Degradation Of Toxic Compounds Research Articles

Effects of biochar, granular activated carbon, and magnetite on the electron transfer of microbials during the anaerobic digestion process: Insights into nitrogen heterocyclic compounds degradation

Anaerobic digestion (AD) of the hydrothermal liquefaction aqueous phase is often inhibited by high levels of nitrogen heterocyclics, which hinder its valorization. Despite the potential benefits of conductive materials in promoting the degradation of toxic compounds through the establishment of direct interspecies electron transfer (DIET), there is still a gap in the understanding of their role and related mechanisms in nitrogen heterocyclic degradation. In this study, the AD process was improved by the addition of conductive materials. Subsequently, the cumulative methane production increased by 7.2% (with biochar), 15.4% (with granular activated carbon), and 24.3% (with magnetite). Besides, The addition of conductive materials significantly improved the complexity and stability of the microbial communities, especially the DIET potential microorganisms—Methanosaetaceae and Syntrophobacteraceae, Anaerolineaceae, Clostridiaceae, Geobacteraceae, Desulfovibrionaceae. Thermodynamic analysis and pyridine degradation pathways further supported enhanced pyridine degradation via the addition of conductive materials.

Hydrodynamics and Energy Analysis in Suspended Catalyst Photocatalytic Membrane Reactors

Photocatalysis is a non-selective advanced oxidation process (AOP) that can be effective for degradation of toxic compounds. Its main drawback however has been high processing costs compared to other AOPs. Suspended catalyst photocatalytic membrane reactors (SPMR) are promising design configuration for implementation of the technology. This work involves experimental and theoretically analysis of the hydrodynamics and energy consumption in a SPMR under crossflow and oscillatory shear conditions. An optimization approach is presented for intensification of the reactor performance that considers the coupling effects of the applied shear and the transmembrane pressure on the hydrodynamics and the specific energy consumption (kWh/m3). The results showed that the optimum shear rate decreases with increasing the membrane area due to the relatively high contribution of the permeate pumping power to the energy consumption which makes the advantages of operating at higher shear rate relevant. This trend changes for larger membranes areas where the energy consumption due to higher shear outweighs the advantage of its performance enhancement resulting in increasing the system specific energy consumption. In general, the latter was found to be higher for a crossflow system compared to an oscillatory membrane design, which in addition to its smaller footprints, can make such design an attractive option for confined and/or limited space applications.

Biomedical,clinical and environmental applications of platinum-based nanohybrids: An updated review

Platinum nanoparticles (Pt NPs) have numerous applications in various sectors, including pharmacology, nanomedicine, cancer therapy, radiotherapy, biotechnology and environment mitigation like removal of toxic metals from wastewater, photocatalytic degradation of toxic compounds, adsorption, and water splitting. The multifaceted applications of Pt NPs because of their ultra-fine structures, large surface area, tuned porosity, coordination-binding, and excellent physiochemical properties. The various types of nanohybrids (NHs) of Pt NPs can be fabricated by doping with different metal/metal oxide/polymer-based materials. There are several methods to synthesize platinum-based NHs, but biological processes are admirable because of green, economical, sustainable, and non-toxic. Due to the robust physicochemical and biological characteristics of platinum NPs, they are widely employed as nanocatalyst, antioxidant, antipathogenic, and anticancer agents. Indeed, Pt-based NHs are the subject of keen interest and substantial research area for biomedical and clinical applications. Hence, this review systematically studies antimicrobial, biological, and environmental applications of platinum and platinum-based NHs, predominantly for treating cancer and photo-thermal therapy. Applications of Pt NPs in nanomedicine and nano-diagnosis are also highlighted. Pt NPs-related nanotoxicity and the potential and opportunity for future nano-therapeutics based on Pt NPs are also discussed.

