CH4 production at moderate H2/CO2 pressures insights on the use of anaerobic granular sludge as biocatalyst

Introduction: The continuous increase in energy consumption and the intensive use of fossil fuels, lead to the emission of greenhouse gases (GHG) and, in particular, to an increase in the concentration of CO2 in the atmosphere. In this context, the improvement in global awareness and the demand for sustainable technologies and products strongly contribute to laid plans to combat climate change. CO2-to-CH4 conversion represents a cutting-edge solution for CO2 capture and use, contributing to the reduction of GHG emission. Catalytic conversion of CO2-to-CH4 have been investigated, however, the high cost associated to the catalysts employed limits their use on a large scale. Biological CO2 methanation can overcome the significant technical and economic challenges of catalytic CO2 methanation. The biological production of CH4 using CO2-rich gases together with H2 is a promising strategy for the production of bioproducts. Hydrogenotrophic methanogens have a crucial role on the direct conversion of CO2+H2 into CH4, hence the importance to study the specific hydrogenotrophic methanogenic activity (SHMA). Methodology: In this work, the effect of initial substrate (H2/CO2) pressure, from 100 to 500 kPa, on the SHMA, on CH4 production rate and on developed microbial communities were evaluated. Two different pressurized bioreactors were studied using anaerobic granular sludge as the biocatalyst and H2/CO2 (80:20, v/v) as sole carbon and energy source. Gaseous compounds were analyzed by GC and archaeal diversity within granular sludge was monitored by 16S r-RNA based techniques. Results: The results showed an increase in the SHMA as well as in the CH4 production rate with the increase of the initial H2/CO2 pressure. This results are very interesting since no inhibitory effects were observed on the microbial activity, demonstrating the resistance of the anaerobic granular sludge. The Illumina results showed that Methanosarcinales, Methanobacteriales and Methanomicrobiales were the three orders that prevailed in the pressurized system, for all the pressures tested. However, hydrogenotrophic methanogens from Methanobacterium and Methanospirillum genera slightly increased their relative abundance, varying from 38% (100 kPa) to 41% (500 kPa) and from 8% (100 kPa) to 12% (500 kPa), respectively. Conclusions: In conclusion, the archaeal community seems to be very stable when submitted to increasing H2/CO2 pressures, highlighting the potential of the anaerobic granular sludge as an efficient microbial platform for the production of added-value compounds from gaseous carbon waste streams.Portuguese Foundation for Science and Technology (FCT): POCI-01-0145-FEDER-031377; strategic funding of UIDB/04469/2020 unit; BioTecNorte operation (NORTE-01-0145-FEDER-000004); FCT doctoral grant PD/BD/128030/2016.info:eu-repo/semantics/publishedVersio

CH4 production at moderate H2/CO2 pressures - insights on the specific hydrogenotrophic methanogenic activity

CO2 is one of the main contributors to greenhouse gases (GHGs), being its emission to the atmosphere one of the major driver of global climate change. Biological methanation of CO2 using renewable H2 provides a promising approach to use of superplus renewable electrical power to produce a gaseous fuel. CH4 is considered an important renewable energy carrier, that has a wide range of applications such as natural gas for distribution. Hydrogenotrophic methanogens are key elements in the CO2/H2 methanation process. Thus the importance to study the specific hydrogenotrophic methanogenic activity (SHMA). The effect of the initial substrate (H2/CO2) pressure on the SHMA was investigated in two different pressurized bioreactors. The results suggest that in addition to the increase of the initial substrate pressure, also the bioreactor configuration influence the SHMA, which is crucial for the success of biological CO2 methanation technologies but also in anaerobic bioreactors treating wastewaters.info:eu-repo/semantics/publishedVersio

