title: Assessing the impact of alumina nanoparticles in an anaerobic consortium: methanogenic and humus reducing activity.
abstract: The impact of γ-Al(2)O(3) nanoparticles (NP) on specific methanogenic activity (SMA) and humus reducing activity (HRA) in an anaerobic consortium was evaluated. SMA in sludge incubations without γ-Al(2)O(3) was always higher compared with those performed in the presence of 100 g/L of γ-Al(2)O(3). Nevertheless, the SMA in incubations with γ-Al(2)O(3) was not completely inhibited, indicating that some methanogenic microorganisms were physiologically active even in the presence of γ-Al(2)O(3) NP during the incubation period (~400 h). SMA and HRA of the anaerobic consortium were also conducted in the presence of γ-Al(2)O(3) NP coated with humic acids (HA). Microbial HA reduction occurred 3.7-fold faster using HA immobilized on γ-Al(2)O(3) NP (HA(Imm)), compared with the control with suspended HA (HA(Sus)). Furthermore, immobilized HA decreased the toxicological effects of γ-Al(2)O(3) NP on methanogenesis. Scanning electron microscopy (SEM) images revealed cell membrane damage in those sludge incubations exposed to uncoated γ-Al(2)O(3) NP. In contrast, cell damage was not observed in incubations with HA-coated γ-Al(2)O(3) NP. Methanogenesis out-competed microbial humus reduction regardless if HA was HA(Imm) or HA(Sus). The present study provides a clear demonstration that HA immobilized in γ-Al(2)O(3) NP are effective terminal electron acceptor for microbial respiration and suggests that HA could mitigate the toxicological effects of metal oxide NP on anaerobic microorganisms.
authors.affiliation: División de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica (IPICyT), Camino a la Presa San José 2055, Col. Lomas 4ª. Sección, San Luis Potosí, SLP, 78216, México. luis.alvarez@ipicyt.edu.mx
authors.forename: Luis H
authors.initials: LH
authors.lastname: Alvarez
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Cervantes
mesh_terms: D000537:Aluminum Oxide / Q000378:metabolism* / Q000633:toxicity; D000693:Anaerobiosis; D008697:Methane / Q000378:metabolism*; D059013:Microbial Consortia; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles; D010084:Oxidation-Reduction; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology*
chemical_list: D012722:Sewage; D000537:Aluminum Oxide; D008697:Methane