Henry Naveau

Clostridium Autoethanogenum, Sp-nov, An Anaerobic Bacterium That Produces Ethanol From Carbon-monoxide

A strictly anaerobic, gram-positive, sporeforming, rod-like, motile bacterium was enriched from rabbit feces, and isolated using carbon monoxide as sole source of energy and carbon. The isolate metabolizes CO with ethanol, acetate and CO2 as end-products. Other substrates used as carbon and energy sources include CO2 plus H2, pyruvate, xylose, arabinose, fructose, rhamnose, and l-glutamate. The optimum temperature for growth is 37°C. The optimum pH for chemolithotrophic growth lies around 5.8 to 6.0 Sulfate is not reduced. Growth is inhibited either by penicillin, chloramphenicol, tetracyclin or ampicillin, each at 100 μg per ml. The isolate has a DNA-base composition of 25.9±0.6% guanine plus cytosine. The isolate represents a new species of Clostridium for which the name Clostridium autoethanogenum is proposed. The type strain is strain JA1-1

Anaerobic Dechlorinating Bacteria

Anaerobic dehalogenation is attracting great interest since it opens new research horizons based on the novel biochemical mechanisms identified in this field such as halorespiration, i.e. the utilization of halogenated compounds as electron acceptors. Moreover, anaerobic bacteria seem to be more efficient than their aerobic counterparts in removing halogen atoms from polyhalogenated compounds. Thus, anaerobic dehalogenation can be considered as a promising means for bioremediation treatments of persistently polluted environments. In this line, identification of pure strains capable of dehalogenation will give important information about the diversity of organisms implicated in this process and also fundamental explanations of the diverse biochemical mechanisms involved. In light of these considerations, we chose to focus this review on the physiological descriptions, dechlorination activities, phylogenetic diversity, and potential biotechnological applications of these pure anaerobic strains capable of dehalogenation.

Transformation and mineralization of 2,4,6-trinitrotoluene (TNT) by manganese peroxidase from the white-rot basidiomycete Phlebia radiata.

The degradation of the nitroaromatic pollutant 2,4,6-trinitrotoluene (TNT) by the manganese-dependent peroxidase (MnP) of the white-rot fungus Phlebia radiata and the main reduction products formed were investigated. In the presence of small amounts of reduced glutathione (10 mM), a concentrated cell-free preparation of MnP from P. radiata exhibiting an activity of 36 nkat/ml (36 nmol Mn(II) oxidized per sec and per ml) transformed 10 mg/l of TNT within three days. The same preparation was capable of completely transforming the reduced derivatives of TNT. When present at 10 mg/l, the aminodinitrotoluenes were transformed in less than two days and the diaminonitrotoluenes in less than three hours. Experiments with 14C-U-ring labeled TNT and 2-amino-4,6-dinitrotoluene showed that these compounds were mineralized by 22% and 76%, respectively, within 5 days. Higher concentrations of reduced glutathione (50 mM) led to a severe inhibition of the degradation process. It is concluded that Phlebia radiata is a good candidate for the biodegradation of TNT as well as its reduction metabolites.

Biodegradation of nitrobenzene by its simultaneous reduction into aniline and mineralization of the aniline formed

Abstract By mixing through a three-reactor system a nitroreducing consortium and an aniline-degrading Comamonas acidovorans, a mixed population was formed which was able to mineralize the nitroaromatic compound nitrobenzene via aniline, its corresponding aminoaromatic compound. The behavior of the mixed population was characterized in batch culture. In the first step, nitrobenzene was reduced to aniline by the reductive consortium and, in the second, oxidative step, aniline was mineralized via catechol and meta cleavage. Even though these two steps may seem incompatible in terms of required redox conditions, they were made to coexist in a single, simple reactor. However, when aeration was optimum for growth, only 16% of the 0.5 mM nitrobenzene introduced was mineralized. Decreasing the aeration led to an increase in the amount of nitrobenzene reduced and decreased its volatilized fraction. A decrease in aeration did not slow down aniline mineralization, although the latter is catalyzed by dioxygenases. This mixed population is thus able to remediate nitrobenzene and also aniline, which is often found with the former in the environment. Using C. acidovorans, which also degrades methylanilines, or other aminoaromatic-compound-degrading organisms, this strategy should be applicable to mineralizing more complex nitroaromatic compounds, like nitrotoluenes or dinitrotoluenes.

