Microbial fuel cells hold great promise as a sustainable biotechnological solution to future energy needs. Current efforts to improve the efficiency of such fuel cells are limited by the lack of knowledge about the microbial ecology of these systems. The purposes of this study were (i) to elucidate whether a bacterial community, either suspended or attached to an electrode, can evolve in a microbial fuel cell to bring about higher power output, and (ii) to identify species responsible for the electricity generation. Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment of a biofuel cell in which glucose was used increased the output from an initial level of 0.6 W m⁻²of electrode surface to a maximal level of 4.31 W m⁻²(664 mV, 30.9 mA) when plain graphite electrodes were used. This result was obtained with an average loading rate of 1 g of glucose liter⁻¹day⁻¹and corresponded to 81% efficiency for electron transfer from glucose to electricity. Cyclic voltammetry indicated that the enhanced microbial consortium had either membrane-bound or excreted redox components that were not initially detected in the community. Dominant species of the enhanced culture were identified by denaturing gradient gel electrophoresis and culturing. The community consisted mainly of facultative anaerobic bacteria, such asAlcaligenes faecalisandEnterococcus gallinarum, which are capable of hydrogen production.Pseudomonas aeruginosaand otherPseudomonasspecies were also isolated. For several isolates, electrochemical activity was mainly due to excreted redox mediators, and one of these mediators, pyocyanin produced byP. aeruginosa, could be characterized. Overall, the enrichment procedure, irrespective of whether only attached or suspended bacteria were examined, selected for organisms capable of mediating the electron transfer either by direct bacterial transfer or by excretion of redox components.

For more than 100 years it was believed that bacteria were the only group responsible for the oxidation of ammonia. However, recently, a new strain o

Summary: Community‐level molecular techniques are widely used in comparative microbial ecology to assess the diversity of microbial communities and their response to changing environments. These include among others denaturing and temperature gradient gel electrophoresis (DGGE/TGGE), single‐strand conformation polymorphism (SSCP), length heterogeneity‐PCR (LH‐PCR), terminal‐restriction fragment length polymorphism (tRFLP) and 16S rRNA gene clone libraries. The amount of data derived from these techniques available in literature is continuously increasing and the lack of a universal way to interpret the raw fingerprint itself makes it difficult to compare between different results. Taking the DGGE technique as an example, we propose a setting‐independent theoretical interpretation of the DGGE pattern, based on a straightforward processing on three levels of analysis: (i) the range‐weighted richness ( Rr ) reflecting the carrying capacity of the system, (ii) the dynamics ( Dy ) reflecting the specific rate of species coming to significance, and (iii) functional organization ( Fo ), defined through a relation between the structure of a microbial community and its functionality. These Rr , Dy and Fo values, each representing a score to describe a microbial community, can be plotted in a 3D graph. The latter represents a visual ecological interpretation of the initial raw fingerprinting pattern.

Summary: Microbial biotechnology has a long history of producing feeds and foods. The key feature of today's market economy is that protein production by conventional agriculture based food supply chains is becoming a major issue in terms of global environmental pollution such as diffuse nutrient and greenhouse gas emissions, land use and water footprint. Time has come to re‐assess the current potentials of producing protein‐rich feed or food additives in the form of algae, yeasts, fungi and plain bacterial cellular biomass, producible with a lower environmental footprint compared with other plant or animal‐based alternatives. A major driver is the need to no longer disintegrate but rather upgrade a variety of low‐value organic and inorganic side streams in our current non‐cyclic economy. In this context, microbial bioconversions of such valuable matters to nutritive microbial cells and cell components are a powerful asset. The worldwide market of animal protein is of the order of several hundred million tons per year, that of plant protein several billion tons of protein per year; hence, the expansion of the production of microbial protein does not pose disruptive challenges towards the process of the latter. Besides protein as nutritive compounds, also other cellular components such as lipids (single cell oil), polyhydroxybuthyrate, exopolymeric saccharides, carotenoids, ectorines, (pro)vitamins and essential amino acids can be of value for the growing domain of novel nutrition. In order for microbial protein as feed or food to become a major and sustainable alternative, addressing the challenges of creating awareness and achieving public and broader regulatory acceptance are real and need to be addressed with care and expedience.