# DBT JRF 2020 — Question 13

Exam: DBT JRF 2020 · Section: B · