沼泽红假单胞菌乙酸光合放氢研究

依据光合细菌生长代谢特性和有机废水降解主要产物类型,11种有机物被用于沼泽红假单胞菌（Rhodopseudomonas palustris）Z菌株的光合产氢研究,其中,乙酸反应体系产氢活性最高。在此基础上,研究了该菌株的生长与产氢动力学行为,探求了影响该菌株光合放氢的主要限制性影响因素。结果表明,该菌株产氢与生长部分相关。种子培养基和菌龄对产氢活性有明显影响。细胞最适产氢和生长所需要的光照强度和温度基本一致。当种子来源于硫酸铵高菌龄预培养物或谷氨酸钠对数期预培养物时,该菌株产氢活性显著增加,产氢延滞期明显缩短。氧浓度和接种量对产氢活性也有显著影响。供氢体和氮源浓度直接决定细胞的生长与光放氢活性。在低于70 mmol/L乙酸钠和15 mmol/L谷氨酸钠时,产氢活性随底物浓度的增加而增强。谷氨酸钠浓度高于15mmol/L时,由于游离NH₄⁺的出现,产氢活性受到抑制,但却明显刺激细胞的生长。在标准状况下,该菌株的最大产氢速率可达19.4 mL·L^-1·h^-1。     

Microaerobic hydrogen production by photosynthetic bacteria in a double-phase photobioreactor

The rate of hydrogen production by the marine nonsulfur photosynthetic bacterium, Rhodovulum sp., increased with increasing light intensity. A light intensity of 1800 W/m(2) hydrogen production rate was achieved at the rate of 9.4 micromol/mg dry weight/h. The hydrogen production of this strain was enhanced by the addition of a small amount of oxygen (12 micromol O(2)/reactor). Intracellular ATP content was most efficiently accumulated under microaerobic, dark conditions. Hydrogen production rate by Rhodovulum sp. was investigated using a double-phase photobioreactor consisting of light and dark compartments. This rate was compared with data obtained using a conventional photobioreactor. Rhodovulum sp. produced hydrogen at a rate of 0.38+/-0.03 micromol/mg dry weight/h under microaerobic conditions using the double-phase photobioreactor. The hydrogen production rate was four times greater under microaerobic conditions, as compared with anaerobic conditions using either type of photobioreactor. Hydrogen production using a double-phase photobioreactor was demonstrated continuously at the same rate for 150 h.     

固定化光合细菌利用有机物产氢的研究

应用固定化细胞技术包埋荚膜红假单胞菌(Rhodopseudomonas capsulata)菌株386．研究在光照下利用有机物产氢的特性。实验观察到,光照培养120小时,悬浮培养物的产氢量为68．2ml·比产氢速率为104．1ml H2/g(生物量)·h;用琼脂包埋后．其产氢能力得到改善,产氢量和比产氢速率分别达到128．4ml和l 9s．8mlH2/g·h。该菌株除可利用苹果酸外,还可利用葡萄糖、乳酸、丙酸等基质高效地产氢。基质浓度只有控制在适当水平时,才具有较高的基质转化产氢效率。此外．菌体生物量、菌龄、培养液pH、光照强度、光照／黑暗时间比以及温度对产氢过程均有不同程度的影响。     

Hydrogen production with R. faecalis RLD-53 isolated from freshwater pond sludge

The Rhodopseudomonas faecalis strain RLD-53 was isolated from freshwater pond sludge and was demonstrated it could produce hydrogen. This study to investigate their ability of hydrogen production under some conditions in batch culture experiments. At pH 7.0, temperature 35 degrees C and light intensity of 4000 lux, the H(2) yield was 2.64 mol-H(2)/mol-acetate, 2.34 mol-H(2)/mol-propionate, 1.75 mol-H(2)/mol-lactate and 3.55 mol-H(2)/mol-malate, respectively. The maximal H(2) production rate of 32.62 ml-H(2)/l/h and H(2) yield of 2.84 mol-H(2)/mol-acetate were achieved when beef extract was used as nitrogen source. Light intensity is the most important factor for H(2) production, H(2) production yield and rate decreased with increasing light intensity and reached highest under light intensity of 3000-5000 lux. Result indicated the strain RLD-53 was a high efficient bacteria for hydrogen production.     

