Mole Of Substrate Research Articles

Valorization of brewery waste slurry with glycerol as co‐substrate for hydrogen and butyrate production using dark fermentation

AbstractBACKGROUNDAmong the methods to produce hydrogen biologically, dark fermentation stands out mainly due to its low operating requirements. Organic wastes, such as brewing industry waste slurries and glycerol, can provide a cost‐effective feedstock with the additional potential of generating value‐added byproducts, while addressing a wastewater treatment issue.RESULTSThe hydrogen production potential in dark fermentation of a high‐strength brewery waste slurry was optimized with a selected seed sludge, initial COD concentration of 50–60 g L−1, pH 6.4 and fermentation time of 30 h. The main end product was butyric acid, accounting for over 50% of the carboxylic acids. The efficiency of the process on the basis of volume of H2 obtained per gram of COD converted into organic acids was 393 ± 5 and 430 ± 6 mL without and with glycerol, respectively, and the molar ratio of H2 per mole of substrate was 71% of the theoretical molar yield when the fermentation is dominated by butyrate as the end product.CONCLUSIONSA proposed brewery sludge treatment system comprising dark fermentation followed by anaerobic digestion is promising and can be more advantageous than anaerobic digestion alone with an increase of 18.5% in energy potential. Alternatively, with recovery of valuable butyrate, a reduction in 4.5 kg of CO2 emissions per cubic meter of sludge treated can be achieved, with a 27% net loss in energy potential. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Developing a self-powered microfluidic microbial electrolysis cell (MEC) for converting oxalate into hydrogen

The present study investigated the capability of coupled microfluidic microbial electrolysis cell-microbial fuel cell (MEC-MFC) to remove oxalate as a toxic end-metabolite and produce hydrogen as an effective antioxidant without any external power. The modification of the system to enhance the hydrogen generation and reduce the number of microfluidic MFCs supporting the external power supply of the microfluidic MEC was implemented by using zinc anode and inoculation of Shewanella oneidensis MR-1 at a simple straight microchannel. The selection of the mentioned elements resulted from the assessment of spiral and straight geometries, nanoparticle growth, and injection rates of the substrate. The open-circuit potential of one microfluidic MFC was obtained at about 1.3 V, which could quickly run MECs. The maximum hydrogen production rate was 1.12 mol H2 mol Substrate−1 day−1, which was 12 times more than the results obtained by the coupled microfluidic MFC-MEC fed by glucose and using a nickel electrode. The performance of the coupled system was characterized by the polarization curves, the evolution of hydrogen production, and the morphology of the formed biofilm on the anode surface.

Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.

Palladium (II)-Salan Complexes as Catalysts for Suzuki-Miyaura C-C Cross-Coupling in Water and Air. Effect of the Various Bridging Units within the Diamine Moieties on the Catalytic Performance.

Water-soluble salan ligands were synthesized by hydrogenation and subsequent sulfonation of salens (N,N’-bis(slicylidene)ethylenediamine and analogues) with various bridging units (linkers) connecting the nitrogen atoms. Pd (II) complexes were obtained in reactions of sulfosalans and [PdCl4]2−. Characterization of the ligands and complexes included extensive X-ray diffraction studies, too. The Pd (II) complexes proved highly active catalysts of the Suzuki–Miyaura reaction of aryl halides and arylboronic acid derivatives at 80 °C in water and air. A comparative study of the Pd (II)–sulfosalan catalysts showed that the catalytic activity largely increased with increasing linker length and with increasing steric congestion around the N donor atoms of the ligands; the highest specific activity was 40,000 (mol substrate) (mol catalyst × h)−1. The substrate scope was explored with the use of the two most active catalysts, containing 1,4-butylene and 1,2-diphenylethylene linkers, respectively.

Recent Progress of Cu-Catalyzed Azide-Alkyne Cycloaddition Reactions (CuAAC) in Sustainable Solvents: Glycerol, Deep Eutectic Solvents, and Aqueous Media.

This mini-review presents a general overview of the progress achieved during the last decade on the amalgamation of CuAAC processes (copper-catalyzed azide-alkyne cycloaddition) with the employment of sustainable solvents as reaction media. In most of the presented examples, the use of water, glycerol (Gly), or deep eutectic solvents (DESs) as non-conventional reaction media allowed not only to recycle the catalytic system (thus reducing the amount of the copper catalyst needed per mole of substrate), but also to achieve higher conversions and selectivities when compared with the reaction promoted in hazardous and volatile organic solvents (VOCs). Moreover, the use of the aforementioned green solvents also permits the improvement of the overall sustainability of the Cu-catalyzed 1,3-dipolar cycloaddition process, thus fulfilling several important principles of green chemistry.

