Fate of selenate metabolized by Enterobacter taylorae isolated from rice straw.

Abstract

Rice straw has been successfully tested as an effective organic source and a carrier of selenate [Se(VI)]-reducing bacteria to remove Se(VI) from agricultural drainage water. In this study, an Se(VI)-reducing bacterium identified as Enterobacter taylorae was isolated from rice straw and used to remove Se(VI) from a 0.5% tryptic soy broth (TSB) and high-salt (15.5 dS m(-)(1)) synthetic agricultural drainage water containing Se(VI) in a range of 500-5000 microg/L. Results showed that E. taylorae reduced 81-94% of the added Se(VI) to elemental Se [Se(0)] in the 0.5% TSB solution during a 5-day experiment. In the high-salt drainage water, Se(VI) reduction was rapid during a 9-day experiment. On the final day of the experiment, Se(0) [75%] and Se(-II) [19%] were the major forms of Se in the drainage water with small amounts of Se(VI), Se(IV), and volatile Se released. The pathway of Se(VI) reduction in the drainage water followed the order Se(VI) --> selenite [Se(IV)] --> Se(0) --> selenide [Se(-II)]. This study suggests that E. taylorae may be used to remediate high-salt Se(VI)-contaminated agricultural drainage water.