Showing papers on "Dark fermentation published in 2005"

Hydrogen production by Rhodobacter sphaeroides strain O.U.001 using spent media of Enterobacter cloacae strain DM11

Abstract: Combined dark and photo-fermentation was carried out to study the feasibility of biological hydrogen production. In dark fermentation, hydrogen was produced by Enterobacter cloacae strain DM11 using glucose as substrate. This was followed by a photo-fermentation process. Here, the spent medium from the dark process (containing unconverted metabolites, mainly acetic acid etc.) underwent photo-fermentation by Rhodobacter sphaeroides strain O.U.001 in a column photo-bioreactor. This combination could achieve higher yields of hydrogen by complete utilization of the chemical energy stored in the substrate. Dark fermentation was studied in terms of several process parameters, such as initial substrate concentration, initial pH of the medium and temperature, to establish favorable conditions for maximum hydrogen production. Also, the effects of the threshold concentration of acetic acid, light intensity and the presence of additional nitrogen sources in the spent effluent on the amount of hydrogen produced during photo-fermentation were investigated. The light conversion efficiency of hydrogen was found to be inversely proportional to the incident light intensity. In a batch system, the yield of hydrogen in the dark fermentation was about 1.86 mol H2 mol−1 glucose; and the yield in the photo-fermentation was about 1.5–1.72 mol H2 mol−1 acetic acid. The overall yield of hydrogen in the combined process, considering glucose as the preliminary substrate, was found to be higher than that in a single process.

Research progress in dark microbial fermentation for bio-hydrogen production

Abstract: Hydrogen deriving from bio-wastes or unused biomass is one of the most promising alternative energy carrier as a sustainable technology in the future.Dark microbial fermentation for the conversion of biomass to biohydrogen has being paid much attention in the world for its advantages of high hydrogen production rate,feasibility in the reactor design and process control,and possibility in integration with waste treatment.Progresses in dark fermentation for bio-hydrogen production achieved in recent years were reviewed in the present paper.In addition to the deeper understanding of the traditional hydrogen-producing bacteria,tools of modern biotechnology and bioinformatics were gradually adopted for the construction of the database of hydrogen-producing bacteria.In the respect of hydrogenase,not only were the related gene identification and the functional analysis important,but also was genetic engineering for improving hydrogenase paid attention.Concerning the combination of biohydrogen production with the waste treatment,many studies had focused on the effects of operating conditions and process optimization.Various wastes had been used for hydrogen conversion and a series of bio-reactors been designed.In addition,the feasibility and economic evaluation of the existing bio-hydrogen process was also discussed in the paper.Finally,new approach for bio-hydrogen in the dark fermentation was indicated.

Preparation of methane-rich biogas comprises anaerobic fermentation of biomass and/or other substrates to raw fermentation gas, biochemical desulfurization of the gas, and photo-biological carbon dioxide reduction of the desulfurized gas

Abstract: Preparation of methane-rich biogas comprises: anaerobic fermentation (1) of biomass and/or other substrates to raw fermentation gas (5), where the process liquid is enriched with oxygen and at least a part of the oxygen comes from an oxygen-enriched, methane-rich fermentation gas (7); biochemical desulfurization (2) of the produced raw fermentation gas; and photo-biological carbon dioxide reduction (3) of the desulfurized fermentation gas, where oxygen-enriched, methane-rich fermentation gas and algal biomass (14) are produced. Preparation of methane-rich biogas comprises: anaerobic fermentation (1) of biomass and/or other substrates to raw fermentation gas, where the process liquid is enriched with oxygen and at least a part of the oxygen comes from an oxygen-enriched, methane-rich fermentation gas (7) that is produced in a photo bioreactor; biochemical desulfurization (2) of the produced raw fermentation gas, results in a separable methane-rich fermentation gas (8) and desulfurized fermentation gas (6);and photo-biological carbon dioxide reduction (3) of the desulfurized fermentation gas, where oxygen-enriched, methane-rich fermentation gas and algal biomass (14) are produced, after which the oxygen-enriched, methane-rich fermentation gas is led to the process of biochemical desulfurization. An independent claim is included for a plant for the production of methane-rich fermentation gas comprising at least a biogas container, a biochemical desulfurization container and a photo-bioreactor container.

Dark hydrogen production by a green microalga, Chlamydomonas reinhardtii UTEX 90

Abstract: The production of hydrogen by Chlamydomonas reinhardtii UTEX 90, a marine green alga, was performed under dark fermentation. The effects of initial nitrogen and phosphorus concentration on the cell growth and the production of hydrogen and organic substances were investigated. In the growth stage, the maximum dry cell weight (DCW) was 3 g/l when the initial ammonium concentration was 15 mM. In the dark fermentation, the maximum hydrogen production was 3.5 μmol/ mg DCW when the initial nitrogen concentration was 7.5 mM. The nitrogen concentration had a greater effect on organic compound and hydrogen production than the phosphorus concentration during the dark fermentation. An investigation of the duration of dark fermentation showed that, at least until three days, dark fermentation should be prolonged for maximum hydrogen production.

Biohydrogen produced through mixture anaerobic biological fermentation

Abstract: The substrate containing glucose was treated with natural anaerobic microorganism bacterium from sullage. The biohydrogen was produced through anaerobic hydrogen fermentation. Under the experimental conditions, the maximum hydrogen productivity was 2.1 mol/mol (H_2/glucose) under the conditions of optimal initial pH value of 5.5. The optimal concentration of glucose was 5～30 g/L. The optimal substrates were glucose, pentose and starch. The hydrogen concentration in the biogas reached 97% without methanogenesis in the gaseous product, after it passed through 5% sodium hydroxide solution. It was found that the fermentation type was a butyric acid type fermentation.

Fermentative biological production of hydrogen by digesting high strength organic wastewater

Abstract: It is a hot research field that biological hydrogen can be produced by digesting high-strength organic wastewater in the acidogenic phase of two-phase anerobes in the world.The research for hydrogen-producing mechanism,process scheme and design,engineering control in practice on fermentative biological hydrogen production is reviewed.There are three types of fermentaive hydrogen-producing metabolic pathways which are butyric acid fermentation,ethanol fermentation and formic acid scission reaction in fermentative hydrogen-producing microorganism.The main process is mixed culture by activated sludge.The processes of pure culture and immobilized cell are developed.The bacteria of genuses of Enterobacter,Clostridium,Citrobacter and the new type of fermentative hydrogen-producing bacteria with the ethanol-fermentation are isolated in the world.The germplasm can be used such as in pure culture,cell immobilization and bioaugmentation.The mixed culture for fermentative hydrogen production under the guidance of the ethanol-type fermentative biohydrogen-producing theory has been established and will be applied in the demonstration factory.