Thermodesulfobacterium hveragerdense sp. nov., and Thermodesulfovibrio islandicus sp. nov., two thermophilic sulfate reducing bacteria isolated from a Icelandic hot spring

Two thermophilic non-sporeforming sulfate-reducing bacteria (SRB) were isolated from microbial mats collected from an Icelandic hot spring. Strain JSP was a gram negative rod, with an average cell size of 2.8 x 0.5 microm. No flagella were found. Growth occurred between 55 and 74 degrees C with an optimum between 70 and 74 degrees C at pH 7.0. The G+C content was 40 mol%. Strain R1Ha3 was a gram negative vibrio-shaped rod with an average cell size of 1.7 x 0.4 microm. Motility was observed mediated by one polar flagellum. The growth optimum at pH 7.0 was 65 degrees C, and growth occurred between 45 and 70 degrees C. The G+C content was 38 mol%. In the presence of sulfate, both strains used lactate, pyruvate and H2 as electron donors. In addition, strain R1Ha3 used formate. Pyruvate was the only substrate supporting fermentative growth of both strains. Growth occurred with sulfate as well as thiosulfate as electron acceptors. Furthermore, strain R1Ha3 reduced nitrate and strain JSP reduced sulfite. Neither of the strains were able to oxidize lactate completely to CO2 and neither of the strains contained desulfoviridin. 16S rDNA sequencing placed strain JSP in the genus Thermodesulfobacterium and strain R1Ha3 in the genus Thermodesulfovibrio. Based on the DNA-DNA hybridization studies and differences in morphology and physiology to their closest relatives the two new isolates were considered as new species. Strain JSP is named Thermodesulfobacterium hveragerdense and strain R1Ha3 Thermodesulfovibrio islandicus.

Quantification of syntrophic fatty acid-beta-oxidizing bacteria in a mesophilic biogas reactor by oligonucleotide probe hybridization

Small-subunit rRNA sequences were obtained for two saturated fatty acid-beta-oxidizing syntrophic bacteria, Syntrophomonas sapovorans and Syntrophomonas wolfei LYB, and sequence analysis confirmed their classification as members of the family Syntrophomonadaceae. S. wolfei LYB was closely related to S. wolfei subsp. wolfei, but S. sapovorans did not cluster with the other members of the genus Syntrophomonas. Five oligonucleotide probes targeting the small-subunit rRNA of different groups within the family Syntrophomonadaceae, which contains all currently known saturated fatty acid-beta-oxidizing syntrophic bacteria, were developed and characterized. The probes were designed to be specific at the family, genus, and species levels and were characterized by temperature-of-dissociation and specificity studies. To demonstrate the usefulness of the probes for the detection and quantification of saturated fatty acid-beta-oxidizing syntrophic bacteria in methanogenic environments, the microbial community structure of a sample from a full-scale biogas plant was determined. Hybridization results with probes for syntrophic bacteria and methanogens were compared to specific methanogenic activities and microbial numbers determined with most-probable-number estimates. Most of the methanogenic rRNA was comprised of Methanomicrobiales rRNA, suggesting that members of this order served as the main hydrogen-utilizing microorganisms. Between 0.2 and 1% of the rRNA was attributed to the Syntrophomonadaceae, of which the majority was accounted for by the genus Syntrophomonas.

The genes coding for the hsp70 (dnaK) molecular chaperone machine occur in the moderate thermophilic archaeon Methanosarcina thermophila TM-1

The hsp70(dnaK) locus of the moderate thermophilic archaeon Methanosarcina thermophila TM-1 was cloned, sequenced, and tested in vitro to measure gene induction by heat and ammonia, i.e., stressors pertinent to the biotechnological ecosystem of this methanogen that plays a key role in anaerobic bioconversions. The locus' genes and organization, 5'-grpE-hsp70(dnaK)-hsp40 (dnaJ)-trkA-3', are the same as those of the closely related mesophile Methanosarcina mazei S-6, but different from those of the only other archaeon for which comparable sequence data exist, the thermophile Methanobacterium thermoautotrophicum deltaH, from another genus, in which trkA is not part of the locus. The proteins encoded in the TM-1 genes are very similar to the S-6 homologs, but considerably less similar to the deltaH proteins. The TM-1 Hsp70(DnaK) protein has the 23-amino acid deletion--by comparison with homologs from gram-negative bacteria first described in the S-6 molecule and later found to be present in all homologs from archaea and gram positives. The genes responded to a temperature elevation in a manner that demonstrated that they are heat-shock genes, functionally active in vivo. Ammonia also induced a heat-shock type of response by hsp70(dnaK), and a similar response by trkA. The data suggest that the moderate thermophile TM-1 has an active Hsp70(DnaK)-chaperone machine in contrast to hyperthermophilic archaea, and that trkA is a stress gene, inasmuch as it responds like classic heat-shock genes to stressors that induce a typical heat-shock response.

