Identification of Free Ammino Acids in Saccharomyces cerevisiae Living Cells after Heavy Metals Ions Biosorbtion

Andreea Stănilă

Abstract


A lot of microorganisms can sorb heavy metals (Zn, Cu, Pb, Cd, Ni, Cr) from aqueous solutions to varying extent. Biosorption depends on parameters such as pH, metal ion and biomass concentrations, physical or chemical pretreatment of biomass. Yeasts of genera Saccharomyces are efficient biosorbents for heavy metal ions. The aim of this study was to identify if the free amino acids present in brewer yeast are involved in metal biosorption due to their capacity to coordinate metal ions. As biosorbent was used  brewer’s yeast living cells type Saccharomices cerevisae. Zinc, lead and copper ions solutions of 1mg/L concentrations were prepared using their salts. The experiments were conducted at pH=5.5, which is the most appropriate for amino acids extraction. The amino acids were identified by HPLC-DAD/-ESI-MS chromatography. The experiments were conducted by mixing metals solution with yeast and shaken at a constant speed of 120 rpm at 200C for 120 minute. The samples were centrifugated at 3000 rpm for 15 minutes and the supernantant was analysed for amino acids identification. The HPLC analysis was performed on a Agilent 1200 system equipped with a binary pump delivery system LC-20 AT, a degasser DGU-20 A3, diode array SPD-M20 A, UV–VIS detector (DAD). Amino acids were identified using an EEZ:Faast Kit for free amino acids, The amino acids identified by HPLC method were glycine (GLY), glutamic acid (GLU), leucine (LEU), isoleucine (ILE), ornithine (ORN), lysine (LYS), histidine (HIS), homophenylalanine (HPHE), tyrosine (TYR), glutamine (GLN), alanine (ALA), valine (VAL), triptophan (TRP), phenylalanine (PHE), α-aminobutyric acid (ABA), asparagines (ASN) in control brewer yeast (before biosorption) and their profile differs according with the metal ions types. According with the peaks area there are differences in the presence of the amino acids due to the possible coordination with metal ions.


Keywords


brewer yeast, amino acids, biosorption, heavy metals.

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