|
Photo-fermentative
Photofermentation is the fermentative conversion of organic substrate to biohydrogen manifested by a diverse group of photosynthetic bacteria by a series of biochemical reactions involving three steps similar to anaerobic conversion. Photofermentation differs from dark fermentation because it only proceeds in the presence of light. For example, photo-fermentation with ''Rhodobacter sphaeroides'' SH2C (or many other purple non-sulfur bacteria) can be employed to convert small molecular fatty acids into hydrogen and other products. Light-dependent pathways Phototropic bacteria Phototropic bacteria produce hydrogen gas via photofermentation, where the hydrogen is sourced from organic compounds. C6H12O6 + 6H2O ->[] 6CO2 + 12H2 Photolytic producers Photolysis, Photolytic producers are similar to phototrophs, but source hydrogen from water molecules that are broken down as the organism interacts with light. Photolytic producers consist of algae and certain photosynthetic bact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Fermentation
Dark fermentation is the fermentative conversion of organic substrate to biohydrogen. It is a complex process manifested by diverse groups of bacteria, involving a series of biochemical reactions using three steps similar to anaerobic conversion. Dark fermentation differs from photofermentation in that it proceeds without the presence of light. Overview Fermentative/hydrolytic microorganisms hydrolyze complex organic polymers to monomers which are further converted to a mixture of lower-molecular-weight organic acids and alcohols by obligatory producing acidogenic bacteria. Utilization of wastewater as a potential substrate for biohydrogen production has been drawing considerable interest in recent years especially in the dark fermentation process. Industrial wastewater as a fermentative substrate for H2 production addresses most of the criteria required for substrate selection viz., availability, cost and biodegradability. Chemical wastewater (Venkata Mohan, ''et al.'', 2007a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Fermentation
Dark fermentation is the fermentative conversion of organic substrate to biohydrogen. It is a complex process manifested by diverse groups of bacteria, involving a series of biochemical reactions using three steps similar to anaerobic conversion. Dark fermentation differs from photofermentation in that it proceeds without the presence of light. Overview Fermentative/hydrolytic microorganisms hydrolyze complex organic polymers to monomers which are further converted to a mixture of lower-molecular-weight organic acids and alcohols by obligatory producing acidogenic bacteria. Utilization of wastewater as a potential substrate for biohydrogen production has been drawing considerable interest in recent years especially in the dark fermentation process. Industrial wastewater as a fermentative substrate for H2 production addresses most of the criteria required for substrate selection viz., availability, cost and biodegradability. Chemical wastewater (Venkata Mohan, ''et al.'', 2007a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fermentative Hydrogen Production
Fermentative hydrogen production is the fermentative conversion of organic substrates to H2. Hydrogen produced in this manner is often called biohydrogen. The conversion is effected by bacteria and protozoa, which employ enzymes. Fermentative hydrogen production is one of several anaerobic conversions. Dark vs photofermentation Dark fermentation reactions do not require light energy. These are capable of constantly producing hydrogen from organic compounds throughout the day and night. Typically these reactions are coupled to the formation of carbon dioxide or formate. Important reactions that result in hydrogen production start with glucose, which is converted to acetic acid: :C6H12O6 + 2 H2O → 2 CH3CO2H + 2 CO2 + 4 H2 A related reaction gives formate instead of carbon dioxide: :C6H12O6 + 2 H2O → 2 CH3CO2H + 2 HCO2H + 2 H2 These reactions are exergonic by 216 and 209 kcal/mol, respectively. Using synthetic biology, bacteria can be genetically altered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodopseudomonas Palustris
''Rhodopseudomonas palustris'' is a rod-shaped, Gram-negative purple nonsulfur bacterium, notable for its ability to switch between four different modes of metabolism. ''R. palustris'' is found extensively in nature, and has been isolated from swine waste lagoons, earthworm droppings, marine coastal sediments, and pond water. Although purple nonsulfur bacteria are normally photoheterotrophic, ''R. palustris'' can flexibly switch among any of the four modes of metabolism that support life: photoautotrophic, photoheterotrophic, chemoautotrophic, or chemoheterotrophic. Etymology ''R. palustris'' is usually found as a wad of slimy masses, and cultures appear from pale brown to peach-colored. Etymologically, ''rhodum'' is a Greek noun meaning rose, ''pseudes'' is the Greek adjective for false, and ''monas'' refers to a unit in Greek. Therefore, ''Rhodopseudomonas'', which implies a unit of false rose, describes the appearance of the bacteria. ''Palustris'' is Latin for marshy, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrohydrogenesis
Electrohydrogenesis or biocatalyzed electrolysis is the name given to a process for generating hydrogen gas from organic matter being decomposed by bacteria. This process uses a modified fuel cell to contain the organic matter and water. A small amount, 0.2–0.8 V of electricity is used, the original article reports an overall energy efficiency of 288% can be achieved (this is computed relative to the amount of electricity used, waste heat lowers the overall efficiency). This work was reported by Cheng and Logan. See also *Biohydrogen *Electrochemical reduction of carbon dioxide *Electromethanogenesis * Fermentative hydrogen production *Microbial fuel cell Microbial fuel cell (MFC) is a type of bioelectrochemical fuel cell system that generates electric current by diverting electrons produced from the microbial oxidation of reduced compounds (also known as fuel or electron donor) on the anode to oxid ... References External linksBiocatalyzed electrolysis{Dead link, date=A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photobiology