Structure of the river sediment microbiomes impacted by anthropogenic land uses, environmental and spatial variations

River sediments are impacted by anthropogenic land uses since they are the major sinks of pollutants. Sediment microbial communities play vital roles in the degradation of toxic compounds and the recycling of nutrients, sustaining healthy aquatic ecosystems. However, sediment microbiomes impacted by both anthropogenic and natural disturbances are not well documented. This study investigated the dynamics of sediment microbiomes in response to major anthropogenic land uses, environmental, and spatial factors across 25 locations along the Ganh Hao river in Vietnam, using high-throughput sequencing targeting the V3–V4 regions of the 16S rRNA gene. The sediment microbiomes were exclusively dominated by Proteobacteria (59–79%). Microbial taxa associated with shrimp farms, a major land use, were koll13, GCA004, Piscirickettsiaceae, Marinicellaceae, and Desulfobulbaceae. The resulting variation partitioning, based on CCA, indicated that spatial factors highly influenced the microbial profile and explained 41.8% of the microbial variation. However, the variation in sediment microbiomes was largely impacted by a combination of environmental factors (i.e., As, Pb and Cu concentrations, pH and EC) and the presence of shrimp farms which, together with spatial variation, explained 77.4% of the microbial variation. Overall, this study provides insights into the spatial structure of river sediment microbiomes and provides the biological signature of sediment microbiome in response to the major anthropogenic land use and seawater intrusion.

Combined effects of direct plasma exposure and pre-plasma functionalized metal-doped graphene oxide nanoparticles on wastewater dye degradation

The current study investigates the combinatorial effect of the photocatalytic performance of plasma pre-treated Ti-Cu-Zn doped graphene oxide (TCZ-GO) nanoparticles (NPs) and advanced oxidation processes of a non-thermal atmospheric pressure plasma on the degradation of reactive orange-122 (RO-122) dye compounds. Firstly, in order to enhance the photocatalytic performance of the synthesized composite NPs, they were subjected to glow discharge plasma treatments operating in different gases (Ar, air, O2 and N2). Their surface morphology, chemical composition and band gap were examined by means of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–Vis spectrophotometry respectively. XPS results revealed that plasma-treated NPs exhibited a higher content of oxygen vacancies and a variation in their oxidation states (Ti4+ → Ti3+, Cu+ → Cu2+). These plasma-induced surface chemical changes hindered the recombination of photo-generated electron-hole pairs which led to a drop in the bandgap of the NPs with N2 plasma-treated NPs acquiring the lowest bandgap. Lastly, the article examined the actual decomposition of RO-122 dye in wastewater by an Ar plasma treatment alone or combined with the plasma-treated TCZ-GO NPs via spectrophotometric analyses, electrical conductivity, pH and total organic carbon (TOC) removal measurements. Moreover, the reactive species produced during the combined plasma/photocatalysis induced degradation were detected in situ by optical emission spectroscopy. Results revealed that the processes carried out by combining N2 plasma-treated TCZ-GO NPs and Ar plasma exhibited the highest degradation efficiency (85 %) due to the generation of more OH and H2O2. Overall, it can be concluded that plasma-aided treatment processes used synergistically as indirect surface functionalization of TCZ-GO NPs and direct plasma treatment of wastewater are extremely efficient in the degradation of toxic compounds and can be extrapolated to various environmental applications.

Direct and efficient elimination of ethyl carbamate by engineered Saccharomyces cerevisiae displaying urethanase

Ethyl carbamate (EC) is a probable human carcinogen (Group 2A) that is naturally formed in fermented foods and alcoholic beverages. In this study, the feasibility of using engineered Saccharomyces cerevisiae strains capable of eliminating EC regardless of its pathway of formation was explored. The gene coding for urethanase (UreA) from Micrococcus species, which can directly convert EC into ethanol and ammonia, was introduced into S. cerevisiae . While the S. cerevisiae strain expressing intracellular UreA degraded only 44.5 mg/L EC, the engineered strain expressing extracellular UreA (MFα SP -UreA) exhibited a much-elevated degradation (341 mg/L) after 84 h. The EC degradation activity of S. cerevisiae was further enhanced by displaying UreA on the yeast cell surface. Specifically, the S. cerevisiae strain displaying UreA (EBY100/Aga2-UreA) using a-agglutinin as an anchoring motif degraded 476 mg/L EC, which was 31% higher than that of the strain expressing MFα SP -UreA. In a bioreactor fermentation batch at pH 5.0 (the optimal pH for UreA activity), the EBY100/pAga2-UreA strain degraded 519 mg/L EC in 84 h. Therefore, this study highlights the benefits of surface display of enzymes to enhance the degradation of toxic compounds by engineered strains of S. cerevisiae . • Ethyl carbamate (EC) is a probable human carcinogen. • The gene coding for urethanase (UreA) was introduced into Saccharomyces cerevisiae. • The EC degradation activity of S. cerevisiae was enhanced by displaying UreA. • A bioreactor fermentation at pH 5.0 resulted in 519 mg/L EC degradation in 84 h.

