Biodegradation最新文献

The microbial fuel cell (MFC) is considered a modern technology used for treating wastewater and recovering electrical energy. In this study, a new dual technology combining MFC and a specialized biofilter was used. The anodic materials in the system were crushed graphite, either without coating (UFB-MFC) or coated with nanomaterials (nano-UFB-MFC). This biofilter served as a barrier to retain and remove turbidity and suspended solids, while also facilitating the role of bacteria in the removal of organic pollutants, phosphates, nitrates, sulfates, oil and greases. The results demonstrated that both systems exhibited high efficiency in treating kitchen wastewater, specifically greywater and dishwashing wastewater with high detergent concentrations. The removal efficiencies of COD, oil and grease, suspended solids, turbidity, nitrates, sulfates, and phosphates in first UFB-MFC were found to be 88, 95, 89, 86, 87, 75, and 94%, respectively, and in Nano-UFB-MFC were 86, 99, 95, 91, 81, 88, and 95%, respectively, with a high efficiency in recovering bioenergy reaching a value of 1.8 and 1.5 A m^-3, respectively. The results of this study demonstrate the potential for developing MFC and utilizing it as a domestic system to mitigate pollution risks before discharging wastewater into the sewer network.

A novel coupling process to replace the traditional multi-stage anammox process-sulfur autotrophic denitrification (SAD) coupled anaerobic ammonium oxidation (anammox) system was designed, which solved problems of nitrate produced in anammox process and low nitrate conversion rate caused by nitrite accumulation in SAD process. Different filter structures (SAD filter and anammox granular sludge) were investigated to further explore the excellent performance of the novel integrated reactor. The results of sequential batch experiments indicated that nitrite accumulation occurred during SAD, which inhibited the conversion of nitrate to dinitrogen gas. When SAD filter and anammox granular sludge were added to packed bed reactor simultaneously, the nitrate removal rate increased by 37.21% and effluent nitrite concentration decreased by 100% compared to that achieved using SAD. The stratified filter structure solved groove flow. Different proportion influence of SAD filter and anammox granular sludge on the stratified filter structure was evaluated. More suitable ratio of SAD filter to anammox granular sludge was 2:1. Proteobacteria (57.26%), Bacteroidetes (20.12%) and Chloroflexi (9.95%) were the main phyla. The dominant genera of denitrification functional bacteria were Thiobacillus (39.80%), Chlorobaculum (3.99%), norank_f_PHOs-HE36 (2.90%) and Ignavibacterium (2.64%). The dominant genus of anammox bacterium was Candidatus_Kuenenia (3.05%).

The persistence and ubiquity of polycyclic aromatic hydrocarbons (PAHs) in the environment necessitate effective remediation strategies. Hence, this study investigated the potential of purified Laccases, TlFLU1L and TpFLU12L, from two indigenous fungi Trichoderma lixii FLU1 (TlFLU1) and Talaromyces pinophilus FLU12 (TpFLU12), respectively for the oxidation and detoxification of anthracene. Anthracene was degraded with v_max values of 3.51 ± 0.06 mg/L/h and 3.44 ± 0.06 mg/L/h, and K_m values of 173.2 ± 0.06 mg/L and 73.3 ± 0.07 mg/L by TlFLU1L and TpFLU12L, respectively. The addition of a mediator compound 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to the reaction system significantly increased the degradation of anthracene, with up to a 2.9-fold increase in v_max value and up to threefold decrease in K_m values of TlFLU1L and TpFLU12L. The GC-MS analysis of the metabolites suggests that anthracene degradation follows one new pathway unique to the ABTS system-hydroxylation and carboxylation of C-1 and C-2 position of anthracene to form 3-hydroxy-2-naphthoic acid, before undergoing dioxygenation and side chain removal to form chromone which was later converted into benzoic acid and CO₂. This pathway contrasts with the common dioxygenation route observed in the free Laccase system, which is observed in the second degradation pathways. Furthermore, toxicity tests using V. parahaemolyticus and HT-22 cells, respectively, demonstrated the non-toxic nature of Laccase-ABTS-mediated metabolites. Intriguingly, analysis of the expression level of Alzheimer's related genes in HT-22 cells exposed to degradation products revealed no induction of neurotoxicity unlike untreated cells. These findings propose a paradigm shift for bioremediation by highlighting the Laccase-ABTS system as a promising green technology due to its efficiency with the discovery of a potentially less harmful degradation pathway, and the production of non-toxic metabolites.