Hydrogen production by photoreactive nanoporous latex coatings of nongrowing Rhodopseudomonas palustris CGA009

Nonuniform light distribution is a fundamental limitation to biological hydrogen production by phototrophic bacteria. Numerous light distribution designs and culture conditions have been developed to reduce self-shading and nonuniform reactivity within bioreactors. In this study, highly concentrated (2.0 x 108 CFU/muL formulation) nongrowing Rhodopseudomonas palustris CGA009 were immobilized in thin, nanoporous, latex coatings. The coatings were used to study hydrogen production in an argon atmosphere as a function of coating composition, thickness, and light intensity. These coatings can be generated aerobically or anaerobically and are more reactive than an equivalent number of suspended or settled cells. Rhodopseudomonas palustris latex coatings remained active after hydrated storage for greater than 3 months in the dark and over 1 year when stored at -80 degrees C. The initial hydrogen production rate of the microphotobioreactors containing 6.25 cm2, 58.4 mum thick Rps. palustris latex coatings illuminated by 34.1 PAR mumol photons m-2 s-1 was 6.3 mmol H2 m-2 h-1 and had a final yield of 0.55 mol H2 m-2 in 120 h. A dispersible latex blend has been developed for direct comparison of the specific activity of settled, suspended, and immobilized Rps. palustris.     

Improved phototrophic H2 production with Rhodopseudomonas palustris WP3-5 using acetate and butyrate as dual carbon substrates

An indigenous purple nonsulfur bacterium Rhodopseudomonas palustris WP3-5 was used to produce hydrogen phototrophically from acetate (HAc) and butyrate (HBu), which are the major soluble products from acidogenic dark fermentation. Statistical experimental design methodology was applied to identify optimal composition of the two carbon substrates in the medium, leading to better H2 production performance of R. palustris WP3-5. Three performance indexes were used to assess the effectiveness of the phototrophic H2 production; they were H2 yield (Y H2), maximum H2 production rate (Rmax) and maximum cumulative H2 evolution (Hmax). An overlay contour plot was used to determine the optimal concentration range of HAc and HBu, taking into account all three performance indexes (i.e., Rmax, Hmax, and Y H2) simultaneously. With the response surface analysis, R. palustris WP3-5 could produce H2 efficiently with the best Rmax, Hmax, and Y H2 of 39.5 ml/h, 2738 ml, and 51.6%, respectively. This performance is superior to most reported values in the literature, indicating that the statistical experimental design is an effective tool to improve phototrophic H2 production with R. palustris WP3-5.     

Oxygen reduction in chloroplast thylakoids results in production of hydrogen peroxide inside the membrane

Hydrogen peroxide production in isolated pea thylakoids was studied in the presence of cytochrome c to prevent disproportionation of superoxide radicals outside of the thylakoid membranes. The comparison of cytochrome c reduction with accompanying oxygen uptake revealed that hydrogen peroxide was produced within the thylakoid. The proportion of electrons from water oxidation participating in this hydrogen peroxide production increased with increasing light intensity, and at a light intensity of 630 micromol quanta m(-2) s(-1) it reached 60% of all electrons entering the electron transport chain. Neither the presence of a superoxide dismutase inhibitor, potassium cyanide or sodium azide, in the thylakoid suspension, nor unstacking of the thylakoids appreciably affected the partitioning of electrons to hydrogen peroxide production. Also, osmolarity-induced changes in the thylakoid lumen volume, as well as variation of the lumen pH induced by the presence of Gramicidin D, had negligible effects on such partitioning. The flow of electrons participating in lumen hydrogen peroxide production was found to be near 10% of the total electron flow from water. It is concluded that a considerable amount of hydrogen peroxide is generated inside thylakoid membranes, and a possible mechanism, as well as the significance, of this process are discussed.     

Agricultural fertilizers as economical alternative for cultivation of Haematococcus pluvialis

A Haematococcus pluvialis strain isolated from the ruins of Ephesus in Turkey was investigated as regards its adaptation to laboratory conditions and maximum growth rate. In the first stage of the experiment, the growth of H. pluvialis was compared in common culture media. Furthermore, in an effort to minimize the culture costs, the second stage of the experiment compared the growth rate in the culture medium selected in the first stage with that in commercial plant fertilizers. The results demonstrated that the maximum cell concentration of 0.90 g/l, corresponding to a growth rate of 0.150 d(-1), was found with an N-P-K 20:20:20 fertilizer under a light intensity of 75 micromol photons m(-2) s(-1) on the 12th day of cultivation.     

H2 metabolism in the photosynthetic bacterium Rhodopseudomonas capsulata: H2 production by growing cultures.