Influence of water matrix components and peroxide sources on the transformation products and toxicity of tebuthiuron under UVC-based advanced oxidation processes

Coupling of UV-C irradiation to different peroxides (H2O2, S2O82− and HSO5−) has great potential to degrade persistent organic compounds due to the formation of HO• or SO4•– species. However, an in-depth comparison between the performance of different UV-C/peroxide processes as a function of (i) target compound degradation, (ii) generated transformation products and (iii) lethal/sub lethal toxicity effects has not yet been performed. To this end a comparison study was carried out to evaluate the effectiveness of different UV-C/peroxide processes using the herbicide tebuthiuron (100 or 500 μg L−1) as a model pollutant. TBH degradation experiments were performed at lab-scale in real municipal wastewater treatment plant effluent and distilled water. Faster degradation occurred by increasing peroxide concentration from 735 to 2206 μmol L−1 in the municipal wastewater treatment plant effluent, mainly for S2O82−. Experiments performed in the presence of peroxide trapping agents – HO• and SO4•– (methoxibenzene) or HO• (2-propanol) – revealed that oxidation in the UV-C/S2O82− system occurs mainly through SO4•–. Lower toxicity for the MWWTP effluent was obtained after oxidative treatments using hydrogen peroxide or monopersulfate as oxidants which react mainly through HO• radicals. Two mechanistic pathways were proposed for tebuthiuron degradation: (i) hydrogen abstraction by HO• (H2O2 and HSO5−) and (ii) electron transfer by SO4•– (S2O82−). In addition, one unprecedented transformation product was identified. In conclusion, results emphasize the relevance of comparing the degradation of toxic compounds in the presence of different peroxide sources and matrices and simultaneouly evaluating responses chemical and biological endpoints.

Effect of tetracycline on bio-electrochemically assisted anaerobic methanogenic systems: Process performance, microbial community structure, and functional genes.

Bio-electrochemically assisted anaerobic methanogenic systems (An-BES) are highly effective in wastewater treatment for methane production and degradation of toxic compounds. However, information on the treatment of antibiotic-bearing wastewater in An-BES is still very limited. This study therefore investigated the effect of tetracycline (TC) on the performance, microbial community, as well as functional and antibiotic resistance genes of An-BES. TC at 1 and 5 mg/L inhibited methane production by less than 4.8% compared to the TC-free control. At 10 mg/L TC, application of 0.5 and 1.0 V decreased methane production by 14 and 9.6%, respectively. Under the effect of 1-10 mg/L TC, application of 1.0 V resulted in a decrease of current from 42.3 to 2.8 mA. TC was mainly removed by adsorption; its removal extent increased by 19.5 and 32.9% with application of 0.5 and 1.0 V, respectively. At 1.0 V, current output was not recovered with the addition of granular activated carbon, which completely removed TC by adsorption. Metagenomic analysis showed that propionate oxidizing bacteria and methanogens were more abundant in electrode biofilms than in suspended culture. Antibiotic resistance genes (ARGs) were less abundant in biofilms than in suspended culture, regardless of whether voltage was applied or not. Application of 1.0 V resulted in the enrichment of Geobacter in the anode and Methanobacterium in the cathode. TC inhibited exoelectrogens, propionate oxidizing bacteria, and the methylmalonyl CoA pathway, leading to a decrease of current output, COD consumption, and methane production. These findings deepen our understanding of the inhibitory effect of TC in An-BES towards efficient bioenergy recovery from antibiotic-bearing wastewater, as well as the response of functional microorganisms to TC in such systems.

