AbstractMethanogenic pathwaysLaukenmann et al., Eng. Life Sci. 2010, 10, 509–514.The application of stable carbon isotopes is a well‐established method to study metabolic pathways. To identify the degradation kinetics and specific methanogenic pathways in biogas production, authors from Mainz and Freising (Germany) have performed a series of anaerobic batch experiments. Isotopic analysis was performed using a new absorption laser spectrometer in addition to conventional MS. The results show large isotope dynamics for maize and cellulose, indicating a temporal change in degradation pathways and/or a change in the relative contribution from different carbon fractions within the substrate. Surprisingly, acetate is completely oxidized into CO2, which is in turn reduced to CH4, while only a minor part of the produced methane is derived from acetate.………………509http://dx.doi.org/10.1002/elsc.201000074magnified imagePopulation dynamicsMunk et al., Eng. Life Sci. 2010, 10, 496–508.Methanogenesis is a unique trait of Archaea that is not present in the domains Bacteria or Eukaryota. Because they are not easy to be cultivated, Munk et al. used molecular biological methods (PCR‐SSCP and quantitative real‐time PCR) to monitor microbial population dynamics qualitatively and quantitatively at distinct stages. Methanogenic activity depends on the presence of trace elements that can arise in biogas production systems particularly when no manure is added. Without compensating supplementation, primarily cobalt and sodium can become limiting in long‐term mono‐digestion of maize silage. These deficiencies apparently triggered process acidification that affects the methanogen populations. Indicator organisms for different process states were identified that can be used to monitor and evaluate the microbiological fermenter status by rapid qPCR analysis.……………496http://dx.doi.org/10.1002/elsc.201000056magnified imageTwo‐phase anaerobic processZielonka et al., Eng. Life Sci. 2010, 10, 515–519.The biogas production process can be divided into four steps carried out by different microorganisms. While the usual batch process is optimized for the methanogenic bacteria, every organism has its own optimal pH and temperature. Two‐phase systems offer the possibility to optimize the biological process more individually. Researchers from the University of Hohenheim now evaluated the energy balance in a two‐phase biogas process based on an anaerobic leach‐bed reactor combined with an anaerobic filter. The two‐phase process showed stable digestion behavior, in spite of a sudden substrate change. However, the tested substrates grass, corn and rye silage showed different suitability for the two‐phase fermentation. Substrates with a longer acid formation period seem to be more suitable for a batch process with acidification in the leach‐bed reactor.……………515http://dx.doi.org/10.1002/elsc.201000071magnified image