Enhanced biodegradation of aromatic pollutants in cocultures of anaerobic and aerobic bacterial consortia

Optimizing intermittent micro-aeration as a strategy for enhancing aniline anaerobic biodegradation: kinetic, ecotoxicity, and microbial community dynamics analyses

Groundwater and soil contamination by aromatic amines (AAs), used in the production of polymers, plastics, and pesticides, often results from improper waste disposal and accidental leaks. These compounds are resistant to anaerobic degradation; however, micro-aeration can enhance this process by promoting microbial interactions. In batch assays, anaerobic degradation of aniline (0.14 mM), a model AA, was tested under three micro-aeration conditions: T30, T15, and T10 (30, 15, and 10 min of micro-aeration every 2 h, respectively). Aniline degradation occurred in all conditions, producing both aerobic (catechol) and anaerobic (benzoic acid) byproducts. The main genera involved in T30 and T15 were Comamonas, Clostridium, Longilinea, Petrimonas, Phenylobacterium, Pseudoxanthomonas, and Thiobacillus. In contrast, in T10 were Pseudomonas, Delftia, Leucobacter, and Thermomonas. While T30 and T15 promoted microbial cooperation for anaerobic degradation and facultative respiration, T10 resulted in a competitive environment due to dominance and oxygen scarcity. Despite aniline degradation in 9.4 h under T10, this condition was toxic to Allium cepa seeds and exhibited cytogenotoxic effects. Therefore, T15 emerged as the optimal condition, effectively promoting anaerobic degradation without accumulating toxic byproducts. Intermittent micro-aeration emerges as a promising strategy for enhancing the anaerobic degradation of AA-contaminated effluents.

Impact analysis of hydraulic residence time and dissolved oxygen on performance efficiency and microbial community in N, N-dimethylformamide wastewater treated by an AnSBR-ASBR

Suitable operating parameters are one of the key factors to efficient and stable biological wastewater treatment of N, N-dimethylformamide (DMF) wastewater. In this study, an improved AnSBR-ASBR reactor (anaerobic sequencing batch reactor, AnSBR, and aerobic SBR, ASBR, run in series) was used to investigated the effects of operating conditions such as hydraulic residence time (HRT), AnSBR stirring speed and ASBR dissolved oxygen (DO) for DMF wastewater treatment. When HRT decreased from 24 h to 12 h, the average removal rates of COD by the AnSBR were 34.59% and 39.54%, respectively. Meanwhile, the removal rate of NH4+-N by ASBR decreased from 88.38% to 62.81%. The DMF removal rate reached the best at 18 h and the expression of dehydrogenase was the highest in the AnSBR. The abundance of Megasphaera, the dominant sugar-degrading bacteria in the AnSBR, continued to decline due to the decrease of HRT. The relative abundance of Methanobacterium gradually increased to 80.2% with the decrease of HRT and that hydrotrophic methanogenesis dominated the methanogenic process. The HRT decrease promoted butyrate and pyruvate metabolism in anaerobic sludge, but the proportion of glycolysis and methane metabolism decreased. The AnSBR-ASBR reactor had the best operation performance when HRT was 18 h, AnSBR speed was 220 r/min, and ASBR DO content was 3-4 mg/L. This study provided an effective reference for the reasonable selection of operating parameters in the treatment of DMF-containing wastewater by the AnSBR-ASBR.

Treatment of pharmaceutical wastewater through activated sludge process-a critical review

The occurrence of pharmaceutical compounds in water is a rising issue in the environment. These drugs in the waste may be toxic to aquatic organisms and humans as they disrupt the endocrine system, cause genotoxicity, etc. Several techniques were used for the treatment of pharmaceutical wastewater, such as physical, chemical, physiochemical, and biological processes like adsorption, chemical coagulation, and activated sludge processes, but these techniques possess several merits and demerits, such as higher installation and operation costs. This technique is used to remove color and turbidity; reduce biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS) to permissible limits for reuse of effluent; and prevent diseases caused by pharmaceutical wastewater. This review focuses on the treatment of pharmaceutical wastewater containing drugs like antibiotics, depressants, and hormones, with the activated sludge process having several advantages like good quality effluent and low installation costs.

Bacterial oxidoreductive enzymes as molecular weapons for the degradation and metabolism of the toxic azo dyes in wastewater: a review

Azo dyes are extremely toxic and pose significant environmental and health risks. Consequently, mineralization and conversion to simple compounds are required to avoid their hazardous effects. A variety of enzymes from the bacterial system are thought to be involved in the degradation and metabolism of azo dyes. Bioremediation, a cost effective and eco-friendly biotechnology, involving bacteria is powered by bacterial enzymes. As mentioned, several enzymes from the bacterial system serve as molecular weapons in the degradation of these dyes. Among these enzymes, azoreductase, oxidoreductase, and laccase are of great interest for the degradation and decolorization of azo dyes. Combination of the oxidative and reductive enzymes is used for the removal of azo dyes from water. The aim of this review article is to provide information on the importance of bacterial enzymes. The review also discusses the genetically modified microorganisms in the biodegradation of azo dyes in polluted water.

A review on the pesticides in coffee: Usage, health effects, detection, and mitigation

Coffee is considered among the most popular beverages and is classified as the second most exported item worldwide. The presence of pesticides in this staple commodity is a challenge to import and export activities, in addition to the fact that pesticides are toxins of public health concern. Even if pesticides are applied properly and their residues are within the acceptable range, it is important to know the fate of these pesticides prior to their ingestion. A plethora of research has been done to optimize methods and thus to have valid procedures to test for the presence of pesticides in coffee. In this review, the analytical methods used in these articles to detect and quantify the pesticides in coffee beans, roasted coffee, and coffee infusion were identified. This review highlights as well the main factors that play a key role in having good separation, identification, and recovery of pesticide residues in the aforementioned items. In addition, the review explains the effect of pesticides on human health and the mitigation techniques for pesticide exposure.

3D printing of recombinant Escherichia coli/Au nanocomposites as agitating paddles towards robust catalytic reduction of 4-nitrophenol

Three-dimensional (3D) printing technology has received remarkable attention in manufacturing catalysts with tailored shapes and high precision, particularly facilitating catalyst recovery, maximizing heat/mass transfer, as well as enhancing catalytic performance. Herein, an engineered recombinant Escherichia coli strain (denoted as e-E. coli) with overexpressing metallothionein (a metal-binding protein) was explored to synthesize Au nanoparticles serving as both reducing and stabilizing agents. Then, the mixed inks containing e-E. coli/Au composite and biocompatible polymers (sodium alginate and gelatin) were extruded based on a direct ink writing method followed by chemical crosslinking to form robust 3D grids with square symmetry. To boost the mass transfer and minimize pressure drop, the monolith catalysts were assembled into agitating paddles and used for liquid-phase batch reactions (volume: 1 L). As such, the reaction solutions were mixed internally via the powered "catalytic paddles" with high mechanical strength, excellent reactivity, and easy recyclability, which could be reused at least 7 cycles without performance loss. Our work provides a novel strategy for the fabrication of supported Au catalysts, and the proof-of-concept "catalytic paddles" by 3D printing technology can be applied to other industrial solution-based reactions.

