Biological carbon dioxide utilisation in food waste anaerobic digesters

Carbon dioxide (CO2) enrichment of anaerobic digesters (AD) was previously identified as a potential on-site carbon revalorisation strategy. This study addresses the lack of studies investigating this concept in up-scaled units and the need to understand the mechanisms of exogenous CO2 utilisation. Two pilot-scale ADs treating food waste were monitored for 225 days, with the test unit being periodically injected with CO2 using a bubble column. The test AD maintained a CH4 production rate of 0.56 ± 0.13 m3 CH4·(kg VSfed d)−1 and a CH4 concentration in biogas of 68% even when dissolved CO2 levels were increased by a 3 fold over the control unit. An additional uptake of 0.55 kg of exogenous CO2 was achieved in the test AD during the trial period. A 2.5 fold increase in hydrogen (H2) concentration was observed and attributed to CO2 dissolution and to an alteration of the acidogenesis and acetogenesis pathways. A hypothesis for conversion of exogenous CO2 has been proposed, which requires validation by microbial community analysis

Incident light orientation lets C4 monocotyledonous leaves make light work differently

Photosynthesis is an important driver of ecosystem sustainability in the face of climate change. Monocotyledonous crop species with C4 photosynthesis such as maize (Zea mays L; corn) and sugar cane are crucial for future food security and biofuel crop requirements, while C4 pasture grasses such as Paspalum are central to natural ecosystems. The global demand for corn will exceed that for wheat and rice by 2020, making it the world's most important crop. Light-driven photosynthesis supports plant biomass production, but plants have also evolved safety valve mechanisms that attenuate the absorption of potentially lethal levels of excess light. The array of survival responses that enables leaves to evade photoinhibition is complex and involves chloroplast and leaf movement as well as the molecular rearrangements that facilitate thermal energy dissipation. Here we report a novel morphological mechanism that allows C4 monocotyledonous leaves to regulate photosynthesis independently on each surface with respect to incident light allowing better adaptation to water deficits and light stress. We show that under abaxial illumination as occurs when monocotyledonous leaves curl in response to water stress the stomata close and photosynthetic metabolism shuts down on the adaxial surface of C4 leaves but these parameters increase in function to the abaxial surface. We discuss how this regulation confers a survival advantage to the C4 relative to C3 leaves which are unable to regulate their dorso-ventral functions in relation to light

Gas to liquid mass transfer in rheologically complex fluids

The increase of studies relaying on gas to liquid mass transfer in digested sludge (shear thinning fluid) necessitates a better understanding of the impact of apparent viscosity (μa) and rheology in process performance. Mass transfer retardation due to μa variations was investigated in a pilot scale absorption bubble column for Newtonian and shear thinning fluids with varied superficial gas velocities (UG). A non-linear reduction of mass transfer efficiency with increasing μa was observed, being the impact higher at low μa ranges and high UG. An increase of 114 cPo in μ from 1.01 to 115 cPo in glycerol solutions saturated with UG = 1.73 cm s−1 led to a reduction of 96% in kLa (α = 0.04), while a comparable raise from 115 to 229 cPo implied a reduction of 52% (α = 0.02). Slug–annular flow regime was identified for shear thinning fluids of high μa (1.0% and 1.5% carboxymethyl cellulose sodium salt solutions), where bubble buoyancy was conditioned by the μ of the fluid at rest and the active volume for mass transfer was reduced because of the presence of stagnant areas. Conditions imitating the rheological variability of anaerobically digested sewage sludge were included within those tested, being a reduction in gas transfer efficiency of 6 percentage points (from 7.6 ± 0.3% to 1.6 ± 0.1%) recorded when increasing μa from 130 to 340 cPo. It is thus recommended that rheology and μa variability are accounted for within the design of gas to liquid mass transfer systems involving digested sewage sludge, in order to avoid reductions in process performance and active volume

Distribution of herpetofauna in caves of Portuguese karst massifs

Amphibians are frequently found exploring subterranean environments. Even though in Europe there are already some reports of amphibians present in subterranean habitats, in Portugal there is a major lack of knowledge of these ecosystems, namely in the karst region. Considering the relevance of amphibians and their current conservational status, it is important to assess their presence in every potential habitat. In order to provide further knowledge over this subject a preliminary survey was carried out in two Portuguese karst massifs, Estremenho and Sicó. A total of 24 caves were surveyed and as result three species (Tarentola mauritanica; Salamandra salamandra and Pleorodeles waltl) were found in Estremenho karst massif, and two species (Triturus marmoratus and Bufo bufo) were observed in Sicó karst massif. Furthermore, evidences were found that P. waltl uses caves for reproduction, which had only been reported once in Spain. This allowed perceiving that herpetofauna species occupy caves of Portuguese karst massifs and are also using them as reproduction sites