Purple photosynthetic bacteria produce H2 from organic compounds by an anaerobic light-dependent electron transfer process in which nitrogenase functions as the terminal catalyst. It has been established that the H2-evolving function of nitrogenase is inhibited by N2 and ammonium salts, and is maximally expressed in cells growing photoheterotrophically with certain amino acids as sources of nitrogen. In the present studies with Rhodopseudomonas capsulata, nutritional factors affecting the rate and magnitude of H2 photoproduction in cultures growing with amino acid nitrogen sources were examined. The highest H2 yields and rates of formation were observed with the organic acids: lactate, pyruvate, malate, and succinate in media containing glutamate as the N source; under optimal conditions with excess lactate, H2 was produced at rates of ca. 130 ml/h per g(dry weight) of cells. Hydrogen production is significantly influenced by the N/C ratio in the growth substrates; when this ratio exceeds a critical value, free ammonia appears in the medium and H2 is not evolved. In the "standard" lactate + glutamate system, both H2 production and growth are "saturated" at a light intesity of ca. 600 ft-c (6,500 lux). Evolution of H2, however, occurs during growth at lithe intensities as low as 50 to 100 ft-c (540 to 1,080 lux), i.e., under conditions of energy limitation. In circumstances in which energy conversion rate and supplies of reducing power exceed the capacity of the biosynthetic machinery, energy-dependent H2 production presumably represents a regulatory device that facilitates "energy-idling." It appears that even when light intensity (energy) is limiting, a significant fraction of the available reducing power and adenosine 5'-triphosphate is diverted to nitrogenase, resulting in H2 formation and a bioenergetic burden to the cell.     

Influence of environmental and nutritional factors in the production of astaxanthin from Haematococcus pluvialis

Astaxanthin extracted from green algae is desirable in the food and pharmaceutical industries due to its antioxidant properties. The green unicellular clear water microalga Haematococcus pluvialis has a high production rate of astaxanthin; indeed, it contains more than 80% astaxanthin content in its cells. This remarkable astaxanthin production is commonly obtained under stress conditions such as nutrient deficiency (N or P), high NaCl concentrations, variations of temperature, and other factors. In this vein, a great research effort has been oriented to determine optimal conditions for astaxanthin production by H. pluvialis.The objective of the present study was the analysis of environmental factors, such as light intensity, aeration and nutrients on the growth and astaxanthin production of H. pluvialis. Maximum growth of H. pluvialis obtained was 3.5x10(5) cells/ml in BBM medium at 28 degrees C under continuous illumination (177 micromol photon m(-2)s(-1)) of white fluorescent light, with continuous aeration (1.5 v.v.m.). Meanwhile, maximal astaxanthin production was 98 mg/g biomass in BAR medium with continuous illumination (345 micromol photon m(-2)s(-1)), with 1 g/l of sodium acetate and without aeration.     

H2, N2, and O2 metabolism by isolated heterocysts from Anabaena sp. strain CA.

Metabolically active heterocysts isolated from wild-type Anabaena sp. strain CA showed high rates of light-dependent acetylene reduction and hydrogen evolution. These rates were similar to those previously reported in heterocysts isolated from the mutant Anabaena sp. strain CA-V possessing fragile vegetative cell walls. Hydrogen production was observed with isolated heterocysts. The ratio of C2H4 to H2 produced ranged from 0.9 to 1.2, and H2 production exhibited unique biphasic kinetics consisting of a 1 to 2-min burst of hydrogen evolution followed by a lower, steady-state rate of hydrogen production. This burst was found to be dependent upon the length of the dark period immediately preceding illumination and may be related to dark-to-light ATP transients. The presence of 100 nM NiCl2 in the growth medium exerted an effect on both acetylene reduction and hydrogen evolution in the isolated heterocysts from strain CA. H2-stimulated acetylene reduction was increased from 2.0 to 3.2 mumol of C2H4 per mg (dry weight) per h, and net hydrogen production was abolished. A phenotypic Hup- mutant (N9AR) of Anabaena sp. strain CA was isolated which did not respond to nickel. In isolated heterocysts from N9AR, ethylene production rates were the same under both 10% C2H2-90% Ar and 10% C2H2-90% H2 with or without added nickel, and net hydrogen evolution was not affected by the presence of 100 nM Ni2+. Isolated heterocysts from strain CA were shown to have a persistent oxygen uptake of 0.7 mumol of O2 per mg (dry weight) per h, 35% of the rate of whole filaments, at air saturating O2 levels, indicating that O2 impermeability is not a requirement for active heterocysts.     

Optimization of glutamate concentration and pH for H production from volatile fatty acids by Rhodopseudomonas capsulata

AIMS: This study attempted to employ response surface methodology (RSM) to evaluate the effects of glutamate concentration and pH on H(2) production from volatile fatty acids by Rhodopseudomonas capsulata. METHODS AND RESULTS: A mixture of acetate, propionate and butyrate was used as a carbon source for the H(2) production by R. capsulata. The H(2) yield and H(2) production rate were strongly affected by the glutamate concentration, pH and their interaction. The predicted maximum H(2) yield of 0.534 was obtained when glutamate concentration and pH were 6.56 mmol l(-1) and 7.29 respectively. On the contrary, the maximum H(2) production rate of 18.72 ml l(-1) h(-1) was achieved at a glutamate concentration of 7.01 mmol l(-1) and pH 7.31. CONCLUSIONS: Taking H(2) yield and H(2) production rate together into account, a glutamate concentration of 6.56-7.01 mmol l(-1) and pH of 7.29-7.31 should be selected for H(2) production from a mixture of acetate, propionate and butyrate by R. capsulata. SIGNIFICANCE AND IMPACT OF THE STUDY: The RSM was a useful tool for maximizing H(2) production by photosynthetic bacteria (PSB).     

The effect of light intensity on hydrogen production by sulfur-deprived Chlamydomonas reinhardtii

The effect of light intensity on hydrogen production by sulfur-deprived Chlamydomonas reinhardtii was studied in situ using either long- or short-term experiments, or alternatively, with samples withdrawn from the photobioreactor. Overall hydrogen production by S-deprived culture was shown to depend on the light intensity and to exhibit regions of light limitation and light inhibition. The optimal incident light intensity for hydrogen production was independent of the method of sulfur deprivation or the initial acetate concentration in the medium (12-34 mM). However, it varied with the Chl concentration and the thickness of the photobioreactor. To calculate the average light intensity in the photobioreactor under different experimental conditions, a special mathematics approach was developed. The optimal average light intensity for H(2) production appeared to be 30-40 microE m(-2)s(-1) and was independent of the Chl or acetate concentrations and the method of S deprivation. The inhibitory effect of high light intensity was related to the enhanced O(2) evolution activity during the photosynthetic stage of sulfur deprivation and to the high activity of photosystem II at the beginning of the H(2)-production phase. Data support the major role of photosystem II in supplying reductants through photosystem I to the hydrogenase throughout the H(2)-production phase.     

厌氧细菌Acetanaerobacterium elongatum从葡萄糖的产氢特性研究

为了了解影响厌氧发酵产氢细菌Acetanaerobacterium elongatumZ7产氢效率的因素,采用生理学方法对其进行了研究。结果表明:乙醇型发酵菌A.elongatumZ7的最适产氢温度为37℃,最适产氢的起始pH为8.0。该菌发酵葡萄糖和阿拉伯糖产氢的能力较强,氢气产率分别为1.55mol H2/mol葡萄糖和1.50mol H2/mol阿拉伯糖。酵母粉是菌株Z7生长和产氢所必须的生长因子;pH影响菌株的生长和葡萄糖利用率;氢压则影响电子流的分配,从而改变代谢产物乙酸和乙醇的比例;当产氢菌与甲烷菌共培养以维持发酵体系低的氢压时,可使氢的理论产量提高约4倍;培养基中乙酸钠浓度>60mmol/L明显抑制产氢。另外,一个只利用蛋白类物质的细菌能够促进菌株Z7对葡萄糖的利用,进而提供氢产量,为生物制氢的工业化生产提供理论参考。     

Hydrogen production by nitrogen-starved cultures of Anabaena cylindrica.

Nitrogen-starved cultures of the alga Anabaena cylindrica 629 produced hydrogen and oxygen continuously for 7 to 19 days. Hydrogen production attained a maximum level after 1 to 2 days of starvation and was followed by a slow decline. The maximum rates were 30 ml of H2 evolved per liter of culture per h or 32 mul of H2 per mg of dry weight per h. In 5 to 7 days the rate of H2 evolution by the more productive cultures fell to one-half its maximum value. The addition of 10(-4) to 5 X 10(-4) M ammonium increased the rate of oxygen evolution and the total hydrogen production of the cultures. H2-O2 ratios were 4:1 under conditions of complete nitrogen starvation and about 1.7:1 after the addition of ammonium. Thus, oxygen evolution was affected by the extent of the nitrogen starvation. Thermodynamic efficiencies of converting incident light energy to free energy of hydrogen via algal photosynthesis were 0.4%. Possible factors limiting hydrogen production were decline of reductant supply and filament breakage. Hydrogen production by filamentous, heterocystous blue-green algae could be used for development of a biophotolysis system.     

