Remediation Technologies for environmental contamination by PAHs: Microbial Fuel Cells

In questo lavoro di ricerca è stata valutata l'influenza dell’ elettrogenesi sulla degradazione degli IPA e sulla disintossicazione operata da consorzi batterici, uno specializzato e un endogeno, in ambiente acquatico. I bioreattori e le MFCs a camera singola, con catodo ad aria, sono stati riempiti con pool microbico (107-108 UCF/mL) inoculato in una soluzione salina Winogradsky da 400 mL contenente nessun'altra fonte di carbonio ma solamente IPA: naftalene (80 ppm), del fenantrene (40 ppm), del pirene (40ppm), benzo (a) pirene (20 ppm). I valori di Power Density (PD) e Current Density (CD) così come il tasso di degradazione di IPA sono stati misurate nel corso del trattamento. La tossicità ambientata è stata valutata mediante test ecotossicologici con Raphidocelis subcapitata. I risultati hanno mostrato un significativo variabilità nei valori di PD e CD, con PD più alto di 380 mW/m3 e 25 mA/m3 dopo all’ incirca un mese di trattamento, inoltre la concentrazione complessiva di IPA è diminuita del 90 in MFC inoculato con batteri (MFC2). I test ecotossicologici hanno dimostrato per le MFC con consorzio un abbassamento del livello di tossicità rispetto agli altri campioni. L’elettrogenesi ha accelerato il metabolismo microbico portando a un miglioramento delle attività degradative e detossificanti dei batteri.Inoltre, in questo lavoro, è stato condotto un esperimento di bonifica mediante celle a combustibile microbico (MFC) su sei campioni di sedimenti marini raccolti nel Golfo di Pozzuoli (area Bagnoli), in Campania (Italia). Questi campioni contenevano elevate concentrazioni di inquinanti, a causa di un'attività di scarico di acciaierie, ora dismessa, durata oltre 80 anni. Le analisi chimiche dei campioni hanno rivelato la presenza di tutti e 16 gli idrocarburi aromatici policiclici (IPA) elencati tra gli "inquinanti prioritari" dai sedimenti US-Environmental Protection Agency, con concentrazione che va da un massimo di 30 ppm (fluorantene) a 0,21 ppm (acenaphthene). Dopo un mese di trattamento, è stata riscontrata una notevole degradazione degli IPA, un abbassamento del livello di tossicità e, inoltre, una buona la produzione di energia con il valori più alti di PD e CD pari a 20 mW/m2 and 118 mA/m2. Confermando, su scala di laboratorio, il potenziale della tecnologia MFC nella bonifica dei sedimenti marini inquinati dagli IPA

SMFC as a tool for the removal of hydrocarbons and metals in the marine environment: a concise research update

Marine pollution is becoming more and more serious, especially in coastal areas. Because of the sequestration and consequent accumulation of pollutants in sediments (mainly organic compounds and heavy metals), marine environment restoration cannot exempt from effective remediation of sediments themselves. It has been well proven that, after entering into the seawater, these pollutants are biotransformed into their metabolites, which may be more toxic than their parent molecules. Based on their bioavailability and toxic nature, these compounds may accumulate into the living cells of marine organisms. Pollutants bioaccumulation and biomagnification along the marine food chain lead to seafood contamination and human health hazards. Nowadays, different technologies are available for sediment remediation, such as physicochemical, biological, and bioelectrochemical processes. This paper gives an overview of the most recent techniques for marine sediment remediation while presenting sediment-based microbial fuel cells (SMFCs). We discuss the issues, the progress, and future perspectives of SMFC application to the removal of hydrocarbons and metals in the marine environment with concurrent energy production. We give an insight into the possible mechanisms leading to sediment remediation, SMFC energy balance, and future exploitation

Use of Biochar-Based Cathodes and Increase in the Electron Flow by Pseudomonas aeruginosa to Improve Waste Treatment in Microbial Fuel Cells