Managing gene expression in Pseudomonas simiae EGD-AQ6 for chloroaromatic compound degradation

Pseudomonas simiae EGD-AQ6 is capable of utilizing chloroaromatic compound i.e., 2-4-D efficiently in its biofilm phenotype. The differential accumulation of intermediate 4-chlorocatechol rates were significant in planktonic and biofilm phenotypes, as well as in the  increased biofilm adapted cell numbers. Interestingly, response surface analysis demonstrated the combined positive effects of 2-4-D degradation and 4-CCA accumulation rates and the gene expression profiles, with significant up-regulation of degradative and biofilm genes, and greater participation of pellicle genes in the biofilm phenotypes than their planktonic counterparts, thereby revealing a phenotype variation. It positively validated the physiological data. Furthermore, the sequence similarity of the 2-4-D catabolic and biofilm-forming proteins (pel ABCDEFG and pga ABCD), which are responsible for building carbohydrate rich extracellular matrix, were significant with the respective organisms. This is the first study, which endorses this strain to be unique in efficient chloro-aromatic degradation through phenotype variation, thereby proving a potential candidate in the improvement of bioremediation technologies.

Biochemical, genotoxic, histological and ultrastructural effects on liver and gills of fresh water fish Channa punctatus exposed to textile industry intermediate 2 ABS

The study was planned to assess the acute toxicity of textile industry intermediate, 2 amino benzene sulfonate (2 ABS) through biochemical, genotoxic, histopathological and ultrastructural (SEM) analysis in liver and gills of fresh water fish Channa punctatus. The fish were subjected to two sublethal concentrations (2.83 mg/30 g b. w. and 5.66 mg/30 g b. w.) for 96 h. A significant (p ≤ 0.05) increment in the enzymatic activity of catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR) was observed followed by decline on CAT-SOD after 96 h of exposure in both the tissues, whereas increment in malondialdehyde (MDA) levels were observed throughout the exposure period for both the concentrations. Comet assay also showed elevated tail length and % tail DNA throughout the exposure period, marking maximum damage after 96 h for both the tissues. Light microscopy divulged several anomalies including: infiltration of lymphocytes, sinusoidal dilations, necrosis, vacuolation in liver and secondary lamellae fusion, telangiectasia and epithelial uplifting in gills. The highest degree of tissue change (DTC) in liver (50.33 ± 0.88) and gill (42.33 ± 2.18) was recorded with the highest concentration after 96 h of exposure. Scanning electron microscopy (SEM) also reaffirmed several alterations in liver and gills of fish. The findings of the present study inflict changes in liver and gills, marking the interference of 2 ABS with the normal functioning by suppressing the enzymatic activity, accelerating the lipid peroxidation, enhancing DNA damage and by disrupting normal architecture of liver and gills, making it toxic towards the fish even at sub-lethal concentrations.

Inhibition of anammox activity by municipal and industrial wastewater pollutants: A review

The use of the anammox process for nitrogen removal has gained popularity across the world due to its low energy consumption and waste generation. Anammox reactors have been used to treat ammonium-rich effluents such as chemical, pharmaceutical, semiconductor, livestock, and coke oven wastewater. Recently, full-scale installations have been implemented for municipal wastewater treatment. The efficiency of biological processes is susceptible to inhibitory effects of pollutants present in wastewater. Considering the increasing number of emerging contaminants detected in wastewater, the impacts of the different types of pollutants on anammox bacteria must be understood. This review presents a compilation of the studies assessing the inhibitory effects of different wastewater pollutants towards anammox activity. The pollutants were classified as antibiotics, aromatics, azoles, surfactants, microplastics, organic solvents, humic substances, biodegradable organic matter, or metals and metallic nanoparticles. The interactions between the pollutants and anammox bacteria have been described, as well as the interactions between different pollutants leading to synergistic effects. We also reviewed the effects of pollutants on distinct species of anammox bacteria, and the main toxicity mechanisms leading to irreversible loss of anammox activity have been identified. Finally, we provided an analysis of strategies to overcome the inhibitory effects of wastewater pollutants on the nitrogen removal performance. We believe this review will contribute with essential information to assist the operation and design of anammox reactors treating different types of wastewaters.

Selecting the best electron donor and operational temperature for the rapid biotransformation of the insensitive munitions compound 2,4-dinitroanisole (DNAN) by anaerobic sludge

2,4-Dinitroanisole (DNAN) is a toxic compound increasingly used by the military that can be released into the environment on the soil of training fields and in the wastewater of manufacturing plants. DNAN's nitro groups are anaerobically reduced to amino groups by microorganisms when electron donors are available. Using anaerobic sludge as the inoculum, we tested different electron donors for DNAN bioreduction at 20 and 30 °C: acetate, ethanol, pyruvate, hydrogen, and hydrogen + pyruvate. Biotic controls without external electron donors and abiotic controls with heat-killed sludge were also assayed. No DNAN conversion was observed in the abiotic controls. In all biotic treatments, DNAN was reduced to 2-methoxy-5-nitroaniline (MENA), which was further reduced to 2,4-diaminoanisole (DAAN). Ethanol or acetate did not increase DNAN reduction rate compared to the endogenous control. The electron donors that caused the fastest DNAN reductions were (rates at 30 °C): H₂ and pyruvate combined (311.28 ± 10.02 μM·d^-1·gSSV^-1), followed by H₂ only (207.19 ± 5.95 μM·d^-1·gSSV^-1), and pyruvate only (36.35 ± 2.95 μM·d^-1·gSSV^-1). Raising the temperature to 30 °C improved DNAN reduction rates when pyruvate, H₂, or H₂ + pyruvate were used as electrons donors. Our results can be applied to optimize the anaerobic treatment of DNAN-containing wastewater.

Potential applications of halophilic microorganisms for biological treatment of industrial process brines contaminated with aromatics

Saline wastewater contaminated with aromatic compounds can be frequently found in various industrial sectors. Those compounds need to be degraded before reuse of wastewater in other process steps or release to the environment. Halophiles have been reported to efficiently degrade aromatics, but their application to treat industrial wastewater is rare. Halophilic processes for industrial wastewater treatment need to satisfy certain requirements: a continuous process mode, low operational expenditures, suitable reactor systems and a monitoring and control strategy. The aim of this review is to provide an overview of halophilic microorganisms, principles of aromatic biodegradation, and sources of saline wastewater containing aromatics and other contaminants. Finally, process examples for halophilic wastewater treatment and potential process monitoring strategies are discussed. To further illustrate the significant potential of halophiles for saline wastewater treatment and to facilitate development of ready-to-implement processes, future research should focus on scale-up and innovative process monitoring and control strategies.

Microbial glycoconjugates in organic pollutant bioremediation: recent advances and applications

The large-scale application of organic pollutants (OPs) has contaminated the air, soil, and water. Persistent OPs enter the food supply chain and create several hazardous effects on living systems. Thus, there is a need to manage the environmental levels of these toxicants. Microbial glycoconjugates pave the way for the enhanced degradation of these toxic pollutants from the environment. Microbial glycoconjugates increase the bioavailability of these OPs by reducing surface tension and creating a solvent interface. To date, very little emphasis has been given to the scope of glycoconjugates in the biodegradation of OPs. Glycoconjugates create a bridge between microbes and OPs, which helps to accelerate degradation through microbial metabolism. This review provides an in-depth overview of glycoconjugates, their role in biofilm formation, and their applications in the bioremediation of OP-contaminated environments.

