Bioremediation of petroleum-contaminated soils: mathematical modelling as a tool for the simulation of alternative strategies

POCI-01-0145-FEDER-016575; ERC Grant n.º 323009; UID/BIO/04469/2013; POCI -01-0145-FEDER-006684; NORTE-01-0145-FEDER-000004; FCOMP-01-0124- FEDER-027462; SFRH/BPD/80528/2011info:eu-repo/semantics/publishedVersio

Garden and food waste co-fermentation for biohydrogen and biomethane production in a two-step hyperthermophilic-mesophilic process

Co-fermentation of garden waste (GW) and food waste (FW) was assessed in a two-stage process coupling hyperthermophilic dark-fermentation and mesophilic anaerobic digestion (AD). In the first stage, biohydrogen production from individual substrates was tested at different volatile solids (VS) concentrations, using a pure culture of Caldicellulosiruptor saccharolyticus as inoculum. FW concentrations (in VS) above 2.9 g L-1 caused a lag phase of 5 days on biohydrogen production. No lag phase was observed for GW concentrations up to 25.6 g L-1. In the co-fermentation experiments, the highest hydrogen yield (46±1 L kg-1) was achieved for GW:FW 90:10% (w/w). In the second stage, a biomethane yield of 682±14 L kg-1 was obtained using the end-products of GW:FW 90:10% co-fermentation. The energy generation predictable from co-fermentation and AD of GW:FW 90:10% is 0.5 MJ kg-1 and 24.4 MJ kg-1, respectively, which represents an interesting alternative for valorisation of wastes produced locally in communities.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER006684), Project SAICTPAC/0040/2015 (POCI-01-0145-FEDER016403) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020– Programa Operacional Regional do Norte. The authors also acknowledge the financial support of FCT and European Social Fund through the grant attributed to A.A. Abreu (SFRH/BPD/82000/2011). Research of A.J. Cavaleiro was supported by the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No 323009.info:eu-repo/semantics/publishedVersio

Ciprofloxacin removal catalysed by conductive carbon materials

Current wastewater treatment technologies are not effective in the removal of pharmaceuticals. In anaerobic bioreactors, the electrons produced during the oxidation of organic matter can potentially be used for the biological reduction of pharmaceuticals. However, these reactions occur generally at a slow rate, due to electron transfer limitations, and might be accelerated through redox mediators (RM). Carbon nanomaterials (CM) have been effective RM in the biological reduction of other pollutants. For instance, CNT@2%Fe were found to increase 76-fold the biological reduction of Acid Orange 10. The magnetic properties of those composites allow their easier recover after the process by using a magnetic field. In this study, CNT and CNT@2%Fe were studied in the anaerobic removal of Ciprofloxacin (CIP). Furthermore, the potential contribution of adsorption and biodegradation processes for CIP removal was assessed. Toxicity assessment is highly important as it is desired that the products formed after the process are not more toxic than the initial compound. Moreover, the evaluation of the possible contribution of nanomaterials used in the process for the final toxic effect of threated solution, is crucial. In this sense, the detoxification of the treated solutions was evaluated towards Vibrio fischeri.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Intensification of methane production from waste frying oil in a biogas-lift bioreactor

"Available online 31 December 2020"Biogas upgrading from anaerobic digestion of waste frying oils (WFO) was accessed in this study. For that, two bioreactors (Rb-biogas-lift bioreactor with gas and liquid recirculation, Rc-control reactor with liquid recirculation) were fed three times per week, with a mixture of WFO, glycerol and volatile fatty acids (VFA). Rb produced 1.4 times more biogas with higher methane content (79%) than Rc (67%). Higher relative abundance of hydrogenotrophic methanogens (34%-39%) was observed in Rb, when compared to Rc (16%-21%). The relative abundance of Sprochaetia class, which includes some homoacetogens/syntrophic acetate oxidizing genera, was also higher in Rb. This work shows that biogas recirculation applied in the biogas-lift bioreactor facilitated WFO degradation, most probably due to the selective enrichment of hydrogenotrophic methanogens. Recirculation of CO2 present in the biogas and reverse homoacetogenesis (i.e. syntrophic acetate oxidation) seem to be the main factors involved in the stimulation of hydrogenotrophic methanogenesis.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Exploring syntrophic relationships in the anaerobic biodegradation of lipids and long chain fatty acids