Efficacy of an organophosphorus hydrolase enzyme (OpdA) in human serum and minipig models of organophosphorus insecticide poisoning

Objectives: Current therapeutic options for organophosphorus (OP) insecticide self-poisoning including atropine and oximes are inadequate and case fatality may exceed 20%. An OP hydrolase enzyme, OpdA, has been used for environmental cleansing of OP insecticides and prevented death in rat and non-human primate models of OP insecticide poisoning if given very quickly after exposure. We here tested OpdA’s ability to break down OP insecticides in human serum and in clinically relevant minipig models of OP insecticide poisoning.Methods: Human serum was spiked with seven diverse WHO Class II OP insecticides (chlorpyrifos, quinalphos, diazinon, dimethoate, fenthion, phenthoate, and profenofos) and the effect of OpdA on degradation measured. The pharmacodynamic and clinical effects of OpdA treatment were studied in Gottingen minipigs orally poisoned with agricultural formulations of dimethoate EC40 or methyl parathion EC60; pharmacodynamic effects were also assessed in profenofos EC50-poisoned pigs.Results: OpdA effectively hydrolysed OP insecticides in human serum, with rates varying from 856 (SD 44) down to 0.107 (SD 0.01) moles of substrate hydrolysed/mole of enzyme/sec (kcat) for quinalphos and phenthoate, respectively, although at rates 2–3 log orders less than found in vitro in buffered solution. It showed clinical benefit in minipig models, reducing the dose of noradrenaline required to sustain an adequate mean arterial pressure after dimethoate (mean 0.149 [SD 0.10] μg/kg/h vs. 1.07 [SD 0.77] μg/kg/h, p < .0001) and methyl parathion (mean 0.077 [SD 0.08] μg/kg/h vs. 0.707 [SD 0.49] μg/kg/h, p < .0001) poisoning. OpdA reduced blood OP insecticide concentration and acetylcholinesterase inhibition after poisoning by dimethoate, methyl parathion, and profenofos insecticides.Conclusions: In vitro incubation of OpdA in human serum showed hydrolysis of diverse OP insecticides, although at lower rates than found in buffer solutions. This activity results in clinical and pharmacodynamic efficacy in vivo against several OP insecticides. These results support the testing of OpdA in further animal models before considering human trials to determine whether it may become an urgently required novel therapeutic agent for OP insecticide self-poisoning.

Modelling thermodynamic feedback on the metabolism of hydrogenotrophic methanogens

The magnitude of the Gibbs free energy change of the substrate transformation that supports the growth of a microbe is decreased when the concentrations of the substrates are decreased and when the concentrations of the products of metabolism are increased. Microbes require a supply of ATP for cell maintenance and growth, and coupling the transformation of substrates to products with the formation of ATP also decreases the magnitude of the Gibbs free energy change. Here we include these three thermodynamic controllers (substrate and product concentration, and ATP formation) in a model of substrate transformation by hydrogenotrophic methanogens that results in a number of realistic behaviours. First, a threshold for substrate use emerges, below which the methanogen cannot metabolise its substrate. Under this model, microbes that capture more of the Gibbs free energy change from substrate transformation in the form of ATP have greater thresholds for their substrate, in line with observations of actual microbes. Second, an apparent saturation constant emerges that is controlled by the thermodynamics of the reaction. This increases with increasing ATP synthesis per substrate, so that methanogens that conserve more ATP grow faster at higher substrate concentrations, but are less competitive at low substrate concentrations. As a result, simply changing the ATP yield (moles of ATP per mole of substrate) results in methanogens with differing ecological strategies through thermodynamic impacts on their metabolism. Third, end-product inhibition through thermodynamic feedback can limit the growth of microbes, and those that capture more ATP per substrate are limited by smaller product concentrations than those that capture less ATP.

Growth yield and selection of nosZ clade II types in a continuous enrichment culture of N2O respiring bacteria

Nitrous oxide (N2 O) reducing microorganisms may be key in the mitigation of N2 O emissions from managed ecosystems. However, there is still no clear understanding of the physiological and bioenergetic implications of microorganisms possessing either of the two N2 O reductase genes (nosZ), clade I and the more recently described clade II type nosZ. It has been suggested that organisms with nosZ clade II have higher growth yields and a lower affinity constant (Ks ) for N2 O. We compared N2 O reducing communities with different nosZI/nosZII ratios selected in chemostat enrichment cultures, inoculated with activated sludge, fed with N2 O as a sole electron acceptor and growth limiting factor and acetate as electron donor. From the sequencing of the 16S rRNA gene, FISH and quantitative PCR of nosZ and nir genes, we concluded that betaproteobacterial denitrifying organisms dominated the enrichments with members within the family Rhodocyclaceae being highly abundant. When comparing cultures with different nosZI/nosZII ratios, we did not find support for (i) a more energy conserving N2 O respiration pathway in nosZ clade II systems, as reflected in the growth yield per mole of substrate, or (ii) a higher affinity for N2 O, defined by μmax /Ks , in organisms with nosZ clade II.

Novel ketone diet enhances physical and cognitive performance.

Ketone bodies are the most energy-efficient fuel and yield more ATP per mole of substrate than pyruvate and increase the free energy released from ATP hydrolysis. Elevation of circulating ketones via high-fat, low-carbohydrate diets has been used for the treatment of drug-refractory epilepsy and for neurodegenerative diseases, such as Parkinson’s disease. Ketones may also be beneficial for muscle and brain in times of stress, such as endurance exercise. The challenge has been to raise circulating ketone levels by using a palatable diet without altering lipid levels. We found that blood ketone levels can be increased and cholesterol and triglycerides decreased by feeding rats a novel ketone ester diet: chow that is supplemented with (R)-3-hydroxybutyl (R)-3-hydroxybutyrate as 30% of calories. For 5 d, rats on the ketone diet ran 32% further on a treadmill than did control rats that ate an isocaloric diet that was supplemented with either corn starch or palm oil (P < 0.05). Ketone-fed rats completed an 8-arm radial maze test 38% faster than did those on the other diets, making more correct decisions before making a mistake (P < 0.05). Isolated, perfused hearts from rats that were fed the ketone diet had greater free energy available from ATP hydrolysis during increased work than did hearts from rats on the other diets as shown by using [31P]-NMR spectroscopy. The novel ketone diet, therefore, improved physical performance and cognitive function in rats, and its energy-sparing properties suggest that it may help to treat a range of human conditions with metabolic abnormalities.—Murray, A. J., Knight, N. S., Cole, M. A., Cochlin, L. E., Carter, E., Tchabanenko, K., Pichulik, T., Gulston, M. K., Atherton, H. J., Schroeder, M. A., Deacon, R. M. J., Kashiwaya, Y., King, M. T., Pawlosky, R., Rawlins, J. N. P., Tyler, D. J., Griffin, J. L., Robertson, J., Veech, R. L., Clarke, K. Novel ketone diet enhances physical and cognitive performance.

Intelligent models to predict hydrogen yield in dark microbial fermentations using existing knowledge

Bioprocess development for hydrogen production requires an excellent understanding of the influence of key operational parameters on hydrogen yields at early stages of the innovation chain. Knowledge on the impact of these key input parameters on fermentative hydrogen yields exist in the public domain. This study builds on this knowledge to implement intelligent models that could predict the hydrogen response on new physicochemical input values. Two Artificial Neural Network (ANN) models for hydrogen production were implemented and assessed using published data from 64 selected studies. For both models the multilayer perceptron (MLP) class of neural network was used with a topology of 5-7-7-1, corresponding to the number of neurons of input, hidden (two) and output layers. The input variables consisted of inoculum type, substrate type, substrate concentration, pH and temperature. The output was the hydrogen yield expressed as mole of hydrogen per mole of substrate (Mol_Model) or as cumulative volume of hydrogen per gram substrate (Vol_Model). A high coefficient of determination (R2) was obtained for Vol_Model (0.90) whereas a low value was observed with Mol_Model (0.46). These findings showed that the Vol_Model efficiently abstracted the non-linear relationship between the considered inputs and biohydrogen yield with a higher prediction accuracy on new physicochemical parameters. Thus, these ANN derived models could be used to navigate the optimization space and shorten the biohydrogen process development time.

