Metabolism of dimethylterephthalate by Aspergillus niger.

Aspergillus niger (AG-1) metabolized dimethylterephthalate through monomethylterephthalate, terephthalate and protocatechuate. Degradation of dimethylterephthalate was followed by extraction of residual dimethylterephthalate from the spent medium. The quantitative UV analysis showed that 58% of the dimethylterephthalate supplement was taken up in 144 h. The metabolites were isolated from resting cell cultures. Thin layer chromatography analysis of the extract revealed the presence of two intermediates, monomethylterephthalate and terephthalate. Use of an inhibitor in resting cell culture experiment demonstrated the accumulation of protocatechuate. The time course of protocatechuate accumulation was also studied. Metabolites were identified by employing various physicochemical methods. Enzyme studies using cell-free extracts exhibited dimethylterephthalate esterase and protocatechuate dioxygenase activities. Protocatechuate was oxidized by the meta cleavage pathway. A tentative pathway for the degradation of DMTP has been proposed in A. niger.

Metabolic pathway of homophthalic acid in Pseudomonas alcaligenes.

A microorganism capable of degrading homophthalic acid as a sole carbon source was isolated from garden soil. The strain was identified as Pseudomonas alcaligenes. The organism degraded homophthalate by a pathway which involved phenylacetate and p-hydroxyphenylacetate as intermediates. The intermediates have been identified by physico-chemical methods. A tentative pathway for the degradation of homophthalate is proposed based on isolation of intermediates, oxygen uptake studies and presence of enzymes involved in the degradation.

Degradation of homophthalic acid byAspergillus niger.

The fungusAspergillus niger degraded homophthalic acid through the involvement ofo-hydroxyphenylacetic acid and homogentisic acid as the metabolic intermediates. Isolation of intermediates was carried out by extracting the spent medium and by using inhibitor in replacement culture techniques. Metabolites were characterized by various physicochemical methods. Oxygen uptake studies and enzyme investigations also confirmed that the degradation of homophthalic acid follows through these intermediates in the fungus.

Metabolism of benzalphthalide by Pseudomonas sp.

A Pseudomonas sp. degraded benzalphthalide to o-phthalate and benzoate. A tentative pathway for the metabolism of benzalphthalide in this Pseudomonas sp. is proposed on the basis of isolated metabolites, oxygraphic assay and enzymatic studies.

Bacterial degradation of benzalphthalide.

APseudomonas sp., isolated by an enrichment culture technique, grew on benzalphthalide at up to 1 g/l as sole carbon source. Cells oxidized both benzalphthalide ando-phthalate at enhanced rates compared with glucose-grown cells, but catechol, gentisate and protocatechuate were oxidized slowly and equally by benzalphthalide-and glucose-grown cells.

Catabolism of homophthalic acid by a soil bacterium.

A microorganism capable of degrading homophthalic acid as a sole source of carbon was isolated from soil. The strain was tentatively identified as Pseudomonas sp. Oxygen uptake studies were carried out with possible intermediates. Assays for several different enzymes were performed. Homophthalic acid may be metabolized by this bacterium via p-hydroxyphenyl acetic acid and homogentisic acid intermediates.

Phthalate metabolism in Pseudomonas fluorescens PHK: purification and properties of 4,5-dihydroxyphthalate decarboxylase.

Pseudomonas fluorescens PHK uses 4,5-dihydroxyphthalate as the sole carbon source for o-phthalate catabolism. This intermediate is the substrate for a decarboxylase of the pathway yielding protocatechuate. The decarboxylase was purified to homogeneity by an affinity chromatography procedure in which the reaction product, protocatechuate, was used as a ligand. We describe some properties of the enzyme, including its apparent molecular weight of 420,000 as determined by gel filtration and of 66,000 after sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis, consistent with a hexameric functional protein. The apparent Km for the substrate 4,5-dihydroxyphthalate was 10.4 microM. The characteristics of this enzyme are compared with those described for the isofunctional enzyme from P. testosteroni.

Biodegradation of the phthalates and their esters by bacteria.

Recent studies on the biodegradation phthalate esters in natural ecosystems, sewage, and laboratory cultures are reviewed. There is ample evidence to demonstrate that bacteria are major elements in the biodegradative processes and that in most situations complete oxidation of the aromatic ring occurs; much less is known about the catabolism of the alcoholic moiety, e.g., 2-ethylhexanol. Evidence is presented to support catabolic pathways in pseudomonads and micrococci that are initiated by successive hydrolyses of the diesters to give the phthalate anion. Thereafter a dioxygenase catalyzes the formation of 4,5-dihydro-4,5-dihydroxyphthalate, which is oxidized by an NAD-dependent dehydrogenase to give 4,5-dihydroxyphthalate, Protocatechuate, formed by decarboxylation of 4,5-dihydroxyphthalate, is the substrate for ring cleavage enzymes. Whereas flurorescent pseudomonads use the beta-ketoadipate pathway, the nonfluorescent strains and micrococci examined use of meta-cleavage (4,5-) route. All the intermediates proposed have been accumulated by enzymes purified from Pseudomonas fluorescens. Isophthalate and terephthalate (anions) are readily used as carbon sources by aerobic bacteria, and preliminary evidence is consistent with catabolic routes for these isomers converging at the ring-cleavage substrate protocatechuate. Some possible effects and interactions of synthetic organic chemicals with the natural microflora, and the influence of other vectors, is discussed in relation to the maintenance of the carbon cycle and environmental pollution.