Pressurized syngas bioconversion: physiological and microbial characterization

ICBM-3 - 3rd International Conference on Biogas MicrobiologySyngas is composed mainly by CO, H2 and CO2 and its fermentation is a promising biological process to produce fuels or commodity chemicals. Experiments under increased initial syngas pressures, up to 5.2×105 Pa, were carried out to evaluate the effects on metabolites production and microbial communities structure. Two strategies were applied: NB non-adapted biomass and SB successively syngas-fed biomass. The rise of syngas pressure from 1.2×105 Pa up to 5.2×105 Pa led to a decrease on CO and H2 consumption rates and CH4 production rate. Moreover, when methanogenesis was partially inhibited, propionate and butyrate were the main metabolites produced from syngas. DGGE profiles showed differences on diversity and on similarity indices (SI) with changes in pressure. Regardless the syngas pressure employed, the archaeal communities had higher SI (above 70%) than bacterial community (48% to 62%). From the Illumina sequencing analysis, it was observed that the relative abundance of bacterial communities tend to decrease (72% to 46%), and archaeal communities increased (25% to 54%) by raising the pressure of syngas from 1.2×105 Pa to 5.2×105 Pa. In the inoculum and biomass incubated at 1.2×105 Pa syngas, 40% of total population were from Proteobacteria phylum and Deltraproteobacteria class and their abundance was reduced 4-fold at 5.2×105 Pa. As a direct effect of high pressures of syngas, organisms belonging to Firmicutes, Synergistetes and Thermotogae phyla increased over 10-fold. The predominant phylotypes at 3×105 Pa and 5.2×105 Pa were related to Methanobacterium genus (archaea) and to Eubacteriaceae, Synergistaceae and Syntrophobacteraceae families (bacteria). These results showed a microbial population enrichment suggesting a high specialization for the substrate.info:eu-repo/semantics/publishedVersio

Pedómetro como ferramenta de intervenção na escola

info:eu-repo/semantics/publishedVersio

Perspetivas de investigação no ensino da educação física: o exemplo do estágio pedagógico do curso de mestrado em ensino de educação física nos ensinos básico e secundário

info:eu-repo/semantics/publishedVersio

Perspectives on syngas fermentation

Book of Abstracts of CEB Annual Meeting 2017The replacement of fossil fuels by renewable energy sources is, nowadays, a worldwide priority. Gasification processes and further bioconversion of syngas appears to be a promising alternative compared to the existing chemical techniques, since this process convert renewable sources into alternative fuels and commodity chemicals, such as CH4, fatty acids, alcohols, etc., additionally contributing to the reduction of greenhouse gases [1]. Nearly any form of organic matter can be transformed through gasification, into syngas, mainly composed of CO, H2 and CO2. The biological conversion of syngas offers several advantages over catalytic processes, specifically the greater resistance to catalyst poisoning and the higher specificity for the substrates [2]. Syngas- and CO-fermenting microorganisms use the Wood-Ljungdahl pathway to produce several multi-carbon compounds such as short- and medium-fatty acids and alcohols. Even though many studies were performed in the last few years, fermentation of syngas still involves practical challenges due to limitations of the process. The major bottleneck of syngas fermentation that blocks the commercialization of this technology is gas-to-liquid mass transfer limitations, since it reduces the microorganisms access to the substrate and consequently reduces the productivity rates. It is of utmost importance the development of alternatives that promote the enhancement of mass transfer, the improvement on the productivity rates from syngas fermentation and the deep study of the biocatalysts involved in syngas bioconversion pathways. Biological syngas conversion has been a research topic at the BRIDGE group since 2009, by studying both technological and microbiological aspects of the process. Previous work developed in our group focused on the use of anaerobic complex microbial communities to obtain enriched cultures and/or pure cultures that could convert syngas or CO into mainly acetate, CH4 and H2. Regarding to the technological aspects of syngas bioconversion process, a multi-orifice baffled bioreactor was used to study the effect of using different reactors designs to improve the gas-liquid mass transfer. Moreover, recent studies conducted at BRIDGE group with collaboration of BIOSYSTEMS group showed that the use of increased pressure (up to 5 bar) to increase gas-liquid mass transfer, leads to different metabolic routes on microorganisms. These results represent a step forward to direct the biochemical pathways of microbial community towards the specific products from syngas. As future perspectives, we aimed to continue a research line on syngas fermentation, by studying different operational approaches for this process and focusing on the production of butanol, 2,3-butanediol and propionate.info:eu-repo/semantics/publishedVersio