Fluorimetric Monitoring of Methanogenesis in Anaerobic Digesters

The fluorimetric determination of co-factor F420. a specific co-enzyme of methanogenic bacteria (1) in mixed liquors during complex laboratory, pilot or industrial biomethanations, leads to a series of new parameters which help, to design improved digesters, to monitor the methanogenic digestions, to obviate operational deviations and to promote optimization of the process. These parameters are: (a) the concentration in co-factor F420 as mol F420 × 1–1 mixed liquor or µmol F420 × g-1 volatile solids in mixed liauor: (b) the food to microorganism ratio CMF420 as g volatile solids added × µmol-5 F420 in mixed liquor × d-1; (c) the specific methane production ratio: QCH4(F420)and 1 CH4 produced × µmol-1 F420 in mixed liquor × d-1; (d) the rate of biosynthesis of co-factor F420 as µmol F420 × 1–1 mixed liquor × d-1; (e) the yields: either YCH4/F420 as 1 CH4 × µmol F420 synthesized or YVSe/F420 as g volatile solids eliminated × µmol-1 F420 synthesized.

Biomethanation of the marine algae Tetraselmis

Biomethanation of algae is an elegant way to convert solar energy into a chemical fuel, i.e. methane. The microbiological process of methanogenesis is leading to a reliable technology. Favorable running conditions were elicited by experiments at the laboratory scale. The process is being developed at the 1-m/sup 3/ scale at Lamezia (Italy). From these experiments, conceptual parameters for a full-scale demonstration plant are calculated.

Mineralization of 14-C-U-ring labeled 4-hydroxylamino-2,6-trinitrotoluene by manganese-dependent peroxidase of the white-rot basidiomycete Phlebia radiata

The in vitro biotransformation of 4-hydroxylamino-2,6-dinitrotoluene (4-OHA-2,6-DNT)—the first identified reduction product of 2,4,6-trinitrotoluene (TNT)—was studied in the presence of a cell-free preparation of manganese-dependent peroxidase (MnP) from the white-rot basidiomycete Phlebia radiata. 4-OHA-2,6-DNT was rapidly oxidized to 4-nitroso-2,6-dinitrotoluene (4-NO-2,6-DNT), part of which reacted with the remaining 4-OHA-2,6-DNT to give 4,4′-azoxy-2,2′,6,6′-tetranitrotoluene. 4-NO-2,6-DNT was also slowly transformed to TNT and 4-amino-2,6-dinitrotoluene (4-A-2,6-DNT). In mineralization tests, 4% of the initial 14C-U-ring labeled 4-OHA-2,6-DNT was recovered as 14CO2. In the presence of up to 10 mM of reduced glutathione (GSH), 4-OHA-2,6-DNT was directly reduced to 4-A-2,6-DNT and the mineralization rate reached 27%. At 25 mM GSH, MnP was inhibited, resulting in an insignificant mineralization rate. The inclusion of GSH in the in vitro system led to a 4-OHA-2,6-DNT deficit in the HPLC mass balances not fully accounted for by the degree of mineralization, but corresponding to unidentified polar compound(s) reflecting up to 65% of the initial substrate. This is the first report of 4-OHA-2,6-DNT mineralization by a fungal MnP and the first clear-cut experimental observation of 4-NO-2,6-DNT, the previously postulated intermediate of microbial TNT metabolism.

