Metaproteomics-informed stoichiometric modeling reveals the responses of wetland microbial communities to oxygen and sulfate exposure.

Climate changes significantly impact greenhouse gas emissions from wetland soil. Specifically, wetland soil may be exposed to oxygen (O2) during droughts, or to sulfate (SO42-) as a result of sea level rise. How these stressors - separately and together - impact microbial food webs driving carbon cycling in the wetlands is still not understood. To investigate this, we integrated geochemical analysis, proteogenomics, and stoichiometric modeling to characterize the impact of elevated SO42- and O2 levels on microbial methane (CH4) and carbon dioxide (CO2) emissions. The results uncovered the adaptive responses of this community to changes in SO42- and O2 availability and identified altered microbial guilds and metabolic processes driving CH4 and CO2 emissions. Elevated SO42- reduced CH4 emissions, with hydrogenotrophic methanogenesis more suppressed than acetoclastic. Elevated O2 shifted the greenhouse gas emissions from CH4 to CO2. The metabolic effects of combined SO42- and O2 exposures on CH4 and CO2 emissions were similar to those of O2 exposure alone. The reduction in CH4 emission by increased SO42- and O2 was much greater than the concomitant increase in CO2 emission. Thus, greater SO42- and O2 exposure in wetlands is expected to reduce the aggregate warming effect of CH4 and CO2. Metaproteomics and stoichiometric modeling revealed a unique subnetwork involving carbon metabolism that converts lactate and SO42- to produce acetate, H2S, and CO2 when SO42- is elevated under oxic conditions. This study provides greater quantitative resolution of key metabolic processes necessary for the prediction of CH4 and CO2 emissions from wetlands under future climate scenarios.

Biochar facilitated Biological CO2 conversion to C2-C6 alcohols and fatty acids.

Microbial CO2 utilization reduces the carbon footprint, providing economic potential. Biochar, rich in minerals and trace metals, can enhance microbial activity. This study investigates poultry litter and switchgrass biochars produced at 350 and 700 °C (PLB350, PLB700, SGB350 and SGB700, respectively) affect CO2 conversion to C2-C6 alcohols and acids by Clostridium muellerianum P21, C. ragsdalei P11 and C. carboxidivorans P7. Fermentations were in 250-mL bottles containing H2:CO2:N2 (60:20:20) shaken at 125 rpm and 37 °C. SGB350 increased alcohol titers by 1.1-2.1 fold, and PLB350 enhanced acid concentrations by 1.2-1.7 fold compared to the control without biochar. About 2.0-3.3 fold more ethanol was formed by strain P11 compared to strains P7 and P21 with SGB350. However, strain P21 produced 2.4-fold more butanol than strain P7 with SGB350, including unique hexanol production. These results highlight the potential of biochar in enhancing C2-C6 alcohol production from CO2, thereby boosting process feasibility.

The effect of Paenibacillus on IDEXX Enterolert results from freshwater stream environments.

Enterolert, a fluorogenic substrate test, is used as a quantitative method for determining freshwater concentrations of Enterococcus for water quality indicators. However, there is some evidence from recent studies suggesting that Enterolert may not suppress false positives due to pollution sources in waterbodies. In this study, we evaluated this method by analyzing field water and sediment samples from four freshwater streams. We also performed a laboratory microcosm study from two of the stream sediments. The Enterolert method was investigated by phenotypic and genomic analyses for accuracy of isolating and quantifying Enterococcus and/or Streptococcus. Additionally, we tested isolates from Enterolert panels for antibiotic resistance. Results from the field and microcosm studies from initial to final time points indicated that false positives were predominantly Paenibacillus spp. and other non-fecal indicator bacteria. Furthermore, the microcosm study indicated shifts from lactic acid to non-lactic acid bacteria between initial to final time points, but Enterococcus concentrations from Enterolert panels remained stable for the duration of the study for both stream sediments. Antibiotic resistance indicated no distinct pattern of resistance or susceptibility to a suite of antibiotics. However, all isolates tested were resistant to bacitracin and nalidixic acid. In conclusion, we found that Enterolert was not exclusively selective for Enterococcus from freshwater environments and that sediment and polluted waterbodies have the potential to skew the presumed concentrations. More research is needed to evaluate the effectiveness and selectivity of the medium used for the fluorogenic substrate test for Enterococcus enumeration.