ICBM-3 - 3rd International Conference on Biogas Microbiology (Abstract Book)[Excerpt] Practical knowledge on anaerobic digestion of waste lipids has been improving for several decades, but the microbiology of these processes remains partially undisclosed, with non-cultivated taxonomic groups often detected in anaerobic communities degrading lipids. This work studies the diversity and physiology of anaerobic microorganisms involved in the metabolism of lipids and long chain fatty acids. Anaerobic culturing procedures were applied for the development of enrichment cultures, and combined with next generation sequencing techniques. Enriched microbial communities specialized in the degradation of triolein (0.3 mmol·L-1) and oleate (1 mmol·L-1) were obtained under methanogenic conditions. Oleatedegrading cultures were also developed in the presence of the external electron acceptors ferric hydroxide (75 mmol·L-1) or sulfate (15 mmol·L-1). Three mesophilic sludges from different origins were used as inocula. [...]info:eu-repo/semantics/publishedVersio

Untangling the role of facultative bacteria in LCFA conversion to methane

Book of Abstracts of CEB Annual Meeting 2017[Excerpt] Palmitate accumulation is frequently reported in continuous methanogenic bioreactors fed with lipidrich wastewater, and facultative bacteria were suggested to be involved in this conversion. In this work, the possible effects of limited oxygen conditions in triggering palmitate formation from oleate were studied. Two bioreactors were operated in parallel, one under strict anaerobic conditions (AnR) and the other with the feeding tank open to the air (FR). Palmitate was the main LCFA in both reactors, but it reached approximately 7 times higher concentrations in the FR than in the AnR (16 and 2 g·L-1 in COD, respectively). Moreover, oleate was more abundant in the AnR than in the FR, presenting concentrations of 1.3 and 0.5 g·L-1, and oxidation-reduction potential values (ORP) of -366 mV and -255 mV were measured. [...]info:eu-repo/semantics/publishedVersio

Hydrocarbon toxicity towards hydrogenotrophic methanogens in oily waste streams

Hydrocarbon-containing wastes and wastewaters are produced worldwide by the activities of the oil and gas industry. Anaerobic digestion has the potential to treat these waste streams, while recovering part of its energy potential as biogas. However, hydrocarbons are toxic compounds that may inhibit the microbial processes, and particularly the methanogens. In this work, the toxicity of hexadecane (030 mM) towards pure cultures of hydrogenotrophic methanogens (Methanobacterium formicicum and Methanospirillum hungatei) was assessed. Significantly lower (p 30 mM for M. formicicum and M. hungatei, respectively, suggesting that toxic effects from aliphatic hydrocarbons towards hydrogenotrophic methanogens may not occur during anaerobic treatment. Hydrocarbon toxicity towards hydrogenotrophic methanogens was further assessed by incubating an anaerobic sludge with H2/CO2 in the presence of a complex mixture of hydrocarbons (provided by the addition of an oily sludge from a groundwater treatment system). Specific methanogenic activity from H2/CO2 decreased 1.2 times in the presence of the hydrocarbons, but a relatively high methane production (~30 mM) was still obtained in the assays containing the inoculum and the oily sludge (without H2/CO2), reinforcing the potential of anaerobic treatment systems for methane production from oily waste/wastewater.This research was funded by the Portuguese Foundation for Science and Technology (FCT) under the scope of project MORE (POCI-01-0145-FEDER-016575) and by the strategic funding of UIDB/04469/2020 unit.info:eu-repo/semantics/publishedVersio