In this paper, we tested the combined use of a biochar-based material at the cathode and of Pseudomonas aeruginosa strain in a single chamber, air cathode microbial fuel cells (MFCs) fed with a mix of shredded vegetable and phosphate buffer solution (PBS) in a 30% solid/liquid ratio. As a control system, we set up and tested MFCs provided with a composite cathode made up of a nickel mesh current collector, activated carbon and a single porous poly tetra fluoro ethylene (PTFE) diffusion layer. At the end of the experiments, we compared the performance of the two systems, in the presence and absence of P. aeruginosa, in terms of electric outputs. We also explored the potential reutilization of cathodes. Unlike composite material, biochar showed a life span of up to 3 cycles of 15 days each, with a pH of the feedstock kept in a range of neutrality. In order to relate the electric performance to the amount of solid substrates used as source of carbon and energy, besides of cathode surface, we referred power density (PD) and current density (CD) to kg of biomass used. The maximum outputs obtained when using the sole microflora were, on average, respectively 0.19 Wm−2kg−1 and 2.67 Wm−2kg−1 , with peaks of 0.32 Wm−2kg−1 and 4.87 Wm−2kg−1 of cathode surface and mass of treated biomass in MFCs with biochar and PTFE cathodes respectively. As to current outputs, the maximum values were 7.5 Am−2 kg−1 and 35.6 Am−2kg−1 in MFCs with biochar-based material and a composite cathode. If compared to the utilization of the sole acidogenic/acetogenic microflora in vegetable residues, we observed an increment of the power outputs of about 16.5 folds in both systems when we added P. aeruginosa to the shredded vegetables. Even though the MFCs with PTFE-cathode achieved the highest performance in terms of PD and CD, they underwent a fouling episode after about 10 days of operation, with a dramatic decrease in pH and both PD and CD. Our results confirm the potentialities of the utilization of biochar-based materials in waste treatment and bioenergy production

Allium ursinum and Allium oschaninii against Klebsiella pneumoniae and Candida albicans Mono- and Polymicrobic Biofilms in In Vitro Static and Dynamic Models

The present study assesses the in vitro antibiofilm potential activity of extracts of wild Allium ursinum and Allium oschaninii. The active ingredients of the extracts were obtained with a technique named Naviglio (rapid solid–liquid dynamic extraction, RSLDE) which is based on an innovative and green solid–liquid extraction methodology. The extracts were tested against models of mono‐ and polymicrobial biofilm structures of clinically antibiotic‐resistant pathogens, Klebsiella pneumoniae ATCC 10031 and Candida albicans ATCC 90028. Biofilms were studied using a static and a dynamic model (microtiter plates and a CDC reactor) on three different surfaces reproducing what happens on implantable medical devices. Antimicrobic activities were determined through minimum inhibitory concentration (MIC), while antibiofilm activity was assessed by minimum biofilm eradication concentration (MBEC) using a crystal violet (CV) biofilm assay and colony forming unit (CFU) counts. Results showed that both Allium extracts eradicated biofilms of the tested microorganisms well; biofilms on Teflon were more susceptible to extracts than those on polypropylene and polycarbonate, suggesting that when grown on a complex substrate, biofilms may be more tolerant to antibiotics. Our data provide significant advances on antibiotic susceptibility testing of biofilms grown on biologically relevant materials for future in vitro and in vivo applications

A first attempt to evaluate the toxicity to Phaeodactylum tricornutum Bohlin exposed to rare earth elements

The increasing use and demand of rare earth elements in many emerging technologies is leading to a potentially higher input to the marine environment. This study compared for the first time the effect of lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), dysprosium (Dy), and erbium (Er) to the microalga Phaeodactylum tricornutum Bohlin. The algal growth inhibition was investigated after 72 h of exposure. The median effect concentrations (EC50) ranged from 0.98 mg/L to 13.21 mg/L and elements were ranked as follows: Gd > Ce > Er > La > Eu > Nd > Dy > Sm. The comparison of predicted no effect concentrations (PNEC) for hazard and risk assessment with measured environmental concentrations showed that ecological risks deriving from REEs could be present, but limited to specific environments like estuarine waters. The results support evidence of actions to manage the REE impact in seawater environments, looking to improve the monitoring tailored to the different and dynamic nature of ecosystems