New Polysilyl Dendritic Precursors of Triazolylferrocenyl and Triazolylcobalticenium Dendrimers—Comparative Electrochemical Study and Stabilization of Small, Catalytically Active Pd Nanoparticles

The 27-ferrocenyl-terminated and the 27-cobalticenium-terminated metallodendrimers 5 and 6, respectively, were synthesized using only hydrosilylation reactions and click methodology. These new metallodendrimers were characterized by 1H and 13C NMR, infrared, and mass spectroscopy, elemental analysis, and cyclic voltammetry. The dendrimers 5 and 6, being isostructural in their neutral forms, show the same intensities for the redox exchange between their neutral and cationic forms, corresponding approximately to the transfer of 27 electrons, as deduced from the Bard–Anson equation. The metallodendrimer 5 was used to form dendrimer-encapsulated palladium nanoparticles (PdDENs). TEM images indeed show that the PdDENs are very small (average diameter = 1.0 nm) and relatively monodisperse. Their catalytic activity was evaluated for the Suzuki–Miyaura C–C coupling with various substituted aryl bromides (0.2 mol% of Pd per mole of substrate used). This activity is lower than that of previously studied dendrimers ...

Palladium Nanoparticles Stabilized by Glycodendrimers and Their Application in Catalysis

AbstractPalladium nanoparticles stabilized by glycodendrimers (PdDSNs) in water were prepared by coordination of PdII to intradendritic triazole ligands upon reaction of K2PdCl4 with the dendrimer in water followed by aqueous NaBH4 reduction to Pd0. TEM images show that the PdDSNs are small (average diameter: 2.3 nm) and relatively monodisperse owing to a low concentration of metal precursor. The catalytic activity of these PdDSNs was evaluated for the reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) by NaBH4 (only 0.2 mol‐% of Pd per mol substrate is used) and for the Miyaura–Suzuki C–C coupling with various substituted aryl bromides (only 0.01 mol‐% of Pd per mol substrate is used). Comparisons of the catalytic activities of these PdDSNs with those of larger PdDSNs (diameter: 14 nm) reveal that smaller NPs catalyze faster 4‐NP reduction than their larger counterparts but lack any notable surface dependency for Suzuki–Miyaura catalysis.

Kinetic analysis of human CYP24A1 metabolism of vitamin D via the C24-oxidation pathway.

CYP24A1 is the multicatalytic cytochrome P450 responsible for the catabolism of vitamin D via the C23- and C24-oxidation pathways. We successfully expressed the labile human enzyme in Escherichiacoli and partially purified it in an active state that permitted detailed characterization of its metabolism of 1,25-dihydroxyvitamin D3 [1,25(OH)2 D3] and the intermediates of the C24-oxidation pathway in a phospholipid-vesicle reconstituted system. The C24-oxidation pathway intermediates, 1,24,25-trihydroxyvitamin D3, 24-oxo-1,25-dihydroxyvitamin D3, 24-oxo-1,23,25-trihydroxyvitamin D3 and tetranor-1,23-dihydroxyvitamin D3, were enzymatically produced from 1,25(OH)2 D3 using rat CYP24A1. Both 1,25(OH)2 D3 and 1,23-dihydroxy-24,25,26,27-tetranorvitamin D3 were found to partition strongly into the phospholipid bilayer when in aqueous medium. Changes to the phospholipid concentration did not affect the kinetic parameters for the metabolism of 1,25(OH)2 D3 by CYP24A1, indicating that it is the concentration of substrates in the membrane phase (mol substrate·mol phospholipid(-1) ) that determines their rate of metabolism. CYP24A1 exhibited Km values for the different C24-intermediates ranging from 0.34 to 15mmol·molphospholipid(-1) , with 24-oxo-1,23,25-trihydroxyvitamin D3 [24-oxo-1,23,25(OH)3 D3] displaying the lowest and 1,24,25-trihydroxyvitamin D3 [1,24,25(OH)3 D3] displaying the highest. The kcat values varied by up to 3.8-fold, with 1,24,25(OH)3 D3 displaying the highest kcat (34min(-1) ) and 24-oxo-1,23,25(OH)3 D3 the lowest. The data show that the cleavage of the side chain of 24-oxo-1,23,25(OH)3 D3 occurs with the highest catalytic efficiency (kcat /Km ) and produces 1-hydroxy-23-oxo-24,25,26,27-tetranorvitamin D3 and not 1,23-dihydroxy-24,25,26,27-tetranorvitamin D3, as the primary product. These kinetic analyses also show that intermediates of the C24-oxidation pathway effectively compete with precursor substrates for binding to the active site of the enzyme, which manifests as an accumulation of intermediates, indicating that they dissociate after each catalytic step.

Glycine betaine as a direct substrate for methanogens (Methanococcoides spp.).

Nine marine methanogenic Methanococcoides strains, including the type strains of Methanococcoides methylutens, M. burtonii, and M. alaskense, were tested for the utilization of N-methylated glycines. Three strains (NM1, PM2, and MKM1) used glycine betaine (N,N,N-trimethylglycine) as a substrate for methanogenesis, partially demethylating it to N,N-dimethylglycine, whereas none of the strains used N,N-dimethylglycine or sarcosine (N-methylglycine). Growth rates and growth yields per mole of substrate with glycine betaine (3.96 g [dry weight] per mol) were similar to those with trimethylamine (4.11 g [dry weight] per mol). However, as glycine betaine is only partially demethylated, the yield per methyl group was significantly higher than with trimethylamine. If glycine betaine and trimethylamine are provided together, trimethylamine is demethylated to dimethyl- and methylamine with limited glycine betaine utilization. After trimethylamine is depleted, dimethylamine and glycine betaine are consumed rapidly, before methylamine. Glycine betaine extends the range of substrates that can be directly utilized by some methanogens, allowing them to gain energy from the substrate without the need for syntrophic partners.

Gas chromatography analysis for hydrogen production from Bacillus subtilis MKMP 2013

Hydrogen is an uncontaminated energy carrier as it releases only water and no green house gas is released. Hence, bio-hydrogen production was aimed from Bacillus subtilis , a gram positive bacteria isolated near solid waste dumped place, Namakkal. The isolated strain was confirmed by 16srRNA sequencing. Phylogenetic tree analysis was performed to know the nearest sequences. The isolated strain was allowed to grow in production medium containing beef, yeast extract, peptone, sodium chloride and sugarcane baggase for 16 days. Since, most of the hydrogen producing bacteria grow at broader pH, no pH control was opted during the study. After incubation period, the gas collected was analysed for hydrogen production by gas chromatography. The obtained sequence was submitted to genbank under the accession number KF484756. Phylogenetic analysis revealed the strain as B. subtilis . The hydrogen gas produced by B. subtilis using sugarcane bagasse was in the range of 1.3–3.3 mol H 2 /mol substrate. From this result, we can conclude that the isolated strain is able to produce hydrogen to certain extent and can be improved by gene modification.

Bio-hydrogen production by Pseudomonas stutzeri KF532951

Hydrogen production by biological means is more advantageous as it utilizes renewable sources and produces very low or no carbondioxide. Since, lignocellulosic feedstocks are cheaper source, the present study was aimed to isolate Pseudomonas stutzeri from soil sample at country bricks chamber furnace. Final confirmation of the strain was done by 16S rRNA sequencing. The GC content was calculated. The isolated strain was inoculated in hydrogen production medium containing sugarcane bagasse replacing glucose. After the incubation period of 16 days, the gas collected was studied for hydrogen production through gas chromatography technique. According to sequencing and phylogenetic tree results, our isolate was found to be P. stutzeri KF532951 . The GC content of our strain was above 53%. Our strain could produce up to 3.4 mol H 2 /mol substrate by water displacement method. On the basis of the above results, it is concluded that our strain is able to produce hydrogen biologically.

In silico evaluation of a complex multi-enzymatic system using one-pot and modular approaches: Application to the high-yield production of hydrogen from a synthetic metabolic pathway

Multi-enzymatic processes are becoming increasingly attractive for the production of chemicals and pharmaceuticals at an industrial level due to a drastic reduction on the down-stream steps that leads to a better exploitation of resources. One-pot processes (all the enzymes placed in the same reactor) are the most commonly used approach although they present a number of limitations. In this work we explore the use of modular processes (enzymes distributed in different reactors) as an alternative to overcome the limitations of one-pot processes. An in silico evaluation of different process alternatives was performed, taking as an example a multi-enzymatic system for high-yield production of hydrogen from biomass catalyzed by a synthetic metabolic pathway composed of 13 enzymes. A modular process where an hyperthermophilic hydrogenase is kept at higher temperature than the rest of the enzymes lead to a 2-fold increase in productivity, whereas a separate reactor that consumes an inhibitor of other enzymes lead to an 8-fold increase in productivity, compared to the one-pot operation. A multi-objective optimization of the one-pot process for the maximization of productivity and yield was also performed using a genetic algorithm. Productivities of up to 355mmol/L/h was expected to be achieved without compromising the high yield of the process (11.3mol of H2 produced per mol substrate) under the conditions studied.