Hydrogen production by nitrogen-starved cultures of Anabaena cylindrica.

Nitrogen-starved cultures of the alga Anabaena cylindrica 629 produced hydrogen and oxygen continuously for 7 to 19 days. Hydrogen production attained a maximum level after 1 to 2 days of starvation and was followed by a slow decline. The maximum rates were 30 ml of H2 evolved per liter of culture per h or 32 mul of H2 per mg of dry weight per h. In 5 to 7 days the rate of H2 evolution by the more productive cultures fell to one-half its maximum value. The addition of 10(-4) to 5 X 10(-4) M ammonium increased the rate of oxygen evolution and the total hydrogen production of the cultures. H2-O2 ratios were 4:1 under conditions of complete nitrogen starvation and about 1.7:1 after the addition of ammonium. Thus, oxygen evolution was affected by the extent of the nitrogen starvation. Thermodynamic efficiencies of converting incident light energy to free energy of hydrogen via algal photosynthesis were 0.4%. Possible factors limiting hydrogen production were decline of reductant supply and filament breakage. Hydrogen production by filamentous, heterocystous blue-green algae could be used for development of a biophotolysis system.     

Geobacter lovleyi sp. nov. strain SZ, a novel metal-reducing and tetrachloroethene-dechlorinating bacterium

A bacterial isolate, designated strain SZ, was obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethene (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination (i.e., chlororespiration). Hydrogen and pyruvate served as alternate electron donors for strain SZ, and the range of electron acceptors included (reduced products are given in brackets) PCE and trichloroethene [cis-DCE], nitrate [ammonium], fumarate [succinate], Fe(III) [Fe(II)], malate [succinate], Mn(IV) [Mn(II)], U(VI) [U(IV)], and elemental sulfur [sulfide]. PCE and soluble Fe(III) (as ferric citrate) were reduced at rates of 56.5 and 164 nmol min(-1) mg of protein(-1), respectively, with acetate as the electron donor. Alternate electron acceptors, such as U(VI) and nitrate, did not inhibit PCE dechlorination and were consumed concomitantly. With PCE, Fe(III) (as ferric citrate), and nitrate as electron acceptors, H(2) was consumed to threshold concentrations of 0.08 +/- 0.03 nM, 0.16 +/- 0.07 nM, and 0.5 +/- 0.06 nM, respectively, and acetate was consumed to 3.0 +/- 2.1 nM, 1.2 +/- 0.5 nM, and 3.6 +/- 0.25 nM, respectively. Apparently, electron acceptor-specific acetate consumption threshold concentrations exist, suggesting that similar to the hydrogen threshold model, the measurement of acetate threshold concentrations offers an additional diagnostic tool to delineate terminal electron-accepting processes in anaerobic subsurface environments. Genetic and phenotypic analyses classify strain SZ as the type strain of the new species, Geobacter lovleyi sp. nov., with Geobacter (formerly Trichlorobacter) thiogenes as the closest relative. Furthermore, the analysis of 16S rRNA gene sequences recovered from PCE-dechlorinating consortia and chloroethene-contaminated subsurface environments suggests that Geobacter lovleyi belongs to a distinct, dechlorinating clade within the metal-reducing Geobacter group. Substrate versatility, consumption of electron donors to low threshold concentrations, and simultaneous reduction of electron acceptors suggest that strain SZ-type organisms have desirable characteristics for bioremediation applications.     

Hydrogen production by photoautotrophic sulfur-deprived Chlamydomonas reinhardtii pre-grown and incubated under high light

