Phytoremediation of tetracycline and oxytetracycline
Date
2005
Authors
Gujarathi, Ninad P., author
Linden, James, advisor
Bhadra, Rajiv, advisor
Wickramasinghe, Ranil, advisor
Rinker, Kristina, committee member
Pruden, Amy, committee member
Smits-Pilon, Elizabeth, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Tetracycline (TC) and Oxytetracycline (OTC), when released to the environment through wastewater streams mainly from concentrated animal feeding operations (CAFO), may induce antibiotic resistance among several bacterial species. Phytoremediation involves the use of plants or plant-secreted metabolites in remediating pollutants from air, water and soil. If proven effective, phytoremediation may provide an inexpensive, efficient means for antibiotic remediation. Two aquatic species, Myriophyllum aquaticum (parrot feather) and Pistia stratiotes (water lettuce), and hairy root cultures of Helianthus annuus (sunflower) are reported to have ability to remove TC and OTC from aqueous media. Root exudates from the three plant systems also exhibit significant antibiotic removal capability. Antibiotic modification is confirmed from the changes in ultraviolet (UV) absorption spectra of the modified antibiotics. Hairy root cultures of H. annuus are used as a model system for the experiments conducted to understand the mechanism of phytoremediation. OTC is used as the representative antibiotic for mechanistic experiments, as well as in bioreactor studies. Both in vivo and in vitro experiments using the hairy root cultures of H. annuus are used to demonstrate that reactive oxygen species (ROS) are secreted by the roots. The ROS inactivate OTC through oxidative modification. The rates of OTC oxidation by the hairy root cultures are enhanced by elicitation of ROS using salicylic acid (SA) and methyl jasmonate (MeJA). Modification of OTC results in oxidation product(s) devoid of anti-microbial activity. When used to treat wastewater from a dairy cow operation, which was spiked with OTC, root exudates significantly reduce OTC as well as biological oxygen demand (BOD) concentrations. The effects of varying physiological conditions, such as pH, temperature and aeration, on the OTC remediating activity of the root exudates are reported. The ROS-mediated modification of OTC by the root exudates is superior under aerobic conditions. A novel, integrated bioreactor system is designed for effective removal of OTC from water, under continuous-flow conditions. The design consists of a pond-microcosm for growth of P. stratiotes, coupled to a continuous flow reactor for contacting ROS and OTC. The reactor configuration with continuous-stirring gives more efficient OTC removal than a plug-flow configuration.
Description
Rights Access
Subject
Phytoremediation
Antibiotic residues
Animal waste