A strictly anaerobic bacterium, strain PCE1, was isolated from a tetrachloroethene-dechlorinating enrichment culture. Cells of the bacterium were motile curved rods, with approximately four lateral flagella. They possessed a gram-positive type of cell wall and contained cytochrome c. Optimum growth occurred at pH 7.2-7.8 and 34-38 degrees C. The organism grew with L-lactate, pyruvate, butyrate, formate, succinate, or ethanol as electron donors, using either tetrachloroethene, 2-chlorophenol, 2,4,6-trichlorophenol, 3-chloro-4-hydroxy-phenylacetate, sulfite, thiosulfate, or fumarate as electron acceptors. Strain PCE1 also grew fermentatively with pyruvate as the sole substrate. L-Lactate and pyruvate were oxidized to acetate. Tetrachloroethene was reductively dechlorinated to trichloroethene and small amounts ( 5%) of cis-1,2-dichloroethene and trans-1,2-dichloroethene. Chlorinated phenolic compounds were dechlorinated specifically at the ortho-position. On the basis of 16S rRNA sequence analysis, the organism was identified as a species within the genus Desulfitobacterium, which until now only contained the chlorophenol-dechlorinating bacterium, Desulfitobacterium dehalogenans.

In the anaerobic fungus Neocallimastix sp. L2 fermentation of glucose proceeds via the Embden-Meyerhof-Parnas pathway. Enzyme activities leading to the formation of succinate, lactate, ethanol, and formate are associated with the cytoplasmic fraction. The enzymes 'malic enzyme,' NAD(P)H:ferredoxin oxidoreductase, pyruvate:ferredoxin oxidoreductase, hydrogenase, acetate:succinate CoA transferase and succinate thiokinase leading to the formation of H2,CO2, acetate, and ATP are localized in microbodies. Thus, these organelles are identified as hydrogenosomes. In addition, the microbodies contain the O2-scavenging enzymes NADH- and NADPH oxidase, while NAD(P)H peroxidase, catalase, or superoxide dismutase could not be detected. In cell-free extracts from zoospores of Neocallimastix sp. L2 the specific activities of hydrogenosomal enzymes as well as the quantities of these proteins are 2- to 6-fold higher than in mycelium extracts. These findings suggest that hydrogenosomes perform an important role--especially in zoospores--as H2-evolving, ATP-generating and O2-scavenging organelles.

A facultatively oligotrophic ultramicrobacterium (strain RB2256) isolated from an Alaskan fjord by extinction dilution in seawater, was grown in batch culture and under single-and dual-substrate-limitation of alanine and glucose in a chemostat. The nature of the uptake systems, and the uptake kinetics and utilization patterns of alanine and glucose were investigated. Glucose uptake was inducible, the system exhibited a narrow substrate specificity, and part of the uptake system was osmotic-shock-sensitive. Half-saturation constants for glucose were between 7 and 74 pM during glucose limitation. The initial step in glucose metabolism was the synthesis of sugar polymers, even during glucose-limited growth. The alanine uptake system was constitutively expressed and was binding-protein-dependent. In addition to L-alanine, nine other amino acids inhibited accumulation of [14C]~-alanine, indicating broad substrate specificity of the alanine transporter. Half-saturation constants between 1.3 and 1-8 pM were determined for alanine uptake during alanine limitation. Simultaneous utilization of glucose and alanine occurred during substrate-limited growth in the chemostat, and during growth in batch culture a t relatively high (mM) substrate concentrations. However, the half-saturation constant for alanine transport during dual-substrate-limitation, i.e. in the presence of glucose, increased almost fivefold. We conclude that mixed substrate utilization is an inherent property of this organism.

The presence or absence of molecular oxygen has been shown to play a crucial role in the degradability of haloaromatic compounds. In the present study, it was shown that anaerobic phototrophic 3-chlorobenzoate (3CBA) metabolism by Rhodopseudomonas palustris DCP3 is oxygen tolerant up to a concentration of 3 μM O2. Simultaneous oxidation of an additional carbon source permitted light-dependent anaerobic 3CBA degradation at oxygen input levels which, in the absence of such an additional compound, would result in inhibition of light-dependent dehalogenation. Experiments under the same experimental conditions with strain DCP3 in coculture with an aerobic 3CBA-utilizing heterotroph, Alcaligenes sp. strain L6, revealed that light-dependent dehalogenation of 3CBA did not occur. Under both oxygen limitation (O2 < 0.1 μM) and low oxygen concentrations (3 μM O2), all the 3CBA was metabolized by the aerobic heterotroph. These data suggest that biodegradation of (halo)aromatics by photoheterotrophic bacteria such as R. palustris DCP3 may be restricted to anoxic photic environments.