Cross-Feedings, Competition, and Positive and Negative Synergies in a Four-Species Synthetic Community for Anaerobic Degradation of Cellulose to Methane.

Complex interactions exist among microorganisms in a community to carry out ecological processes and adapt to changing environments. Here, we constructed a quad-culture consisting of a cellulolytic bacterium (Ruminiclostridium cellulolyticum), a hydrogenotrophic methanogen (Methanospirillum hungatei), an acetoclastic methanogen (Methanosaeta concilii), and a sulfate-reducing bacterium (Desulfovibrio vulgaris). The four microorganisms in the quad-culture cooperated via cross-feeding to produce methane using cellulose as the only carbon source and electron donor. The community metabolism of the quad-culture was compared with those of the R. cellulolyticum-containing tri-cultures, bi-cultures, and mono-culture. Methane production was higher in the quad-culture than the sum of the increases in the tri-cultures, which was attributed to a positive synergy of four species. In contrast, cellulose degradation by the quad-culture was lower than the additive effects of the tri-cultures which represented a negative synergy. The community metabolism of the quad-culture was compared between a control condition and a treatment condition with sulfate addition using metaproteomics and metabolic profiling. Sulfate addition enhanced sulfate reduction and decreased methane and CO2 productions. The cross-feeding fluxes in the quad-culture in the two conditions were modeled using a community stoichiometric model. Sulfate addition strengthened metabolic handoffs from R. cellulolyticum to M. concilii and D. vulgaris and intensified substrate competition between M. hungatei and D. vulgaris. Overall, this study uncovered emergent properties of higher-order microbial interactions using a four-species synthetic community. IMPORTANCE A synthetic community was designed using four microbial species that together performed distinct key metabolic processes in the anaerobic degradation of cellulose to methane and CO2. The microorganisms exhibited expected interactions, such as cross-feeding of acetate from a cellulolytic bacterium to an acetoclastic methanogen and competition of H2 between a sulfate reducing bacterium and a hydrogenotrophic methanogen. This validated our rational design of the interactions between microorganisms based on their metabolic roles. More interestingly, we also found positive and negative synergies as emergent properties of high-order microbial interactions among three or more microorganisms in cocultures. These microbial interactions can be quantitatively measured by adding and removing specific members. A community stoichiometric model was constructed to represent the fluxes in the community metabolic network. This study paved the way toward a more predictive understanding of the impact of environmental perturbations on microbial interactions sustaining geochemically significant processes in natural systems.

Clostridium muellerianum sp. nov., a carbon monoxide-oxidizing acetogen isolated from old hay.

An acid/alcohol-producing, Gram-stain-positive, obligately anaerobic, rod-shaped, non-motile, non-spore forming acetogen, designated as strain P21T, was isolated from old hay after enrichment with CO as the substrate. Spores not observed even after prolonged incubation (30 days). Phylogenetic analysis of the 16S rRNA gene sequence of strain P21T showed it was closely related to Clostridium carboxidivorans DSM 15243T (97.9%), Clostridium scatologenes DSM 757T (97.7 %) and Clostridium drakei DSM 12750T (97.7 %). The genome is 5.6 Mb and the G+C content is 29.4 mol%. Average nucleotide identity between strain P21T, C. carboxidivorans, C. scatologenes and C. drakei was 87.1, 86.4, 86.4 %, respectively. Strain P21T grew on CO:CO2, H2:CO2, l-arabinose, ribose, xylose, fructose, galactose, glucose, lactose, mannose, cellobiose, sucrose, cellulose, starch, pyruvate, choline, glutamate, histidine, serine, threonine and casamino acids. End products of metabolism were acetate, butyrate, caproate, ethanol and hexanol. Dominant cellular fatty acids (>10 %) were C16 : 0 (41.5 %), C16 : 1 ω7c/C16 : 1 ω6c (10.0 %), and a summed feature containing cyclo C17 : 1/C18 : 0 (17.3 %). Based on the phenotypic, chemotaxonomic, phylogenetic and phylogenomic analyses, strain P21T represents a new species in the genus Clostridium, for which the name Clostridium muellerianum sp. nov. is proposed. The type strain is P21T (=DSM 111390T=NCIMB 15261T).