The anthropogenic activities toward meeting the energy requirements have resulted in an alarming rise in environmental pollution levels. Among pollutants, polycyclic aromatic hydrocarbons (PAHs) are the most predominant due to their persistent and toxic nature. Amidst the several pollutants depuration methods, bioremediation utilizing biodegradation is the most viable alternative. This study investigated the biodegradation efficacy using developed microbial consortium PBR-21 for 2-4 ringed PAHs named naphthalene (NAP), anthracene (ANT), fluorene (FLU), and pyrene (PYR). The removal efficiency was observed up to 100 ± 0.0%, 70.26 ± 4.2%, 64.23 ± 2.3%, and 61.50 ± 2.6%, respectively, for initial concentrations of 400 mg L^-1 for NAP, ANT, FLU, and PYR respectively. Degradation followed first-order kinetics with rate constants of 0.39 d^-1, 0.10 d^-1, 0.08 d^-1, and 0.07 d^-1 and half-life $\left(t_{1/2}\right)$  of 1.8 h, 7.2 h, 8.5 h, and 10 h, respectively. The microbial consortia were found to be efficient towards the co-contaminants with 1 mM concentration. Toxicity examination indicated that microbial-treated PAHs resulted in lesser toxicity in aquatic crustaceans (Artemia salina) than untreated PAHs. Also, the study suggests that indigenous microbial consortia PBR-21 has the potential to be used in the bioremediation of PAH-contaminated environment.

Groundwater is the most important source for drinking water in The Netherlands. Groundwater quality is threatened by the presence of pesticides, and biodegradation is a natural process that can contribute to pesticide removal. Groundwater conditions are oligotrophic and thus biodegradation can be limited by the presence and development of microbial communities capable of biodegrading pesticides. For that reason, bioremediation technologies such as bioaugmentation (BA) can help to enhance pesticide biodegradation. We studied the effect of BA using enriched mixed inocula in two column bioreactors that simulate groundwater systems at naturally occurring redox conditions (iron and sulfate-reducing conditions). Columns were operated for around 800 days, and two BA inoculations (BA1 and BA2) were conducted in each column. Inocula were enriched from different wastewater treatment plants (WWTPs) under different redox-conditions. We observed a temporary effect of BA1, reaching 100% removal efficiency of the pesticide 2,4-D after 100 days in both columns. In the iron-reducing column, 2,4-D removal was in general higher than under sulfate-reducing conditions demonstrating the influence of redox conditions on overall biodegradation. We observed a temporary shift in microbial communities after BA1 that is relatable to the increase in 2,4-D removal efficiency. After BA2 under sulfate-reducing conditions, 2,4-D removal efficiency decreased, but no change in the column microbial communities was observed. The present study demonstrates that BA with a mixed inoculum can be a valuable technique for improving biodegradation in anoxic groundwater systems at different redox-conditions.

Heavy metals can severely influence the mineralisation of organic pollutants in a compound-polluted environment. However, to date, no study has focused on the effects of heavy metals on the active organic pollutant-degrading microbial communities to understand the bioremediation mechanism. In this study, toluene was used as the model organic pollutant to explore the effects of soils with different levels of heavy metal pollution on organic contaminant degradation in the same area via stable isotope probing (SIP) and 16 S rRNA high-throughput sequencing. Heavy metals can seriously affect toluene biodegradation and regulate the abundance and diversity of microbial communities. SIP revealed a drastic difference in the community structure of active toluene degraders between the unpolluted and heavy metal-polluted soils. All SIP-identified degraders were assigned to nine bacterial classes, among which Alphaproteobacteria, Gammaproteobacteria, and Bacilli were shared by both treatments. Among all active degraders, Nitrospira, Nocardioides, Conexibacteraceae, and Singulisphaera were linked to toluene biodegradation for the first time. Notably, the type of active degrader and microbial diversity were strongly related to biodegradation efficiency, indicating their key role in toluene biodegradation. Overall, heavy metals can affect the microbial diversity and alter the functional microbial communities in soil, thereby influencing the removal efficiency of organic contaminants. Our findings provide novel insights into the biodegradation mechanism of organic pollutants in heavy metal-polluted soils and highlight the biodiversity of microbes involved in toluene biodegradation in compound-polluted environments.