Caldicellulosiruptor kristjanssonii sp. nov., a cellulolytic, extremely thermophilic, anaerobic bacterium

A cellulolytic anaerobic bacterium, strain I77R1BT, was isolated from a biomat sample of an Icelandic, slightly alkaline, hot spring (78 degrees C). Strain I77R1BT was rod-shaped, non-spore-forming, non-motile and stained Gram-negative at all stages of growth. It grew at 45-82 degrees C, with an optimum growth temperature around 78 degrees C. At 70 degrees C, growth occurred at pH 5.8-8.0, with an optimum near pH 7.0. At the optimum temperature and pH, with 2 g cellobiose l-1 as substrate, strain I77R1BT had a generation time of 2 h. During growth on Avicel, strain I77R1BT produced acetate, hydrogen and carbon dioxide as major fermentation products together with small amounts of lactic acid and ethanol. The strain fermented many substrates, including cellulose, xylan, starch and pectin, but did not grow with casein peptone, pyruvate, D-ribose or yeast extract and did not reduce thiosulfate to H2S. The G+C ratio of the cellular DNA was 35 mol%. Comparative 16S rDNA analysis placed strain I77R1BT among species of Caldicellulosiruptor. The closest relative was Caldicellulosiruptor lactoaceticus. Hybridization of total DNA showed 42% hybridization to C. lactoaceticus and 22% hybridization to Caldicellulosiruptor saccharolyticus. A new species, Caldicellulosiruptor kristjanssonii sp. nov. (I77R1BT) is proposed.

A comprehensive model of anaerobic bioconversion of complex substrates to biogas

A dynamic model describing the anaerobic degradation of complex material, and codigestion of different types of wastes, was developed based on a model previously described (Angelidaki et al., 1993). In the model, the substrate is described by its composition of basic organic components, i.e., carbohydrates, lipids, and proteins, the concentration of intermediates such as volatile fatty acids and long-chain fatty acids, and important inorganic components, i.e., ammonia, phosphate, cations, and anions. This allows dynamic changes of the process during a shift of substrate composition to be simulated by changing the input substrate data. The model includes 2 enzymatic hydrolytic steps, 8 bacterial steps and involves 19 chemical compounds. The model also includes a detailed description of pH and temperature characteristics. Free ammonia, acetate, volatile fatty acids, (VFA) and long-chain fatty acids (LCFA) constitute the primary modulating factors in the model. The model was tested with success in lab-scale reactors codigesting manure with glycerol trioleate or manure with gelatin. Finally, the model was validated using results from a full-scale biogas plant codigesting manure together with a proteinous wastewater and with bentonite-bound oil, which is a waste with high content of lipids. Copyright 1999 John Wiley & Sons, Inc.

Immobilization patterns and dynamics of acetate-utilizing methanogens immobilized in sterile granular sludge in upflow anaerobic sludge blanket reactors

Sterile granular sludge was inoculated with either Methanosarcina mazeii S-6, Methanosaeta concilii GP-6, or both species in acetate-fed upflow anaerobic sludge blanket (UASB) reactors to investigate the immobilization patterns and dynamics of aceticlastic methanogens in granular sludge. After several months of reactor operation, the methanogens were immobilized, either separately or together. The fastest immobilization was observed in the reactor containing M. mazeii S-6. The highest effluent concentration of acetate was observed in the reactor with only M. mazeii S-6 immobilized, while the lowest effluent concentration of acetate was observed in the reactor where both types of methanogens were immobilized together. No changes were observed in the kinetic parameters (Ks and mumax) of immobilized M. concilii GP-6 or M. mazeii S-6 compared with suspended cultures, indicating that immobilization does not affect the growth kinetics of these methanogens. An enzyme-linked immunosorbent assay using polyclonal antibodies against either M. concilii GP-6 or M. mazeii S-6 showed significant variations in the two methanogenic populations in the different reactors. Polyclonal antibodies were further used to study the spatial distribution of the two methanogens. M. concilii GP-6 was immobilized only on existing support material without any specific pattern. M. mazeii S-6, however, showed a different immobilization pattern: large clumps were formed when the concentration of acetate was high, but where the acetate concentration was low this strain was immobilized on support material as single cells or small clumps. The data clearly show that the two aceticlastic methanogens immobilize differently in UASB systems, depending on the conditions found throughout the UASB reactor.