Genome Sequence of Clostridium sp. Strain P21, a CO-Fermenting Acetogen Isolated from Old Hay.

Here, we report the genome sequence of Clostridium sp. strain P21, isolated from old hay from Stillwater, Oklahoma. This announcement describes the generation and annotation of the 5.6-Mb genomic sequence of strain P21, which will aid in studies targeting genes involved in the enhancement of acid-alcohol production.

Biochar enhanced ethanol and butanol production by Clostridium carboxidivorans from syngas.

Biochar has functional groups, pH buffering capacity and cation exchange capacity (CEC) that can be beneficial in syngas fermentation. This study examined the properties of biochar made from switchgrass (SGBC), forage sorghum (FSBC), red cedar (RCBC) and poultry litter (PLBC), and their effects on ethanol and butanol production from syngas using Clostridium carboxidivorans. Experiments were performed in 250 mL bottle reactors with a 50 mL working volume at 37 °C fed syngas containing CO:H2:CO2 (40:30:30 by volume). Results showed that PLBC and SGBC enhanced ethanol production by 90% and 73%, respectively, and butanol production by fourfold compared to standard yeast extract medium without biochar (control). CO and H2 utilization in PLBC and SGBC media increased compared to control. PLBC had the highest pH buffering capacity, CEC and total amount of cations compared with SGBC, FSBC and RCBC, which could have contributed to its highest enhancement of ethanol and butanol production.

Genome Sequence of Acetomicrobium hydrogeniformans OS1.

Acetomicrobium hydrogeniformans, an obligate anaerobe of the phylum Synergistetes, was isolated from oil production water. It has the unusual ability to produce almost 4 molecules H2/molecule glucose. The draft genome of A. hydrogeniformans OS1 (DSM 22491T) is 2,123,925 bp, with 2,068 coding sequences and 60 RNA genes.

A semi-continuous system for monitoring microbially influenced corrosion.

Microbially influenced corrosion (MIC), also known as biocorrosion, has significant impacts on the environment and economy. Typical systems to study biocorrosion are either dynamic (once-through flow) or static (serum bottle incubations). Dynamic systems can be materials and personnel intensive, while static systems quickly become nutrient limiting and exhibit long incubations. A semi-continuous biocorrosion cell was developed to address these issues. Low carbon shim steel was used as a test surface. Initial results revealed that 50 ppm glutaraldehyde (GLT), a common oil field biocide, in an abiotic cell was 3.6 times more corrosive (24.5 × 10-3 mm/y) than a biocorrosion cell inoculated with a sulfate-reducing bacteria (SRB) enrichment (6.73 × 10-3 mm/y). The SRB inoculated cell treated with GLT (50 ppm) reduced the corrosion rate from 6.73 × 10-3 mm/y to 3.68 × 10-3 mm/y. It was hypothesized that a biocide-surfactant combination would enhance biocide activity, thereby lowering corrosion in a semi-continuous biocorrosion cell. The biocide and surfactant were GLT (30 ppm) and Tween 80 (TW80; 100 ppm). MIC of SRB increased in the presence of a non-inhibitory concentration of GLT (23.4 × 10-3 mm/y), compared to the untreated +SRB condition (8.29 × 10-3 mm/y). The non-ionic surfactant alone reduced MIC (4.57 × 10-3 mm/y) and even more so in combination with GLT (3.69 × 10-3 mm/y). Over 50% of 16S rDNA sequences in the biofilm on the test surface were identified as belonging to the genera Desulfovibrio and Desulfomicrobium. The utility of a semi-continuous system for MIC studies and biocide testing was demonstrated. The concept of regular partial medium replacement is applicable to different corrosion cell and corrosion coupon geometries. Biocide-surfactant combinations may have the potential to reduce the concentration of biocides used in the field. In addition, a semi-defined medium for enumerating Acid-Producing Bacteria (APB) was developed, resulting in higher recoveries compared to a standard phenol red medium (e.g., 1.1 × 104 APB/cm2 vs < 4 × 10-1 APB/cm2).

