Inhibitory impact of the anticancer drug doxorubicin on anaerobic microbial community.

The inhibitory effect of the anticancer drug doxorubicin (DOX) on biogas production was evaluated in short-term and long-term exposure assays. The short-term assays reached the DOX IC50 value on 648 ± 50 µg·L-1. In addition, it was found that inhibition caused by the exposure of 10×103 µg·L-1 was reversible after removing DOX from the feeding synthetic medium. Furthermore, DOX can be rapidly sorbed by the biomass (despite the low Kow), which might contribute to the inhibitory effect. The results of long-term exposure assays, when the DOX volumetric loading rate was increased from 100 µgDOX·L-1·day-1 to 200 µgDOX·L-1·day-1, showed that biogas production and COD removal decreased rapidly. However, the methanogenic Archaeas could recover from this exposure, corroborating the results on short-term exposure assays. In conclusion, DOX can play a key role in inhibiting biological wastewater treatment processes if its concentration in hospital wastewater treatment plants increases abruptly.

Antibiotics in wastewater: From its occurrence to the biological removal by environmentally conscious technologies.

In this critical review, we explored the most recent advances about the fate of antibiotics on biological wastewater treatment plants (WWTP). Although the occurrence of these pollutants in wastewater and natural streams has been investigated previously, some recent publications still expose the need to improve the detection strategies and the lack of information about their transformation products. The role of the antibiotic properties and the process operating conditions were also analyzed. The pieces of evidence in the literature associate several molecular properties to the antibiotic removal pathway, like hydrophobicity, chemical structure, and electrostatic interactions. Nonetheless, the influence of operating conditions is still unclear, and solid retention time stands out as a key factor. Additionally, the efficiencies and pathways of antibiotic removals on conventional (activated sludge, membrane bioreactor, anaerobic digestion, and nitrogen removal) and emerging bioprocesses (bioelectrochemical systems, fungi, and enzymes) were assessed, and our concern about potential research gaps was raised. The combination of different bioprocess can efficiently mitigate the impacts generated by these pollutants. Thus, to plan and design a process to remove and mineralize antibiotics from wastewater, all aspects must be addressed, the pollutant and process characteristics and how it is the best way to operate it to reduce the impact of antibiotics in the environment.

Laccase as an efficacious approach to remove anticancer drugs: A study of doxorubicin degradation, kinetic parameters, and toxicity assessment.

The degradation of an anticancer drug by laccase was investigated for the first time, bringing a new approach to treat these hazardous substances through the direct enzymatic application. Degradations of doxorubicin by laccase were performed in different enzymatic concentrations, pH values and temperatures through kinetic studies. The highest enzymatic degradation of doxorubicin was achieved at pH 7 and 30 ºC, which resembles effluent characteristics from wastewater treatment plants. Assays were carried out in different doxorubicin concentrations to comprehend the enzymatic kinetics of degradation. Michaelis-Menten kinetic parameters obtained were maximum velocity obtained (Vmax) of 702.8 µgDOX h-1 L-1 and Michaelis-Menten constant (KM) of 4.05 µM, which showed a good affinity for the substrate. The toxicity was evaluated against L-929 cell line, and the degraded doxorubicin solution did not show a reduction in cell viability in the concentration of 250 µg L-1. In contrast, the doxorubicin shows a reduction of 27% in cell viability. Furthermore, in the highest tested concentration (1000 µg L-1), enzymatic degradation reduced in up 41.4% the toxicity of doxorubicin, which indicates laccase degrades doxorubicin to non-toxic compounds. In conclusion, this study provides a new application to laccase since the results showed great potential to remove anticancer drugs from effluents.

Tetracyclines lead to ammonium accumulation during nitrification process.

