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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.

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 onMono- 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 ofThe 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.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).

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).

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.

Algae have multiple similarities with fungi, with both belonging to the Thallophyte, a polyphyletic group of non-mobile organisms grouped together on the basis of similar characteristics, but not sharing a common ancestor. The main difference between algae and fungi is noted in their metabolism. In fact, although algae have chlorophyll-bearing thalloids and are autotrophic organisms, fungi lack chlorophyll and are heterotrophic, not able to synthesize their own nutrients. However, our studies have shown that the extremophilic microalga Galderia sulphuraria (GS) can also grow very well in heterotrophic conditions like fungi. This study was carried out using several approaches such as scanning electron microscope (SEM), gas chromatography/mass spectrometry (GC/MS), and infrared spectrophotometry (ATR-FTIR). Results showed that the GS, strain ACUF 064, cultured in autotrophic (AGS) and heterotrophic (HGS) conditions, produced different biomolecules. In particular, when grown in HGS, the algae (i) was 30% larger, with an increase in carbon mass that was 20% greater than AGS, (ii) produced higher quantities of stearic acid, oleic acid, monounsaturated fatty acids (MUFAs), and ergosterol, (iii) produced lower quantities of fatty acid methyl esters (FAMEs) such as methyl palmytate, and methyl linoleate, saturated fatty acids (SFAs), and poyliunsaturated fatty acids (PUFAs). ATR-FTIR and principal component analysis (PCA) statistical analysis confirmed that the macromolecular content of HGS was significantly different from AGS. The ability to produce different macromolecules by changing the trophic conditions may represent an interesting strategy to induce microalgae to produce different biomolecules that can find applications in several fields such as food, feed, nutraceutical, or energy production.

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 behavior 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/m2 and 1.6 A/m2, respectively, with a maximum OCV of 557 mV. Unexpectedly, the compost-based MFCs kept significant electric outputs (854 mV, 467 mW/m2 kg, and 114 mA/m2 kg) after being reactivated 2 years later its set-up, thus demonstrating its potential as long-term operation energy system.

Microbial Fuel Cells (MFCs) remedial technology was used for the degradation of Polycyclic Aromatic Hydrocarbons (PAHs) in marine sediments taken in front of the brownfleld steelwork facility of Bagnoli, Gulf of Pozzuoli, South Western Italy. PAHs levels were quite high and up to 30 mu g/g for fluoranthene and 0.21 mu g/g d.w. L of sediments for acenaphthene. Heavy PAHs prevailed vs light PAHs in the sediment samples before, during and after the treatment by MFCs. Different degradation rates were measured according to the complexity of each PAH, as expected. Among all PAHs, naphthalene showed after four weeks the highest degradation rate (86%), while just the 10% of Indenol[1,2,3-c,d]pyrene was degraded. MFCs achieved their highest performance in terms of Power Density (PD) after two weeks, with values ranging between 20.4 mW/m(2) and 3.17 mW/m(2) of anodic surface. CD values were normalized to the anodic surface as well, falling within a maximum of 204.8 mA/m(2) and a minimum of 9.5 mA/m(2). Even though the dynamics of PAHs degradation in MFCs and the influence of other pollutants (like metals) on MFCs performance as well as the potential mobilization of pollutants in consequence of microbial activity have to be ascertained, our preliminary results prove the high potentialities of MFCs for in-situ marine sediments remediation. (C) 2019 Elsevier Ltd. All rights reserved.

The influence of microelectrogenesis on PAHs degradation and detoxification operated by Pseudomonadaceae, Bacillaceae, Staphylococcaceae and Enterobacteriaceae was investigated in water environment. Single chamber, air-cathode MFCs and bioreactors were filled with the microbial pool (10(7)-10(8) CFUmL(-1)) inoculated in a 400mL Winogradsky saline solution containing no other carbon and energy source than naphthalene (80 ppm), phenanthrene (40 ppm), pyrene (40 ppm), benzo(a)pyrene (20 ppm). MFCs and bioreactors operated at 25 degrees C for thirteen weeks. Power Density (PD) and Current Density (CD) outputs as well as PAHs degradation rate were measured. The toxic effect of PAHs suspension vs.Raphidocelis subcapitata was quantified by EC1, EC20, EC50, LOEC and NOEC calculations. The results showed a significant variability in PD and CD outputs, with highest PD of 300 mW m(-3) and 25 mA m(-3). After 5 weeks, the overall PAHs concentration in MFCs decreased of a 90%. COD and TOC removal respectively of 62% and 73% after 11 weeks was achieved in MFC inoculated with bacteria (MFC2). Ecotoxicological tests showed for MFCs a lower toxic effect vs.P.subcapitata when bacteria are present. Microelectrogenesis just sped up microbial metabolism rather than take advantage from the interaction of PAHs with graphite electrodes.

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.

The possible utilization of MFCs technology to the remediation of waters polluted by Polyclicic Aromatic Hydrocarbons (PAHs) was explored in this work. Ten microbial strains, isolated in urban environment, were inoculated in a MFC (three replicates) fuelled by 400 ml Winogradsky saline solution containing no other carbon and energy sources than anthracene (100 ppm), naphthalene (200 ppm), phenantrene (100 ppm), pyrene (100 ppm), benzo(a)pyrene (50 ppm) and incubated at 25°C. The performances were evaluated in terms of Power Density (PD), Current Density (CD), PAHs degradation rate and toxicity vs Daphnia magna and Lepidium sativum. A significant variability in PD (486 μW/m3 on average) was measured along with a maximum CD of 9 mA/m3. A degradation of 53% (naphthalene), 28% (anthracene and phenanthrene), 17% (pyrene) and 25% (benzo(a)pyrene) but, an increase in ecotoxicity vs L.sativum was measured in Winogradsky solutions+PAHs after one month.