Abstract

RANGEL-GARCIA, María de L.; RODRIGUEZ-MARTINEZ, Jesús; GARZA-GARCIA, Yolanda  and  MARTINEZ-HERNANDEZ, José L.. Optimization of iron ions to eliminate pyocyanine in the degradation reaction of Toluene, Benzene and Phenol by Pseudomonas aeruginosa. Agrociencia [online]. 2010, vol.44, n.2, pp.235-247. ISSN 2521-9766.

A wide range of xenobiotic substances represent a serious problem as environmental pollutants because of their toxicity, among them are found aromatic compounds that can be biodegraded by microorganisms, which use them as their source of carbon and energy. The genus Pseudomonas is outstanding for its multiple biotechnological applications due to its remarkable metabolic versatility. It is capable of producing useful metabolites, enzymatic transformations, biodegradation and bioremediation in soil, as well as in water polluted with oil and pesticides. In this study, cells of P. aeruginosa were used to degrade toluene, benzene and phenol. The strain was cultivated in a solid mineral medium, and the following optimal concentrations were established for the development of viable cells: 0.31, 0.19, and 0.13 M for toluene, benzene and phenol. The environments with limited concentrations of Fe(III) favored the production of pyocyanine, a pigment that can interfere in the analytical method of aromatic compound biodegradation. This effect was eliminated by increasing the concentration of iron ions in the medium. On this basis, the mineral culture medium was optimized and established at 0.04 g L^-1 FeSO₄ in presence of toluene (0.03 M). With this initial concentration, a rate of biodegradation of 75 % was obtained. The specific degradation tests for the aromatic compounds showed that the P. aeruginosa strain used can degrade toluene, benzene and phenol. The rates of degradation were higher for toluene (58.4 °/o) and benzene (70.11 °/o) with the initial concentrations of 0.14 M and 0.16 M. Degradation was less for phenol (24.65 %) with an initial concentration of 0.10 M. The degrading capacity of P. aeruginosa was directly proportional to its growth in the presence of the xenobiotic substances studied. A larger amount of cell protein was exhibited in cultures with benzene (1.4982 mg mL^-1) and toluene (0.8629 mg mL^-1), and less in the cultures grown in presence of phenol (0.4431 mg mL^-1), indicating that deficient bacterial development (biomass) can result in suboptimal biodegradation.

Keywords : Pseudomonas aeruginosa; degradation; pyocyanine; xenobiotics.

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