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).

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.

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.

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.

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.

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.

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.

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.

Tolumonas osonensis sp. nov., isolated from anoxic freshwater sediment, and emended description of the genus Tolumonas.

A polyphasic taxonomic study was performed on a strain of an unknown Gram-negative, non-motile, saccharolytic, facultatively anaerobic bacterium, strain OCF 7(T), isolated from anoxic freshwater sediment. The strain grew optimally at 22 °C and pH 7.5, and was able to grow under strictly anaerobic conditions. Major fermentation products from glucose metabolism were formate, acetate, ethanol and lactate. Comparative 16S rRNA gene sequence analysis indicated that strain OCF 7(T) was phylogenetically related to the type strain of Tolumonas auensis (97.2 % similarity) within the family Aeromonadaceae of the Gammaproteobacteria. However, OCF 7(T) did not produce toluene from phenylacetate, phenylalanine, phenoxyacetate, phenylsuccinate or phenylbutyrate in the presence of glucose. Phenol was not produced from tyrosine or phenoxyacetate in the presence of glucose. Dominant fatty acids of this micro-organism included C(16 : 0), C(18 : 1)ω7c and C(16 : 1)ω7c (and/or iso-C(15 : 0) 2-OH). Major polar lipids were phosphatidylglycerol and phosphatidylethanolamine, and the respiratory quinone was menaquinone MK-8. The genomic DNA G+C content of strain OCF 7(T) was 52.1 mol%. Based on phylogenetic and phenotypic evidence, strain OCF 7(T) should be classified as a representative of a novel species of Tolumonas, for which the name Tolumonas osonensis sp. nov. is proposed; the type strain is OCF 7(T) ( = DSM 22975(T) = ATCC BAA-1908(T)). An emended description of the genus Tolumonas is also given.

Effect of trace metals on ethanol production from synthesis gas by the ethanologenic acetogen, Clostridium ragsdalei.

The effect of trace metal ions (Co²+, Cu²+, Fe²+, Mn²+, Mo6+, Ni²+, Zn²+, SeO4⁻ and WO4⁻) on growth and ethanol production by an ethanologenic acetogen, Clostridium ragsdalei was investigated in CO:CO2-grown cells. A standard acetogen medium (ATCC medium no. 1754) was manipulated by varying the concentrations of trace metals in the media. Increasing the individual concentrations of Ni²+, Zn²+, SeO4⁻ and WO4⁻ from 0.84, 6.96, 1.06, and 0.68 µM in the standard trace metals solution to 8.4, 34.8, 5.3, and 6.8 µM, respectively, increased ethanol production from 35.73 mM under standard metals concentration to 176.5, 187.8, 54.4, and 72.3 mM, respectively. Nickel was necessary for growth of C. ragsdalei. Growth rate (µ) of C. ragsdalei improved from 0.34 to 0.49 (day⁻¹), and carbon monoxide dehydrogenase (CODH) and hydrogenase (H2ase)-specific activities improved from 38.45 and 0.35 to 48.5 and 1.66 U/mg protein, respectively, at optimum concentration of Ni²+. At optimum concentrations of WO4⁻ and SeO4⁻, formate dehydrogenase (FDH) activity improved from 32.3 to 42.6 and 45.4 U/mg protein, respectively. Ethanol production and the activity of FDH reduced from 35 mM and 32.3 U/mg protein to 1.14 mM and 8.79 U/mg protein, respectively, upon elimination of WO4⁻ from the medium. Although increased concentration of Zn²+ enhanced growth and ethanol production, the activities of CODH, FDH, H2ase and alcohol dehydrogenase (ADH) were not affected by varying the Zn²+ concentration. Omitting Fe²+ from the medium decreased ethanol production from 35.7 to 6.30 mM and decreased activities of CODH, FDH, H2ase and ADH from 38.5, 32.3, 0.35, and 0.68 U/mg protein to 9.07, 7.01, 0.10, and 0.24 U/mg protein, respectively. Ethanol production improved from 35 to 54 mM when Cu²+ was removed from the medium. The optimization of trace metals concentration in the fermentation medium improved enzyme activities (CODH, FDH, and H2ase), growth and ethanol production by C. ragsdalei.

Anaerobes: a piece in the puzzle for alternative biofuels.

Although much newsprint is devoted to the subject of reducing the United States and other major developed countries dependence on their respective foreign energy sources; the most challenging issues for society is to provide long-term, sustainable energy sources to accommodate the global population as a whole. The projected population of planet Earth for the year 2050 is estimated to be in excess of 9 billion. With hydrocarbon-based energy becoming limiting it is unlikely that one type of energy will alone replace our dependence on this source. So-called "green" technologies that include solar, wind and wave powers are now being explored to reduce on traditional hydrocarbon-based fuel sources. The diverse and functional properties of microbes, and in particular anaerobes, are now being utilized in the production of biofuels and may provide one piece of the jigsaw for future energy requirements. Here we present some results of a screening program to identify and characterize a number of carbon monoxide oxidizing, ethanol-producing acetogenic anaerobes phylogenetically located within the Clostridiales.