Purification and characterization of the 3-chloro-4-hydroxy-phenylacetate reductive dehalogenase of Desulfitobacterium hafniense

The membrane-bound 3-chloro-4-hydroxyphenylacetate (Cl-OHPA) reductive dehalogenase from the chlorophenol-reducing anaerobe Desulfitobacterium hafniense was purified 11.3-fold to apparent homogeneity in the presence of the detergent CHAPS. The purified dehalogenase catalyzed the reductive dechlorination of Cl-OHPA to 4-hydroxyphenylacetate with reduced methyl viologen as the electron donor at a specific activity of 103.2 nkat/mg protein. SDS-PAGE revealed a single protein band with an apparent molecular mass of 46.5 kDa. The enzyme contained 0.68 +/- 0.2 mol corrinoid, 12.0 +/- 0.7 mol iron, and 13.0 +/- 0.7 mol acid-labile sulfur per mol subunit. The N-terminal amino acid sequence of the enzyme was determined and no significant similarity was found to any protein present in the gene bank.

Heat-shock response in Methanosarcina mazei S-6

The dnaK locus of Methanosarcina mazei S-6, a mesophilic organism of the phylogenetic domain Archaea, contains the heat-shock genes 5'-grpE-dnaK-dnaJ-3'. Parameters known to affect the response of these genes in organisms of the other two domains, Bacteria and Eucarya, were tested to determine their effects on the archaeal homologs. The mRNA from the three genes increased after heat shock more in lamina than in single cells (these S-6 morphologic stages can be grown in the same substrate). Single cells in early stationary phase showed the highest levels of dnaK mRNA after heat shock, as compared with cells in exponential, or in late stationary, phase. The dnaK mRNA always had the size of a monocistronic transcript. dnaK was also found in the thermophileMethanosarcina thermophila TM-1, and its response to heat shock showed distinctive characteristics. However, dnaK was not revealed in other archaea: three hyperthermophiles (Methanothermus fervidus,Methanococcus jannaschii, and Sulfolobus sp.), and one mesophilic methanogen (Methanospirillum hungateii).

Whole-cell hybridization of Methanosarcina cells with two new oligonucleotide probes

Two new oligonucleotide probes targeting the 16S rRNA of the methanogenic genus Methanosarcina were developed. The probes have the following sequences (Escherichia coli numbering): probe SARCI551, 5'-GAC CCAATAATCACGATCAC-3', and probe SARCI645, 5'-TCCCGGTTCCAAGTCTGGC-3'. In situ hybridization with the fluorescently labelled probes required several modifications of standard procedures. Cells of Methanosarcina mazeii S-6 were found to lyse during the hybridization step if fixed in 3% formaldehyde and stored in 50% ethanol. Lysis was, however, not observed with cells fixed and stored in 1.6% formaldehyde-0.85% NaCl. Extensive autofluorescence of the cells was found upon hybridization in the presence of 5 mM EDTA, but successful hybridization could be obtained without addition of this compound. The mounting agent Citifluor AF1, often used in conjugation with the fluorochrome fluorescein, was found to wash the labelled probes out of the cells. Stable labelling could be obtained with rhodamine-labelled probes when the specimen was mounted in immersion oil, and high hybridization intensities of the Methanosarcina cells were found even in the presence of biomass from an anaerobic reactor. The inherent high autofluorescence of the biomass could be lowered by use of a highly specific narrow-band filter. The probes were found to be specific for Methanosarcina and useful for detection of this genus in samples from anaerobic reactors.

