Electricity generation by direct oxidation of glucose in mediatorless microbial fuel cells. (1/138)

Abundant energy, stored primarily in the form of carbohydrates, can be found in waste biomass from agricultural, municipal and industrial sources as well as in dedicated energy crops, such as corn and other grains. Potential strategies for deriving useful forms of energy from carbohydrates include production of ethanol and conversion to hydrogen, but these approaches face technical and economic hurdles. An alternative strategy is direct conversion of sugars to electrical power. Existing transition metal-catalyzed fuel cells cannot be used to generate electric power from carbohydrates. Alternatively, biofuel cells in which whole cells or isolated redox enzymes catalyze the oxidation of the sugar have been developed, but their applicability has been limited by several factors, including (i) the need to add electron-shuttling compounds that mediate electron transfer from the cell to the anode, (ii) incomplete oxidation of the sugars and (iii) lack of long-term stability of the fuel cells. Here we report on a novel microorganism, Rhodoferax ferrireducens, that can oxidize glucose to CO(2) and quantitatively transfer electrons to graphite electrodes without the need for an electron-shuttling mediator. Growth is supported by energy derived from the electron transfer process itself and results in stable, long-term power production.  (+info)

Caenibacterium thermophilum gen. nov., sp. nov., isolated from a thermophilic aerobic digester of municipal sludge. (2/138)

A bacterial strain, N2-680(T) (=DSM 15264(T)=LMG 21760(T)), isolated from a thermophilic aerobic digester of municipal sludge, was characterized with respect to its morphology, physiology and taxonomy. Phenotypically, the isolate was a Gram-negative rod with a polar flagellum, catalase- and oxidase-positive, containing cytoplasmic inclusions of poly-beta-hydroxybutyrate and had an optimal growth temperature of about 47 degrees C. Strain N2-680(T) was unable to reduce nitrate and could use organic acids, amino acids and carbohydrates as single carbon sources. Chemotaxonomic analysis revealed that ubiquinone 8 was the major respiratory quinone of this organism and that phosphatidylethanolamine and phosphatidylglycerol were the major polar lipids. At 50 degrees C, the major components in fatty acid methyl ester analysis were C(16 : 0) and cyclo-C(17 : 0). The highest 16S rDNA sequence identity of isolate N2-680(T) was to Leptothrix mobilis and Ideonella dechloratans (95.7 %) and to Rubrivivax gelatinosus and Aquabacterium commune (95.6 %). 16S rDNA sequence similarities to species of two related thermophilic genera, Caldimonas manganoxidans and Tepidimonas ignava, were lower (93.6 and 94.7 %). On the basis of phylogenetic analyses and physiological and chemotaxonomic characteristics, it is proposed that isolate N2-680(T) represents a new genus and species, for which the name Caenibacterium thermophilum gen. nov., sp. nov. is proposed.  (+info)

QUANTITATIVE STUDIES OF THE EFFECT OF ORGANIC SUBSTRATES AND 2,4-DINITROPHENOL ON HETEROTROPHIC CARBON DIOXIDE FIXATION IN HYDROGENOMONAS FACILIS. (3/138)

