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Freshwater ecosystems are responsible for an important part of the methane (CH4) emissions which are likely to change with global warming. This study aims to evaluate temperature-induced (from 5 to 20 °C) changes on microbial community structure and methanogenic pathways in five sub-Antarctic lake sediments from Magallanes strait to Cape Horn, Chile. We combined in situ CH4 flux measurements, CH4 production rates (MPRs), gene abundance quantification and microbial community structure analysis (metabarcoding of the 16S rRNA gene). Under unamended conditions, a temperature increase of 5 °C doubled MPR while microbial community structure was not affected. Stimulation of methanogenesis by methanogenic precursors as acetate and H2/CO2, resulted in an increase of MPRs up to 127-fold and 19-fold, respectively, as well as an enrichment of mcrA-carriers strikingly stronger under acetate amendment. At low temperatures, H2/CO2-derived MPRs were considerably lower (down to 160-fold lower) than the acetate-derived MPRs, but the contribution of hydrogenotrophic methanogenesis increased with temperature. Temperature dependence of MPRs was significantly higher in incubations spiked with H2/CO2 (c. 1.9 eV) compared to incubations spiked with acetate or unamended (c. 0.8 eV). Temperature was not found to shape the total microbial community structure, that rather exhibited a site-specific variability among the studied lakes. However, the methanogenic archaeal community structure was driven by amended methanogenic precursors with a dominance of Methanobacterium in H2/CO2-based incubations and Methanosarcina in acetate-based incubations. We also suggested the importance of acetogenic H2-production outcompeting hydrogenotrohic methanogenesis especially at low temperatures, further supported by homoacetogen proportion in the microcosm communities. The combination of in situ-, and laboratory-based measurements and molecular approaches indicates that the hydrogenotrophic pathway may become more important with increasing temperatures than the acetoclastic pathway. In a continuously warming environment driven by climate change, such issues are crucial and may receive more attention.

This study was focused on the suitability of dandelion plant as part of a biorefinery scheme in which anaerobic degradation (biomethanization) for biogas production is the ending process. Inulin as the main compound in the tuberous root was selected as substrate and tested at different concentrations (5, 10 and 15 g TS L−1). The presence of bicarbonate as a buffer on anaerobic digestion was assessed as well. Methane production curves were fitted with the modified Gompertz equation. Methane production yield (YCH4), specific maximum methane production rate (SRMAX) and the first-order hydrolysis constant (kH) were affected by the substrate concentration. Bicarbonate was found not to be determinant for the overall biomethanization process because no significant effect over the YCH4was achieved in the presence or absence of bicarbonate; between 0.19 to 0.23 m3 kg-1 VS added. However, kHand SRMAX were affected by the presence of this inorganic compound. Without the addition of bicarbonate, kHand SRMAX decreased as the TS increased. These results will be key for a dandelion biorefinery proof-of-concept under the proposed conditions.

This chapter presents factors or considerations to be taken into account when selecting the procedure or method for obtaining extracts and bioactive compounds. The genus Taraxacum has proved to have several interesting properties and there are numerous techniques and bioassays used to test the antimicrobial properties of extracts. However, the extraction process is crucial to optimize the final biological outcomes. Extraction procedures that until now have been used are simple and inexpensive, however, we wanted to report a series of studies that group valuable results, which could be useful for future studies, enhancing the research carried out by authors from all over the world and also allowing the interrelated study of this genus.

Plants have been used in traditional medicine for centuries as antibacterial and antifungal agents. Taraxacum spp., commonly known as dandelion, is a well-known herbal remedy with a long history; however, limited scientific information is available to explain its traditional use. This review aims to provide current information and a general overview of the available literature concerning the antibacterial and antifungal properties of the Taraxacum genus to support its potential as a powerful herbal medicine. Though Taraxacum has demonstrated that it is capable of inhibiting the growth of a wide range of bacteria and fungi, the technical aspects of methodology lack standardization, and, therefore, the overall results of processing are difficult to compare between studies. Phytochemical composition and antimicrobial activity in Taraxacum are neither directly related, nor does the published data provide sufficient information for identifying the group of unique extraction conditions that are optimal against specific microorganisms. Antimicrobial research indicates that this plant is a promising species for treating several common infections in humans, animals, and plants.