The key role of oxygen in the bioremoval of 2,4-diaminoanisole (DAAN), the biotransformation product of the insensitive munitions compound 2,4-dinitroanisole (DNAN), over other electron acceptors

Insensitive munitions compounds, such as 2,4-dinitroanisole (DNAN), are replacing conventional explosives. DNAN is anaerobically reduced to 2,4-diaminoanisole (DAAN), a toxic aromatic amine. However, the removal of DAAN under different redox conditions is yet to be elucidated. Herein, we analyzed DAAN consumption in biotic and abiotic microcosms when exposed to different redox conditions (without added electron acceptor, without added electron acceptor but with pyruvate as a co-substrate, with sulfate, with nitrate, and with oxygen), using an anaerobic sludge as inoculum. We observed that DAAN autoxidation, an abiotic reaction, was significant in microaerobic environments. DAAN also reacted abiotically with heat-killed sludge up to a saturation limit of 67.4 μmol DAAN (g VSS heat-killed sludge)^-1. Oxygen caused the fastest removal of DAAN in live sludge among the conditions tested. Treatments without added electron acceptors (with or without pyruvate) presented similar DAAN removal performances, although slower than the treatment with oxygen. Sulfate did not exhibit any effect on DAAN removal compared to the treatment without added electron acceptors. Nitrate, however, inhibited the process. An enrichment culture from the microcosms exposed to oxygen could be developed using DAAN as the sole substrate in microaerobic conditions. The enrichment profoundly changed the microbial community. Unclassified microorganisms accounted for 85% of the relative abundance in the enrichment culture, suggesting that DAAN microaerobic removal might have involved organisms that were not yet described. Our results suggest that DAAN microaerobic treatment can be coupled to DNAN anaerobic reduction in sludge, improving the treatment of DNAN-containing wastewaters.

Evaluation of the efficiency of chlorpyrifos-ethyl remediation by Methylobacterium radiotolerans and Microbacterium arthrosphaerae using response of some biochemical biomarkers

This study reveals out detoxifying and antioxidant enzyme response of Gammarus pulex exposed/polluted to chlorpyrifos-ethyl insecticide before and after biodegradation/bioremediation by Methylobacterium radiotolerans and Microbacterium arthrosphaerae. Cytochrome P450 1A1, glutathione S-transferase, catalase, and superoxide dismutase activities in G. pulex exposed to chlorpyrifos-ethyl before and after bioremediation/biodegradation by these two bacteria during 24 and 96 h tested by using commercial ELISA kits. The activity of catalase enzyme was decreased depending on chlorpyrifos-ethyl before and after bioremediation/biodegradation the enzyme activity was increased repeatedly. Superoxide dismutase activity level increased after chlorpyrifos-ethyl exposure in 96 h (p > 0.05). Following bioremediation, superoxide dismutase enzyme activity decreased again during 24 h (p > 0.05) and increased during 96 h (p < 0.05). Statistical differences were not found in cytochrome P450 1A1 enzyme activity before and after the process (p > 0.05). No significant differences were determined during the activity of glutathione S-transferase in 24 h (p > 0.05). The activities of glutathione S-transferase were increased after exposure of chlorpyrifos-ethyl during 96 h. After bioremediation; the activity of glutathione S-transferase increased even more (p < 0.05). The results determined that activities of G. pulex at superoxide dismutase, catalase, and glutathione S-transferase are common biomarkers for revealing out the efficiency of bioremediation of chlorpyrifos-ethyl with these two types of soil bacteria. Graphical abstract.

Statistical evaluation of the bioremediation performance of Ochrobactrum thiophenivorans and Sphingomonas melonis bacteria on Imidacloprid insecticide in artificial agricultural field

BACKGROUND

Pesticides are applied directly on the soil or on the vegetation, and thus, they can reach the receiving environment easily. In this way, environmental damage that stems from pesticides also affects public health and the natural habitat. Pesticides are one of the most harmful pollutant groups in terms of human health, fauna and the environment. They penetrate the application field and the applicator right after the application and start to show adverse effects.

METHODS

The bioremediation of the Imidacloprid (C9H10ClN5O2) insecticide, which is used commonly in Mediterranean climate, was compared with some soil bacteria in artificially prepared fields. For this purpose, firstly, it was determined whether the soil samples taken from a field where cotton was cultivated in Adana in Turkey was suitable for bioremediation. Then, the bacteria were isolated from these soils with the 16sRNA method. The enhanced microbial consortia of these isolated bacteria were inoculated to the artificial fields, meanwhile, the recommended concentrations of Imidacloprid were added to these agricultural fields. Imidacloprid, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5) and Total Organic Carbon (TOC) measurements were performed every day for two weeks on the filtrate samples taken from the artificial fields.

RESULTS

As a result of the monitoring, it was determined that Ochrobactrum thiophenivorans (Ot) and Sphingomonas melonis (Sm) species and their mixtures could eliminate the Imidacloprid pesticide within two weeks' time. The removal efficiencies were 100% for active ingredient for each bacterium and their mixtures while COD were 97% and 96% for Ot. and Sm., respectively. TOC and BOD5 removal rates were 97% for both types and their mixtures in one or two-week period. Mixture of Ot and Sm shows 98.5% for COD, BOD5 parameters and 97.5% for TOC parameter.

CONCLUSIONS

The results that will be obtained will help in the rehabilitation of the receiving environments that are exposed to pesticides in our country and take precautions to avoid the accumulation of pesticides in the body of the humans who are at the top of the food chain.

Microaerated UASB reactor treating textile wastewater: The core microbiome and removal of azo dye Direct Black 22

Sequential anaerobic and aerobic processes have been recommended to treat textile wastewater reliably. In this work, the focus was on finding an energetically more competitive system to remove tetra-azo dye Direct Black 22 (DB22). We operated two upflow anaerobic sludge blanket (UASB) reactors (R1 and R2) in three phases (PI, PII, and PIII). R1 was operated as a conventional UASB, while R2 was microaerated in the upper part (0.18 ± 0.05 mg O₂. L^-1), aiming to remove DB22 simultaneously with the aromatic amine byproducts. PI consisted of feeding reactors with synthetic textile wastewater (STW), PII had higher salinity in the STW, and PIII was the same as PII, plus sulfate. The results showed that color and COD removal efficiencies were similar for both reactors (67-72% for R1 and 59-78% for R2) without a substantial influence of oxygen in R2. However, microaeration played a crucial role in R2 by removing the anaerobically formed aromatic amines; during PIII, the effluent was 16 times less toxic than that of R1. The microbial community that developed in the sludge bed of both reactors was quite similar, with the core microbiome represented by Trichococcus, Syntrophus and Methanosaeta genera. The increase in salinity in PII and PIII promoted a shift in the microbial community, excluding salty-sensitive genera from the core microbiome. The putative genera Brevundimonas and Ornatilinea were associated to aromatic amine microaerobic removal. Therefore, there is a potential application of a compact microaerated anaerobic system for textile wastewater treatment.