McFadden, Bruce A. (Washington State University, Pullman), and H. Robert Homann. Quantitative studies of the effect of organic substrates and 2,4-dinitrophenol on heterotrophic carbon dioxide fixation in Hydrogenomonas facilis. J. Bacteriol. 86:971-977. 1963.-Whole cells of Hydrogenomonas facilis under heterotrophic conditions fixed levels of C(14)O(2) which depended upon the nature of the carbon source being oxidized. It was established that oxidative rates varied as a function of p(CO2). Therefore, all studies were conducted in the presence of 1.5 mole% CO(2) in the gas phase. With glucose-grown cells supplied with glucose as substrate, the heterotrophic fixation was curtailed 98% by the addition of 8.3 x 10(-4)m 2,4-dinitrophenol (DNP). A coupling between reductive fixation of CO(2) and heterotrophic oxidation of substrate is consistent with the observed effect of DNP. The efficiency of coupling of fixation with oxidation was studied for acetate, d-glucose, l-glutamate, d,l-lactate, d-ribose, and succinate as substrates. Kinetic studies showed that the efficiency of coupling (expressed as disintegrations per minute of C(14) per microliter of O(2)) was initially time-variable for all substrates; however, it approached a constant value after 30 to 45 min for acetate, glutamate, lactate, and succinate. The initial variation of the ratio with time was due primarily to C(14)O(2) uptake, which was nonlinear with time. Control studies in the absence of exogenous substrate indicated that CO(2) fixation may also be linked to oxidation of endogenous stores accumulated during heterotrophic growth. d-Ribose appears to be the most promising substrate for short-term fixation studies owing to the rapid incorporation of C(14) and the unusually low endogenous fixation rate by cells grown on ribose. Calculations reveal that, after isotopic equilibrium has occurred, the amount of CO(2) utilized during glucose oxidation is almost 50% of O(2) uptake during the same interval. Even during succinate oxidation, which was shown to be coupled much less effectively with CO(2) fixation, the CO(2) utilized during the same interval is 8% of O(2) uptake.  (+info)

UTILIZATION OF AROMATIC AMINO ACIDS BY HYDROGENOMONAS FACILIS. (4/138)

DeCicco, B. T. (Rutgers, The State University, New Brunswick, N.J.), and W. W. Umbreit. Utilization of aromatic amino acids by Hydrogenomonas facilis. J. Bacteriol. 88:1590-1594. 1964.-An auxotrophic mutant of Hydrogenomonas facilis was isolated which requires tryptophan, phenylalanine, and p-aminobenzoic acid (PABA) for growth. With glucose as the main carbon and energy source, the quantitative requirements for tryptophan and PABA were at normal microgram levels, but the requirement for phenylalanine was very large and approached substrate concentrations. The large phenylalanine requirement is due to a rapid oxidation and degradation of phenylalanine by the mutant. The utilization of both phenylalanine and glucose is adaptive, and the presence of phenylalanine partially inhibits the induction of the glucose-utilizing system. Wild-type H. facilis can utilize either phenylalanine or tyrosine for growth. Tracer studies indicated that during growth on phenylalanine, the aromatic ring is opened and degraded. Wild-type cells grown on either phenylalanine or tyrosine can oxidize phenylalanine, tyrosine, or phenylpyruvate without a lag. Another inducible pathway enables H. facilis to utilize either quinate or 3,4-dihydroxybenzoate for growth, and sequential adaptation studies revealed that quinate is converted to 3,4-dihydroxybenzoate during its degradation. Mutants may be obtained which can also utilize 2,5-dihydroxybenzoate for growth.  (+info)

CHARACTERIZATION OF POLY-BETA-HYDROXYBUTYRATE EXTRACTED FROM DIFFERENT BACTERIA. (5/138)

Lundgren, D. G. (Syracuse University, Syracuse, N.Y.), R. Alper, C. Schnaitman and R. H. Marchessault. Characterization of poly-beta-hydroxybutyrate extracted from different bacteria. J. Bacteriol. 89:245-251. 1965.-Poly-beta-hydroxybutyrate (PHB) from different bacterial genera was studied with regard to its crystal structure, infrared absorption, intrinsic viscosity, and electron microscopy. All PHB samples precipitated from dilute chloroform solution gave identical X-ray diffractograms confirming uniformity of crystal structure, and uniformity of molecular structure, based on the similarity of the recorded infrared spectra, was also established. Crystal morphology was also similar, showing the reported "lath" shape structure for purified polymer from Bacillus cereus. Intrinsic viscosity ranged from 0.04 to 11.5 depending upon the polymer treatment; polymer molecular weights, based upon viscometry, could be estimated to range from 1,000 to 250,000. It is concluded that the same basic molecule is involved in all PHB present in the bacterial kindgom.  (+info)

CHARACTERISTICS AND INTERMEDIATES OF SHORT-TERM C-14-O-2 INCORPORATION DURING RIBOSE OXIDATION BY HYDROGENOMONAS FACILIS. (6/138)