Butanol and hexanol production in Clostridium carboxidivorans syngas fermentation: Medium development and culture techniques.

Clostridium carboxidivorans was grown on model syngas (CO:H2:CO2 [70:20:10]) in a defined nutrient medium with concentrations of nitrogen, phosphate and trace metals formulated to enhance production of higher alcohols. C. carboxidivorans was successfully grown in a limited defined medium (no yeast extract, no MES buffer and minimal complex chemical inputs) using an improved fermentation protocol. Low partial pressure of CO in the headspace, coupled with restricted mass transfer for CO and H2, was required for successful fermentation. In the absence of substrate inhibition (particularly from CO), growth limitation increased production of alcohols, especially butanol and hexanol. Concentrations of butanol (over 1.0g/L), hexanol (up to 1.0g/L) and ethanol (over 3.0g/L) were achieved in bottle fermentations. Minimal medium and controlled supply of CO and H2 should be used in characterizing candidate butanol and hexanol producing strains to select for commercial potential.

Butanol production from hydrothermolysis-pretreated switchgrass: Quantification of inhibitors and detoxification of hydrolyzate.

The present study evaluated butanol production from switchgrass based on hydrothermolysis pretreatment. The inhibitors present in the hydrolyzates were measured. Results showed poor butanol production (1g/L) with non-detoxified hydrolyzate. However, adjusting the pH of the non-detoxified hydrolyzate to 6 and adding 4 g/L CaCO3 increased butanol formation to about 6g/L. There was about 1g/L soluble lignin content (SLC), and various levels of furanic and phenolic compounds found in the non-detoxified hydrolyzate. Detoxification of hydrolyzates with activated carbon increased the butanol titer to 11 g/L with a total acetone, butanol and ethanol (ABE) concentration of 17 g/L. These results show the potential of butanol production from hydrothermolysis pretreated switchgrass.

Improved conversion efficiencies for n-fatty acid reduction to primary alcohols by the solventogenic acetogen "Clostridium ragsdalei".

"Clostridium ragsdalei" is an acetogen that ferments synthesis gas (syngas, predominantly H2:CO2:CO) to ethanol, acetate, and cell mass. Previous research showed that C. ragsdalei could also convert propionic acid to 1-propanol and butyric acid to 1-butanol at conversion efficiencies of 72.3 and 21.0 percent, respectively. Our research showed that C. ragsdalei can also reduce pentanoic and hexanoic acid to the corresponding primary alcohols. This reduction occurred independently of growth in an optimized medium with headspace gas exchange (vented and gassed with CO) every 48 h. Under these conditions, conversion efficiencies increased to 97 and 100 % for propionic and butyric acid, respectively. The conversion efficiencies for pentanoic and hexanoic acid to 1-pentanol and 1-hexanol, respectively, were 82 and 62 %. C. ragsdalei also reduced acetone to 2-propanol at a conversion efficiency of 100 %. Further, we showed that C. ragsdalei uses an aldehyde oxidoreductase-like enzyme to reduce n-fatty acids to the aldehyde intermediates in a reaction that requires ferredoxin and exogenous CO.

Process development for biological production of butanol from Eastern redcedar.

Eastern redcedar is an invasive softwood species in Oklahoma and across grasslands in the Central Plains of the United States and potential feedstock for butanol production. Butanol has higher energy content than ethanol and can be upgraded to jet and diesel fuels. The objective of this study was to develop a process for production of butanol from redcedar. Results showed that Clostridium acetobutylicum ATCC 824 and Clostridium beijerinckii NCIMB 8052 did not grow in fermentation medium with citrate buffer. However, both strains grew in the medium with acetate buffer, resulting in 3-4g/L greater butanol than without acetate. Detoxification of redcedar hydrolyzate was required to increase butanol concentration from 1 to 13g/L. Hydrolyzate was detoxified by activated carbon to remove inhibitors. Fermentations in detoxified redcedar hydrolyzate reached 13g/L butanol and 19g/L total ABE, comparable to glucose control. This shows the potential for redcedar use in butanol production.

Mixed culture syngas fermentation and conversion of carboxylic acids into alcohols.

