Bioassay Kits for Ecotoxicological Testing of Wastewaters with Nanoparticles

Abstract

Volume 2 • Issue 3 • 1000e139 Biochem Anal Biochem ISSN:2161-1009 Biochem, an open access journal Evaluation of complex wastewaters should include acute/chronic ecotoxicological tests [1] and the potential for endocrine disruption [2,3] to complement the physicochemical characterization. The advantages of bioassay (with a bacterium, alga or crustacean) are simplicity, speed and low cost for monitoring toxicity over time. Its strongest attribute is usefulness as a primary screening test for a broad spectrum of toxicants. Several bioassay kits are commercially available, including the Lux-fluoro, Polytox, Microtox and Thamnotox kits that require no specialized equipment. A combined approach using instrumental methods for chemical analysis and bioassays for ecotoxicological testing would be extremely important to hazard/risk assessment of wastewater treatment plant discharges. The Lux-fluoro test was developed for the rapid detection and quantification of environmental pollutants with genotoxic and/or cytotoxic potential [4]. This bacterial test system uses two different reporter genes whose products and reactions can be measured easily and simultaneously by optical methods. Genotoxicity is measured by the increase of bioluminescence in genetically modified bacteria which carry a plasmid with a complete lux operon for the enzyme luciferase from the marine photobacterium P. leiognathi. If the deoxyribonucleic acid (DNA) in these bacteria is damaged by a genotoxic chemical, the SOS promoter is turned on and the lux operon is expressed. Other genetically modified bacteria carry the gene for the green fluorescent protein from the jellyfish Aequora victoria downstream from a constitutively expressed promoter. These bacteria are fluorescent under common growth conditions. If their cellular metabolism is disturbed by the action of cytotoxic chemicals, the fluorescence decreases in a dose-proportional manner. A temperature-controlled microplate reader capable of sequential reading of luminescence and fluorescence can be programmed for repeating the measurement cycle at 30°C from 10 min up to 8 hours of continuous incubation [5]. The Microtox assay is based on the luminescent mechanism of freeze dried Photobacterium phosphoreum or Vibrio fischeri [6]. If metabolic processes are changed upon cell damage by a toxic substance, a reduction in light output can be detected within 5 to 30 minutes. After correcting the effects of color and turbidity on bacterial light output measurements [7], an EC5O concentration can be calculated as a toxicity value for comparison against a control substance to evaluate relative toxicity [8]. Microtox is probably the most sensitive test that can be used in a screening phase. The test has recently been used to quantify the impact of storage time on toxic compounds formed in the electrochemical treatment of phenol. Chlorinated phenols exhibited little toxicity change while highly toxic benzoquinone exhibited 92% loss of its initial toxicity over 18 days [9].