Photobiology is the scientific study of the beneficial and harmful interactions of light (technically, non-ionizing radiation) in living organisms. The field includes the study of photophysics, photochemistry, photosynthesis, photomorphogenesis, visual system, visual processing, circadian rhythms, photomovement, bioluminescence, and ultraviolet radiation effects. The division between ionizing radiation and non-ionizing radiation is typically considered to be a photon energy greater than 10 eV, which approximately corresponds to both the first ionization energy of oxygen, and the ionization energy of hydrogen at about 14 eV. When photons come into contact with molecules, these molecules can absorb the energy in photons and become excited. Then they can react with molecules around them and stimulate "Photochemistry, photochemical" and "photophysical" changes of molecular structures. Photophysics This area of Photobiology focuses on the physical interactions of light and matter. Whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photohydrogen
In photochemistry, photohydrogen is hydrogen produced with the help of artificial or natural light. This is how the leaf of a tree splits water molecules into protons (hydrogen ions), electrons (to make carbohydrates) and oxygen (released into the air as a waste product). - A 14 minute video of the '''' broadcast about hydrogen cars that aired on , July 26, 2005. Hosted by |
Photochemistry
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–750 nm) or infrared radiation (750–2500 nm). In nature, photochemistry is of immense importance as it is the basis of photosynthesis, vision, and the formation of vitamin D with sunlight. Photochemical reactions proceed differently than temperature-driven reactions. Photochemical paths access high energy intermediates that cannot be generated thermally, thereby overcoming large activation barriers in a short period of time, and allowing reactions otherwise inaccessible by thermal processes. Photochemistry can also be destructive, as illustrated by the photodegradation of plastics. Concept Grotthuss–Draper law and Stark-Einstein law Photoexcitation is the first step in a photochemical process where the reactant is elevated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Production
Hydrogen production is the family of industrial methods for generating hydrogen gas. As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas and other light hydrocarbons, partial oxidation of heavier hydrocarbons, and coal gasification. Other methods of hydrogen production include biomass gasification, zero-CO2-emission methane pyrolysis, and electrolysis of water. The latter processes, methane pyrolysis as well as water electrolysis can be done directly with any source of electricity, such as solar power. The production of hydrogen plays a key role in any industrialized society, since hydrogen is required for many essential chemical processes. In 2020, roughly 87 million tons of hydrogen was produced worldwide for various uses, such as oil refining, and in the production of ammonia (NH3) (through the Haber process) and methanol (CH3OH) (through reduction of carbon monoxide O, and also as a fuel in transportation. The glo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fermentation (biochemistry)
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology. In microorganisms, fermentation is the primary means of producing adenosine triphosphate (ATP) by the degradation of organic nutrients anaerobically. Humans have used fermentation to produce foodstuffs and beverages since the Neolithic age. For example, fermentation is used for preservation in a process that produces lactic acid found in such sour foods as pickled cucumbers, kombucha, kimchi, and yogurt, as well as for producing alcoholic beverages such as wine and beer. Fermentation also occurs within the gastrointestinal tracts of all an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biohydrogen
Biohydrogen is H2 that is produced biologically. Interest is high in this technology because H2 is a clean fuel and can be readily produced from certain kinds of biomass. Many challenges characterize this technology, including those intrinsic to H2, such as storage and transportation of a noncondensible gas. Hydrogen producing organisms are poisoned by O2. Yields of H2 are often low. Biochemical principles The main reactions involve fermentation of sugars. Important reactions start with glucose, which is converted to acetic acid: :C6H12O6 + 2 H2O -> 2 CH3COOH + 2 CO2 + 4 H2 A related reaction gives formate instead of carbon dioxide: :C6H12O6 + 2 H2O -> 2 CH3COOH + 2 HCOOH + 2 H2 These reactions are exergonic by 216 and 209 kcal/mol, respectively. H2 production is catalyzed by two hydrogenases. One is called eFehydrogenase; the other is called iFehydrogenase. Many organisms express these enzymes. Notable examples are members of the genera Clostridium, Desulfovibr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sustainable Energy
Energy is sustainable if it "meets the needs of the present without compromising the ability of future generations to meet their own needs". Most definitions of sustainable energy include considerations of environmental aspects such as greenhouse gas emissions and social and economic aspects such as energy poverty. Renewable energy sources such as wind, hydroelectric power, solar, and geothermal energy are generally far more sustainable than fossil fuel sources. However, some renewable energy projects, such as the clearing of forests to produce biofuels, can cause severe environmental damage. The role of non-renewable energy sources in sustainable energy has been controversial. Nuclear power is a low-carbon source whose historic mortality rates are comparable to wind and solar, but its sustainability has been debated because of concerns about radioactive waste, nuclear proliferation, and accidents. Switching from coal to natural gas has environmental benefits, including a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