Production performance of nursery graded eel Anguilla bicolor bicolor in recirculating aquaculture system

The growth rate highly varies in nurseries of eel. Variations in size lead to competition in obtaining feed, this causes stunting of smaller fish. This situation leads to high production costs due to poor feed utilization efficiency. Grading needs to be done periodically to improve nursery production performance. Water quality is controlled by a recirculation system that can support production performance through the degradation of toxic compounds. This study aims to analyze the production and nursery performance of graded eel (Anguilla bicolor bicolor) that graded in the same batch in a recirculation system. Completely randomized design (CRD) consisting of three treatments with four replications was used in this research. The treatments included nursery of graded eels for 60 days in three groups of initial weight size, namely 0,35±0,00 g (A); 0,50±0,00 g (B); and 1,04±0,00 g (C). There were 344 eels (A), 239 eels (B), and 116 eels (C) in each replication. The best nursery production performance was obtained in the treatment of 1,04±0,00 g, and the best nursery business performance was obtained in the treatment of 0,50±0,00 g.

Genomic analysis provides novel insights into diversification and taxonomy of Allorhizobium vitis (i.e. Agrobacterium vitis)

BackgroundAllorhizobium vitis (formerly named Agrobacterium vitis or Agrobacterium biovar 3) is the primary causative agent of crown gall disease of grapevine worldwide. We obtained and analyzed whole-genome sequences of diverse All. vitis strains to get insights into their diversification and taxonomy.ResultsPairwise genome comparisons and phylogenomic analysis of various All. vitis strains clearly indicated that All. vitis is not a single species, but represents a species complex composed of several genomic species. Thus, we emended the description of All. vitis, which now refers to a restricted group of strains within the All. vitis species complex (i.e. All. vitis sensu stricto) and proposed a description of a novel species, All. ampelinum sp. nov. The type strain of All. vitis sensu stricto remains the current type strain of All. vitis, K309T. The type strain of All. ampelinum sp. nov. is S4T. We also identified sets of gene clusters specific to the All. vitis species complex, All. vitis sensu stricto and All. ampelinum, respectively, for which we predicted the biological function and infer the role in ecological diversification of these clades, including some we could experimentally validate. All. vitis species complex-specific genes confer tolerance to different stresses, including exposure to aromatic compounds. Similarly, All. vitis sensu stricto-specific genes confer the ability to degrade 4-hydroxyphenylacetate and a putative compound related to gentisic acid. All. ampelinum-specific genes have putative functions related to polyamine metabolism and nickel assimilation. Congruently with the genome-based classification, All. vitis sensu stricto and All. ampelinum were clearly delineated by MALDI-TOF MS analysis. Moreover, our genome-based analysis indicated that Allorhizobium is clearly separated from other genera of the family Rhizobiaceae.ConclusionsComparative genomics and phylogenomic analysis provided novel insights into the diversification and taxonomy of Allorhizobium vitis species complex, supporting our redefinition of All. vitis sensu stricto and description of All. ampelinum. Our pan-genome analyses suggest that these species have differentiated ecologies, each relying on specialized nutrient consumption or toxic compound degradation to adapt to their respective niche.

Utilization of natural polysaccharide from Tamarindus indica L. seeds for the effective reduction of pollutants in cheese processed wastewater

The present study was targeted to treat the cheese factory processed wastewater by using natural coagulants. The results were compared with the CPCB wastewater discharge limit and most of the parameters were exceeded the standard limit. In the present investigation, the processed wastewater was subjected to treatment with Tamarindus indica L. plant seed as a coagulating agent. The processed wastewater was treated with Tamarindus indica L. seed powder which is rich in polysaccharides. The proximate analysis confirmed the presence of higher content of carbohydrates, protein, and fiber. Different dosages were used for the treatment. Accurately 0.4 gm was recorded as optimum dosage for the effective removal of pollutants includes 71% of TDS and 75% of COD from the cheese processed wastewater. The GC-MS analysis of raw and treated cheese processed wastewater was carried out and the results showed the degradation of toxic compounds and reduction of pollutants from the processed wastewater. FTIR analysis of T.indica L. seed powder disclosed various chemical group presence and proved higher efficiency in seed treatment.