Didática da educação física: perspetivas, interrogações e alternativas

info:eu-repo/semantics/publishedVersio

Microbiological contamination in different food service units associated with food handling

Background: A microbiological analysis of samples taken from hands of food handlers and utensils/crockery in food service units was used to assess the risk of food contamination. We aimed to assess indicators of microbiological contamination in different food service units. Methods: We used data for an official inspection proposal (2018–2019) in different food service units serving a district in Northeast Portugal. We showed the proportion of positive samples for each microorganism assessed in samples taken from hands and kitchen utensils/crockery. Results: Out of 471 samples taken from hands of food handlers, 26.8% (n = 126) were classified as “unsatisfactory” due to the presence of at least Escherichia coli, Staphylococcus aureus and/or total and fecal coliforms. Such a proportion varied according to the type of food service unit with a higher proportion being observed in Canteens (40.0%) and in Retirement Home/Day Care Centers (37.8%). More than one third of 649 samples taken from kitchen utensils/crockery were classified as “unsatisfactory” (n = 181; 27.9%) or “bad” (n = 49; 7.6%). There were significant differences in these proportions across food service units, with a higher proportion of “unsatisfactory” samples being observed in Fishmongers and Butcher Shops/Charcuteries (50.0% and 45.1%, respectively), while a higher proportion of “bad” samples was observed in both Pastry/Bakery and Fishmonger establishments (33.3%), followed by Butcher Shops/Charcuteries (14.1%). Conclusions: Our results emphasize the need of awareness of hygiene practices among food handlers of different food service units, particularly in Fishmongers, Pastry/Bakery establishments and Butcher Shops/Charcuteries, highlighting the need of a periodic hygienic evaluation.info:eu-repo/semantics/publishedVersio

Herbal choline as an alternative to choline chloride in the diet of nursery piglets

O objetivo deste trabalho foi avaliar a substituição da suplementação de cloreto de colina por colina herbal na dieta de leitões na creche. O delineamento experimental foi em blocos ao acaso (peso inicial e sexo) com 80 leitões, em cinco tratamentos, com oito repetições. Os tratamentos consistiram em: controle negativo, dieta basal com suplementação de 300 mg kg-1 de colina via cloreto de colina, dieta basal com suplementação de 600 mg kg-1 de colina via cloreto de colina, dieta basal com suplementação de 100 mg kg-1 de colina herbal e dieta basal com suplementação de 200 mg kg-1 de colina herbal. Dados de desempenho zootécnico, parâmetros sanguíneos e viabilidade econômica foram analisados. A suplementação de colina herbal aumenta o peso corporal e o consumo diário de ração em leitões na creche. A suplementação com 100 mg kg-1 de colina herbal apresenta o maior retorno sobre o investimento. A colina herbal pode ser utilizada como fonte de suplementação de colina na dieta de leitões na creche, para substituir o cloreto de colina.The objective of this work was to evaluate the replacement of choline chloride supplementation by herbal choline in the diet of nursery piglets. The experimental design was randomized complete blocks (initial weight and sex) with 80 piglets, in five treatments, with eight replicates. The treatments consisted of: negative control, basal diet supplemented with 300 mg kg-1 choline via choline chloride, basal diet supplemented with 600 mg kg-1 choline via choline chloride, basal diet supplemented with 100 mg kg-1 herbal choline, and basal diet supplemented with 200 mg kg-1 herbal choline. Zootechnical performance data, blood parameters, and economic viability were analyzed. Herbal choline supplementation increases the body weight and daily feed intake of nursery piglets. The supplementation with 100 mg kg-1 herbal choline presents the highest return on investment. Herbal choline can be used as a source of choline supplementation in the diet of nursery piglets to replace choline chloride