Trace metals and persistent organic pollutants fingerprint on the particle flux in the deep subtropical NE Atlantic

Particle flux material collected in 2000 m depth in the Northeast Atlantic at 33°N and 22°W was analyzed for trace metals and persistent organic pollutants. Element enrichment factors relative to lithogenic Al were elevated indicating possible anthropogenic contributions for all trace metals except V. Polycyclic aromatic hydrocarbons, polychlorinated biphenyls and the pesticide DDT exhibited median fluxes of 10.40 μg m^-2d^-1,0.29 μg m^-2 d^-1, and 0.90 μg m^-2 d^-1, respectively. Flux composition reflected long range transport, with low molecular weight and low-chlorinated compounds dominating ∑₁₅PAH and ∑₂₃PCB. PAH isomer ratios identified fossil fuel combustion as the main ∑₁₅PAH source. The composition of ∑₄DDT suggested inputs of the fresh technical pesticide during high dust intensity periods. Pollutant fluxes showed seasonality linked to export production in the region, as well as a dependence on annual and sub-annual dust input events.

Research on complexation ability, aromaticity, mobility and cytotoxicity of humic-like substances during degradation process by electrochemical oxidation

The humic-like substances were the main organic components in most wastewater (e.g. domestic sewage, toilet wastewater and landfill leachate). Two types of actual humic-like substances (fulvic acid (FA) and biologically treated landfill leachate (BTLL)) were selected to describe the changes in the properties of humic-like substances (complexation ability, aromaticity and mobility) during electrochemical oxidation. Meanwhile, the acute cytotoxicity of FA and BTLL was also tested by acute toxicological test of luminescent bacteria. The results showed that the consumption of coordinating groups such as phenolic groups and hydrogen bonds reduced the complexation ability of FA and BTLL. The functional groups were degraded with the removal order of quinone group, phenolic group and aromatic group, and finally realized the molecular saturation and aromaticity decrease for humic-like substances. The mobility of FA and BTLL was decreased because of the enhancement of hydrophobicity during electrolysis process. Furthermore, the available chlorine produced during electrochemical oxidation was the main acute cytotoxicity substance, therefore, it is necessary to remove it before discharge in order to reduce ecological risks. This study provides a basis for understanding and evaluating the electrochemical degradation process of humic-like substances in detail.

Defining Division of Labor in Microbial Communities

In order to survive and reproduce, organisms must perform a multitude of tasks. However, trade-offs limit their ability to allocate energy and resources to all of these different processes. One strategy to solve this problem is to specialize in some traits and team up with other organisms that can help by providing additional, complementary functions. By reciprocally exchanging metabolites and/or services in this way, both parties benefit from the interaction. This phenomenon, which has been termed functional specialization or division of labor, is very common in nature and exists on all levels of biological organization. Also, microorganisms have evolved different types of synergistic interactions. However, very often, it remains unclear whether or not a given example represents a true case of division of labor. Here we aim at filling this gap by providing a list of criteria that clearly define division of labor in microbial communities. Furthermore, we propose a set of diagnostic experiments to verify whether a given interaction fulfills these conditions. In contrast to the common use of the term, our analysis reveals that both intraspecific and interspecific interactions meet the criteria defining division of labor. Moreover, our analysis identified non-cooperators of intraspecific public goods interactions as growth specialists that divide labor with conspecific producers, rather than being social parasites. By providing a conceptual toolkit, our work will help to unambiguously identify cases of division of labor and stimulate more detailed investigations of this important and widespread type of inter-microbial interaction.

Biotransformation of 4-nitrophenol by co-immobilized Geobacter sulfurreducens and anthraquinone-2-sulfonate in barium alginate beads

Geobacter sulfurreducens and anthraquinone-2-sulfonate (AQS) were used suspended and immobilized in barium alginate during the biotransformation of 4-nitrophenol (4-NP). The assays were conducted at different concentrations of 4-NP (50-400 mg/L) and AQS, either in suspended (0-400 μM) or immobilized form (0 or 760 μM), and under different pH values (5-9). G. sulfurreducens showed low capacity to reduce 4-NP in absence of AQS, especially at the highest concentrations of the contaminant. AQS improved the reduction rates from 0.0086 h^-1, without AQS, to 0.149 h^-1 at 400 μM AQS, which represent an increment of 17.3-fold. The co-immobilization of AQS and G. sulfurreducens in barium alginate beads (AQS_i-G_i) increased the reduction rates up to 4.8- and 7.2-fold, compared to incubations with G. sulfurreducens in suspended and immobilized form, but in absence of AQS. AQS_i-G_i provides to G. sulfurreducens a barrier against the possibly inhibiting effects of 4-NP.

Toxicity of aromatic pollutants and photooxidative intermediates in water: A QSAR study

Extensive commercial use of aromatic hydrocarbons results with significant amounts of these chemicals and related by-products in waters, causing a severe ecological and health threat, thus requiring an increased attention. This study was aimed at developing models for prediction of the initial toxicity of the aromatic water-pollutants (expressed as EC₅₀ and TU₀) as well as the toxicity of their intermediates at half-life of the parent pollutant (TU_1/2). For that purpose, toxicity toward Vibrio fischery was determined for 36 single-benzene ring compounds (S-BRCs), diversified by the type, number and position of substituents. Quantitative structure-activity relationship (QSAR) methodology paired with genetic algorithm optimization tool and multiple linear regression was applied to obtain the models predicting the targeted toxicity, which are based on pure structural characteristics of the tested pollutants, avoiding thus additional experimentation. Upon derivation of the models and extensive analysis on training and test sets, 4-, 4- and 5-variable models (for EC₅₀ and TU₀, TU_1/2, respectively) were selected as the most predictive possessing 0.839<R²< 0.901 and 0.789<Q²< 0.859. The analysis of the selected descriptors indicated three major structural characteristics influencing the toxicity: electronegativity, geometry and electrotopological states of the molecule. Degradation kinetics determining as well the pathways of intermediates formation, reflected over ionization potential, was found to be an important parameter determining the toxicity in half-life.

Polycyclic and organochlorine hydrocarbons in sediments of the northern South China Sea

We investigated the concentration distribution and composition of organic pollutants in sediments of the shelf and the deep northern South China Sea (NSCS). Concentrations of polycyclic aromatic hydrocarbons (Σ₁₅PAH; 10.69-66.45 ng g^-1), Dichlorodiphenyltrichloroethane (Σ₄DDT; 0-0.82 ng g^-1), and polychlorinated biphenyls (Σ₂₄PCB; 0-0.12 ng g^-1) are below established sediment quality guidelines, suggesting no environmental risk. Surprisingly, concentrations increase from the shelf to the deep NSCS, and are higher in the east of the study area. The organic pollutant composition indicates PAH mainly derived from pyrogenic sources, and mostly degraded DDT and PCB. However, in the deep NSCS, considerable contribution of petrogenic PAH, low chlorinated PCB and p,p'-DDT suggest more recent input from different sources compared to the shelf. From these results we infer that organic pollution in the NSCS does not originate from the Pearl River Estuary but from the NE SCS, SW of Taiwan.

