Bacterial Strains From Tannary Waste Polluted Soil Showed Heavy Metal Resistance and Bioaccumulation Capacity

Tanning is the process of treating skins and hides of animals to produce leather. Variouschemicals are being used in this process and accordingly, tannery wastewater contains the varietyof toxic heavy metals like chromium, cadmium, cobalt, lead, nickel, selenium and arsenic (۱).Hence these regions are suitable sources for obtaining heavy metal resistance bacteria withapplication in bioremediation. In this study we isolated the bacterial strains from tannery effluentpolluted soil and evaluated their resistance to some heavy metals and their potentials forapplication in bioremediation process. The desired dilutions of soils were inoculated in thenutrient agar media containing ۵۰ ppm of each arsenic, chromium, copper, lead and zinc ions. Atotal of ۱۲ strains were obtained where their tolerances to heavy metals for the arsenic,chromium, copper, lead and zinc were as ۲۰۰۰ ppm, ۲۹۰۰ ppm, ۱۶۰۰ ppm, ۳۳۰۰ ppm, and ۱۶۰۰ppm, respectively. In order to identify the bioaccumulation capacity of these strains, bacterialsuspensions were inoculated in the ۱۰۰ml Erlenmeyer flasks containing nutrient broth thatsupplemented by ۵۰ ppm of each mentioned metals. The cultures were kept at ۳۰ oC andagitation at ۱۵۰ rpm for ۷۲ hours. Bacterial cell pellets were removed by centrifugation (۱۰۰۰ gfor ۱۰ min) and the supernatants were passed through ۰.۴۵ μm filters. The potentials of bacterialstrains to accumulate metals were determined based on the measurements of the remainingamount of primary metals in the supernatant by the inductively coupled plasma optical emissionspectrometry (ICP-OES) (SPECTRO ARCOS, Germany) (۲). The highest remediation rates forarsenic, chromium, copper, lead and zinc were as ۶.۷% (strain TP۴), ۱۳.۱% (strain TN۳), ۹.۹%(strain TP۴), ۷۶.۹% (strain TN۳), and ۱.۲% (strain TN۳), respectively. The results of this studyshowed that tannery waste contaminated soils are good candidates to obtain of bacterial strainswith the potentials in bioremediation.