Assessment of electron transfer mechanisms during a long-term sediment microbial fuel cell operation

The decentralized production of bioelectricity as well as the bioremediation of contaminated sediments might be achieved by the incorporation of an anode into anaerobic sediments and a cathode suspended in the water column. In this context, a sediment microbial fuel cell microcosm was carried out using different configurations of electrodes and types of materials (carbon and stainless steel). The results showed a long-term continuous production of electricity (>300 days), with a maximum voltage of approximately 100 mV reached after ~30 days of operation. A twofold increase of voltage was noticed with a twofold increase of surface area (~30 mV to ~60 mV vs. 40 cm2 to 80 cm2), while a threefold increase was obtained after the substitution of a carbon anode by one of stainless steel (~20 mV to ~65 mV vs. 40 cm2 to 812 cm2). Cyclic voltammetry was used to evaluate sediment bacteria electroactivity and to determine the kinetic parameters of redox reactions. The voltammetric results showed that redox processes were limited by the diffusion step and corresponded to a quasi-reversible electron charge transfer. These results are encouraging and give important information for the further optimization of sediment microbial fuel cell performance towards the long-term operation of sediment microbial fuel cell devices.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 doNorte. The authors also acknowledge the fellowship awarded to Gilberto Martins (SFRH/BPD/80528/2011) under the scope of the program POPH/ESF.info:eu-repo/semantics/publishedVersio

Classification of apple and pear species from Alcobaça region (Portugal) and their cultivars with machine learning algorithms

Principal Component Analysis (PCA) transforms the original variable into new ones called principal components (PC). These PC´s are calculated attributing a coefficient for each original variables proportional to their contribution into this transformation in order to maximize the variances of the first few components [1]. The main objective is to reduce the dimensionality, while keeping the contribution of all initial variables in order to provide a visual pattern recognition [2]. PCA biplot graphs with both scores and loadings provide information on the influence of each variable on a given sample. The hierarchical clustering was also employed in order to highlight the similarities among samples. The following variables were determined through ethanolic extracts of apple and pear varieties from the Alcobaça region (Portugal) using spectrophotometric analysis: DPPH radical scavenging, -carotene bleaching, total phenolic content, total flavonoid content, and fructose content. The results show that a very high correlation exists among the variables antioxidant capacity through DPPH, total phenolics content and total flavonoids, while the fructose content shows independent behavior in relation to the other ones. The graph of scores for the first two PCs, which explain 90% of variance, shows three different clusters with different apple and pear species. It can be concluded from these results that the fructose content allows to separate apples and pears while antioxidant capacity through DPPH, total phenolics content and total flavonoids content can be used to separate different cultivars of each fruit. This study shows that multivariate analysis, with special focus on PCA, can be a valuable tool for the separation of different fruit species and their cultivars highlighting the similarities and differences among them.This study was carried out in the frame of the clabel+ project: Innovative Natural, Nutritious and Consumer Oriented “Clean Label” Foods with the reference POCI-01-0247-FEDER-046080 financed by the Competitiveness and Internationalization Thematic Operational Programme (PO CI), under the COMPETE2020, PORTUGAL2020 Partnership Agreement, through the co-financing of European Regional Development Fund (FEDER). J. D. Teixeira would like to thank to clabel+ project for his fellowship (28/2021/BI). The authors thank Patricia Vicente for her support in the field work. The work was supported by UIDB/00211/2020 with funding from FCT/MCTES through national funds. C. Almeida also acknowledges the financial support by LA/P/0045/2020 (ALiCE), UIDB/00511/2020 and UIDP/00511/2020 (LEPABE), funded by national funds through FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Development of hemostatic materials made of electrochemically oxidized bacterial cellulose

Book of Abstracts of CEB Annual Meeting 2017[Excerpt] Cellulose is the most abundant polysaccharide in nature, being the main constituent of plant cell walls. It can undergo structural modification by oxidative methods, making it absorbable when implanted in the organism, contrarily to what happens with the non-oxidized cellulose. This way it can be used as raw material in medical devices, such as absorbable hemostatic materials and as a barrier to prevent postoperative adhesions. Cellulose can also be produced by bacteria (mainly from the species Glucanocetobacter xylinus), being this way known as bacterial cellulose (BC). With the increasing use of the hemostatic materials based on oxidized cellulose in surgical procedures, there has also been an increase in the number of case studies that describe post-operative complications associated with the use of these materials. BC has improved characteristics and unique properties compared with polysaccharide derived from plants, namely a higher biocompatibility. It has therefore been the subject of increased research over the past years allowing its application in various fields, especially in biomedical applications [1]. This project aims to develop a hemostatic material to reduce post-operative complications, based on the oxidized BC, using electrochemical oxidation methods [2]. These methods are based on the stable nitroxyl radicals commercially available. [...]info:eu-repo/semantics/publishedVersio

Impact of an external electron acceptor on phosphorus mobility between water and sediments

The present work assessed the impact of an external electron acceptor on phosphorus fluxes between water-sediment interface. Microcosm experiments simulating a sediment microbial fuel cell (SMFC) were carried out and phosphorus was extracted by an optimized combination of three methods. Despite the low voltage recorded, ∼96 mV (SMFC with carbon paper anode) and ∼146 mV (SMFC with stainless steel scourer anode), corresponding to a power density of 1.15 mW/m2 and 0.13 mW/m2, it was enough to produce an increase in the amounts of metal bound phosphorus (14% vs 11%), Ca-bound phosphorus (26% vs 23%) and refractory phosphorus (33% vs 28%). These results indicate an important role of electroactive bacteria in the phosphorus cycling and open a new perspective for preventing metal bound phosphorus dissolution from sediments.The authors are indebted and grateful to the Regional Department of Water Resources and Land Planning (Azores) and its staff. The authors also acknowledge the Grant SFRH/BPD/8052812011 from the Foundation for Science and Technology, Portugal, awarded to Gilberto Martins