Thermoanaerobacter mathranii sp. nov., an ethanol-producing, extremely thermophilic anaerobic bacterium from a hot spring in Iceland

The extremely thermophilic ethanol-producing strain A3 was isolated from a hot spring in Iceland. The cells were rod-shaped, motile, and had terminal spores; cells from the mid-to-late exponential growth phase stained gram-variable but had a gram-positive cell wall structure when viewed by transmission electron microscopy. Strain A3 used a number of carbohydrates as carbon sources, including xylan, but did not utilize microcrystalline cellulose. Fermentation end products were ethanol, acetate, lactate, CO2, and H2. The temperature optimum for growth was between 70 and 75 degrees C, and growth occurred in the range of 50-75 degrees C. The pH range for growth was 4.7-8.8, with an optimum at pH 7.0. Strain A3 was sensitive to tetracycline, chloramphenicol, penicillin G, neomycin, and vancomycin at 100 mg/l but was not sensitive to chloramphenicol and neomycin at 10 mg/l, which indicates that strain A3 belongs to the eubacteria. Addition of 50.66 kPa H2 or 2% NaCl did not affect growth. The isolate grew in the presence of exogenously added 4% (w/v) ethanol. The G+C ratio was 37 mol%. 16S rDNA studies revealed that strain A3 belongs to the genus Thermoanaerobacter. Genotypic and phenotypic differences between strain A3 and other related species indicate that strain A3 can be assigned to a new species, and the name Thermoanaerobacter mathranii is proposed.

An improved enzyme-linked immunosorbent assay for whole-cell determination of methanogens in samples from anaerobic reactors

An enzyme-linked immunosorbent assay was developed for the detection of whole cells of methanogens in samples from anaerobic continuously stirred tank digesters treating slurries of solid waste. The assay was found to allow for quantitative analysis of the most important groups of methanogens in samples from anaerobic digesters in a reproducible manner. Polyclonal antisera against eight strains of methanogens were employed in the test. The specificities of the antisera were increased by adsorption with cross-reacting cells. The reproducibility of the assay depended on the use of high-quality microtiter plates and the addition of dilute hydrochloric acid to the samples. In an experiment on different digester samples, the test demonstrated a unique pattern of different methanogenic strains present in each sample. The limited preparatory work required for the assay and the simple assay design make the test well suited for routine analysis of large numbers of samples and thus for process surveillance during operation of biogas digesters.

Combined removal of nitrate and carbon in granular sludge: substrate competition and activities

Granular sludge from an upflow anaerobic sludge blanket reactor treating synthetic waste water containing a mixture of volatile fatty acids and nitrate showed a removal efficiency of nearly 100% for both nitrogen and carbon. This activity was achieved by a combined process of denitrification and methanogenesis under conditions of surplus carbon. Under batch conditions the two processes proceeded clearly separated in time with first denitrification dominating and excluding methanogenesis. However, as soon as nitrate was depleted, methane production was initiated, showing that the inhibition of methanogenesis by nitrate was reversible. Of the volatile fatty acids supplied to the reactor, i.e. acetate, propionate, and butyrate, the denitrifying population clearly preferred butyrate and propionate even though acetate could also be metabolized. Consequently, growth of syntrophic volatile fatty acid degraders was suppressed by the denitrifiers in cases of low C:N ratios in the medium, leaving acetate as the major substrate for methanogenesis.

Introduction of a de novo bioremediation activity into anaerobic granular sludge using the dechlorinating bacterium DCB-2

The strictly anaerobic, pentachlorophenol (PCP) degrading bacterium DCB-2 was immobilized in an Upflow Anaerobic Sludge Blanket (UASB) reactor containing sterile granules. PCP and lactate were fed to the reactor and the concentration of chlorophenols in the effluent were monitored for 641 days. PCP was found to be degraded and transformed into 3,4,5-trichlorophenol in the reactor where DCB-2 introduced PPCP was still transformed to 3,4,5-trichlorophenol when the hydraulic retention time was decreased to six hours which was much lower than the generation time of DCB-2 insuring no free living cells in the reactor. This indicated that DCB-2 was immobilized in the granular layer. A control reactor that contained only sterile granules did not dechlorinate PCP indicating that the performance in the inoculated reactor was only due to the introduced bacteria. Immobilization of DCB-2 in the granules was further demonstrated by adding an antibody raised against DCB-2 to sliced granules. Bacteria thus visualized formed a net structure inside the granules. No DCB-2 bacteria could be found in granules from the control reactor. When lactate was omitted from the influent, the reactor still dechlorinated PCP in accordance with our findings that lactate was not used by DCB-2. This suggested that the reducing equivalents for reductive dechlorination were derived from the granules themselves. The reactor performance was 120 mumol.l reactor-1.day-1, comparable to the best described performance of a UASB-reactor and to aerobic reactors. Our study demonstrates that granules can be constructed which possess specific abilities such as a dechlorinating activity and at the same time be high performing. This result have implications for eco-engineering of granules for anaerobic treatment of contaminated waters.