Hexadecane toxicity towards pure cultures of methanogens

Petroleum industry generates large volumes of hydrocarbon-containing wastewater, that may be treated and valorized by anaerobic conversion to methane. This process is performed by complex microbial communities and is only thermodynamically feasible at low hydrogen partial pressure, which is generally accomplished by the activity of hydrogenotrophic methanogens. However, alkanes, polyaromatic hydrocarbons and BTEX were shown to inhibit methanogenesis in mixed microbial cultures. This may be due to a direct inhibition of the methanogens, or may result from indirect inhibition, by disrupting the microbial relationships in the complex communities. To get more insights on this topic, the toxicity of aliphatic hydrocarbons towards pure cultures of hydrogenotrophic methanogens was assessed in this work. Aliphatic hydrocarbons represent the largest fraction of crude oil or petroleum-derived products, and hexadecane (HC) was chosen as model compound. Methane production from H2/CO2 (80:20%, 1.7x105 Pa) by Methanobacterium formicicum and Methanospirillum hungatei was measured in the presence of increasing HC concentrations (1, 5, 15 and 30 mM), and was compared with the controls without HC. For both methanogens, the methane production rate was significantly lower (p30 mM could be estimated for M. formicicum and M. hungatei, respectively. Therefore, M. hungatei is more tolerant to the presence of HC than M. formicicum, possibly due to the differences in cell wall structure and membrane lipid composition of the two species. Moreover, the relatively high IC50 values obtained are most likely related with the low HC solubility. Considering the typical range of hydrocarbon concentrations in wastewater from the petroleum industry, toxic effects from aliphatic hydrocarbons towards hydrogenotrophic methanogens will not be expected to occur during the anaerobic treatment of these type of wastewater.This study was supported by FCT under the scope of project MORE (PTDC/AAGTEC/3500/2014; POCI-01-0145-FEDER-016575), of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Addition of electron acceptors stimulates methanogenesis from lipids by anaerobic sludge

Incubation of anaerobic sludge with triolein or oleate in the presence of nitrate or sulphate led to an increased methane production, relatively to incubations without inorganic electron acceptor. Faster methane production was obtained in assays amended with nitrate. Methanogenesis occurred after the reduction of alternative electron acceptors

The protective effect of Pseudomonas in syntrophic fatty acids degradation under microaerophilic conditions

Micro-aeration has been used in anaerobic digestion (AD) systems to improve some aspects of this multifunctional and flexible technology. The addition of vestigial amounts of oxygen is usually associated with an increase of the relative abundance of facultative anaerobic bacteria (FAB) in the microbial community. Besides being involved in fermentation/acidogenesis, FAB have been referred to act as a protective shield against the damaging effects of oxidative environments to the strict anaerobic organisms of these communities. The microbial relationships between FAB, syntrophic bacteria and methanogens were investigated, during the degradation of short (C4), medium (C8) and long (C16) chain fatty acids by two syntrophic cultures (Syntrophomonas species and a methanogenic partner) in the presence of facultative bacteria (two Pseudomonas sp.). Pseudomonas were added to the pre-grown syntrophic pair, along with the substrate and a range of O2 concentrations (0-10% v/v). The grown cultures then were transferred a second time, with the same substrate and to all the O2 conditions previously tested. The cultures were followed through CH4, VFA, LCFA and pH measurements. In the presence of O2 (up to 2%) an effective syntrophic relationship, as well as the maintenance of methanogenic activity, was only possible in the presence of FAB. Cultures exposed to O2 in the first incubation performed well when transferred back to anaerobic conditions. Moreover, at the second phase, Pseudomonas maintained its protective shield effect and most of the cultures previously developed under micro-aerobic conditions could also maintain its activity. This work demonstrates that the presence of Pseudomonas contributes for a more resilient and functional syntrophic consortium degrading fatty acids under micro-aerobic conditions.info:eu-repo/semantics/publishedVersio