Photorelease of amino acids from novel thioxobenzo[f]benzopyran ester conjugates

Aiming at the enhancement of the performance of (9-methoxy-3-oxo-3H-benzo[f]benzopyran-1-yl) methyl ester as photocleavable protecting group for the carboxylic acid function at long-wavelengths, 9-methoxy-3-thioxo-3H-benzo[f]benzopyran-L-valine and L-phenylalanine model conjugates were prepared through a thionation reaction of the corresponding oxo-benzobenzopyrans. These thioxobenzobenzopyran derivatives were subjected to photocleavage reactions in the same conditions as the parent oxo-benzobenzopyrans at different wavelengths of irradiation, and photocleavage kinetic data was obtained. It was found that the exchange of the carbonyl by a thiocarbonyl group enhanced the performance of the heterocyclic protecting group at 419 nm by improving the photolysis rates, making it an appropriate group for practical applications at long wavelengths.Fundo Europeu de Desenvolvimento Regional (FEDER) - POCI 2010Fundação para a Ciência e a Tecnologia (FCT) - REDE/1517/RMN/200

Differences in chemical composition and antioxidant activity of three propolis samples collected in the same apiary

Financial support provided by FCT (PD/BD/128276/2017), under the Doctoral Programme Agrichains - PD/00122/2012

Bioconversion of carbon dioxide in anaerobic digesters for on-site carbon capture and biogas enhancement - A review

Energy consumption of the water sector presents an increasing energy demand, contrary to GHG mitigation aims. As a result, research aimed at capturing emitted CO2 and at developing treatment technologies with a low energy demand and increased renewable energy production has increased, leading to a surge in implementation of anaerobic digestion (AD). Valorization of the biogenic CO2 emitted with biogas AD (estimated at over 1 MtCO2 per annum for the UK water and organic waste sectors), presents an opportunity to further reduce carbon footprint and support energy supply decarburization. This paper reviews bioconversion of CO2 into CH4 in ADs (without addition of H2) as a means to valorize CO2 emissions. The review has concluded this to be a promising solution to reduce carbon footprint and uplift renewable energy production. However, in order to increase readiness for implementation (1) the mechanisms of CO2 utilization need to be elucidated, including the sources of additional H2 needed, (2) studies need to report more thoroughly the conditions of CO2 injection and (3) trials where ADs are integrated with gas to liquid mass transfer technologies need to be performed

Photoactivable oxobenzopyranoxazole esters of 5-aminolevulinic acid

Comunicação em painel P51 no 1st European Young Chemists Meeting/ 5th Portuguese Young Chemists Meeting, Guimarães, Portugal, 26-29 Abril 2016.In this communication we report the synthesis of new oxobenzopyranoxazoles 1a,b as photolabile protecting groups and their conjugation with 5-(N-butyloxycarbonyl)aminolevulinic acid 2 via an ester bond. The study of the photolytic behaviour of the resulting conjugates in different conditions was carried out in a photochemical reactor by irradiation at 254, 300, 350 and 419 nm, monitored by HPLC-UV and 1H NMR.Thanks are due to the Foundation for Science and Technology (Portugal) for financial support through project PEstC/QUI/UI0686/2013 (F-COMP-01-0124-FEDER-037302) FEDER-COMPETE, FCT-Portugal. A PhD grant to A.M.S.S. (SFRH/BD/80813/2011) is also acknowledged. The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased in the framework of the National Program for Scientific Reequipment, with funds from POCI 2010 (FEDER) and FCT.info:eu-repo/semantics/publishedVersio

Photolysis at long wavelengths of amino acid ester derivatives based on 4-methyl-6-methoxy-2-oxo-2H-naphtho[1,2-b]pyrans

Ester derivatives of fused 4-methyl-6-methoxy-2-oxo-2H- naphtho[1,2-b]pyran, using valine and phenylalanine as model bifunctional molecules were synthesised, to assess its applicability as a photocleavable protecting group, for solution phase organic synthesis and in caging applications, at longer wavelengths. The behaviour of the corresponding derivatives towards photolysis was evaluated by irradiation in mixture of HEPES buffer and acetonitrile or methanol, in a photochemical reactor at 350 and 419 nm, followed by HPLC/UV monitoring. Time-resolved fluorescence measurements were used to elucidate the dynamics.Fundação para a Ciência e a Tecnologia (FCT) -PTDC/QUI/69607/2006, SFRH/BD/61459/2009Fundo Europeu de Desenvolvimento Regional (FEDER) - REDE/1517/RMN/200