Higher alcohols such as n-butanol and n-hexanol have higher energy density than ethanol, are more compatible with current fuel infrastructure, and can be upgraded to jet and diesel fuels. Several organisms are known to convert syngas to ethanol, but very few can produce higher alcohols alone. As a potential solution, mixed culture fermentation between the syngas fermenting Alkalibaculum bacchi strain CP15 and propionic acid producer Clostridium propionicum was studied. The monoculture of CP15 produced only ethanol from syngas without initial addition of organic acids to the fermentation medium. However, the mixed culture produced ethanol, n-propanol and n-butanol from syngas. The addition of propionic acid, butyric acid and hexanoic acid to the mixed culture resulted in a 50% higher conversion efficiency of these acids to their respective alcohols compared to CP15 monoculture. These findings illustrate the great potential of mixed culture syngas fermentation in production of higher alcohols.

Youngiibacter fragilis gen. nov., sp. nov., isolated from natural gas production-water and reclassification of Acetivibrio multivorans as Youngiibacter multivorans comb. nov.

A taxonomic study employing a polyphasic approach was performed on a novel anaerobic bacterium isolated from natural gas production-water. The bacterium stained Gram-negative and consisted of non-motile, non-spore-forming, rod-shaped cells. Products of glucose or starch fermentation were ethanol, CO2, formate, acetate and H2. The predominant fatty acids were C16 : 0 ALDE and summed feature 3 comprising C16 : 1ω7c and/or C16 : 1ω6c. The DNA G+C content was 45.5 mol%. 16S rRNA gene sequence analysis demonstrated that the nearest phylogenetic neighbours of the novel strain were Acetivibrio multivorans DSM 6139(T) (98.5 %) and Proteiniclasticum ruminis JCM 14817(T) (95.4 %). The DNA-DNA hybridization value between the novel organism and Acetivibrio multivorans PeC1 DSM 6139(T) was determined to be only 30.2 %, demonstrating the separateness of the two species. Based on phylogenetic, phenotypic and chemotaxonomic evidence that clearly distinguished strain 232.1(T) from Proteiniclasticum ruminis and other close relatives, it is proposed that the novel isolate be classified as representing a novel species of a new genus within the family Clostridiaceae, Youngiibacter fragilis gen. nov., sp. nov. The type strain of the type species is 232.1(T) ( = ATCC BAA-2257(T) = DSM 24749(T)). In addition, Acetivibrio multivorans is proposed to be reclassified as Youngiibacter multivorans comb. nov.

Continuous syngas fermentation for the production of ethanol, n-propanol and n-butanol.

Syngas fermentation to fuels is a technology on the verge of commercialization. Low cost of fermentation medium is important for process feasibility. The use of corn steep liquor (CSL) instead of yeast extract (YE) in Alkalibaculum bacchi strain CP15 bottle fermentations reduced the medium cost by 27% and produced 78% more ethanol. When continuous fermentation was performed in a 7-L fermentor, 6g/L ethanol was obtained in the YE and YE-free media. When CSL medium was used in continuous fermentation, the maximum produced concentrations of ethanol, n-propanol and n-butanol were 8 g/L, 6 g/L and 1 g/L, respectively. n-Propanol and n-butanol were not typical products of strain CP15. A 16S rRNA gene-based survey revealed a mixed culture in the fermentor dominated by A. bacchi strain CP15 (56%) and Clostridium propionicum (34%). The mixed culture presents an opportunity for higher alcohols production from syngas.

Optimization of a corn steep medium for production of ethanol from synthesis gas fermentation by Clostridium ragsdalei.