We have previously demonstrated that Chlamydomonas reinhardtii can produce hydrogen under strictly photoautotrophic conditions during sulfur deprivation [Tsygankov et al. (2006); Int J Hydrogen Energy 3:1574-1584]. The maximum hydrogen photoproduction was achieved by photoautotrophic cultures pre-grown under a low light regime (25 microE m(-2) s(-1)). We failed to establish sustained hydrogen production from cultures pre-grown under high light (100 microE m(-2) s(-1)). A new approach for sustained hydrogen production by these cultures is presented here. Assuming that stable and reproducible transition to anerobiosis as well as high starch accumulation are important for hydrogen production, the influence of light intensity and dissolved oxygen concentration during the oxygen evolving stage of sulfur deprivation were investigated in cultures pre-grown under high light. Results showed that light higher than 175 microE m(-2) s(-1) during sulfur deprivation induced reproducible transition to anerobiosis, although the total amount of starch accumulation and hydrogen production were insignificant. The potential PSII activity measured in the presence of an artificial electron acceptor (DCBQ) and an inhibitor of electron transport (DBMIB) did not change in cultures pre-grown under 20 microE m(-2) s(-1) and incubated under 150 microE m(-2) s(-1) during sulfur deprivation. In contrast, the potential PSII activity decreased in cultures pre-grown under 100 microE m(-2) s(-1) and incubated under 420 microE m(-2) s(-1). This indicates that cultures grown under higher light experience irreversible inhibition of PSII in addition to reversible down regulation. High dissolved O(2) content during the oxygen evolving stage of sulfur deprivation has a negative regulatory role on PSII activity. To increase hydrogen production by C. reinhardtii pre-grown under 100 microE m(-2) s(-1), cultures were incubated under elevated PFD and decreased oxygen pressure during the oxygen evolving stage. These cultures reproducibly reached anaerobic stage, accumulated significant quantities of starch and produced significant quantities of H(2). It was found that elevation of pH from 7.4 to 7.7 during the oxygen producing stage of sulfur deprivation led to a significant increase of accumulated starch. Thus, control of pH during sulfur deprivation is a possible way to further optimize hydrogen production by photoautotrophic cultures.     

An alternative approach to the traditional mixotrophic cultures of Haematococcus pluvialis Flotow (Chlorophyceae)

In traditional mixotrophic cultures of microalgae, all the inorganic nutrients and organic carbon sources are supplied in the medium before inoculation. In this study, however, an alternative approach was adopted in Haematococcus pluvialis Flotow, a microalga capable of growing mixotrophically on sodium acetate (Na-Ac). First, the cells were grown under 75 micromol photons m-2 s-1 phototrophically without Na-Ac until the stationary phase and then exposed to five different light regimes by the addition of Na-Ac, e.g., dark, 20, 40, 75 and 150 micromol photons m-2 s-1. Dry weight (DW), pigments and especially cell number in alternative mixotrophy (AM) were higher than traditional mixotrophy (TM). Cell number in AM almost doubled up from 21.7 to 42.9 x 104 cells mL-1 during 5 day exposure to Na-Ac, whereas the increase was only 1.2-fold in TM. Maximum cell density was reached in 75 micromol photons m-2 s-1 among the light intensities tested. We propose that Na-Ac in TM of H. pluvialis can not be utilized as efficient as in AM. With this respect, AM is of several advantages against TM such as a much higher cell density in a batch culture period and minimized risk of contamination due to the shorter exposure of cells to organic carbon sources. In consequence, this method may be used for other strains of the species, and even for the other microalgal species able to grow mixotrophically.     

Isolation and characterization of a hydrogen- and ethanol-producing Clostridium sp. strain URNW

Identification, characterization, and end-product synthesis patterns were analyzed in a newly identified mesophilic, anaerobic Clostridium sp. strain URNW, capable of producing hydrogen (H?) and ethanol. Metabolic profiling was used to characterize putative end-product synthesis pathways of the Clostridium sp. strain URNW, which was found to grow on cellobiose; on hexose sugars, such as glucose, sucrose, and mannose; and on sugar alcohols, like mannitol and sorbitol. When grown in batch cultures on 2 g cellobiose·L?1, Clostridium sp. strain URNW showed a cell generation time of 1.5 h, and the major end-products were H2, formate, carbon dioxide (CO?), lactate, butyrate, acetate, pyruvate, and ethanol. The total volumetric H? production was 14.2 mmol·(L culture)?1 and the total production of ethanol was 0.4 mmol·(L culture)?1. The maximum yield of H? was 1.3 mol·(mol glucose equivalent)?1 at a carbon recovery of 94%. The specific production rates of H?, CO?, and ethanol were 0.45, 0.13, and 0.003 mol·h?1·(g dry cell mass)-1, respectively. BLAST analyses of 16S rDNA and chaperonin 60 (cpn60) sequences from Clostridium sp. strain URNW revealed a 98% nucleotide sequence identity with the 16S rDNA and cpn60 sequences from Clostridium intestinale ATCC 49213. Phylogenetic analyses placed Clostridium sp. strain URNW within the butyrate-synthesizing clostridia.