RESUMEN
In bioelectrochemical systems (BES), the catalytic activity of anaerobic microorganisms generates electrons at the anode which can be used, for example, for the production of electricity or chemical compounds. BES can be used for various purposes, including wastewater treatment, production of electricity, fuels and chemicals, biosensors, bioremediation, and desalination. Electrochemically active microorganisms are widely present in the environment and they can be found, in sediment, soil, compost, wastewaters and their treatment plants. Exoelectrogens are microorganisms capable of donating electrons to anode electrode or accepting electrons from cathode electrode and are mainly responsible for current generation or use in BES. However, current generation from fermentable substrates often requires the presence of electrochemically inactive microorganisms that break down complex substrates into metabolites which can be further utilized by exoelectrogens. The growth and electron transfer efficiency of anaerobes depend on several parameters, such as system architecture, electrode material and porosity, electrode potential and external resistance, pH, temperature, substrate concentration, organic loading rate, and ionic strength. In this chapter, the principles and microbiology of bioelectrochemical systems as well as selective factors for exoelectrogens are reviewed. The anaerobic microorganisms and their electron transfer mechanisms at the anode and cathode are described and future aspects are briefly discussed.
Asunto(s)
Bacterias Anaerobias/fisiología , Fuentes de Energía Bioeléctrica/microbiología , Bioensayo/instrumentación , Técnicas Biosensibles/instrumentación , Electroquímica/instrumentación , Electrodos/microbiología , Transferencia de Energía/fisiología , Diseño de Equipo , Evaluación de la Tecnología BiomédicaRESUMEN
Sulfate-reducing fluidized-bed bioreactor (FBR) fed with ethanol-lactate mixture was operated at 35 degrees C for 540 days to assess mine wastewater treatment, biological hydrogen sulfide production capacity and acetate oxidation kinetics. During the mine wastewater treatment period with synthetic wastewater, the sulfate reduction rate was 62 mmol SO(4)(2-)L(-1)d(-1) and Fe and Zn precipitation rates were 11 mmol Fe L(-1)d(-1) and 1 mmol Zn L(-1)d(-1). After this, the hydrogen sulfide production was optimized, resulting in sulfate reduction rate of 100 mmol SO(4)(2-)L(-1)d(-1) and H(2)S production rate of 73.2 mmol H(2)SL(-1)d(-1). The limiting step in the H(2)S production was the rate of acetate oxidation, being 50 mmol acetate L(-1)d(-1). Therefore, FBR batch assays were designed to determine the acetate oxidation kinetics, and following kinetic parameters were obtained: K(m) of 63 micromol L(-1) and V(max) of 0.76 micromol acetate g VSS(-1)min(-1). The present study demonstrates high-rate hydrogen sulfide production and high-rate mine wastewater treatment with ethanol and lactate fed fluidized-bed bioreactor.
Asunto(s)
Reactores Biológicos/microbiología , Etanol/metabolismo , Sulfuro de Hidrógeno/metabolismo , Residuos Industriales/prevención & control , Ácido Láctico/metabolismo , Minería , Aguas del Alcantarillado/microbiología , Biodegradación Ambiental , Sulfuro de Hidrógeno/aislamiento & purificaciónRESUMEN
Batch experiments were conducted to investigate the thermophilic biohydrogen production using an enrichment culture from a Turkish hot spring. Following the enrichment, the culture was heat treated at 100 degrees C for 10 min to select for spore-forming bacteria. H(2) production was accompanied by production of acetate, butyrate, lactate and ethanol. H(2) production was associated by acetate-butyrate type fermentation while accumulation of lactate and ethanol negatively affected the H(2) yield. H(2) production was highest in the temperature range from 49.6 to 54.8 degrees C and optimum values for initial pH and concentrations of iron, yeast extract and glucose were 6.5, 40 mg/l, 4-13.5 g/l, respectively. PCR-DGGE profiling showed that the heat treated culture consisted of species closely affiliated to genus Thermoanaerobacterium.
Asunto(s)
Manantiales de Aguas Termales/microbiología , Hidrógeno/química , Acetatos/química , Anaerobiosis , Butiratos/química , Relación Dosis-Respuesta a Droga , Fermentación , Glucosa/química , Calor , Concentración de Iones de Hidrógeno , Hierro/química , Cinética , Reacción en Cadena de la Polimerasa , Thermoanaerobacterium/metabolismo , Microbiología del AguaRESUMEN
A thermophilic, rod-shaped, motile, Gram-positive, spore-forming bacterium strain 70B(T) was isolated from a geothermally active underground mine in Japan. The temperature and pH range for growth was 50-81 degrees C (optimum 71 degrees C) and 6.2-9.8 (optimum pH 7-7.5), respectively. Growth occurred in the presence 0-2% NaCl (optimum 1% NaCl). Strain 70B(T) could utilize glucose, fructose, mannose, mannitol, pyruvate, cellobiose and tryptone as substrates. Thiosulfate was used as electron acceptor. Major whole-cell fatty acids were iso-C(15:0), C(16:0) DMA (dimethyl acetal), C(16:0) and anteiso-C(15:0). The G+C mol% of the DNA was 44.2%. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the closest relatives of strain 70B(T) were Thermosediminibacter oceani DSM 16646(T) (94% similarity) and Thermosediminibacter litoriperuensis DSM 16647 (93% similarity). The phenotypic, chemotaxonomic and phylogenetic properties suggest that strain 70B(T) represents a novel species in a new genus, for which the name Thermovorax subterraneus gen. nov., sp. nov. is proposed. The type strain of Thermovorax subterraneus is 70B(T) (=DSM 21563 = JCM 15541).