Nickel biosorption by Acinetobacter baumannii and Pseudomonas aeruginosa isolated from industrial wastewater

Abstract

Nickel biosorption ability was evaluated in two bacterial strains: Acinetobacter baumannii UCR-2971 and Pseudomonas aeruginosa UCR-2957, resulting in greatest adsorption at pH 4.5 and a residence time of 100 minutes. Biosorption isotherms showed that the process follows the Langmuir model. The maximum adsorption rates (N max ) were 8.8 and 5.7 mg·g -1 for A. baumannii and P. aeruginosa, respectively; however, affinity constants suggest that P. aeruginosa (K=1.28) has higher affinity for nickel than A. baumannii (K=0.68). It is suggested that both strains could be used for wastewater treatment, as long as the concentration of Ni 2+ is within the range of mg·L Nickel is an important environmental inorganic pollutant, with allowed levels under 0.04 mg·L -1 in human consumption water. Higher concentrations affect normal flora in ecosystems and are toxic for human beings.Conventional chemical methods for heavy metal removal from wastewater (precipitation, filtration, ion-exchange, reduction-oxidation) are expensive and ineffective, particularly when metal concentration is low (4,12,13). Thus, biotechnological methods such as biosorption are emerging as an interesting alternative. Since cells are metabolically inactive in non-viable biomass systems, metal interactions occur at the superficial level (14). Bacteria express a wide range of complex molecules on their cell wall, which confer anionic net charge to the cell surface at acidic pH values (13). In Gram negative bacteria, the lipopolysaccharide, a highly anionic structure, has been identified as the main binding site for metals (9). When the cell wall is in direct contact with the environment, negatively charged groups are able to attract and bind metallic cations based on electrostatic forces, without cellular energy consumption, an effect that is favored by the high surfacevolume ratio in bacteria (3,5).In this work, nickel biosorption ability was investigated using bacteria isolated from wastewater contaminated with heavy metals (34.9 ± 9.0 mg Ni 2+ ·L -1 ; 31.5 ± 4.0 mg Pb 2+ ·L -1 ). The sample was aseptically filtered (0.45 µm membrane); the residues were resuspended in 100 mL Trypticase Soybean Broth (TSB, Difco) and incubated at 25ºC for four days. Then, 0.1 mL from the TSB were inoculated in Blood Agar, Cetrimide Agar (Difco), and Mac Conkey Agar (Oxoid) plates and incubated for 48 hours at 25ºC. Isolated strains were identified using the automatic VITEK system (BioMèrieux, Inc); Acinetobacter baumannii (UCR-2971) and Pseudomonas aeruginosa (UCR-2957) were the selected strains. For biomass production, these strains were inoculated in TSB and agitated (80 rpm) in a thermal bath (Orbit 3540, Labline), for 72 hours at 28ºC. The TSB was centrifuged at 5000 rpm for 10 minutes and biomass was washed three times with sterile distilled water and dried at 56ºC for 48 hours. The inocula of each adsorption

Biosorption characteristic of Alcaligenes sp. BAPb.1 for removal of lead(II) from aqueous solution

“…Then, both biosorption rate and biosorption capacity declined as the pH increased from 5 to 7. At low pH (3-4), functional anionic active sites might protonate at the biosorbent surface, bringing about a large number of cationic groups in solution, which could restrict the biosorption process for lead(II) (Rodriguez et al 2006). More carboxyl groups might dissociate from the biomass surface when the pH increased from 4 to 5.5, which enhanced ion exchange capacity of the biosorbent and improved the combination of lead ions with the anionic ligands (Hubbe et al 2011).…”

Biosorption of nickel by Pseudomonas cepacia 120S and Bacillus subtilis 117S

“…Nickel is an important environmental inorganic pollutant with permissible levels under 0.04 mg l 21 in human consumption water (Rodrigues et al 2006). Nickel ion is one of the heavy metals frequently encountered in raw wastewater streams from industries such as non-ferrous metal, mineral processing, paint formulation, electroplating, porcelain enameling, copper sulfate manufacture and steam electric power plants (Padmavathy et al 2003).…”

REMOVAL OF CADMIUM AND LEAD BY ADAPTED STRAINS OF Pseudomonas aeruginosa AND Enterobacter cloacae

“…Among these, conventional methods of remediation such as filtration, precipitation or ion exchange, are costly and at times ineffective (Panchanadikar 1994, Cañizares-Villanueva 2000, Vieira and Volesky 2000, while biological systems or biosorbents, including bacteria, fungi or algae are cheaper and frequently more effective, especially when metal concentrations are low (Rodríguez et al 2006).…”