H2 production from CO, formate or starch using the hyperthermophilic archaeon, Thermococcus onnurineus

The hyperthermophilic archaeon, Thermococcus onnurineus, was grown in media supplemented with either CO, formate, or starch. H(2) was produced with each substrate with respective maximum rates of 1.55, 3.83 and 2.66 mmol H(2)/l h. The yields (mol H(2)/mol substrate) were 0.98, 1 and 3.13, respectively. This microbe is the first example where a single microorganism can grow and produce H(2) using CO, formate or starch as substrate.

Kinetic Resolution of (R,S)-2-Butanol Using Enzymatic Synthesis of Esters

Kinetic resolution of (R,S)-2-butanol using enzymatic synthesis of esters has been studied. (R,S)-2-Butanol is commonly found as a racemic mixture, and the products of its esterification are racemic mixtures too. This work is of great significance in the field of the enzymatic kinetic resolution due to the little information found in literature about the resolution of (R,S)-2-butanol as pure compound. So, this article is a contribution about the enzymatic resolution of (R,S)-2-butanol. The reaction here studied is the esterification/transesterification of (R,S)-2-butanol in organic media (n-hexane) using as biocatalyst the lipase Novozym 435®. The main target of this study is to analyze the influence of certain variables in this reaction. Some of these variables are acyl donor (acids and esters), concentration of substrates, enzyme/substrate ratio, and temperature. The main conclusions of this study are the positive effect of higher substrates concentration (1.5 M) and larger amount of enzyme (13.8 g mol(-1) substrate) on kinetic resolution rate but not a very noticeable effect on enantiomeric excesses. The longer the carboxylic acid chain is, the better results are obtained. Besides to achieve a satisfactory kinetic resolution, it is recommendable to select reaction times (180 min) at which the highest substrate enantiomeric excess is reached (~60%). The temperature has not an appreciable influence on the resolution in the range studied (40-60 °C). When an ester (vinyl acetate) is used as acyl donor, the resolution shows better results than when using a carboxylic acid as acyl donor (ee(s) ~90% at 90 min). Moreover, Michaelis-Menten parameters, v(max) and K(M), were determined, 0.04 mol l(-1) min(-1) and 0.41 mol l(-1), respectively.

Description of Anaerobaculum hydrogeniformans sp. nov., an anaerobe that produces hydrogen from glucose, and emended description of the genus Anaerobaculum

A novel anaerobic, moderately thermophilic, NaCl-requiring fermentative bacterium, strain OS1T, was isolated from oil production water collected from Alaska, USA. Cells were Gram-negative, non-motile, non-spore-forming rods (1.7-2.7×0.4-0.5 µm). The G+C content of the genomic DNA of strain OS1T was 46.6 mol%. The optimum temperature, pH and NaCl concentration for growth of strain OS1T were 55 °C, pH 7 and 10 g l(-1), respectively. The bacterium fermented D-fructose, D-glucose, maltose, D-mannose, α-ketoglutarate, L-glutamate, malonate, pyruvate, L-tartrate, L-asparagine, Casamino acids, L-cysteine, L-histidine, L-leucine, L-phenylalanine, L-serine, L-threonine, L-valine, inositol, inulin, tryptone and yeast extract. When grown on D-glucose, 3.86 mol hydrogen and 1.4 mol acetate were produced per mol substrate. Thiosulfate, sulfur and L-cystine were reduced to sulfide, and crotonate was reduced to butyrate with glucose as the electron donor. 16S rRNA gene sequence analysis indicated that strain OS1T was related to Anaerobaculum thermoterrenum (99.7 % similarity to the type strain), a member of the phylum Synergistetes. DNA-DNA hybridization between strain OS1T and A. thermoterrenum DSM 13490T yielded 68 % relatedness. Unlike A. thermoterrenum, strain OS1T fermented malonate, maltose, tryptone, L-leucine and L-phenylalanine, but not citrate, fumarate, lactate, L-malate, glycerol, pectin or starch. The major cellular fatty acid of strain OS1T was iso-C15:0 (91 % of the total). Strain OS1T also contained iso-C13:0 3-OH (3 %), which was absent from A. thermoterrenum, and iso-C13:0 (2 %), which was absent from Anaerobaculum mobile. On the basis of these results, strain OS1T represents a novel species of the genus Anaerobaculum, for which the name Anaerobaculum hydrogeniformans sp. nov. is proposed. The type strain is OS1T (=DSM 22491T=ATCC BAA-1850T). An emended description of the genus Anaerobaculum is also given.