Harvesting Energy Using Compost as a Source of Carbon and Electrogenic Bacteria

Compost is widely used to improve soil fertility for its chemical-physical properties, with particular regard to the abundance of humic substances. Compared to the untreated organic solid waste, the use of compost in Microbial Fuel Cells (MFCs) could offer different advantages like the strong reduction of fermentative processes. The use of compost in MFCs in combination with soil or mixed with other substrates had been reported by some researchers to improve the performance of MFCs fed with agro-industrial residues and plant-MFCs. In this chapter, we report the results of an experiment carried out using a compost of vegetable residues as feedstock in a single chamber, air cathode MFCs. We investigated the behaviour of two MFCs serially connected, the possibility to use compost as a long-term source of energy in MFCs, the influence of cathode surface /cell volume ratio on MFCs performance in terms of power and current density. Our results showed for MFCs serially connected a maximum PD and CD of 234 mW/m 2 and 1.6 A/m 2 respectively, with a maximum OCV of 557 mV. Unexpectedly, the compost-based MFCs kept significant electric outputs (854 mV, 467 mW/m 2 kg and 114 mA/m 2 kg) after being reactivated two years later its setup thus demonstrating its potential as long-term operation energy system

Evaluation of the Pathogenic-Mixed Biofilm Formation of Pseudomonas aeruginosa/Staphylococcus aureus and Treatment with Limonene on Three Different Materials by a Dynamic Model

Background: Biofilms have been found growing on implantable medical devices. This can lead to persistent clinical infections. The highly antibiotic-resistant property of biofilms necessitates the search for both potent antimicrobial agents and novel antibiofilm strategies. Natural product-based anti-biofilm agents were found to be as efficient as chemically synthesized counterparts with fewer side effects. In the present study, the effects of limonene as an antibiofilm agent were evaluated on Pseudomonas aeruginosa and Staphylococcus aureus biofilm formed on different surfaces using the CDC model system in continuous flow. The flgK gene and the pilA gene expression in P. aeruginosa, and the icaA gene and eno gene in S. aureus, which could be considered as efficient resistance markers, were studied. Methods: Mono- and dual-species biofilms were grown on polycarbonate, polypropylene, and stainless-steel coupons in a CDC biofilm reactor (Biosurface Technologies, Bozeman, MT, USA). To evaluate the ability of limonene to inhibit and eradicate biofilm, a sub-MIC concentration (10 mL/L) was tested. The gene expression of P. aeruginosa and S. aureus was detected by SYBR Green quantitative Real-Time PCR assay (Meridiana Bioline, Brisbane, Australia). Results: The limonene added during the formation of biofilms at sub-MIC concentrations works very well in inhibiting biofilms on all three materials, reducing their growth by about 2 logs. Of the same order of magnitude is the ability of limonene to eradicate both mono- and polymicrobial mature biofilms on all three materials. Greater efficacy was observed in the polymicrobial biofilm on steel coupons. The expression of some genes related to the virulence of the two microorganisms was differently detected in mono- and polymicrobial biofilm. Conclusions: These data showed that the limonene treatment expressed different levels of biofilm-forming genes, especially when both types of strains alone and together grew on different surfaces. Our findings showed that limonene treatment is also very efficient when biofilm has been grown under shear stress causing significant and irreversible damage to the biofilm structure. The effectiveness of the sanitation procedures can be optimized by applying antimicrobial combinations with natural compounds (e.g., limonene)

A Preliminary Evaluation on the Antifungal Efficacy of VT-1161 against Persister <i>Candida albicans</i> Cells in Vulvovaginal Candidiasis