Protective effect of Ginkgo biloba extract against genotoxic stress

info:eu-repo/semantics/publishedVersio

Regional apple and pear cultivars from Alcobaça region (Portugal): comparison of the antioxidant properties of the edible part and by-products

Food waste is commonly defined as a decrease, at all stages of the food system from production to consumption, in mass and/or quality, of food that was originally intended for human consumption, regardless of the cause [1]. To avoid food waste, we aimed to characterize the antioxidant capacity of regional cultivars of apples and pears, for which there are still scarce data. Moreover, different parts of the fruits (peels, seeds and mesocarp) were analysed individually in order to evaluate the potential of by-products to be used a valuable source of natural antioxidants [2], which are believed to be responsible for human health benefits such as anticancer and cardioprotective effects [3]. The objective of this work was to determine the antioxidant properties [4] and fructose content of both by-products (peels and seeds) and edible part of five different Portuguese apple cultivars (Pardo Lindo, Pêro de Borbela, Noiva, Pêro Coimbra and Repinau) and five pear cultivars (Bela-Feia, Torres Novas, Carapinheira Roxa, Lambe-os-Dedos and Amorim), produced in Alcobaça region (Alcobaça), in two consecutive years. The antioxidant properties were evaluated through antioxidant capacity tests (DPPH radical scavenging and -carotene bleaching) and total phenolic content and total flavonoids assays. By-products showed better antioxidant capacity, than the edible part in all cultivars, but the fructose content was very similar in the three parts of the fruits. The results indicate that regional apples´ by-products presented greater potential than regional pears´ by-products. In this line they have potential to be used as a valuable source of antioxidant compounds, which can be further used, by food, cosmetics, food packaging or food supplements industries.This study was carried out in the frame of the clabel+ project: Innovative Natural, Nutritious and Consumer Oriented “Clean Label” Foods with the reference POCI-01-0247-FEDER-046080 financed by the Competitiveness and Internationalization Thematic Operational Programme (POCI), under the COMPETE2020, PORTUGAL2020 Partnership Agreement, through the co-financing of European Regional Development Fund (FEDER). J. D. Teixeira would like to thank to clabel+ project for his fellowship (28/2021/BI). The authors thank Patricia Vicente for her support in the field work. The work was supported by UIDB/00211/2020 with funding from FCT/MCTES through national funds. C. Almeida also acknowledges the financial support by LA/P/0045/2020 (ALiCE), UIDB/00511/2020 and UIDP/00511/2020 (LEPABE), funded by national funds through FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Towards implementation of a benthic microbial fuel cell in lake Furnas (Azores) : phylogenetic affiliation and electrochemical activity of sediment bacteria

This work was conducted to examine the composition and electrochemical activity of the bacterial community inhabiting lake Furnas sediments (Azores). Fingerprinting analysis of the bacterial 16S rRNA gene fragment was done by denaturing gradient gel electrophoresis. The sequences retrieved from lake Furnas sediments were affiliated to Bacteroidetes/Chlorobi group, Chloroflexi, Alfa-, Delta-, and Gamma-subclasses of Proteobacteria, Cyanobacteria, and Gemmatimonadetes. A cyclic voltammetric study was carried out with an enriched sediment bacterial suspension in a standard two chamber electrochemical cell using a carbon paper anode. Cyclic voltammograms (scan rate of 50 mV/s) showed the occurrence of oxidation–reduction reactions at the carbon anode surface. The benthic microbial fuel cell operated with lake Furnas sediments presented a low power density (1 mW/m2) indicating that further work is required to optimise its power generation. These results suggested that sediment bacteria, probably from the Delta- and Gamma-subclasses of Proteobacteria, were electroactive under tested conditions.Fundação para a Ciência e a Tecnologia (FCT) - bolsa SFRH/BD/25639/2005, SFRH/BD/38331/2007Regional Department of Water Resources and Land Planning, Geosciences Department, University of Azores; Foundation for Science and Technology/F.C.T., PortugalUniversity Azore

Células de combustível microbianas : um processo inovador para produção de energia e tratamento de águas residuais em sistemas descentralizados

A produção de energia constitui uma base essencial para o desenvolvimento humano. Neste quadro, a capacidade de determinados microrganismos oxidarem matéria orgânica e transferirem eletrões para um ânodo e, por essa via, permitirem a produção direta de eletricidade representa uma efetiva oportunidade tecnológica. Este novo processo, designado por célula de combustível microbiana, constitui uma abordagem de produção de energia elétrica com capacidade para ser acoplada ao tratamento de águas residuais, apresentando elevado potencial para integrar fluxos de eletricidade e tratamento de águas residuais em sistemas descentralizados. No presente trabalho efetuaram-se ensaios eletroquímicos de voltametria cíclica, os quais permitiram reforçar a importância da transferência direta de eletrões e da formação de biofilme eletroactivo na superfície do eléctrodo. O desempenho da MFC para produção de bioeletricidade e tratamento de águas residuais foi efectuado com comunidades microbianas anódicas mista e pura (Geobacter sulfurreducens). As densidades de potência instantânea atingiram máximos de 710 W/m3 com uma cultura pura e 823 W/m3 com a mista, sendo que a remoção de carbono da água residual atingiu valores médios de 83%