Biodegradation Pathway and Detoxification of β-cyfluthrin by the Bacterial Consortium and Its Bacterial Community Structure.

In the process of microbial degradation of pyrethroid pesticides, the synergistic effect of the microbial community is more conducive to the complete degradation of toxic compounds than a single strain. At present, the degradation pathway of pyrethroids in a single strain has been well revealed, but the synergistic metabolism at the community level has not been well explained. This study elucidated the bacterial community succession, metabolic pathway, and phytotoxicity assessment during β-cyfluthrin biodegradation by a novel bacterial consortium enriched from contaminated soil. The results showed that the half-life of β-cyfluthrin at different initial concentrations of 0.25, 0.5, 0.75, and 1.0 mg mL-1 were 4.16, 7.34, 12.81, and 22.73 days, respectively. Enterobacter was involved in β-cyfluthrin degradation metabolism in the initial stage, and other bacterial genera (Microbacterium, Ochrobactrum, Pseudomonas, Hyphomicrobiaceae, Achromobacter, etc.) significantly contribute to the degradation of intermediate metabolites in the later stages. Functional gene prediction and metabolite analysis showed that xenobiotic biodegradation and metabolism, especially benzoate degradation and metabolism by cytochrome P450 were the major means of β-cyfluthrin degradation. Further, two degradation pathways of β-cyfluthrin were proposed, which were mainly ester hydrolysis and oxidation to degrade β-cyfluthrin through the production of carboxylesterase and oxidoreductase. In addition, the inoculated bacterial consortium could degrade β-cyfluthrin residues in water and soil and reduce its phytotoxicity in Medicago sativa. Hence, this novel bacterial consortium has important application in the remediation environments polluted by β-cyfluthrin.

Combinatorial effects of non-thermal plasma oxidation processes and photocatalytic activity on the inactivation of bacteria and degradation of toxic compounds in wastewater.

The simultaneous presence of hazardous chemicals and pathogenic microorganisms in wastewater is tremendously endangering the environment and human health. Therefore, developing a mitigation strategy for adequately degrading toxic compounds and inactivating/killing microorganisms is urgently needed to protect ecosystems. In this paper, the synergetic effects of the photocatalytic activity of TiO2 and Cu–TiO2 nanoparticles (NPs) and the oxidation processes of non-thermal atmospheric pressure plasma (NTAPP) were comprehensively investigated for both the inactivation/killing of common water contaminating bacteria (Escherichia coli (E. coli)) and the degradation of direct textile wastewater (DTW). The photocatalytic NPs were synthesized using the hydrothermal method and further characterized employing field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV-Vis DRS) and photoluminescence (PL). Results revealed the predominant presence of the typical anatase phase for both the flower-like TiO2 and the multipod-like Cu–TiO2 structures. UV-Vis DRS and PL analyses showed that the addition of Cu dopants reduced the bandgap and increased oxygen defect vacancies of TiO2. The inactivation of E. coli in suspension and degradation of DTW were then examined upon treating the aqueous media with various plasma alone and plasma/NPs conditions (Ar plasma, Ar + O2 plasma and Ar + N2 plasma, Ar plasma + TiO2 NPs and Ar plasma + Cu–TiO2 NPs). Primary and secondary excited species such as OH˙, O, H and N2* generated in plasma during the processes were recognized by in situ optical emission spectrometry (OES) measurements. Several other spectroscopic analyses were further employed to quantify some reactive oxygen species (ROS) such as OH, H2O2 and O3 generated during the processes. Moreover, the changes in the pH and electrical conductivity (EC) of the solutions were also assessed. The inactivation of bacteria was examined by the colony-forming unit (CFU) method after plating the treated suspensions on agar, and the degradation of organic compounds in DTW was further validated by measuring the total organic carbon (TOC) removal efficiency. All results collectively revealed that the combinatorial plasma-photocatalysis strategy involving Cu–TiO2 NPs and argon plasma jet produced higher concentrations of ROS and proved to be a promising one-step wastewater treatment effectively killing microorganisms and degrading toxic organic compounds.