Adsorption and oxidation of 3-nitro-1,2,4-triazole-5-one (NTO) and its transformation product (3-amino-1,2,4-triazole-5-one, ATO) at ferrihydrite and birnessite surfaces

The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently being used to replace conventional explosives such as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), but the environmental fate of this increasingly widespread IMC remains poorly understood. Upon release from unexploded solid phase ordinances, NTO exhibits high aqueous solubility and, hence, potential mobilization to groundwater. Adsorption and abiotic transformation at metal oxide surfaces are possible mechanisms for natural attenuation. Here, the reactions at ferrihydrite and birnessite surfaces of NTO and its biotransformation product, 3-amino-1, 2, 4-triazol-5-one (ATO), were studied in stirred batch reactor systems at controlled pH (7.0). The study was carried out at metal oxide solid to solution ratios (SSR) of 0.15, 1.5 and 15 g kg^-1. The samples were collected at various time intervals up to 3 h after reaction initiation, and analyzed using HPLC with photodiode array and mass spectrometric detection. We found no detectable adsorption or transformation of NTO upon reaction with birnessite, whereas ATO was highly susceptible to oxidation by the same mineral, showing nearly complete transformation within 5 min at 15 g kg^-1 SSR to urea, CO_2(g) and N_2(g). The mean surface-area-normalized pseudo-first order rate constant (k) for ATO oxidation by birnessite across all SSRs was 0.05 ± 0.022 h^-1 m^-2, and oxidation kinetics were independent of dissolved O₂ concentration. Both NTO and ATO were resistant to oxidation by ferrihydrite. However, NTO showed partial removal from solution upon reaction with ferrihydrite at 0.15 and 1.5 g kg^-1 SSR and complete loss at 15 g kg^-1 SSR due to strong adsorption. Conversely, ATO adsorption to ferrihydrite was much weaker than that measured for NTO.

Biodegradation of bispyribac sodium by a novel bacterial consortium BDAM: Optimization of degradation conditions using response surface methodology

Bispyribac sodium (BS), is a selective, systemic and post emergent herbicide used to eradicate grasses and broad leaf weeds. Extensive use of this herbicide has engendered serious environmental concerns. Hence it is important to develop strategies for bioremediation of BS in a cost effective and environment friendly way. In this study a bacterial consortium named BDAM, comprising three novel isolates Achromobacter xylosoxidans (BD1), Achromobacter pulmonis (BA2), and Ochrobactrum intermedium (BM2), was developed by virtue of its potential for degradation of BS. Different culture conditions (temperature, pH and inoculum size) were optimized for degradation of BS by the consortium BDAM and the mutual interactions of these parameters were analysed using a 2³ full factorial central composite design (CCD) based on Response Surface Methodology (RSM). The optimal values for temperature, pH and inoculum size were found to be 40 °C, 8 and 0.4 g/L respectively to achieve maximum degradation of BS (85.6%). Moreover, the interactive effects of these parameters were investigated using three dimensional surface plots in terms of maximum fitness function. Importantly, it was concluded that the newly developed consortium is a potential candidate for biodegradation of BS in a safe, cost-effective and environmentally friendly manner.

Aerobic Biodegradation Characteristic of Different Water-Soluble Azo Dyes

This study investigated the biodegradation performance and characteristics of Sudan I and Acid Orange 7 (AO7) to improve the biological dye removal efficiency in wastewater and optimize the treatment process. The dyes with different water-solubility and similar molecular structure were biologically treated under aerobic condition in parallel continuous-flow mixed stirred reactors. The biophase analysis using microscopic examination suggested that the removal process of the two azo dyes is different. Removal of Sudan I was through biosorption, since it easily assembled and adsorbed on the surface of zoogloea due to its insolubility, while AO7 was biodegraded incompletely and bioconverted, the AO7 molecule was decomposed to benzene series and inorganic ions, since it could reach the interior area of zoogloea due to the low oxidation-reduction potential conditions and corresponding anaerobic microorganisms. The transformation of NH₃-N, SO₄²⁻ together with the presence of tryptophan-like components confirm that AO7 can be decomposed to non-toxic products in an aerobic bioreactor. This study provides a theoretical basis for the use of biosorption or biodegradation mechanisms for the treatment of different azo dyes in wastewater.

Quinone-functionalized activated carbon improves the reduction of congo red coupled to the removal of p-cresol in a UASB reactor

In this research was immobilized anthraquinone-2-sulfonate (AQS) on granular activated carbon (GAC) to evaluate its capacity to reduce congo red (CR) in batch reactor and continuous UASB reactors. The removal of p-cresol coupled to the reduction of CR was also evaluated. Results show that the immobilization of AQS on GAC (GAC-AQS) achieved 0.469mmol/g, improving 2.85-times the electron-transferring capacity compared to unmodified GAC. In batch, incubations with GAC-AQS achieved a rate of decolorization of 2.64-fold higher than the observed with GAC. Decolorization efficiencies in UASB reactor with GAC-AQS were 83.9, 82, and 79.9% for periods I, II, and III; these values were 14.9-22.8% higher than the obtained by reactor with unmodified GAC using glucose as energy source. In the fourth period, glucose and p-cresol were simultaneously fed, increasing the decolorization efficiency to 87% for GAC-AQS and 72% for GAC. Finally, reactors efficiency decreased when p-cresol was the only energy source, but systems gradually recovered the decolorization efficiency up to 84% (GAC-AQS) and 71% (GAC) after 250 d. This study demonstrates the longest and efficient continuous UASB reactor operation for the reduction of electron-accepting contaminant in presence of quinone-functionalized GAC, but also using a recalcitrant pollutant as electron donor.

Anaerobic biodegradation of (emerging) organic contaminants in the aquatic environment

Although strictly anaerobic conditions prevail in several environmental compartments, up to now, biodegradation studies with emerging organic contaminants (EOCs), such as pharmaceuticals and personal care products, have mainly focused on aerobic conditions. One of the reasons probably is the assumption that the aerobic degradation is more energetically favorable than degradation under strictly anaerobic conditions. Certain aerobically recalcitrant contaminants, however, are biodegraded under strictly anaerobic conditions and little is known about the organisms and enzymatic processes involved in their degradation. This review provides a comprehensive survey of characteristic anaerobic biotransformation reactions for a variety of well-studied, structurally rather simple contaminants (SMOCs) bearing one or a few different functional groups/structural moieties. Furthermore it summarizes anaerobic degradation studies of more complex contaminants with several functional groups (CMCs), in soil, sediment and wastewater treatment. While strictly anaerobic conditions are able to promote the transformation of several aerobically persistent contaminants, the variety of observed reactions is limited, with reductive dehalogenations and the cleavage of ether bonds being the most prevalent. Thus, it becomes clear that the transferability of degradation mechanisms deduced from culture studies of SMOCs to predict the degradation of CMCs, such as EOCs, in environmental matrices is hampered due the more complex chemical structure bearing different functional groups, different environmental conditions (e.g. matrix, redox, pH), the microbial community (e.g. adaptation, competition) and the low concentrations typical for EOCs.