McFadden, B. A. (Washington State University, Pullman), and H. R. Homann. Characteristics and intermediates of short-term C(14)O(2) incorporation during ribose oxidation by Hydrogenomonas facilis. J. Bacteriol. 89:839-847. 1965.-Ribose-grown cells of Hydrogenomonas facilis, which had been suspended in growth medium and were oxidizing ribose, were exposed to HC(14)O(3) (-) of high specific activity. The uptake was proportional to cell mass. Short-term uptake (less than 2 min) was completely inhibited by 10(-3)m 2,4-dinitrophenol (DNP) or by <4 x 10(-6)mm-chlorocarbonyl cyanide phenylhydrazone, and to the extent of 42% by 5 x 10(-5)m DNP. The following observations were made in kinetic studies (8, 16, 35, 67, 96, and 181 sec) of fixation in the presence of ribose. Glutamate was extensively labeled in periods up to 3 min. It was one of the major early products, containing 30% of the label at 8 sec. The sugar phosphate fraction was not detectably labeled at 8 or 16 sec, but its C(14)-content increased rapidly to 27% at 35 sec and then slowly decreased. Label in phosphoglycerate, phosphoenolpyruvate, and alanine did not appear until 35 sec, and did not exceed about 7, 2, and 3%, respectively, of the total extracted radioactivity. Adenosine triphosphate and adenosine diphosphate were heavily labeled after fixation in a pilot study for 125 sec. Although considerable radioactivity incorporated during the pilot study was intractable by the extraction procedure employed, virtually no C(14) was found in the residue in poly-beta-hydroxybutyric acid. A large number of amino acids and organic acids and some organic phosphates were not detectably labeled in any of the experiments. Omission of ribose greatly diminished incorporation, particularly into glutamate.  (+info)

NICKEL-DEPENDENT CHEMOLITHOTROPHIC GROWTH OF TWO HYDROGENOMONAS STRAINS. (7/138)

Bartha, R. (University of Washington, Seattle), and E. J. Ordal. Nickel-dependent chemolithotrophic growth of two Hydrogenomonas strains. J. Bacteriol. 89:1015-1019. 1965.-The trace element requirements for growth of facultative chemolithotrophic Hydrogenomonas strains H1 and H16 were investigated under both autotrophic and heterotrophic conditions. The organisms were grown in a mineral medium, rendered deficient in trace elements by extraction with 8-hydroxyquinoline and chloroform, and, in some cases, by coprecipitation with copper. The organic substrates, succinate and fumarate, used for heterotrophic growth were treated in a similar fashion. Acetate and butyrate were purified by redistillation. It was found that iron alone was required for heterotrophic growth (optimal concentration, 1.5 x 10(-6)m Fe(+++)), but cells grown chemolithotrophically on molecular hydrogen required the addition of nickel. The yield of protein was proportional to the nickel added, reaching a maximum at 3 x 10(-7)m Ni(++). Manganese, cobalt, copper, and zinc, alone or in combination, failed to substitute for nickel in the experiments with Hydrogenomonas. Although nickel is required specifically for the chemolithotrophic growth of Hydrogenomonas, nickel deficiency did not affect: (i) the synthesis or activation of hydrogenase, (ii) the Knallgas reaction, (iii) the assimilation of CO(2) by resting cells, or the synthesis of the storage material poly-beta-hydroxybutyric acid. It is suggested that nickel participates in some reaction involved in CO(2) fixation by growing cells.  (+info)

Nutritional requirements for Hydrogenomonas eutropha. (8/138)

Repaske, Roy (National Institute of Allergy and Infectious Diseases, Bethesda, Md.). Nutritional requirements for Hydrogenomonas eutropha. J. Bacteriol. 83: 418-422. 1962.-A simple apparatus for the autotrophic cultivation of Hydrogenomonas eutropha in 100-ml shake cultures is described. Nitrogen, in the form of ammonium, nitrate, or urea, was used for growth; nitrite could not be utilized. Optimal growth occurred at pH 6.4 to 6.8 at 30 C. H. eutropha grew best in an atmosphere containing 15 to 25% oxygen and 10% carbon dioxide. Below these concentrations each of the gases was limiting. Growth was shown to be dependent on iron, and the rate of growth was a function of iron concentration and its state of oxidation.  (+info)

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