Biosorption of silver by Stenotrophomonas maltophilia strain MS8 isolated from wastewater of Silversmith's workshop in Isfahan

Detection of the microorganisms resistant to toxic metals is the first step in the process of bioremediation. The purpose of this study was isolation of silver-resistant bacteria, determination of their minimum inhibitory concentration (MIC) and investigation on the biosorption in vitro. Sampling was carried out from the wastewater of two Silversmith’s workshop in Isfahan and effluent of the wastewater treatment plant phase 2 input in Shahinshahr. The agar dilution method and PHG II culture medium containing concentrations of 0.5, 1, 2, 4, 8, 16, 32 mM of Ag (NO3)was used to separate the metal-resistant bacteria and determine the minimum inhibitory concentration (MIC). Finally, the ribotyping method was used to identify the silver-resistant bacteria. In this study seven silver-resistant bacteria were isolated, among them Ag5 showed the highest resistance to silver (MIC = 6mM). Based on the molecular analysis, this isolate belonged to a new strain, called as Stenotrophomonas maltophilia strain MS8, and its formation was deposited as KP742984 in Gene Bank (NCBI). This strain was able to absorb 11.39% of silver from medium in vitro after 120 minute and could growth well in the presence of silver. According to the results of this study, it seems that this isolate is a good candidate for biological removal of silver from contaminated wastewater in the future.