Sequential anaerobic-aerobic biodegradation of emerging insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO)

Insensitive munitions, such as 3-nitro-1,2,4-triazol-5-one (NTO), are being considered by the U.S. Army as replacements for conventional explosives. Environmental emissions of NTO are expected to increase as its use becomes widespread; but only a few studies have considered the remediation of NTO-contaminated sites. In this study, sequential anaerobic-aerobic biodegradation of NTO was investigated in bioreactors using soil as inoculum. Batch bioassays confirmed microbial reduction of NTO under anaerobic conditions to 3-amino-1,2,4-triazol-5-one (ATO) using pyruvate as electron-donating cosubstrate. However, ATO biodegradation was only observed after the redox condition was switched to aerobic. This study also demonstrated that the high-rate removal of NTO in contaminated water can be attained in a continuous-flow aerated bioreactor. The reactor was first fed ATO as sole energy and nitrogen source prior to NTO addition. After few days, ATO was removed in a sustained fashion by 100%. When NTO was introduced together with electron-donor (pyruvate), NTO degradation increased progressively, reaching a removal efficiency of 93.5%. Mineralization of NTO was evidenced by the partial release of inorganic nitrogen species in the effluent, and lack of ATO accumulation. A plausible hypothesis for these findings is that NTO reduction occurred in anaerobic zones of the biofilm whereas ATO was mineralized in the bulk aerobic zones of the reactor.

Influence of redox mediators and salinity level on the (bio)transformation of Direct Blue 71: kinetics aspects

The rate-limiting step of azo dye decolorization was elucidated by exploring the microbial reduction of a model quinone and the chemical decolorization by previously reduced quinone at different salinity conditions (2-8%). Microbial experiments were performed in batch with a marine consortium. The decolorization of Direct Blue 71 (DB71) by the marine consortium at 2% salinity, mediated with anthraquinone-2,6-disulfonate (AQDS), showed the highest rate of decolorization as compared with those obtained with riboflavin, and two samples of humic acids. Moreover, the incubations at different salinity conditions (0-8%) performed with AQDS showed that the highest rate of decolorization of DB71 by the marine consortium occurred at 2% and 4% salinity. In addition, the highest microbial reduction rate of AQDS occurred in incubations at 0%, 2%, and 4% of salinity. The chemical reduction of DB71 by reduced AQDS occurred in two stages and proceeded faster at 4% and 6% salinity. The results indicate that the rate-limiting step during azo decolorization was the microbial reduction of AQDS.

Microbial toxicity and biodegradability of perfluorooctane sulfonate (PFOS) and shorter chain perfluoroalkyl and polyfluoroalkyl substances (PFASs)

Perfluorooctane sulfonate (PFOS) and related perfluoroalkyl and polyfluoroalkyl substances (PFASs) are emerging contaminants that have been widely applied in consumer and industrial applications for decades. However, PFOS has raised public concern due to its high bioaccumulative character, environmental persistence, and toxicity. Shorter PFASs such as perfluorobutane sulfonate (PFBS) and polyfluoroalkyl compounds have been proposed as alternatives to PFOS but it is unclear whether these fluorinated substances pose a risk for public health and the environment. The objective of this research was to investigate the microbial toxicity and the susceptibility to microbial degradation of PFOS and several related fluorinated compounds, i.e., short-chain perfluoroalkyl and polyfluoroalkyl sulfonic and carboxylic acids. None of the compounds tested were toxic to the methanogenic activity of anaerobic wastewater sludge even at very high concentrations (up to 500 mg L^-1). All PFASs evaluated were highly resistant to microbial degradation. PFOS was not reductively dehalogenated by the anaerobic microbial consortium even after very long periods of incubation (3.4 years). Similarly, the tested short chain perfluoroalkyl substances (i.e., PFBS and trifluoroacetic acid) and a polyfluoroalkyl PFOS analogue, 6 : 2 fluorotelomer sulfonic acid (FTSA) were also resistant to anaerobic biodegradation. Likewise, no conclusive evidence of microbial degradation was observed under aerobic conditions for any of the short-chain perfluoroalkyl and polyfluoroalkyl carboxylic acids tested after 32 weeks of incubation. Collectively, these results indicate that PFOS and its alternatives such as short chain perfluoroalkyl sulfonates and carboxylates and their polyfluorinated homologues are highly resistant to microbial degradation.

A Combinatorial Algorithm for Microbial Consortia Synthetic Design

Synthetic biology has boomed since the early 2000s when it started being shown that it was possible to efficiently synthetize compounds of interest in a much more rapid and effective way by using other organisms than those naturally producing them. However, to thus engineer a single organism, often a microbe, to optimise one or a collection of metabolic tasks may lead to difficulties when attempting to obtain a production system that is efficient, or to avoid toxic effects for the recruited microorganism. The idea of using instead a microbial consortium has thus started being developed in the last decade. This was motivated by the fact that such consortia may perform more complicated functions than could single populations and be more robust to environmental fluctuations. Success is however not always guaranteed. In particular, establishing which consortium is best for the production of a given compound or set thereof remains a great challenge. This is the problem we address in this paper. We thus introduce an initial model and a method that enable to propose a consortium to synthetically produce compounds that are either exogenous to it, or are endogenous but where interaction among the species in the consortium could improve the production line.

Profiles and inventories of organic pollutants in sediments from the central Beibu Gulf and its coastal mangroves

Sediment cores from the central Beibu Gulf and its northern coastal mangroves were analyzed for polycyclic aromatic hydrocarbons (PAH), the organo-chlorine pesticides dichlorodiphenyltrichloroethane (DDT) and hexachlorobenzene (HCB), and polychlorinated biphenyls (PCB), to reconstruct the organic pollution history of developing south-west China. Reflecting regional development, in the gulf ∑PAH (38-74 ng g(-1)) decreased towards the surface after peak concentrations near 10 cm, while ∑DDT (ND - 0.5 ng g(-1)) increased due to fresh inputs, and HCB (ND - 0.04 ng g(-1)) occurred only in surface sediments. Profiles in mangrove sediments showed a continuing local scale increase in ∑PAH (29-438 ng g(-1)) as well as ∑DDT (0.2-41.0 ng g(-1)) and HCB (0.01-1.01 ng g(-1)) pollution, despite some variability. No trend was evident for ∑PCB (ND - 0.22 ng g(-1)), which was not detected in the central gulf. Calculated loads estimate that 2816 ng cm(-2) PAHs and 7 ng cm(-2) DDTs are stored in depositional areas of the Beibu Gulf. Mangrove sediments, threatened by land-use-change, contain 1400-4600 ng cm(-2) PAHs and 34-39 ng cm(-2) DDTs.

Engineering microbial consortia for controllable outputs

Much research has been invested into engineering microorganisms to perform desired biotransformations; nonetheless, these efforts frequently fall short of expected results due to the unforeseen effects of biofeedback regulation and functional incompatibility. In nature, metabolic function is compartmentalized into diverse organisms assembled into robust consortia, in which the division of labor is thought to lead to increased community efficiency and productivity. Here we consider whether and how consortia can be designed to perform bioprocesses of interest beyond the metabolic flexibility limitations of a single organism. Advances in post-genomic analysis of microbial consortia and application of high-resolution global measurements now offer the promise of systems-level understanding of how microbial consortia adapt to changes in environmental variables and inputs of carbon and energy. We argue that, when combined with appropriate modeling frameworks, systems-level knowledge can markedly improve our ability to predict the fate and functioning of consortia. Here we articulate our collective perspective on the current and future state of microbial community engineering and control while placing specific emphasis on ecological principles that promote control over community function and emergent properties.

