Role of macro and micro elements on bioleaching of silica from Indian chromite ore by Aspergillus niger AB200

Department of Chemical Engineering, Biotechnology Division, Calcutta University,
92, Acharya Prafulla Chandra Road, Kolkata-700 009, India
E-mail : deblina.ball@gmail.com
Manuscript received 30 December 2010, accepted 31 December 2010

Bioleaching of silica from chromite ore by Aspergillus niger AB₂₀₀ is performed to increase the chromium concentration in low grade chromite ore. The present study discuss about the role of nutritional factors necessary for the growth as well as bioleaching of silica from chromite. Besides carbon and nitrogen sources, the organism require macro elements like KH₂PO₄, KCI, MgSO₄.7H₂O, NaH₂PO₄ for their proper growth and silica bioleaching. Withdrawal of these elements from the fermentation media shows a significant decrease in both growth and bioleaching process. Elements like NaCI, CaCI₂ were found to have no significant effect on growth of the organism and bioleaching process. Among the micro elements, Fe²+ and Mn²+ showed a significant increase in the bioleaching of silica from chromite ore. zn2+, Nil+ (below 10 μg/ml) concentration and Cu²+ (below 5 μg/ml) were found to have no significant effect, but with increase in concentration, all three elements were found to inhibit growth and bioleaching. Co²+, Mo⁶+, v³+ were found to have no significant role in this process. After optimization of the fermentation media (glucose - 10%, NaNO₃ - 0.2%, KH₂PO₄ - 0.1%, KCI - 0.05%, MgSO₄.7H₂O - 0.06%, Naii2P04 - 0.05%, FeSO4.71120 - 15 )μg/ml, ·MnSO₄.H₂O- 10 μg/ml), 73.76% silica was found to be leached out from the ore.