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.

Sequencing of multiple clostridial genomes related to biomass conversion and biofuel production.

Modern methods to develop microbe-based biomass conversion processes require a system-level understanding of the microbes involved. Clostridium species have long been recognized as ideal candidates for processes involving biomass conversion and production of various biofuels and other industrial products. To expand the knowledge base for clostridial species relevant to current biofuel production efforts, we have sequenced the genomes of 20 species spanning multiple genera. The majority of species sequenced fall within the class III cellulosome-encoding Clostridium and the class V saccharolytic Thermoanaerobacteraceae. Species were chosen based on representation in the experimental literature as model organisms, ability to degrade cellulosic biomass either by free enzymes or by cellulosomes, ability to rapidly ferment hexose and pentose sugars to ethanol, and ability to ferment synthesis gas to ethanol. The sequenced strains significantly increase the number of noncommensal/nonpathogenic clostridial species and provide a key foundation for future studies of biomass conversion, cellulosome composition, and clostridial systems biology.

Alkalibaculum bacchi gen. nov., sp. nov., a CO-oxidizing, ethanol-producing acetogen isolated from livestock-impacted soil.

Phenotypic and phylogenetic studies were performed on three strains of an acetogenic bacterium isolated from livestock-impacted soil. The bacterium stained Gram-negative and was a non-spore-forming rod that was motile by peritrichous flagella. The novel strains had an optimum pH for growth of 8.0-8.5 and utilized H2 : CO2, CO : CO2, glucose, fructose, mannose, turanose, ribose, trimethylamine, pyruvate, methanol, ethanol, n-propanol and n-butanol as growth substrates. Acetate was produced from glucose. Acetate, CO2 and ethanol were produced from CO : CO2. 16S rRNA gene sequence analysis indicated that the novel strains formed a new subline in the family Eubacteriaceae (rRNA cluster XV) of the low G+C-containing Gram-positive bacteria of the class Clostridia. The DNA G+C base composition was 34 mol%. Cell wall analysis revealed the existence of a novel B-type peptidoglycan similar to the B2α-type (B4) configuration with a variation containing aspartic acid. Based on phylogenetic and phenotypic evidence, it is proposed that the new isolates represent a novel genus and species, for which the name Alkalibaculum bacchi gen. nov., sp. nov. is proposed. The type strain of the type species is CP11(T) (=ATCC BAA-1772(T)=DSM 22112(T)).

Post-consumer use efficacies of preservatives in personal care and topical drug products: relationship to preservative category.

Ninety-six used personal care and topical OTC drug items collected from consumers in the USA were examined for the presence of microbial contaminants. Of the eye and face product type containing global preservative chemistries (i.e., acceptable for use in Japan without major restrictions), 55% yielded numbers of microorganisms in excess of 500 CFU/g (P < 0.1814). For the mascara products with global preservative chemistries, 79% yielded numbers of microorganisms in excess of 500 CFU/g (P < 0.024). Products containing global preservative chemistries accounted for 88% (n = 14) of the products that had microbial contents above 10(4) CFU/g (P < 0.001). Prominent contaminants were species of Staphylococcus, Pseudomonas, Klebsiella, Streptococcus, Lactobacillus, Bacillus, Corynebacterium, and yeast. In general, under the stress of consumer use, products preserved with global preservative chemistries did not maintain as adequate preservation as products with non-global preservatives.

Carbon metabolism of the moderately acid-tolerant acetogen Clostridium drakei isolated from peat.

A moderately acid-tolerant, malodorous bacterium, strain FP, was isolated from peat that had a pore water pH of c. 4.2. The 16S rRNA gene sequence of FP was closely related to that of acetogens Clostridium drakei, Clostridium scatologenes, and Clostridium carboxidivorans. The DNA-DNA reassociation values obtained with DNA from FP and that of these three acetogens approximated 80%, 64%, and 59%, respectively, indicating that FP was a new strain of C. drakei. FP had broad pH and temperature ranges (3.6-7.4 and 5-40 degrees C, respectively), and metabolized a wide range of substrates, including cellobiose, glucose, xylose, vanillate, ferulate, lactate, propanol, formate, H(2)-CO(2), and CO-CO(2). Acetate was the primary reduced end product, and substrate/product stoichiometries were indicative of acetogenesis at circumneutral pH. Butyrate and H(2) became significant products from glucose at low pH. FP tolerated and could consume moderate amounts of O(2). These results (1) demonstrate that peat can harbor acetogens with a broad substrate range and tolerance to transient exposure to O(2), and (2) confirm that C. drakei, the type strain of which was originally isolated from an acidic coal mine pond, occurs in moderately acidic habitats.

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).

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.