanase, and cellulases under solid-state fermentation (SSF). Effects of parameters on key enzymes (cellulase, xylanase, and laccase) in biodegradation during SSF were investigated. Under the optimized SSF conditions, the FPA, xylanase activity, and laccase activity reached 110.47 FPU/g, 5787.59 IU/g, and 24.45 IU/g, respectively, on day 12. The obtained recombinant T. reesei SSF system achieved efficient degradation of rice straw with the final mass loss up to 51.16% which was 1.4-fold higher than the host strain. Further, bioconversion of rice straw into a novel laccase-enriched koji for persistent organic pollutants bioremediation (LKPB) was conducted by the optimized SSF system. LKPB was found to degrade persistent organic pollutants (POPs) effectively without the addition of mediators. 4-h removal rates of three POPs mediated by LKPB (87.21% for 2,4,5-trichlorophenol, 92.45% for nonylphenol, and 90.73% for oxytetracycline) were comparable to those achieved by laccase-co-mediator system. The newly established recombinant T. reesei SSF system could be potential to effectively degrade lignocellulosic wastes as well as organic pollutants.Graphical abstract