The effect of tetracyclines used for swine food-production (tetracycline and oxytetracycline) on enriched nitrifying bacteria cultures over time was investigated in this study. Short-term exposure assays were performed in different concentrations of each antibiotic, using ammonia oxidizing bacteria (AOB) culture and nitrifying bacteria. The results pointed out a higher inhibitory effect of tetracycline on both bacterial communities. The AOB was more sensitive to antibiotic exposure when compared to the nitrifying culture. Although high antibiotic concentrations were applied, the half maximal inhibitory concentration (IC50) was achieved only for the AOB culture exposed to tetracycline at a concentration of 273 mg L-1. Nonetheless, the long-term exposure assay demonstrated a reduction of the tetracycline inhibition effect against AOB. The exposure to 100 mg L-1 of tetracycline (TC) did not show relevant influence over ammonium conversion efficiency; however, at 128 mg L-1 of TC, the efficiency decreased from 94% to 72%. Further investigation revealed that TC reduced the final effluent quality due to the development of a resistance mechanism by AOB culture against this antibiotic. This mechanism involves increasing the excretion of extracellular polymeric substances (EPS) and soluble microbial products (SMP), which probably increases BOD, and reduces ammonia consumption by the bacterial culture.

Potential of enzymatic process as an innovative technology to remove anticancer drugs in wastewater.

Anticancer drugs are a class of pharmaceutical compounds that have been found in hospital, domestic, and industrial wastewaters and also in surface waters. They have been showing recalcitrance to conventional wastewater treatment technologies and present a potential risk to environment and human health, since they exhibit cytotoxic, teratogenic, and carcinogenic among other effects in higher organisms, even at low concentrations. The presence of these compounds in the environment is a recent challenge for wastewater treatment and some alternative strategies to remove them were already studied, such as white-rot fungi (WRF) technologies. Despite promising results, processes involving fungi are complex, have high reaction times, and require nutrient addition for fungus growth and maintenance. Due to this potential, strategies to make the technology feasible were studied, such as the possibility for direct application of enzymes secreted by WRF. Enzymatic processes were studied in the removal of other pharmaceuticals such as antibiotics, anti-inflammatory, and steroid hormones; however, to the best of our knowledge, there is a gap on literature about their direct action on anticancer drugs.

Inhibition of an enriched culture of ammonia oxidizing bacteria by two different nanoparticles: Silver and magnetite.

Metal and metal oxide nanoparticles are getting attention over the past years. They can be used to several purposes, especially in commercial and medical applications. Undoubtedly, this lead to higher production and, consequently, increasing the risks of exposition, once they can be released into environment without a proper control. However, their impact over the bacteria present in wastewater treatment plants (WWTP), manly over nitrifying bacteria, which are the most susceptible to toxic compounds, are still not very well established. Herein it was investigated the impact of silver nanoparticles (AgNP) and magnetite nanoparticles (FeNP), separately, over an ammonia oxidizing bacteria (AOB), during short-term exposure tests and it was also verified their impact on bacterial surface. The concentrations assessed were from 0 to 30mgAgNPL-1 and from 0 to 1000mgFeNPL-1. Results showed that AOB specific nitrite production rate reduced 90% when exposed to 30mgAgNPL-1, and in almost 71% in the presence of 1000mgFeNPL-1. The concentration necessary to reduce 50% of AOB activity was 10.75mgAgNPL-1 and 483.01mgFeNPL-1 highlighting that AgNP can be 45 times more toxic to AOB than FeNP. Both nanoparticles attached to bacterial surface, even in the lower concentration tested, hindering AOB activity due to changes in the membrane permeability. Once nanoparticles remain attached in the biological sludge, which is used as fertilizer to soil, they can affect not only WWTP performance but also hindering soil quality and the ecosystem balance.

Magnetite nanoparticles influence the ammonium-oxidizing bacteria activity during nitritation process.

