Biological Treatment of a Pulp and Paper Industry Effluent by Pleurotus spp.

In this work, the ability of Pleurotus spp.:P. sajor-caju; P. platypus and P. citrinopileatus to treat pulp and paper mill effluent on a laboratory and pilot scale were studied. On the laboratory scale treatment, P. sajor-caju decolorized the effluent by 66.7% on day 6 of incubation. Inorganic chloride liberated by P. sajor-caju was 230.9% (814.0 mg/dl) and the COD was reduced by 61.3% (1302.0 mg/dl) on day 10 of treatment. In the pilot scale treatment maximum decolorization was obtained by P. sajor-caju (60.1%) on day 6 of the incubation. Inorganic chloride content was increased by 524.0 mg/dl (113.0%) and the COD was reduced by 1442.0 mg/dl (57.2%) by P. sajor-caju on day 7 of incubation. These results revealed that the treatment of pulp and paper mill effluent by P. sajor-caju proved as better candidate for the purpose than P. platypus and P. citrinopileatus.     

Anaerobic degradation of phenol via carboxylation to 4-hydroxybenzoate: in vitro study of isotope exchange between 14CO2 and 4-hydroxybenzoate

Extracts of denitrifying bacteria grown anaerobically with phenol and nitrate catalyzed an isotope exchange between ¹⁴CO₂ and the carboxyl group of 4-hydroxybenzoate. This exchange reaction is ascribed to a novel enzyme, phenol carboxylase, initiating the anaerobic degradation of phenol by para-carboxylation to 4-hydroxybenzoate. Some properties of this enzyme were determined by studying the isotope exchange reaction. Phenol carboxylase was rapidly inactivated by oxygen; strictly anoxic conditions were essential for preserving enzyme activity. The exchange reaction specifically was catalyzed with 4-hydroxybenzoate but not with other aromatic acids. Only the carboxyl group was exchanged; [U-¹⁴C]phenol was not exchanged with the aromatic ring of 4-hydroxybenzoate. Exchange activity depended on Mn²⁺ and inorganic phosphate and was not inhibited by avidin. Ortho-phosphate could not be substituted by organic phosphates nor by inorganic anions; arsenate had no effect. The pH optimum was between pH 6.5–7.0. The specific activity was 100 nmol ¹⁴CO₂ exchange · min^-1 · mg^-1 protein. Phenol grown cells contained 4-hydroxybenzoyl CoA synthetase activity (40 nmol · min^-1 · mg^-1 protein). The possible role of phenol carboxylase and 4-hydroxybenzoyl CoA synthetase in anaerobic phenol metabolism is discussed.     

Anaerobic degradation of methoxylated aromatic compounds by Clostridium methoxybenzovorans and a nitrate-reducing bacterium Thauera sp. strain Cin3,4

The coupling of growth of the o-demethylating bacterium, Clostridium methoxybenzovorans SR3, with a nitrate-reducing bacterium able to degrade aromatic compounds, Thauera sp. Cin3,4, allowed complete mineralization of poorly oxidizable methoxylated aromatic compounds such as vanillate, isovanillate, vanilline, anisate, ferulate and veratrate. C. methoxybenzovorans o-demethylated these aromatic compounds to their corresponding hydroxylated derivatives and fermented the side chains to acetate and butyrate. The hydroxylated compounds and the fermentation end-products in the C. methoxybenzovorans spent growth medium were then completely metabolized to CO₂ on inoculation with the Thauera strain. Kinetic studies with veratrate indicated that C. methoxybenzovorans initially o-demethylated the substrate to vanillate and then further to protocatechuate together with the production of acetate and butyrate from the demethylated side chains. Protocatechuate, acetate and butyrate were then utilized as a carbon source by the Thauera strain aerobically or anaerobically in the presence of nitrate. The results therefore suggest that mono- or dimethoxylated aromatic compounds can be completely mineralized by coupling the growth of a fermentative bacterium with a nitrate-reducing bacterium, and a metabolic pathway for this is proposed.     

Biodegradation and detoxification of nicotine in tobacco solid waste by a Pseudomonas sp.

A Pseudomonas sp. grew with nicotine optimally 3 g l^–1 and at 30 °C and pH 7. Nicotine was fully degraded within 10 h. The resting cells degraded nicotine in tobacco solid waste completely within 6 h in 0.02 m sodium phosphate buffer (pH 7) at maximally 56 mg nicotine h^–1 g dry cell^–1.     

Biomethanation of a cellulose-based substrate in the presence and absence of a cellulolytic bacterium

The effect of co-culturing a methanogen isolated from a paper mill waste (PMW) with cellulolytic bacteria isolated from the intestinal fluids of the silver cricket (Lepisma saccharina) on the biomethanation of filter paper strips was examined. The autoclaved filter paper strips were subjected to biomethanation in AC 21 medium inoculated with methanogen PMW in the presence and in absence of a co-culture of cellulolytic bacteria. In spite of poor initial response, methane production in the presence of the cellulolytic co-culture were found to increase gradually upto 25 days, after which a reduction in methane production was observed. Analysis of the results in terms of increased cellulose degradation in the presence of cellulolytic bacteria has been made. This revised version was published online in July 2006 with corrections to the Cover Date.     

