Study of the Bioremediation of Atrazine under Variable Carbon and Nitrogen Sources by Mixed Bacterial Consortium Isolated from Corn Field Soil in Fars Province of Iran

Atrazine herbicide that is widely used in corn production is frequently detected in water resources. The main objectives of this research were focused on assessing the effects of carbon and nitrogen sources on atrazine biodegradation by mixed bacterial consortium and by evaluating the feasibility of using mixed bacterial consortium in soil culture. Shiraz corn field soil with a long history of atrazine application has been explored for their potential of atrazine biodegradation. The influence of different carbon compounds and the effect of nitrogen sources and a different pH (5.5–8.5) on atrazine removal efficiency by mixed bacterial consortium in liquid culture were investigated. Sodium citrate and sucrose had the highest atrazine biodegradation rate (87.22%) among different carbon sources. Atrazine biodegradation rate decreased more quickly by the addition of urea (26.76%) compared to ammonium nitrate. Based on the data obtained in this study, pH of 7.0 is optimum for atrazine biodegradation. After 30 days of incubation, the percent of atrazine reduction rates were significantly enhanced in the inoculated soils (60.5%) as compared to uninoculated control soils (12%) at the soil moisture content of 25%. In conclusion, bioaugmentation of soil with mixed bacterial consortium may enhance the rate of atrazine degradation in a highly polluted soil. 1. Introduction Atrazine, 6-chloro-N2-ethyl-N4-isopropyl-1, 3, 5 atrazine, 4-diamine, is a selective herbicide that has been extensively used in corn production to control many broad-leaf and some grassy weeds. Atrazine has long-term reproductive and endocrine-disrupting effects and a probable human carcinogen [1]. International Agency for Research on Cancer (IARC) has concluded atrazine as a group 2B carcinogen. The maximum contaminant level (MCL) for atrazine in drinking water established by the USEPA is 3.0 μgL？1 [2]. Atrazine is moderately persistent in the environment and despite its low solubility, water resources contamination, it has become an international issue [3]. The major dissipation route for atrazine is biodegradation, runoff, and leaching [4, 5]. The rate of biodegradation of atrazine is reduced due to the adsorption, and desorption, and its bioavailability is the rate-limiting step in biodegradation [6]. Bioremediation is currently used to clean a wide variety of chemicals. There are basically two approaches to bioremediation: biostimulation and bioaugmentation [7]. Bioaugmentation is the addition of acclimated indigenous bacteria that can degrade the contaminant at accelerated rates. The