Granulation in thermophilic upflow anaerobic sludge blanket (UASB) reactors

The state of the art for thermophilic UASB reactors is discussed focusing on the start-up of UASB reactors, the influence of the waste water composition and temperature on the development and maintenance of thermophilic granules, and the microbial composition and structure of thermophilic granules.

Isomerization of n- and i-butyrate in anaerobic methanogenic systems

Studies of the degradation of the two isomeric forms of butyrate in different anaerobic environments showed isomerization between n- and i-butyrate. Degradation rates were similar for the different examined systems and degradation rates for n-butyrate degradation were generally higher than for i-butyrate. Degradation rates for n-butyrate ranged from 0.52 to 1.39 day-1, while the rates for i-butyrate were from 0.46 to 1.15 day-1. Production of isomers was not observed when the volatile fatty acid degradation was inhibited by addition of bromoethane sulfonic acid, indicating that isomerization was coupled to the methanogenic degradation of the acid. The degree of isomerization observed during n-butyrate degradation was similar to the degree during i-butyrate degradation. Experiments indicated that the isomerization degree was higher for the thermophilic than for the mesophilic inocula.

Extremely thermophilic cellulolytic anaerobes from Icelandic hot springs

Anaerobic enrichment cultures with Avicel as substrate and inoculated with biomat samples from Icelandic hot springs were cultured at 70 degrees C or 78 degrees C and examined for the presence of microorganisms that produce extracellular cellulolytic and xylanolytic enzymes. From four enrichments grown at 78 degrees C eighteen strains were isolated. Five of the strains were screened for their substrate utilization, and on the basis of differences in morphology and substrates used, the two most unique strains were selected for further characterization. All cellulolytic cultures were rod-shaped and non-sporeforming. Motility was not observed. Cells stained gram-negative at various stages of the growth phase. During growth on Avicel, most cultures produced acetate as the major fermentation product, with smaller amounts of lactic acid and ethanol. Carbon dioxide and hydrogen were also produced. The phenotypic characteristics of the enrichment cultures and of isolates are described and assessed in relation to temperature and pH in the hot spring environment. A comparison is made between Icelandic strains isolated in our laboratory and strains isolated from hot springs from other parts of the world. The biotechnological potential of this group of bacteria is briefly discussed.

Interspecies Electron Transfer during Propionate and Butyrate Degradation in Mesophilic, Granular Sludge

Granules from a mesophilic upflow anaerobic sludge blanket reactor were disintegrated, and bacteria utilizing only hydrogen or formate or both hydrogen and formate were added to investigate the role of interspecies electron transfer during degradation of propionate and butyrate. The data indicate that the major electron transfer occurred via interspecies hydrogen transfer, while interspecies formate transfer may not be essential for interspecies electron transfer in this system during degradation of propionate and butyrate.

Methanogenesis in thermophilic biogas reactors

Methanogenesis in thermophilic biogas reactors fed with different wastes is examined. The specific methanogenic activity with acetate or hydrogen as substrate reflected the organic loading of the specific reactor examined. Increasing the loading of thermophilic reactors stabilized the process as indicated by a lower concentration of volatile fatty acids in the effluent from the reactors. The specific methanogenic activity in a thermophilic pilot-plant biogas reactor fed with a mixture of cow and pig manure reflected the stability of the reactor. The numbers of methanogens counted by the most probable number (MPN) technique with acetate or hydrogen as substrate were further found to vary depending on the loading rate and the stability of the reactor. The numbers of methanogens counted with antibody probes in one of the reactor samples was 10 times lower for the hydrogen-utilizing methanogens compared to the counts using the MPN technique, indicating that other non-reacting methanogens were present. Methanogens that reacted with the probe against Methanobacterium thermoautotrophicum were the most numerous in this reactor. For the acetate-utilizing methanogens, the numbers counted with the antibody probes were more than a factor of 10 higher than the numbers found by MPN. The majority of acetate utilizing methanogens in the reactor were Methanosarcina spp. single cells, which is a difficult form of the organism to cultivate in vitro. No reactions were observed with antibody probes raised against Methanothrix soehngenii or Methanothrix CALS-1 in any of the thermophilic biogas reactors examined. Studies using 2-14C-labeled acetate showed that at high concentrations (more than approx. 1 mM) acetate was metabolized via the aceticlastic pathway, transforming the methyl-group of acetate into methane. When the concentration of acetate was less than approx. 1 mM, most of the acetate was oxidized via a two-step mechanism (syntrophic acetate oxidation) involving one organism oxidizing acetate into hydrogen and carbon dioxide and a hydrogen-utilizing methanogen forming the products of the first microorganism into methane. In thermophilic biogas reactors, acetate oxidizing cultures occupied the niche of Methanothrix species, aceticlastic methanogens which dominate at low acetate concentrations in mesophilic systems. Normally, thermophilic biogas reactors are operated at temperatures from 52 to 56 degrees C. Experiments using biogas reactors fed with cow manure showed that the same biogas yield found at 55 degrees C could be obtained at 61 degrees C after a long adaptation period. However, propionate degradation was inhibited by increasing the temperature.