(Bio)transformation of 2,4-dinitroanisole (DNAN) in soils

Recent studies have begun to assess the environmental fate and toxicity of 2,4-dinitroanisole (DNAN), an insensitive munition compound of interest to defense agencies. Aerobic and anaerobic DNAN biotransformation in soils was evaluated in this study. Under aerobic conditions, there was little evidence of transformation; most observed removal was attributed to adsorption and subsequent slow chemical reactions. Under anaerobic conditions, DNAN was reductively (bio)transformed and the rate of the transformation was positively correlated with soil organic carbon (OC) up to a threshold of 2.07% OC. H2 addition enhanced the nitroreduction rate compared to endogenous treatments lacking H2. Heat-killed treatments provided rates similar to the endogenous treatment, suggesting that abiotic factors play a role in DNAN reduction. Ten (bio)transformation products were detected by high-resolution mass spectrometry. The proposed transformation pathway involves reduction of DNAN to aromatic amines, with putative reactive nitroso-intermediates coupling with the amines to form azo dimers. Secondary reactions include N-alkyl substitution, O-demethylation (sometimes followed by dehydroxylation), and removal of an N-containing group. Globally, our results suggest that the main reaction DNAN undergoes in anaerobic soils is nitroreduction to 2-methoxy-5-nitroaniline (MENA) and 2,4-diaminoanisole (DAAN), followed by anaerobic coupling reactions yielding azo-dimers. The dimers were subsequently subject to further (bio)transformations.

Continuous treatment of the insensitive munitions compound N-methyl-p-nitro aniline (MNA) in an upflow anaerobic sludge blanket (UASB) bioreactor

N-methyl-p-nitroaniline (MNA) is an ingredient of insensitive munitions (IM) compounds that serves as a plasticizer and helps reduce unwanted detonations. As its use becomes widespread, MNA waste streams will be generated, necessitating viable treatment options. We studied MNA biodegradation and its inhibition potential to a representative anaerobic microbial population in wastewater treatment, methanogens. Anaerobic biodegradation and toxicity assays were performed and an up-flow anaerobic sludge blanket reactor (UASB) was operated to test continuous degradation of MNA. MNA was transformed almost stoichiometrically to N-methyl-p-phenylenediamine (MPD). MPD was not mineralized; however, it was readily autoxidized and polymerized extensively upon aeration at pH = 9. In the UASB reactor, MNA was fully degraded up to a loading rate of 297.5 μM MNA d(-1). Regarding toxicity, MNA was very inhibitory to acetoclastic methanogens (IC50 = 103 μM) whereas MPD was much less toxic, causing only 13.9% inhibition at the highest concentration tested (1025 μM). The results taken as a whole indicate that anaerobic sludge can transform MNA to MPD continuously, and that the transformation decreases the cytotoxicity of the parent pollutant. MPD can be removed through extensive polymerization. These insights could help define efficient treatment options for waste streams polluted with MNA.

Efficient and microbial communities for pollutant removal in a distributed-inflow biological reactor (DBR) for treating piggery wastewater

To treat piggery wastewater with a low C/N ratio, a novel distributed-inflow biological reactor (DBR) was developed that assures the proper organic flow for an efficient denitrification process.

Organic pollutants in the central and coastal Beibu Gulf, South China Sea

Surface sediments from the central and coastal Beibu Gulf, southern China, were analyzed for persistent organic pollutants. The absence of polychlorinated biphenyls (PCB; generally below detection limit), low concentrations of polycyclic aromatic hydrocarbons (PAH; 24-647 ng g(-1)), and locally high contamination with organo-chloro pesticides (DDT; 0.03-92 ng g(-1)) reflect the early stages of development in southwest China, with human activities dominated by agriculture and low impact of industry. Concentrations of PCB and PAH indicate no ecological risk, while DDT accumulation poses a probable toxic risk in coastal but not in shelf sediments. Diagnostic ratios suggest PAH originating mainly from combustion of biomass and diesel fuels, and recent DDT use in agriculture and antifouling paint. Distribution patterns along the coastal-shelf-gradient indicate mainly airborne transport of PAH and waterborne transport of DDT. In the central Gulf, also water column samples reveal low concentrations of PAH (1.7-7.8 ng L(-1)) and DDT (0.006-0.053 ng L(-1)).

Culturing oil sands microbes as mixed species communities enhances ex situ model naphthenic acid degradation

Oil sands surface mining for bitumen results in the formation of oil sands process water (OSPW), containing acutely toxic naphthenic acids (NAs). Potential exists for OSPW toxicity to be mitigated by aerobic degradation of the NAs by microorganisms indigenous to the oil sands tailings ponds, the success of which is dependent on the methods used to exploit the metabolisms of the environmental microbial community. Having hypothesized that the xenobiotic tolerant biofilm mode-of-life may represent a feasible way to harness environmental microbes for ex situ treatment of OSPW NAs, we aerobically grew OSPW microbes as single and mixed species biofilm and planktonic cultures under various conditions for the purpose of assaying their ability to tolerate and degrade NAs. The NAs evaluated were a diverse mixture of eight commercially available model compounds. Confocal microscopy confirmed the ability of mixed and single species OSPW cultures to grow as biofilms in the presence of the NAs evaluated. qPCR enumeration demonstrated that the addition of supplemental nutrients at concentrations of 1 g L(-1) resulted in a more numerous population than 0.001 g L(-1) supplementation by approximately 1 order of magnitude. GC-FID analysis revealed that mixed species cultures (regardless of the mode of growth) are the most effective at degrading the NAs tested. All constituent NAs evaluated were degraded below detectable limits with the exception of 1-adamantane carboxylic acid (ACA); subsequent experimentation with ACA as the sole NA also failed to exhibit degradation of this compound. Single species cultures degraded select few NA compounds. The degradation trends highlighted many structure-persistence relationships among the eight NAs tested, demonstrating the effect of side chain configuration and alkyl branching on compound recalcitrance. Of all the isolates, the Rhodococcus spp. degraded the greatest number of NA compounds, although still less than the mixed species cultures. Overall, these observations lend support to the notion that harnessing a community of microorganisms as opposed to targeted isolates can enhance NA degradation ex situ. Moreover, the variable success caused by NA structure related persistence emphasized the difficulties associated with employing bioremediation to treat complex, undefined mixtures of toxicants such as OSPW NAs.

Aromatic amine contents, component distributions and risk assessment in sludge from 10 textile-dyeing plants

Aromatic amines (AAs), which are components of synthetic dyes, are recalcitrant to the wastewater treatment process and can accumulate in sludge produced by textile-dyeing, which may pose a threat to the environment. A comprehensive investigation of 10 textile-dyeing plants was undertaken in Guangdong Province in China. The contents and component distributions of AAs were evaluated in this study, and a risk assessment was performed. The total concentrations of 14 AAs (Σ14 AAs) varied from 11 μg g(-1)dw to 82.5 μg g(-1)dw, with a mean value of 25 μg g(-1)dw. The component distributions of AAs were characterized by monocyclic anilines, of which 2-methoxy-5-methylaniline and 5-nitro-o-toluidine were the most dominant components. The risk quotient (RQ) value was used to numerically evaluate the ecological risk of 14 AAs in the environment. The result showed that the 14 AAs contents in textile-dyeing sludge may pose a high risk to the soil ecosystem after being discarded on soil or in a landfill.