Fermentation of biomass derived synthesis gas to ethanol is a sustainable approach that can provide more usable energy and environmental benefits than food-based biofuels. The effects of various medium components on ethanol production by Clostridium ragsdalei utilizing syngas components (CO:CO(2)) were investigated, and corn steep liquor (CSL) was used as an inexpensive nutrient source for ethanol production by C. ragsdalei. Elimination of Mg(2+), NH(4) (+) and PO(4) (3-) decreased ethanol production from 38 to 3.7, 23 and 5.93 mM, respectively. Eliminating Na(+), Ca(2+), and K(+) or increasing Ca(2+), Mg(2+), K(+), NH(4) (+) and PO(4) (3-) concentrations had no effect on ethanol production. However, increased Na(+) concentration (171 mM) inhibited growth and ethanol production. Yeast extract (0.5 g l(-1)) and trace metals were necessary for growth of C. ragsdalei. CSL alone did not support growth and ethanol production. Nutrients limiting in CSL were trace metals, NH(4) (+) and reducing agent (Cys: cysteine sulfide). Supplementation of trace metals, NH(4) (+) and CyS to CSL (20 g l(-1), wet weight basis) yielded better growth and similar ethanol production as compared to control medium. Using 10 g l(-1), the nutritional limitation led to reduced ethanol production. Higher concentrations of CSL (50 and 100 g l(-1)) were inhibitory for cell growth and ethanol production. The CSL could replace yeast extract, vitamins and minerals (excluding NH(4) (+)). The optimized CSL medium produced 120 and 50 mM of ethanol and acetate, respectively. The CSL could provide as an inexpensive source of most of the nutrients required for the syngas fermentation, and thus could improve the economics of ethanol production from biomass derived synthesis gas by C. ragsdalei.

Physiological response of Clostridium carboxidivorans during conversion of synthesis gas to solvents in a gas-fed bioreactor.

Clostridium carboxidivorans P7 is one of three microbial catalysts capable of fermenting synthesis gas (mainly CO, CO(2) , and H(2) ) to produce the liquid biofuels ethanol and butanol. Gasification of feedstocks to produce synthesis gas (syngas), followed by microbial conversion to solvents, greatly expands the diversity of suitable feedstocks that can be used for biofuel production beyond commonly used food and energy crops to include agricultural, industrial, and municipal waste streams. C. carboxidivorans P7 uses a variation of the classic Wood-Ljungdahl pathway, identified through genome sequence-enabled approaches but only limited direct metabolic analyses. As a result, little is known about gene expression and enzyme activities during solvent production. In this study, we measured cell growth, gene expression, enzyme activity, and product formation in autotrophic batch cultures continuously fed a synthetic syngas mixture. These cultures exhibited an initial phase of growth, followed by acidogenesis that resulted in a reduction in pH. After cessation of growth, solventogenesis occurred, pH increased and maximum concentrations of acetate (41 mM), butyrate (1.4 mM), ethanol (61 mM), and butanol (7.1 mM) were achieved. Enzyme activities were highest during the growth phase, but expression of carbon monoxide dehydrogenase (CODH), Fe-only hydrogenases and two tandem bi-functional acetaldehyde/alcohol dehydrogenases were highest during specific stages of solventogenesis. Several amino acid substitutions between the tandem acetaldehyde/alcohol dehydrogenases and the differential expression of their genes suggest that they may have different roles during solvent formation. The data presented here provide a link between the expression of key enzymes, their measured activities and solvent production by C. carboxidivorans P7. This research also identifies potential targets for metabolic engineering efforts designed to produce higher amounts of ethanol or butanol from syngas. .

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.

Fermentative production of ethanol from syngas using novel moderately alkaliphilic strains of Alkalibaculum bacchi.

Ethanol production from syngas using three moderately alkaliphilic strains of a novel genus and species Alkalibaculum bacchi CP11(T), CP13 and CP15 was investigated in 250 ml bottle fermentations containing 100ml of yeast extract medium at 37 °C and pH 8.0. Two commercial syngas mixtures (Syngas I: 20% CO, 15% CO(2), 5% H(2), 60% N(2)) and (Syngas II: 40% CO, 30% CO(2), 30% H(2)) were used. Syngas I and Syngas II represent gasified biomass and coal, respectively. The maximum ethanol concentration (1.7 g l(-1)) and yield from CO (76%) were obtained with strain CP15 and Syngas II after 360 h. CP15 produced over twofold more ethanol with Syngas I compared to strains CP11(T) and CP13. In addition, CP15 produced 18% and 71% more ethanol using Syngas II compared to strains CP11(T) and CP13, respectively. These results show that CP15 is the most promising for ethanol production because of its higher growth and ethanol production rates and yield compared to CP11(T) and CP13.