Biodegradation of the phthalates and their esters by bacteria.

Abstract

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.

Humic acid induces apoptosis in human premyelocytic leukemia HL-60 cells

“…Chemical and infrared spectroscopic analyses have revealed the presence of aromatic rings, and phenolic hydroxyl, ketonyl, quinone carbonyl, carboxyl, and alkoxyl groups in humic acid (Burges et al, 1964). Degradation of HA through oxidation, reduction, or microbial reaction can produce resorcinol, ortho-and meta-phthalic acids, and other phenolic compounds (Burges et al, 1964;Keyser et al, 1976;Choudhry, 1981).…”

A monograph on the remediation of hazardous phthalates

“…Two strains of Pseudomonas, i.e. P. fluorescens PHK and Pseudomonas testosteroni were reported to produce esterase for the initial hydrolysis of DMP [117]. The metabolism of DBP by Pseudomonas alcaligenes is initiated by de-esterification reaction under anaerobic conditions [118].…”

Degradation of Dimethyl Isophthalate byViarovorax paradoxusStrain T4 Isolated from Deep-Ocean Sediment of the South China Sea

“…Several studies were conducted on elimination of phthalate ester pollutants in the 1970s; however, isophthalate ester was not one of those investigated (Wang and Zhou 1995;Kleerebezem et al 1999a,b;Keyser et al 1976;Liu and Chi 2003;Aleshchenkova et al 1997;Babu and Vaidyanathan 1982). In these studies, both aerobic and anaerobic conditions were investigated for the fate of chemicals.…”