Screening and identification of efficient strain in selenium oxyanions sorption in order to biological wastewater treatment

Abstract

Introduction: Selenium is an element with antioxidant activities that plays roles in thyroid hormone homeostasis, immunity and also fertility. Nevertheless, selenium toxicity (selenosis) causes problems for humans such as abnormalities of the nervous system, gastrointestinal problems and hair loss. Thus, this study was performed with the aim of bacterial biosorbent isolation in order to remove selenium contaminant from wastewater. Materials and methods: In this research, at first using modified Luria- Bertani agar (mLBA) medium with certain concentration of sodium selenate salt, isolation of bacterial isolates was done from three collected wastewater and sludge samples from Khouzestan industrial factories. After determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the sorption capacity and the percentage of metal removal efficiency (%RE) were investigated by atomic absorption spectrophotometer using metabolically active and inactive samples belonging to an efficient isolate. Identification was performed by morphological, biochemical and molecular methods. Results: Among 73 attained bacterial isolates at the first stage, 8 selenate oxyanion resistant isolates were gathered. Among these, AMS1-S8 isolate with MIC= 600­mM and MBC= 1200­mM were selected for more studies. Attained results in sorption mechanism determination stage showed that the sorption capacity in metabolically active sample is more than the inactive samples. Based on the identification results, it is revealed that this isolate belongs to the Enterobacter genus. This isolate is deposited as accession JQ965667 in the GeneBank database. Discussion and conclusion: The results showed that active biomass of selected isolate, have most sorption capacity and %RE and among the other isolates, have high partial resistance against selenate. Therefore, it can be a relatively ideal option for the bioremediation of polluted environments