Effects of hydrogen and formate on the degradation of propionate and butyrate in thermophilic granules from an upflow anaerobic sludge blanket reactor

Degradation of propionate and butyrate in whole and disintegrated granules from a thermophilic (55 degrees C) upflow anaerobic sludge blanket reactor fed with acetate, propionate, and butyrate as substrates was examined. The propionate and butyrate degradation rates in whole granules were 1.16 and 4.0 mumol/min/g of volatile solids, respectively, and the rates decreased 35 and 25%, respectively, after disintegration of the granules. The effect of adding different hydrogen-oxidizing bacteria (both sulfate reducers and methanogens), some of which used formate in addition to hydrogen, to disintegrated granules was tested. Addition of either Methanobacterium thermoautotrophicum delta H, a hydrogen-utilizing methanogen that does not use formate, or Methanobacterium sp. strain CB12, a hydrogen- and formate-utilizing methanogen, to disintegrated granules increased the degradation rate of both propionate and butyrate. Furthermore, addition of a thermophilic sulfate-reducing bacterium (a Desulfotomaculum sp. isolated in our laboratory) to disintegrated granules improved the degradation of both substrates even more than the addition of methanogens. By monitoring the hydrogen partial pressure in the cultures, a correlation between the hydrogen partial pressure and the degradation rate of propionate and butyrate was observed, showing a decrease in the degradation rate with increased hydrogen partial pressure. No significant differences in the stimulation of the degradation rates were observed when the disintegrated granules were supplied with methanogens that utilized hydrogen only or hydrogen and formate. This indicated that interspecies formate transfer was not important for stimulation of propionate and butyrate degradation.

Effect of medium composition and sludge removal on the production, composition, and architecture of thermophilic (55 degrees C) acetate-utilizing granules from an upflow anaerobic sludge blanket reactor

A thermophilic upflow anaerobic sludge blanket (UASB) reactor degrading acetate was started by applying published methods (W. M. Wiegant and A. W. A. de Man, Biotechnol. Bioeng. 28:718-77, 1986) for production of granules dominated by Methanothrix spp. The reactor was inoculated with thermophilic digested sludge. No granules were observed during the first 7 months of start-up of the UASB reactor. However, after the concentrations of potassium, phosphate, ammonium, and magnesium in the medium were gradually increased, granules developed, indicating that there was a critical concentration of one or more of the ions required for production of granules from the starting material. After several years of stable operation, the effect of removing 60% of the granular sludge was investigated. Immunologic qualitative and quantitative studies showed that removal of the granular sludge resulted in an increase in the number of the predominant methanogens, antigenically related to Methanosarcina thermophila TM-1 and Methanosarcina mazeii S-6, and Methanobacterium thermoautotrophicum delta H and GC1. These changes were accompanied by modifications of the microanatomy of the granules, as demonstrated histochemically and immunohistochemically. The results indicated that different catabolic pathways dominated in different regions of the granules, i.e., acetate oxidation in the middle of the granules, where there is a low acetate concentration, and an aceticlastic reaction in the outer surfaces, with a high acetate concentration. The results also showed that removal of granules from a UASB reactor which has been under steady-state operation for a long period can improve the reactor's performance via formation of denser and larger granules with improved microbial activities.