The rates of bacterial growth in nature are often restricted by low concentrations of oxygen or carbon substrates. In the present study the metabolic properties of 24 isolates that had been isolated using various concentrations of 3-chlorobenzoate, benzoate and oxygen as well as using continuous culture at high and low growth rates were determined to investigate the effects of these parameters on the metabolism of monoaromatic compounds. Bacteria were enriched from different sampling sites and subsequently isolated. In batch culture this was done both under low oxygen (2% O(2)) and air-saturated concentrations. Chemostat enrichments were performed under either oxygen or 3-chlorobenzoate limiting conditions. Bacteria metabolizing aromatics with gentisate or protocatechuate as intermediates (gp bacteria) as well as bacteria metabolizing aromatic compounds via catechols (cat bacteria) were isolated from batch cultures when either benzoate or 3CBA were used as C sources, regardless of the enrichment conditions applied. In contrast, enrichments performed in chemostats at low dilution rates resulted in gp-type organisms only, whereas at high dilution rates cat-type organisms were enriched, irrespective of the oxygen and 3-chlorobenzoate concentration used during enrichment. It is noteworthy that the gp-type of bacteria possessed relatively low µ(max) values on 3CBA and benzoate along with relatively high substrate and oxygen affinities for these compounds. This is in contrast with cat-type of bacteria, which seemed to be characterized by high maximum specific growth rates on the aromatic substrates and relatively high apparent half saturation constants. In contrast, bacteria degrading chlorobenzoate via gentisate or protocatechuate may possibly be better adapted to conditions leading to growth at reduced rates such as low oxygen and low substrate concentrations.

The treatment of actual olive mill wastewaters, coming from an evaporation pond subjected to climatic conditions, was studied by the heterogeneous Fenton process with the laboratory catalyst Fe-Ce-O 70/30. Investigating the impact of the solid load, hydrogen peroxide concentration, and pH over the methodology efficiency a full factorial experimental design was followed by results stating that the amount of Fe-Ce-O 70/30 and pH had a high influence on final depuration, while [H 2 O 2 ] was not statistically relevant. Reduced models based on those data showed some ability to predict chemical oxygen demand (COD) removal, final effluent biodegradability, and iron leached concentration. Also respirometric and luminescence techniques were used to evaluate toxicity. The recommend operational conditions gathered up when each one of the response factors was optimized were diverse. From those, it seemed appropriate to run with high Fe-Ce-O loads (1.5 g/L) allied with pH ) 4 and [H 2 O 2 ] ) 115 mM since, even if COD degradation (24%) was not the highest one, the final effluent was very biodegradable (BOD 5 /COD ) 0.54) allowing the application of an activated sludge post-treatment. Furthermore, for these conditions, catalyst stability was safeguarded since Fe elution was low (0.12 mg/L). Finally, the catalytic system involving Fenton's peroxidation Fe-Ce-O 70/30 was revealed to be promising for real olive mill wastewaters biodegradability improvement and toxicity removal enabling a proper postbioremediation.

Desulfovibrio salexigens strain Mastl was isolated from the oxic/anoxic interface of a marine sediment. Growth under sulfate‐reducing conditions was accompanied by polyglucose accumulation in the cell with every substrate tested. Highest polyglucose storage was found with glucose (0.8–1.0 g polyglucose (g protein)−1), but the growth rate with this substrate was very low (0.015 h−1). Anaerobically grown cells of strain Mastl exhibited immediate oxygen‐dependent respiration. The endogenous oxygen reduction rate was proportional to the polyglucose content. The rate of aerobic respiration of pyruvate was also directly related to the polyglucose content indicating that this organism was only able to respire with oxygen as long as polyglucose was present. Maximum oxygen reduction rates were found at air saturating concentrations and were relatively low (3–50 nmol O2 min−1 (mg protein)−1). Catalase was constitutively present in anaerobically grown cells. When batch cultures were exposed to oxygen, growth ceased immediately and polyglucose was oxidized to acetate within 40–50 h. Like the oxygen reduction activity, the nitro blue tetrazolium (NBT)‐reduction activity in these cells was proportional to the polyglucose content. Under anaerobic starvation conditions there was no correlation between the NBT‐reduction activity and polyglucose concentration and polyglucose was degraded slowly within 240 h. The ecological significance of aerobic polyglucose consumption is discussed.

The accessibility of glucuronoxylan from a refined, bleached Eucalyptus globulus industrial kraft pulp in 0–18% aqueous NaOH solution at room temperature (25°C) was studied. The extraction profile revealed a maximum extraction of xylan in the pulp at about 10–12% NaOH concentration and was explained by the maximum swelling of the pulp according to the Gibbs-Donnan equilibrium. The kinetics of xylan removal and the monitoring of its structural features were performed at 5 and 10% NaOH concentrations. The maximum yields of xylans with 10% and 5% NaOH were as high as 90% and 60% for 2 h extraction, respectively. The structural features of xylan were assessed by acid methanolysis and one-dimensional (1D)/two-dimensional (2D) nuclear magnetic resonance (NMR), and the molecular weight by size exclusion chromatography (SEC). The xylan extracted with 10% NaOH had a slightly higher molecular weight and a lower branching with uronic moieties than the xylan extracted with 5% NaOH. The former was less pure (contained more β-cellulose) than the latter. Structural studies by NMR resulted in the conclusion that there are at least two types of xylans removed from the pulp: one xylan with relatively high 4-O-methyl-α-D-glucuronosyl [MeGlcA-(1→] and [→2)-MeGlcA-(1→] substituents and another xylan with a much lower substitution with uronic residues.