Gas-phase methyl ethyl ketone biodegradation in a tubular biofilm reactor: microbiological and bioprocess aspects

A novel type of bioreactor was designed to clean VOCs-containing air.The operation of this reactor consists in mixing the polluted gas and a mistof nutrient solution in the presence of microorganisms in order to maximizecontact and transfer between gas, liquid and microorganisms and to promotethe degradation kinetics and the relative removal efficiency of thepollutant. A bacterial consortium acclimatized to MEK and containing apreponderance of Alcaligenes denitrificans was established under non-axenicconditions. On the tubular reactors glass walls, a continuous biofilm wasdeveloped. This biofilm was rapidly contaminated by two fungi able todegrade MEK: Geotrichum candidum and Fusarium oxysporum. Their abundance inthe reactor is probably linked to the acidic conditions inside the biofilmand to their broader tolerance for low pH values concomitant with MEKdegradation. In the reactor, a maximum volumetric degradation rate of 3.5 kgMEK/m3reactor·d was obtained for arelative removal efficiency of 35%, whereas the latter was maintainedat 70% for more modest applied loadings of 1.5 kgMEK/m3reactor ·d. In liquid batchcultures, a biomass originating from the biofilm was able to degrade 0.40gMEK/gDCW·h at the optimal pH of 7. Aregular cycle of detachment-recolonization was observed during the operationof the bioreactor. The maximal degradation activity was obtained with a thinbiofilm and was not increased as the biofilm grew in thickness. The overalldegradation rate of the process did not appear to be limited by thediffusion of oxygen inside the biofilm. Over short periods of time, the MEKtransfer from the gaseous phase to the biofilm was neither affected by thepresence of the mist nor by the wetting of the biofilm. A better control ofthe biofilm pH led to improved performance in terms of removal rate but notin terms of relative elimination efficiency.

Abiotic transformation of catechol and 1-naphthol in aqueous solution - Influence of environmental factors

The abiotic transformation of catechol and 1-naphthol singly and in mixtures was tested in sterile Tris-HCl buffer with regard to several environmental factors including temperature (7 degrees C, 20 degrees C and 30 degrees C), lighting conditions, pH (between 7.0 and 8.5) and dissolved oxygen (at partial pressures of 0.0, 220, 2200, 11000 and 22000 Pa). Irrespective of lighting conditions. catechol autoxidation was confirmed in aerated medium with a rate independent of the presence of 1-naphthol but proportional to the dissolved oxygen concentration, to the pH (its half-disappearance occurred in 24h at pH 8.5) and, to a lesser extent, to the incubating temperature (at 20 degrees C, 20% disappeared in 10 days at pH 7.0). Under alkaline conditions, the reaction of the anionic form (catecholate) with an equimolar concentration of molecular oxygen (O2) led presumably to hydrogen peroxide anion (HO2-) and coloured polymerization products. When tested alone, 1-naphthol was not significantly influenced either by lighting conditions, incubating temperature or dissolved oxygen concentration. It was also found to be quite stable with respect to pH, with a 15-fold weaker transformation rate than for catechol at the highest pH used. When tested in a mixture with catechol, 1-naphthol was found to be involved in a new chemical oxidation reaction catalyzed by catecholate. The transformation of one mole of 1-naphthol consumes four moles of oxygen. In the presence of catechol, the stoichiometry of the 1-naphthol transformation, under the influence of oxygen, suggests the possible formation of 2,5,6,8-tetrahydroxy 1,4-naphthoquinone via Lawsone (2-hydroxy 1,4-naphthoquinone) and naphthopurpurine (2,5,8-trihydroxy 1,4-naphthoquinone) as hypothetic intermediates. This is the first report of the autoxidation of 1-naphthol, catalyzed by catechol, in aqueous solution, in the absence of UV irradiation.

Biodegradation of 2,4,6-trinitrotoluene (TNT) by the white-rot basidiomycete Phlebia radiata

Phlebia radiatatransformed 2,4,6-trinitrotoluene (TNT), as well as its first reduction products, the aminodinitrotoluenes, into 4-hydroxylamino-2,6-dinitrotoluene (4-OHA-2,6-DNT) and 4-amino-2,6-dinitrotoluene (4-A-2,6-DNT). No extracellular peroxidases were involved in this step. The ligninolytic extracellular fluid, assumed to contain peroxidases, did not reduce TNT. However, ligninolytic peroxidases are implicated in the transformation of the first reduction products of TNT.