Bioremediation of Wastewater Using Yeast Strains: An Assessment of Contaminant Removal Efficiency

Abstract

The main goal of wastewater treatment is to significantly reduce organic compounds, micronutrients (nitrogen and phosphorus) and heavy metals and other contaminants (pathogens, pharmaceuticals and industrial chemicals). In this work, the efficiency of removing different contaminants (COD, NO3−, NO2−, NH4+, PO43−, SO42−, Pb2+, Cd2+) from synthetic wastewater was tested using five different yeast strains: Kluyveromyces marxianus CMGBP16 (P1), Saccharomyces cerevisiae S228C (P2), Saccharomyces cerevisiae CM6B70 (P3), Saccharomyces cerevisiae CMGB234 (P4) and Pichia anomala CMGB88 (P5). The results showed a removal efficiency of up to 70% of COD, 97% of nitrate, 80% of nitrite, 93% of phosphate and 70% of sulfate ions for synthetic wastewater contaminated with Pb2+ (43 mg/L) and Cd2+ ions (39 mg/L). In contrast, the results showed an increase in ammonium ions, especially in the presence of Pb2+ ions. The yeast strains showed a high capacity to reduce Pb2+ (up to 96%) and Cd2+ (up to 40%) ions compared to the initial concentrations. In presence of a crude biosurfactant, the removal efficiency increased up to 99% for Pb2+ and 56% for Cd2+ simultaneously with an increase in yeast biomass of up to 11 times. The results, which were obtained in the absence of aeration and in neutral pH conditions, proved a high potential for practical applications in the biotreatment of the wastewater and the recovery of Pb and Cd ions, with a high benefit–cost ratio.

Yarrowia lipolytica CMGB32 Biosurfactants Produced Using n-Hexadecane: Developing Strategies for Environmental Remediation

“…This trend demonstrates the positive influence of a biosurfactant on the faster growth of R. mucilaginosa cultures. However, a particular case was observed regarding the water contaminated with cadmium ions, where the lag period was 22 h, which was probably due to the more pronounced toxic effect of Cd 2+ ions on the tested strains [31].…”

“…The biosurfactant was obtained using a protocol described previously by Nicula et al [31]. The cell-free broth obtained after filtering the supernatant was further used as a crude biosurfactant [32,33].…”

“…Synthetic wastewater was prepared by adapting the formulations outlined by [31,34] comprising the following components: 200 mg/L D-glucose, 200 mg/L sucrose, 70 mg/L yeast extract, 66.73 mg/L (NH 4 ) 2 SO 4 , 10.91 mg/L NH 4 Cl, 4.43 mg/L KH 2 PO 4 , 21 mg/L MgSO 4 •7H 2 O, 2.68 mg/L MnSO 4 •H 2 O, 30 mg/L NaHCO 3 , 19.74 mg/L CaCl 2 , 0.14 mg/L FeCl 3 •6H 2 O, 330 mg/L NaNO 3 , and 390 mg/L NaNO 2 . For experiments regarding the removal efficiency of heavy metal ions, synthetic wastewater was contaminated with Pb 2+ (32 mg/L, (CH 3 COO) 2 Pb) and Cd 2+ (30 mg/L, Cd(NO 3 ) 2 ) ions.…”

“…The amount of obtained yeast biomass was determined gravimetrically, at the end of the experiment, by filtering the samples in a vacuum tube through filter paper with pores of 0.45 µm, followed by drying at room temperature [31].…”

“…The biosurfactant showed high thermal stability (50% at 4 • C and 41% at 70 • C), with the E 24 % values being also stable at NaCl concentrations between 2 and 6% (53% for NaCl 2% and 4%, 47% for NaCl 6%), decreasing for higher 8% and 10% concentrations (31% and 28%, respectively). In our previous study, it was shown that the biosurfactant produced by the Y. lipolytica CMGB 32 strain is essentially a lipoprotein composed of a high amount of aromatic amino acids [31]. The aromatic amino acid residues, such as tyrosine and tryptophan, are involved in establishing energetically favorable interactions with molecules from the surrounding environment (interaction strongly influenced by temperature and ionic strength) [42,43].…”