Degradation of 2,4-dichlorophenol by Bacillus sp. isolated from an aeration pond in the Baikalsk pulp and paper mill (Russia)

A pure culture of 2,4-dichlorophenol (2,4-DCP)-degrading bacteria was isolated from a natural enrichment that had been adapted to chlorophenols in the aeration pond of the Baikalsk pulp and paper mill (Russia). The bacteria were identified by 16S rDNA intergenic region analysis, using PCR with universal primers. Comparative analysis of the 16S rDNA sequence (1545 bp) in the GenBank database revealed that these bacteria are related to Bacillus cereus GN1. Degradation of 2,4-DCP was studied using this culture in liquid medium under aerobic conditions, at initial concentrations of 20–560 μM 2,4-DCP. The 2,4-DCP degradation rates by B. cereus GN1 could be determined at concentrations up to 400 μM. However, higher concentrations of 2,4-DCP (560 μM) were inhibitory to cell growth.     

Biological treatment of a pulp and paper industry effluent by Fomes lividus and Trametes versicolor

White rot fungi Fomes lividus and Trametes versicolor, isolated from the Western Ghats region of Tamil Nadu, India, were used to treat pulp and paper industry effluents on a laboratory scale and in a pilot scale. On the laboratory scale a maximum decolourization of 63.9% was achieved by T. versicolor on the fourth day. Inorganic chloride at a concentration of 765 mg/l, which corresponded to 227% of that in the untreated effluent, was liberated by F. lividus on the 10th day. The chemical oxygen demand (COD) was also reduced to 1984 mg/l (59.3%) by each of the two fungi. On the pilot scale, a maximum decolourization of 68% was obtained with the 6-day incubation by T. versicolor, inorganic chloride 475 mg/l (103%) was liberated on the seventh day by T. versicolor, and the COD was reduced to 1984 mg/l corresponding to 59.32% by F. lividus. These results suggested that F. lividus seems to be another candidate efficient for dechlorination of wastewater.     

Studies on the anaerobic degradation of benzoic acid and 2-aminobenzoic acid by a denitrifying Pseudomonas strain

The growth of a denitrifying Pseudomonas strain on benzoic acid and 2-aminobenzoic acid (anthranilic acid) has been studied. The organism grew aerobically on benzoate, 2-aminobenzoate, and gentisate, but not on catechol or protocatechuic acid. These and other findings suggest that aerobic degradation of benzoic acid was via gentisic acid. Under completely anaerobic conditions in the presence of nitrate, benzoate and 2-aminobenzoate (5 mM each) were oxidized to CO₂ with the concurrent reduction of NO ₃ ^- to NO ₂ ^- . Only after complete NO ₃ ^- consumption was NO ₂ ^- reduced to N₂. Cells contained a NADP-specific 2-oxoglutaate dehydrogenase, in contrast to a NAD-specific pyruvate dehydrogenase. During anaerobic metabolism of [carboxyl-¹⁴C]benzoic acid, 16% of the label of metabolized benzoic acid was incorporated into cell material; this excludes intermediary decarboxylation during anaerobic metabolism. Extracts catalysed the activation of benzoic acid and a variety of its derivatives to the respective aryl-coenzyme A thioesters, ATP being cleaved to AMP and PP_i; two synthetase activites were present. Extracts from 2-aminobenzoate-grown cells catalyzed a NADH-dependent reduction of 2-aminobenzoyl-CoA (100 nmol·min^-1·mg^-1 cell protein) to an unidentified CoA thioester, with a stoichiometric release of NH₃ and a stoichiometry of 3 mol NADH oxidized per mol 2-aminobenzyol-CoA reduced when tested under aerobic conditions. The 2-aminobenzoyl-CoA reductase activity was lacking in anaerobic benzoate-grown cells and in aerobic cells. This is taken as evidence that 2-aminobenzoyl-CoA reductase is a key enzyme in a novel reductive pathway of anaerobic 2-aminobenzoic acid metabolism.Dedicated to Prof. Charles W. Evans     

Detection and characterisation of catechol 2,3-dioxygenase in an indigenous soil <Emphasis Type="Italic">Pseudomonad</Emphasis> by MALDI-TOF MS using a column separation

The key enzyme catalyzing the second step in the phenol degradation meta-cleavage pathway (C23O) has been purified to homogeneity from a new bacterial strain, which belongs to genus Pseudomonas. The species was growing on phenol as carbon source. The C23O was detected and identified by absorption spectroscopy. The protein was isolated using sucrose density centrifugation and anion exchange chromatography. The purified protein showed a molecular mass of 32 kDa to sodium dodecyl sulfate polyacrylamid gel electrophoresis and an isoelectric point of 5 estimated by analytical isoelectrical focusing. Matrix-assisted laser desorption ionization-time of flight mass spectrometry and peptide mapping was attempted for the identification of the isolated protein and proteins involved in the metabolic pathway.     

Oxidation of glycerol,lactate, and propionate by Propionibacterium freudenreichii in a poised-potential amperometric culture system

Growth of Propionibacterium freudenreichii was studied with glycerol, lactate, and propionate as energy sources and a three-electrode poised-potential amperometric electrode system with hexacyanoferrate (III) as mediator. In batch culture experiments with glycerol and lactate as substrates, hexacyanoferrate (III) was completely reduced. Growth yields increased and the fermentation patterns were shifted towards higher acetate formation with increasing hexacyanoferrate (III) concentrations (0.25–8.0 mM). In experiments with regulated electrodes, glycerol, lactate, and propionate were oxidized to acetate and CO₂, and the electrons were quantitatively transferred to the working electrode. Growth yields of 29.0, 13.4 and 14.2 g cell material per mol were calculated, respectively. The high cell yield obtained during propionate oxidation cannot be explained solely by substrate level phosphorylation indicating that additional energy was conserved via electron transport phosphorylation. Furthermore, this result indicated complete reversibility of the methyl-malonyl-CoA pathway in propionic acid bacteria.