Ecological perspectives on synthetic biology: insights from microbial population biology

The metabolic capabilities of microbes are the basis for many major biotechnological advances, exploiting microbial diversity by selection or engineering of single strains. However, there are limits to the advances that can be achieved with single strains, and attention has turned toward the metabolic potential of consortia and the field of synthetic ecology. The main challenge for the synthetic ecology is that consortia are frequently unstable, largely because evolution by constituent members affects their interactions, which are the basis of collective metabolic functionality. Current practices in modeling consortia largely consider interactions as fixed circuits of chemical reactions, which greatly increases their tractability. This simplification comes at the cost of essential biological realism, stripping out the ecological context in which the metabolic actions occur and the potential for evolutionary change. In other words, evolutionary stability is not engineered into the system. This realization highlights the necessity to better identify the key components that influence the stable coexistence of microorganisms. Inclusion of ecological and evolutionary principles, in addition to biophysical variables and stoichiometric modeling of metabolism, is critical for microbial consortia design. This review aims to bring ecological and evolutionary concepts to the discussion on the stability of microbial consortia. In particular, we focus on the combined effect of spatial structure (connectivity of molecules and cells within the system) and ecological interactions (reciprocal and non-reciprocal) on the persistence of microbial consortia. We discuss exemplary cases to illustrate these ideas from published studies in evolutionary biology and biotechnology. We conclude by making clear the relevance of incorporating evolutionary and ecological principles to the design of microbial consortia, as a way of achieving evolutionarily stable and sustainable systems.

Chemical characterization and anaerobic biodegradability of hydrothermal liquefaction aqueous products from mixed-culture wastewater algae

This study examined the chemical characteristics and the anaerobic degradability of the aqueous product from hydrothermal liquefaction (HTL-ap) from the conversion of mixed-culture algal biomass grown in a wastewater treatment system. The effects of the HTL reaction times from 0 to 1.5 h, and reaction temperatures from 260 °C to 320 °C on the anaerobic degradability of the HTL-ap were quantified using biomethane potential assays. Comparing chemical oxygen demand data for HTL-ap from different operating conditions, indicated that organic matter may partition from organic phase to aqueous phase at 320 °C. Moderate lag phase and the highest cumulative methane production were observed when HTL-ap was obtained at 320 °C. The longest lag phase and the smallest production rate were observed in the process fed with HTL-ap obtained at 300 °C. Nevertheless, after overcoming adaptation issues, this HTL-ap led to the second highest accumulated specific methane production. Acetogenesis was identified as a possible rate-limiting pathway.

Decolorization and biogas production by an anaerobic consortium: effect of different azo dyes and quinoid redox mediators

The inhibitory effect of azo dyes and quinoid compounds on an anaerobic consortium was evaluated during a decolorization process and biogas production. In addition, the impact of quinoid compounds such as lawsone (LAW) and anthraquinone-2,6-disulfonate (AQDS) on the rate of decolorization of Direct Blue 71 (DB71) was assessed. The anaerobic consortium was not completely inhibited under all tested dye concentrations (0.1-2 mmol l(-1)), evidenced by an active decolorization process and biogas production. The presence of quinoid compounds at different concentrations (4, 8, and 12 mmol l(-1)) also inhibited biogas production compared to the control incubated without the quinoid compounds. In summary, the anaerobic consortium was affected to a greater extent by increasing the quantity of azo dyes or quinoid compounds. Nevertheless, at a lower concentration (1 mmol l(-1)) of quinoid compounds, the anaerobic consortium effectively decolorized 2 mmol l(-1) of DB71, increasing up to 5.2- and 20.4-fold the rate of decolorization with AQDS and LAW, respectively, compared to the control lacking quinoid compounds.

Catalytic performance of functionalized polyurethane foam on the reductive decolorization of Reactive Red K-2G in up-flow anaerobic reactor under saline conditions

Soluble anthraquinone compounds including anthraquinone-2-sulfonate (AQS) and anthraquinone-2,6-disulfonate can accelerate anaerobic decolorization of azo dyes. To realize the application of these compounds, the catalytic performance and stability of AQS-modified polyurethane foam (AQS-PUF) for Reactive Red K-2G decolorization were investigated in an up-flow anaerobic bioreactor under saline conditions. The results showed that the optimal influent pH value and hydraulic retention time were 7 and 10 h, respectively, in a continuous-flow bioreactor amended with AQS-PUF (R1). Under the above conditions, R1 (93.8 % color removal) displayed better decolorization performance than the bioreactor amended with PUF (R2, 64 % color removal) in 10 days, when influent K-2G concentration was 50 mg/L. Moreover, compared with R2, R1 could more effectively cope with 50-400 mg/L K-2G and exhibited better stability with over 85 % color removal efficiency within 75 days. Further bacterial community analysis using polymerase chain reaction-denaturing gradient gel electrophoresis showed that AQS-reducing bacteria played an important role in accelerating K-2G decolorization in R1. Extracellular polymeric substances analysis found that biofilm formed on AQS-PUF had very limited negative effects on K-2G decolorization. The catalytic performance of used AQS-PUF only decreased less than 9 % in batch experiments. These findings indicate that AQS-PUF has potential application for the treatment of azo dye-containing wastewater.

Plant-associated bacteria degrade defense chemicals and reduce their adverse effects on an insect defoliator

Phytophagous insects must contend with numerous secondary defense compounds that can adversely affect their growth and development. The gypsy moth (Lymantria dispar) is a polyphagous herbivore that encounters an extensive range of hosts and chemicals. We used this folivore and a primary component of aspen chemical defenses, namely, phenolic glycosides, to investigate if bacteria detoxify phytochemicals and benefit larvae. We conducted insect bioassays using bacteria enriched from environmental samples, analyses of the microbial community in the midguts of bioassay larvae, and in vitro phenolic glycoside metabolism assays. Inoculation with bacteria enhanced larval growth in the presence, but not absence, of phenolic glycosides in the artificial diet. This effect of bacteria on growth was observed only in larvae administered bacteria from aspen foliage. The resulting midgut community composition varied among the bacterial treatments. When phenolic glycosides were included in diet, the composition of midguts in larvae fed aspen bacteria was significantly altered. Phenolic glycosides increased population responses by bacteria that we found able to metabolize these compounds in liquid growth cultures. Several aspects of these results suggest that vectoring or pairwise symbiosis models are inadequate for understanding microbial mediation of plant-herbivore interactions in some systems. First, bacteria that most benefitted larvae were initially foliar residents, suggesting that toxin-degrading abilities of phyllosphere inhabitants indirectly benefit herbivores upon ingestion. Second, assays with single bacteria did not confer the benefits to larvae obtained with consortia, suggesting multi- and inter-microbial interactions are also involved. Our results show that bacteria mediate insect interactions with plant defenses but that these interactions are community specific and highly complex.