With nanotechnology dissemination, nanomaterials' (NMs) release into the environment is inevitable and may adversely affect the wastewater treatment processes. Among the NMs, the iron oxide nanoparticles have a considerable commercial potential, mainly because their magnetic properties, high catalytic ability and antimicrobial activity. However, few studies have examined their potential effect on the biological wastewater treatment. In this process, ammonium-oxidizing bacteria (AOB) are sensitive to the presence of inhibitory compounds and are useful as biosensors to assess contaminant toxicity information. Thus, this work aimed to assess the effect of commercial magnetite nanoparticles (Fe3O4-NPs) on AOB activity. Kinetic experiments were carried out where AOB were exposed in a short-term period (14 h) to different concentrations (from 0.2 to 1.0 g L-1) of Fe3O4-NPs. A decrease of the 61.33% in the NO2--N production rate was observed to the highest concentration of Fe3O4-NPs studied, compared with the control sample. The Fe3O4-NPs concentration that reduces 50% of NO2--N production rate (IC-50) was estimated 0.483 g Fe3O4-NP L-1. Scanning electron microscopy images revealed that NPs remained incorporated in the biomass (sludge). These results suggest that NPs can reach the environment through sludge disposal, mainly in cases of the reuse as soil fertilizer.

Silver nanoparticles temporarily retard NO2 - production without significantly affecting N2 O release by Nitrosomonas europaea.

Nitrifying bacteria are highly susceptible to silver nanoparticles (AgNPs). However, the effect of sublethal exposure to AgNPs after their release of nitrogenous compounds of environmental concern (e.g., the greenhouse gas nitrous oxide [N2 O] and the common water pollutant nitrite [NO2 -]) has not been systematically investigated. The present study reports the effect of AgNPs (and potentially released silver ions [Ag(+) ]) on NO2 - and N2 O production by Nitrosomonas europaea, and on the transcription of the associated genes. The release of NO2 - was more negatively affected than the production of N2 O. For example, exposure to AgNPs at 0.075 mg/L temporarily enhanced N2 O production (by 12%) without affecting nitrite release, whereas higher AgNP concentrations (>0.25 mg/L) inhibited NO2 - release (by >12%) but not N2 O production. Transcriptomic analyses corroborated these trends; AgNPs at 0.075 mg/L increased the expression of the nitric oxide reductase gene (norQ) associated with N2 O production (by 5.3-fold to 12.8-fold), whereas both 0.075 mg/L of Ag(+) and 0.75 mg/L of AgNPs down-regulated the ammonia monooxygenase gene (amoA2; by 0.08-fold to 0.15-fold and 0.32-fold to 0.64-fold, respectively), the nitrite reductase gene (nirK; by 0.01-fold to 0.02-fold and 0.22-fold to 0.44-fold, respectively), and norQ (by 0.11-fold to 0.15-fold and 0.32-fold to 0.57-fold, respectively). These results suggest that AgNP release to sewage treatment plants and land application of AgNP-containing biosolids should be minimized because of their potential temporary stimulation of N2 O release and interference with nitrification. Environ Toxicol Chem 2015;34:2231-2235. © 2015 SETAC.

Differential sensitivity of nitrifying bacteria to silver nanoparticles in activated sludge.

Nitrification is known as one of the most sensitive processes affected when activated sludge is exposed to antimicrobial silver nanoparticles (AgNPs). The impact of AgNPs and their released silver ions (Ag(+) ) on the abundance, activity, and diversity of different nitrifying bacteria in wastewater treatment plants (WWTPs), however, is poorly understood. The present study investigated the impacts of 2 sizes of AgNPs (5 nm and 35 nm) and Ag(+) ions on the nitrifier community in activated sludge, including both ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Ammonia-oxidizing bacteria were more sensitive to AgNPs than the NOB; a 5-d and 7-d exposure of activated sludge to 35 nm AgNPs (40 ppm) significantly reduced AOB abundance to 24% and 19%, respectively. This finding was confirmed further by a decrease in activated sludge ammonia oxidation activity measured by (14) C-labeled bicarbonate uptake. In contrast, neither AgNPs (up to 40 ppm) nor Ag(+) (1 ppm) affected the abundance of NOB. Both 5 nm and 35 nm AgNPs decreased the diversity of AOB, as indicated by denaturing gradient gel electrophoresis with ammonia monooxygenase gene (amoA) primers, although some unknown Nitrosomonas species were relatively resistant to AgNPs. The generally greater resistance of NOB than AOB to AgNPs suggests that the accumulation of bacteriostatic nitrite in WWTPs is unlikely to be exacerbated due to the accidental or incidental release of AgNPs.