Persister cells are a small fraction of the microbial population that survive lethal concentrations of antimicrobial agents. Candida albicans causes vaginal candidiasis, including recurrent vulvovaginal candidiasis, and may survive common antifungal treatments. The triazole VT-1161 is an antifungal agent that specifically targets fungal CYP51, as opposed to the human CYP enzyme. This work illustrates a new role of VT-1161 in eradicating the biofilm created from the persister cells of a primary biofilm of a clinical vaginal isolate of C. albicans. Antifungal activity was determined by the minimum inhibitory concentration (MIC), and the primary biofilm was treated with amphotericin B to obtain persister cells that were able to form a new biofilm. Results obtained using the new azole VT-1161 showed that VT-1161 not only eradicated a secondary biofilm formed from the persister-derived biofilm and counteracted the adhesion of C. albicans in vitro to human cells but also ameliorated C. albicans-induced infection in vivo in Galleria mellonella larvae, suggesting that it could be proposed as an alternative therapeutic strategy for the treatment of recurrent candidiasis

Pseudomonas anguilliseptica Strain-A1 Degradation of Polycyclic Aromatic Hydrocarbons in Soil Microcosms: Focus on Detoxification Activity and Free Water-Soluble Protein Extracts Kinetics and Efficiency

Pseudomans anguilliseptica-A1 strain, isolated in an urban area, improved the efficiency of a microbial consortium, composed of Bacillaceae, Staphylococcacea, Xantomonadaceae and Enterbacteriaceae, whose ability to degrade five Polycyclic Aromatic Hydrocarbons (PAHs) among the priority pollutants was previously ascertained. Six soil microcosms were prepared with a slurry (60% soil, 40% water) artificially contaminated with anthracene (0.4 mg g-1), phenanthrene (0.2 mg g-1), naphthalene (0.2 mg g-1), pyrene (mg g-1) and benzo(a)pyrene (0.1 mg g-1) and opportunely aerated for two months. PAHs were monthly quantified by inverse phase High Performance Liquid Chromatography (HPLC), coupled with UV-Vis spectrophotometry and spectrofluorimetry. Acute toxicity assays vs Dapnia magna and Lepidium sativum, and chronic essays vs Ceriodaphnia dubia were monthly performed. Our results showed a 100% degradation for naphthalene, 99.14% for anthracene, 99.23% for phenanthrene, 86% for pyrene and 72.5% for benzo[a]pyrene after two months of treatment. A sterile P. anguilliseptica-A1 lysate in Na-K buffer added with each of the chosen PAHs (53%, wtPAHs/volsusp), operated at 30°C the oxidative degradation of naphthalene, pyrene, benzo(a)pyrene and anthracene in a few hours, while the phenanthrene enzyme degradation process took about 15 h. The GC-MS analysis revealed interesting metabolite structures such as 2- hydroxynaphthalene, 9,10-phenanthrenedione, 2,2’ diphenic acid and methyl 4-hydroxybenzoate. The direct utilization of enzymes/microbial extracts from P. anguilliseptica-A1 could present specific advantages such as availability and a fast PAHs degradation time in bioremediation processes

Prevalence, Resistance Patterns and Biofilm Production Ability of Bacterial Uropathogens from Cases of Community-Acquired Urinary Tract Infections in South Italy

Community-acquired urinary tract infections represent the most common infectious diseases in the community setting. Knowing the antibiotic resistance patterns of uropathogens is crucial for establishing empirical treatment. The aim of the current study is to determine the incidence of the causative agents of UTIs and their resistance profiles. Patients of all ages and both sexes were enrolled in the study, and admitted to San Ciro Diagnostic Center in Naples between January 2019 and Jun 2020. Bacterial identification and antibiotic susceptibility testing were carried out using Vitek 2 system. Among the 2741 urine samples, 1702 (62.1%) and 1309 (37.9%) were negative and positive for bacterial growth, respectively. Of 1309 patients with infection, 760 (73.1%) were females and 279 (26.9%) were males. The greatest number of positive cases were found in the in the elderly (>61 years). Regarding uropathogens, 1000 (96.2%) were Gram-negative while 39 (3.8%) were Gram-positive strains. The three most isolated pathogenic strains were Escherichia coli (72.2%), Klebsiella pneumoniae (12.4%), and Proteus mirabilis (9.0%). Strong biofilm formation ability was observed in about 30% of the tested isolates. The low resistance rates recorded against nitrofurantoin, fosfomycin, piperacillin–tazobactam, and gentamicin could suggest them as the most appropriate therapies for CA-UTIs