Heavy metal tolerance and removal efficiency of the Rhodotorula mucilaginosa and Saccharomyces boulardii planktonic cells and biofilm

Sandra Grujić,Ljiljana Čomić,Sava Vasić,Aleksandar Ostojić,Ivana Radojević

doi:10.5937/kgjsci1840217g

Abstract

The impact of heavy metals, cadmium (Cd2+), zinc (Zn2+) and nickel (Ni2+) on planktonic cells and biofilm of Rhodotorula mucilaginosa and Saccharomyces boulardii was examined. The metal tolerance testing was performed by MBECTM-HTP assay. The minimum inhibitory concentration (MICp) and minimum lethal concentration (MLCp) were determined as well as the minimum biofilm eradication concentration (MBEC). Biofilm was more tolerant on the presence of heavy metals than the planktonic cells. The planktonic cells of R. mucilaginosa were tolerant to high concentrations of Cd2+, Zn2+ and Ni2+, while the planktonic cells of S. boulardii tolerated Zn2+, exclusively. The R. mucilaginosa biofilm was tolerant to all of the tested metal concentrations and the obtained results were confirmed by fluorescence microscopy. S. boulardii did not show ability of biofilm formation. Metal removal efficiency of the R. mucilaginosa planktonic cells and biofilm were also tested. The R. mucilaginosa biofilm showed higher efficiency in metals removing compared to the planktonic cells. Until now, the heavy metal tolerance and the removal efficiency (Cd2+, Zn2+ and Ni2+) analyzes were performed solely on planktonic cells of Rhodotorula species. In this study, we investigated the metal removal efficiency of R. mucilaginosa planktonic cells and biofilm and compared the obtained results.

Highlights

An understanding of the nature of heavy metals, their relationships and toxicity or deficiency problems associated with them, is important for environmental protection
Our findings suggest that biofilm and planktonic populations show different levels of tolerance to heavy metals
Understanding this difference is significant for understanding the microbial ecology of environments polluted with heavy metals, as well as the basics of biofilm tolerance to antimicrobial agents in general

Summary

Introduction

An understanding of the nature of heavy metals, their relationships and toxicity or deficiency problems associated with them, is important for environmental protection. As more and more analytical data become available in the world literature, it is evident that considerable areas in many parts of the world have been contaminated with heavy metals, which present potential toxicity problems (ALLOWAY, 1995). A wide range of methods for the heavy metals removal from contaminated environment are being used. Most of them are not efficient in removing low concentrations of metals, have high energy requests, lead to accumulation of toxic sludge and other waste products, requiring a careful disposal of waste (AHALYA et al, 2003). Microbial biomass is considered as an alternative for the heavy metals removal (ALLURI et al, 2007)

Methods

Results

Conclusion