Investigating Mercury Interactions of Rhodotorula Toruloides IR-1395 for Mercury Bioremediation Processes in Aquatic Environments

Abstract

Introduction: Nowadays, heavy metals pollution is one of the most important environmental problems. Due to the high cost of common refining methods, the use of microbial biomass is recommended to clean up heavy metals. The aim of this study was the evaluation of interactions of Rhodoterula toruloides strain IR-1395 with mercury.Materials and methods: In this study, the growth rate and interactions of strain IR-1395 with mercury in Sucrose Broth medium were investigated and the amount of mercury accumulated was measured using the Spectrophotometry method. Then, in order to determine the best biosorption conditions, the effect of parameters such as pH, mercury concentration, biomass concentration, contact time and temperature were measured. Also, the biosorption was investigated by treated cells with 2, 4 dinitrophenol and autoclave. Finally, the biosorbent was characterized by Scanning Electron Microscope with Energy Dispersive X-Ray Analysis. Results: Studies showed that the maximum growth rate of strain IR-1395 was after 36h and then it enters the stationary phase. Also, this strain was able to the biosorption and bioaccumulation (61.86%) and 10.17% biovolatilization of mercury from the medium at the concentration of 10 mg/l of chloride mercury during seven days. In study of factors affecting on the mercury biosorption, it is indicated that the optimal pH was 4. The highest biosorption was observed at 300 mg /l of mercury in 10 minutes at 15 ˚C. Mercury adsorption using treated biomass by autoclaved and 2,4 dinitrophenoltreatment has reduced than control samples. Finally, the results of the EDX confirmed the biosorption of mercury by this yeast.Discussion and conclusion: By study of the various interactions of strain IR-1395 with mercury and its potential in biosorption, it was found that this strain is a valuable microorganism in mercury bioremediation processes from contaminated aquatic environments.

Keywords

• bioaccumulation
• biosorption
• mercury
• volatilization
• rhodoterula toruloides