Isolation, identification and heavy metal biosorption assessment of yeast isolates indigenous to abandoned mine sites of Itogon Benguet, Philippines

Abstract

Water samples collected from abandoned mining sites in Itogon, Benguet, Philippines were screened for metal resistant microorganisms, in particular yeasts that will be used to remove toxic metals such as Zn, Cu, Pb, Cr and Ni from aqueous media. Among the five yeast strains selected and five heavy metals tested, Nodulisporium sp. exhibited the highest removal efficiency of 80% and biosorption capacity of 56.7 mg g-1 for Pb. This was based on the model equation for each metal that was generated to derive optimum response for removal efficiency. The metal accumulation potential for all selected yeast isolates was generally higher at the lower initial metal concentration of 25 mg L-1, indicating rapid metal absorbing ability of the isolate and that adsorption sites in the biomass are taking up available metal ions more quickly. An increased removal capability was observed when the best isolate was applied in a semi-continuous treatment system thru an Aerobic Cascading Filter Bed Baffled Reactor (ACFBBR). The reactor design including the packing material remarkably enhanced the contact between the yeast biomass and Pb contaminated wastewater resulting in a much greater biosorption capacity of 170.14 mg g-1 as compared to the biosorption of 56.7 mg g-1 achieved during the batch adsorption experiment.