Influence of pH and Temperature on Enumeration of Cellulose- and Hemicellulose-Degrading Thermophilic Anaerobes in Neutral and Alkaline Icelandic Hot Springs

Cellulose- and hemicellulose-degrading thermophilic anaerobes were enumerated in biomat samples of various temperatures from two different hot springs in the Hveragerǒi area of Iceland: one spring had a pH near 7, the second had a pH near 9. The most-probable-number technique was used for enumeration of bacteria in the samples, with media at many different temperatures (37 to 90°C) and two pH values (7 and 9). There were generally more xylan-degrading then cellulose-utilizing organisms in both environments. There was no growth at 80°C in the neutral spring or at 37°C in the alkaline spring. However, there were large numbers of both types of organisms in the alkaline spring at 80°C and in the neutral spring at 37°C. No cultures grew from the most-probable-number tubes inoculated with the Hveragerǒi samples and incubated at 90°C or with media at pH 9. However, xylan-degrading cultures at 70°C were enriched at pH 9 with samples from some other Icelandic hot springs.

Introduction of a de novo bioremediation ability, aryl reductive dechlorination, into anaerobic granular sludge by inoculation of sludge with Desulfomonile tiedjei

Methanogenic upflow anaerobic granular-sludge blanket (UASB) reactors treat wastewaters at a high rate while simultaneously producing a useful product, methane; however, recalcitrant environmental pollutants may not be degraded. To impart 3-chlorobenzoate (3-CB)-dechlorinating ability to UASB reactors, we inoculated granular sludge in UASB reactors with either a pure culture of Desulfomonile tiedjei (a 3-CB-dechlorinating anaerobe) or a three-member consortium consisting of D. tiejei, a benzoate degrader, and an H2-utilizing methanogen. No degradation occurred in an uninoculated control reactor which was started with the same granular sludge, but inoculated reactors and granules from the inoculated UASB systems rapidly transformed 3-CB (54 mumol/day/g of granule biomass). After several months at a hydraulic retention time of 0.5 day, much shorter than the generation time of D. tiedjei, the reactors still dechlorinated 3-CB. This indicated that the bacteria were immobilized in the reactor granules, and by using an antibody probe for D. tiedjei, we demonstrated that this microorganism had colonized the sludge granules. These results represent the first addition of a pure culture or a defined microbial mixture to a viable waste treatment process to introduce a specific de novo degradative pathway into a granular-sludge consortium.

Effect of magnesium on methanogenic subpopulations in a thermophilic acetate-degrading granular consortium

The effects of Mg2+ on thermophilic (55 degrees C) granules grown on acetate in 0.2-liter upflow anaerobic sludge blanket reactors were studied. The methanogens in the granules were identified and counted by using antibody probes and the antigenic fingerprinting method. Packets of large coccoidal cells antigenically related to Methanosarcina thermophila TM-1 were scarce in the absence of Mg2+ but increased with increasing Mg2+ concentrations up to 30 mM; Methanosarcina packets immunologically related to Methanosarcina barkeri R1M3 showed a similar trend, and their numbers increased up to 100 mM Mg2+. The number of single cells antigenically related to TM-1, R1M3, and Methanosarcina mazei S-6 were scarce at low Mg2+ concentrations but increased drastically at 30 and 100 mM Mg2+. The number of rod-shaped bacteria antigenically related to Methanobacterium thermoautotrophicum GC1 and delta H was highest with no Mg2+ present, and their numbers decreased with increasing concentrations of the cation. These quantitative data, obtained by counting cells in suspensions made from disrupted granules, were confirmed by microscopic observation of the methanogenic subpopulations in thin histologic sections of the granules.

Influence of a supplemental carbon source on anaerobic dechlorination of pentachlorophenol in granular sludge

Anaerobic dechlorination of pentachlorophenol (PCP) was studied in two upflow anaerobic sludge blanket reactors. One reactor received glucose (0.9 g liter-1) as an additional carbon source; the other one served as a control. The concentration of PCP in the medium was 4.5 and 3.0 mg liter-1 in the experimental and control reactors, respectively. The reactors were inoculated with granular sludge previously grown on sugar-containing wastewater. After 10 months of continuous operation, the removal of PCP was 99% in the glucose-amended reactor, whereas the removal in the control reactor varied between 32 and 77%. Furthermore, 94% of the PCP was completely dechlorinated in the glucose reactor compared with a maximum of 20% in the control reactor. In the same period, the amount of biomass in the glucose reactor had increased by approximately 150% compared with that in the control reactor, where no growth of the sludge bed occurred. Batch culture activity tests showed that the addition of glucose had a stimulatory effect on the dechlorination rate of PCP per gram of volatile solids. This indicated that the better performance of the glucose-amended reactor was due to a higher concentration of biomass and a direct stimulatory effect of glucose on the dechlorination rate. The pattern of dechlorination of PCP showed that an initial para cleavage was followed by two ortho cleavages.