In this article, the degradability by Aspergillus niger and Aspergillus clavatus of three bio-based polyurethane (PU) foams is compared to previous degradability studies involving a Pseudomonas sp. bacterium and similar initial materials (Spontón et al. in Int. Biodet. Biodeg. 85:85-94, 2013, https://doi.org/10.1016/j.ibiod.2013.05.019 ). First, three new polyester-polyurethane foams were prepared from mixtures of castor oil (CO), maleated castor oil (MACO), toluene diisocyanate (TDI), and water. Then, their degradation tests were carried out in an aqueous medium, and employing the two mentioned fungi, after their isolation from the environment. From the degradation tests, the following was observed: (a) the insoluble (and slightly collapsed) foams exhibited free hydroxyl, carboxyl, and amine moieties; and (b) the water soluble (and low molar mass) compounds contained amines, carboxylic acids, and glycerol. The most degraded foam contained the highest amount of MACO, and therefore the highest concentration of hydrolytic bonds. A basic biodegradation mechanism was proposed that involves hydrolysis and oxidation reactions.

Landfill leachate raises a huge risk to human health and the environment as it contains a high concentration of organic and inorganic contaminants, heavy metals, ammonia, and refractory substances. Among leachate treatment techniques, the biological methods are more environmentally benign and less expensive than the physical-chemical treatment methods. Over the last few years, fungal-based treatment processes have become popular due to their ability to produce powerful oxidative enzymes like peroxidases and laccases. Fungi have shown better removal efficiency in terms of color, ammonia, and COD. However, their use in the treatment of leachate is relatively recent and still needs to be investigated. This review article assesses the potential of fungi and fungal-derived enzymes in treating landfill leachate. The review also compares different enzymes involved in the fungal catabolism of organic pollutants and the enzyme degradation mechanisms. The effect of parameters like pH, temperature, contact time, dosage variation, heavy metals and ammonia are discussed. The paper also explores the reactor configuration used in the fungal treatment and the techniques used to improve leachate treatment efficacy, like pretreatment and fungi immobilisation. Finally, the review summarises the limitations and the future direction of work required to adapt the fungal application for leachate treatment on a large scale.

To date, enumerable fungi have been reported to participate in the biodegradation of several notorious plastic materials following their isolation from soil of plastic-dumping sites, marine water, waste of mulch films, landfills, plant parts and gut of wax moth. The general mechanism begins with formation of hydrophobin and biofilm proceding to secretion of specific plastic degarding enzymes (peroxidase, hydrolase, protease and urease), penetration of three dimensional substrates and mineralization of plastic polymers into harmless products. As a result, several synthetic polymers including polyethylene, polystyrene, polypropylene, polyvinyl chloride, polyurethane and/or bio-degradable plastics have been validated to deteriorate within months through the action of a wide variety of fungal strains predominantly Ascomycota (Alternaria, Aspergillus, Cladosporium, Fusarium, Penicillium spp.). Understanding the potential and mode of operation of these organisms is thus of prime importance inspiring us to furnish an up to date view on all the presently known fungal strains claimed to mitigate the plastic waste problem. Future research henceforth needs to be directed towards metagenomic approach to distinguish polymer degrading microbial diversity followed by bio-augmentation to build fascinating future of waste disposal.

Landfills are widely employed as the primary means of solid waste disposal. However, this practice generates landfill gas (LFG) which contains methane (CH₄), a potent greenhouse gas, as well as various volatile organic compounds and volatile inorganic compounds. These emissions from landfills contribute to approximately 25% of the total atmospheric CH₄, indicating the imperative need to valorize or treat LFG prior to its release into the atmosphere. This review first aims to outline landfills, waste disposal and valorization, conventional gas treatment techniques commonly employed for LFG treatment, such as flares and thermal oxidation. Furthermore, it explores biotechnological approaches as more technically and economically feasible alternatives for mitigating LFG emissions, especially in the case of small and aged landfills where CH₄ concentrations are often below 3% v/v. Finally, this review highlights biofilters as the most suitable biotechnological solution for LFG treatment and discusses several advantages and challenges associated with their implementation in the landfill environment.