Biosorption of Chromium Ions by Streptomyces mutabilis Isolated from Industrial Wastewater Treatment Plant

The removal of heavy metals by actinomycetes has been the subject of many investigations as they are used as potential heavy metal sorbents. This study aimed to evaluate chromium biosorption activity of some actinomycetes isolated from wastewater sample collected from Industrial Wastewater Treatment Plant (IWWTP), Jeddah, Saudi Arabia. About 35 different isolates of actinomycetes were obtained on starch nitrate medium with 100 ppm of chromium ions. The removal of chromium from growth medium was maximum by isolate FM2 which was selected and identified as a species belonging to the genus Streprotnyces. The 16S rRNA sequence of this isolate showed the highest similarity (98%) with Streptomyces mutabilis and identified as S. mutabilis FM2. The growth of the previous isolates was determined after 5 days at 30 C in the presence of different chromium oxide concentrations, 50- 300 mg/l. The minimum inhibitory concentration (MIC) of this isolate for Cr (VI) was 135 mg/1. By dead biomass of the previous isolate FM2 (1g/1), the biosorption capacity measured by Plasma Atomic Emission Spectrometer ICPE-9000 of the bacterial strain for Cr (VI) ion was 800 mg/1 which was 380/0 of the initial metal ion concentration. The maximum biosorption process for the tested isolate was recorded at pH 7, optimum temperature at 45 C. Biosorbent mass of 0 - 1.5 g was tested for removal of chromium. The result showed that the adsorption capacities against the heavy metal Cr (VI) were increased with increasing the weight of the used dry biomass. The genus Streptomyces was the most potent in removing of heavy metals and S. mutabilis biomass has a good potential to be used in removal of chromium from wastewater. Their use in real life situation can alleviate pollution and increase the quality of water for human consumption and sanitary purposes. Initial concentration of metal ion, pH and cell biomass affect chromium biosorption process by the dried cells of Streptomyces mutabilis.