Enhancing 2,6-dichlorophenol degradation and nitrate removal in the nano-zero-valent iron (nZVI) solid-phase denitrification system

Nano-zero-valent iron (nZVI), as a typical nano-material, has been recently used in wastewater treatment and combination with bioreactors. Using nZVI coupled denitrification system research the effect and influence of nZVI enhanced denitrification sludge on the degradation of toxic compounds and system performance. The nZVI coupled denitrification system showed better resistance to 2,6-DCP impact, and the concentrations of effluent NO2− and NO3− were below 2.0 mg/L. At the same time, the addition of nZVI enabled the denitrification system to quickly adapt to the toxic environment of 2,6-DCP within 15 days, and the degradation efficiency of 2,6-DCP reached 99.9%. The released SMP reduced after nZVI coupled with denitrification sludge in 2,6-DCP environment, which could improve the effluent water quality. Nuclear magnetic resonance spectroscopy showed that the addition of nZVI would change the structure of EPS in denitrification sludge. After 90 days of operation, the dominant bacteria in the denitrifying sludge have undergone great changes. Moreover, Thauera was responsible as the dominant bacteria for degrading 2,6-DCP in the denitrification system. The increased in the proportion of functional bacteria with nitrate_reduction, nitrogen_respiration, nitrate_respiration and nitrite_respiration in the presence of NZVI further reveals the mechanism of enhanced denitrification.

Elucidation of a mechanism for the heterogeneous electro-fenton process and its application in the green treatment of azo dyes

Vast efforts are directed today toward the development of efficient, green methods for the degradation of toxic compounds, especially those that are water-soluble. Though Fenton reactions are commonly used in wastewater treatment, their mechanisms and the active species involved remain obscure due to their mechanistic complexity. In this work, the mechanism of an electro-Fenton reaction, in which a FeLaO3 catalyst was entrapped in a sol-gel matrix, was studied in the presence of azo dyes as the model for toxic compounds. Increased knowledge about this important mechanism will confer greater control over related processes and enable a more efficient and green degradation method. DFT calculations showed that in the presence of Fe(IV), OH are formed under acidic conditions and that both the iron and hydroxyl species function as oxidation reagents in the degradation process. The structure of the formed Fe(IV) embedded in the solid matrix was not the typical tetravalent structure. Entrapment in the sol-gel matrix stabilized the catalyst, enhanced its efficiency and enabled it to be recycled. Sol-gel matrices constitute a simple method for the degradation of stable and toxic compounds under extreme pH conditions. The findings of this study are highly significant for the treatment of typically acidic wastewaters.

Surface modification of zero-valent iron nanoparticles with β-cyclodextrin for 4-nitrophenol conversion

Environmental pollution causes irreversible damage to ecosystems and their structure. Therefore, the development of novel remedial techniques is a must for an effective response to emerging contaminants and those already persisting in the environment. The nanosized zero-valent iron (nZVI) is considered as an important nanostructure for the degradation of toxic compounds. Furthermore, the degradative potential of nZVI may be improved by surface modification. In this work nZVI was functionalized with β-cyclodextrin (β-CD), which is considered to be an environmentally-friendly and cheap adsorbent for toxic pollutants. Such a ‘green’ improvement not only enhances the activity of nZVI but also enables the conversion of 4-nitrophenol to 4-aminophenol, which under standard conditions is persistent and does not significantly react with bare nZVI. This research may help to find a solution to treat persistent organic pollutants (POPs) in aqueous environment.

Lowering the inhibition of sugarcane vinasse as a culture medium for oleaginous fungi through oxidative pre‐treatment aiming at the degradation of toxic compounds

