Characterization of the biosorption of fast black azo dye K salt by the bacterium Rhodopseudomonas palustris 51ATA strain

BACKGROUND: Removal of dyes from wastewater by microorganisms through adsorption, degradation, or accumulation has been investigated. Biological methods used for dye treatment are generally always effective and environmentally friendly. In this study, biosorption of the Fast Black K salt azo dye by the bacterium Rhodopseudomonas palustris 51ATA was studied spectrophotometrically, at various pH (2­10), temperatures (25°C, 35°C, and 45°C) and dye concentrations (25­400 mg L-1). RESULTS: The bacterial strain showed extremely good dye-removing potential at various dye concentrations. IR studies at different temperatures showed that the dye was adsorbed on the bacterial surface at lower temperatures. Characteristics of the adsorption process were investigated by Scatchard analysis at 25°C and 35°C. Scatchard analysis of the equilibrium binding data for the dye on this bacterium gave rise to linear plots, indicating that the Langmuir model could be applied. The regression coefficients obtained for the dye from the Freundlich and Langmuir models were significant and divergence from the Scatchard plot was observed. CONCLUSION: The adsorption behavior of the dye on this bacterium was expressed by the Langmuir, Freundlich, and Temkin isotherms. The adsorption data with respect to various temperatures provided an excellent fit to the Freundlich isotherm. However, when the Langmuir and Temkin isotherm models were applied to these data, a good fit was only obtained for the dye at lower temperatures, thus indicating that the biosorption ability of R. palustris 51ATA is dependent on temperature, pH, and dye concentration.

The potential use of anoxygenic phototrophic bacteria for treating latex rubber sheet wastewater

A total of 92 isolates of the purple non sulphur photosynthetic bacteria (PNSB) were isolated from 23 samples of wastewater obtained from rubber sheet manufacturing processes from various places of southern, Thailand. The isolate DK6 had the best potential for use in wastewater treatment as it can out-compete indigenous strains of PNSB when grown with them under conditions of microaerobic-light conditions. The isolate DK6 was identified as being most closely allied to Rhodopseudomonas blastica. The optimal pH and temperature for cell growth were between 6.5-7.5 and 30ºC, respectively. Optimum growth of DK6 was obtained after supplementing the wastewater from a latex rubber sheet processing plant with 0.50 percent (NH4)2SO4 and 1 mg/L nicotinic acid under conditions of microaerobic-light (3000 lux). Using these optimum conditions for growth, indigenous microorganisms reduced the initial chemical oxygen demand (COD) of the wastewater from 7,328 to 3371 mg/L a reduction of 54 percent and the biochemical oxygen demand (BOD) (initial BOD 4967 mg/L) by 70 percent. Using the same conditions and either a pure culture of DK6 or a mixed culture (DK6 plus indigenous microorganisms) a reduction of 90 percent of both COD and BOD was achieved. Chemical analysis of the cultures after treatment of the enriched wastewater shows that the protein content of the pure DK6 was 65.2 percent of the dry weight, and in mixed culture the protein content was 66.7 percent. Hence, single cell protein (SCP) may be a possible bi- product of the treatment process.

Photobiodegradation of pyridine by Rhodopseudomonas palustris JA1.

A purple non-sulfur bacterium isolated from dairy effluent was identified as Rps. palustris JA1. This organism was able to grow on pyridine as sole source of carbon in a light dependent anaerobic process with a doubling time of 30 h. Intermediates of pyridine photobiodegradation were identified as glycine and malonate, produced in stoichiometric molar ratios with simultaneous utilization, yielding biomass.

Adaptación de Rhodopseudomonas palustris a cambios de condiciones atmosféricas / Adaptation of Rhodopseudomonas palustris to changes in atmospheric conditions

El burbujeo de O2 95%-N2 5% a un cultivo de Rhodopseudomonas palustris crecido en condiciones fotosintéticas provoca un cese inmediato de la síntesis de bacterioclorofila y una disminución de la actividad de la enzima delta-aminolevulinato sintetasa (ALA-S), sin alterar el crecimiento bacteriano. Al cesar el gaseado el nivel enzimático se recupera rápidamente pero el de bacterioclorofila lo hace más lentamente. El agregado de cloramfenicol al cesar el gaseado, no afecta la recuperación de la actividad enzimática. En cambio, si se lo agrega desde el inicio del gaseado, la actividad igual decae pero su recuperación es menor que en ausencia del antibiótico. La enzima de extractos de células gaseadas muestra activación espontánea a 40-C Se postula el efecto de distintos activadores sobre diversas formas de la enzima ALA-S para explicar estos hechos