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Chapter 15 : Optimizing Mixed-Culture Bioprocessing To Convert Wastes into Bioenergy
Category: Applied and Industrial Microbiology
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The most efficient systems for biodegradation of polymeric organic compounds are mixed cultures that have evolved in some insect and mammalian guts. The efficiency and economic viability of converting organic wastes to biofuels depends on the characteristics of the waste material, especially the chemical composition and the concentrations of the components that can be converted into products that can be used as fuels. As mixed-culture fermentation involves large microbial communities, only certain compounds can be produced. Some products cannot be generated because they are converted to other compounds by the mixed culture more quickly than they are formed. When glucose-containing waste streams, such as those that are high in starch or cellulose, are used to produce bioenergy, butyrate may be one of the most important organic acid products. The hydrogen yield in mixed-culture bioprocessing can be increased by physically separating the anaerobic oxidation of sugars from hydrogen production by conducting the reactions in the anode and cathode, respectively, of a microbial fuel cell (MFC). Diverse microbial communities with metabolic flexibility should be more resistant to bacteriophage attack because different species or strains with similar metabolic functions can take over. Bioaugmentation can be used when modeling or systems biology analysis shows that a metabolic pathway that is needed to produce a useful energy carrier or its precursor is missing from the community metabolome.
View of a farm-based anaerobic digester in Iowa.
Schematic of biological butanol production from waste slurries.
Schematic of a microbial fuel cell for hydrogen generation in the cathode (left panel) and electrical power generation (right panel). The surface of the anodic electrode is positive, and the surface of the cathodic electrode is negative. Electron current is from the anode to the cathode.
Composition and concentration of potential waste-derived feedstocks for biofuels production
Maximum power densities achieved in dual-chamber MFCs using various substrates and inocula during optimization efforts