AbstractBACKGROUNDThe utilization of vinasse as a feasible culture medium for fungi is hindered by the presence of inhibitory compounds, such as phenols and other recalcitrant structures. This work analyzes the effect of different homogeneous advanced oxidation processes (AOP) to lower the concentration of inhibitory phenolic compounds in vinasse, and to test the effects of the pre‐treatment on the growth of an oleaginous fungal strain. Vinasse was treated using a batch system with the addition of ferrous ion (Fe2+) (Fenton), in the presence of UV, and with the addition of hydrogen peroxide (H2O2).RESULTSAll of the reaction systems were able to partially degrade the chemical oxygen demand, ranging from 18.4% up to 54.1% in the factorial results. The pre‐treated vinasse samples were assayed for the growth performance of Mucor circinelloides, demonstrating that the control value of 3.54 g L−1 was increased to values as high as 4.84 g L−1, also followed by an increase of ≈73% in terms of lipid productivity.CONCLUSIONDifferent AOP were tested to degrade phenolic compounds present in vinasse, demonstrating that the optimum condition (Fe2+/UV at alkaline pH) provided a culture medium for M. circinelloides that increased the biomass accumulation by ≈35% and the lipid productivity by >70% when compared to the control. © 2020 Society of Chemical Industry

Developing a method for measurement of dehydrogenase activity in biological wastewater treatment processes applied for toxic compounds degradation

Biological wastewater treatment processes are among the environmentally friendly techniques for degradation of organic compounds. They are also preferred to the physical and chemical processes which are due to the ability of biological processes to treat wide range of organic compounds with lower operational costs. However, biological processes are usually affected by variation in the inlet wastewater quality and quantity. In order to investigate the performance of the wastewater treatment plant, various parameters in case of effluent quality such as COD, BOD, TSS, TDS etc. are required to be measured. Microorganisms in bioreactors use various enzymes to degrade the organic contaminants. Higher toxic organic load on the biological process may lead to the deterioration of the process performance which is due to the reduction in microbial activity of the biomass. Dehydrogenase enzyme produced in biological processes could be used as an indicator for the biological wastewater treatment. Present study introduces a simple and modified method for evaluation of biological wastewater treatment process measuring dehydrogenase activity. In the present study, the effective parameters such as incubation time and types of solvent were investigated and the best procedure is developed for measuring the dehydrogenase activity in biological wastewater treatment process.

X-ray crystallographic structure of BshB, the zinc-dependent deacetylase involved in bacillithiol biosynthesis.

Many gram-positive bacteria produce bacillithiol to aid in the maintenance of redox homeostasis and degradation of toxic compounds, including the antibiotic fosfomycin. Bacillithiol is produced via a three-enzyme pathway that includes the action of the zinc-dependent deacetylase BshB. Previous studies identified conserved aspartate and histidine residues within the active site that are involved in metal binding and catalysis, but the enzymatic mechanism is not fully understood. Here we report two X-ray crystallographic structures of BshB from Bacillus subtilis that provide insight into the BshB catalytic mechanism.

Response of intestine microbiota, digestion, and immunity in Pacific white shrimp Litopenaeus vannamei to dietary succinate

Succinate (SA) is the precursor of propionate that influence the intestine physiological function of animals. In this study, we investigated the microbiome, digestive, and immune responses in the intestines of Pacific white shrimp Litopenaeus vannamei fed diets containing different levels of SA: 0 g/kg (Control), 2.5 g/kg (SA1), 5.0 g/kg (SA2), and 10.0 g/kg (SA3) for 56 days. The results showed that dietary SA improved the intestine mucosa morphology, increased the short-chain fatty acids contents, and altered the intestine microbiota composition. Specifically, SA increased the abundances of Proteobacteria and decreased the abundance of Bacteroidetes. The beneficial bacteria including Ruegeria, Lutimonas, Mameliella, and Sphingomonas were enriched in response to dietary SA; these genus might be involved in nutrient metabolism and the degradation of toxic compounds and pollutants. Additionally, dietary SA also improved the activity of digestive enzymes (amylase, lipase, trypsin, and pepsin) and immune enzymes (total antioxidant capacity, phenoloxidase, total nitric oxide synthase, and nitric oxide), and the expression of immune-related genes (prophenoloxidase, anti-lipopolysaccharide factor, lysozyme, heat shock protein 70, thioredoxin, mucin-1, mucin-2, mucin-5 AC, mucin-5B, and mucin-19) in the intestine of the shrimp. These results revealed that dietary SA had a positive effect on the intestine health of L. vannamei by modulating the microbial composition and SCFA contents, and enhancing the digestive and immune response in the shrimp intestine.