Potential for thermophilic (50 degrees C) anaerobic dechlorination of pentachlorophenol in different ecosystems

Thermophilic (50 degrees C) anaerobic biodegradation of pentachlorophenol (PCP) was investigated by using different inocula from natural ecosystems and anaerobic digesters. The inocula tested were three freshwater sediments, four anaerobic sewage sludge samples from digesters treating sludge from wastewater plants with various industrial inputs, and digested manure from an anaerobic reactor. Only one digested-sludge sample and the manure sample were from thermophilic environments. The initial PCP concentration was 7.5 or 37.5 microM. After 8 months, PCP had disappeared from the sediment samples and various, less chlorinated intermediates were present. Additions of extra PCP were degraded within 4 weeks, and a maximal observed dechlorination rate of 1.61 mumol/liter/day in the vials with addition of 7.5 microM PCP and 7.50 mumol/liter/day in the vials with addition of 37.5 microM PCP were measured for a freshwater sediment. In contrast, only 2.8 to 17.5% of the initial PCP added had disappeared from the sludge samples after 8 months of incubation. The complex pattern of intermediates formed indicated that the dechlorination of PCP proceeded via different pathways, involving at least two different populations in the dechlorination processes.

Effects of lipids on thermophilic anaerobic digestion and reduction of lipid inhibition upon addition of bentonite

The effect of bentonite-bound oil on thermophilic anaerobic digestion of cattle manure was investigated. In digestor experiments, addition of oil was found to be inhibitory during start-up and the inhibitory effect was less pronounced when the oil was added in the form of bentonite-bound oil compared to when the oil was added alone. After adaptation of the digestors, very rapid degradation of oil was observed and more than 80% of the oil was degraded within a few hours after daily feeding. In batch experiments, glyceride trioleate was found to be inhibitory to thermophilic anaerobic digestion when the concentrations were higher than 2.0 g/l. However, addition of bentonite (a clay mineral) at concentrations of 0.15% and 0.45% was found to partly overcome this inhibition. Addition of calcium chloride in concentration of 3 mM (0.033% w/v) showed a similar positive effect on the utilization of oil, but the effect was lower than with bentonite.

Acetate Production by Methanogenic Bacteria

Methanosarcina barkeri MS and 227 and Methanosarcina mazei S-6 produced acetate when grown on H 2 -CO 2 , methanol, or trimethylamine. Marked differences in acetate production by the two bacterial species were found, even though methane and cell yields were nearly the same. M. barkeri produced 30 to 75 μmol of acetate per mmol of CH 4 formed, but M. mazei produced only 8 to 9 μmol of acetate per mmol of CH 4 .

Temperature Compensation in Methanosarcina barkeri by Modulation of Hydrogen and Acetate Affinity

The affinity of Methanosarcina barkeri 227 for acetate and hydrogen at different incubation temperatures was investigated. Increasing the temperature from 20 to 37�C resulted in a 4.5-fold increase in K m for acetate and a 4.8-fold increase for hydrogen. The corresponding increase in V max for acetate was 8.3-fold (5.4-fold for hydrogen). This response implied a decrease in the temperature coefficient (Q 10 ) and hence a decrease in the temperature dependency as a function of decreasing substrate concentration.

Dynamics of Methane Production, Sulfate Reduction, and Denitrification in a Permanently Waterlogged Alder Swamp

The dynamics of sulfate reduction, methane production, and denitrification were investigated in a permanently waterlogged alder swamp. Molybdate, an inhibitor of sulfate reduction, stimulated methane production in soil slurries, thus suggesting competition for common substrates between sulfate-reducing and methane-producing bacteria. Acetate, hydrogen, and methanol were found to stimulate both sulfate reduction and methane production, while trimethylamine mainly stimulated methane production. Nitrate addition reduced both methane production and sulfate reduction, either as a consequence of competition or poisoning of the bacteria. Sulfate-reducing bacteria were only slightly limited by the availability of electron acceptors, while denitrifying bacteria were seriously limited by low nitrate concentrations. Arrhenius plots of the three processes revealed different responses to temperature changes in the slurries. Methane production was most sensitive to temperature changes, followed by denitrification and sulfate reduction. No significant differences between slope patterns were observed when comparing summer and winter measurements, indicating similar populations regarding temperature responses.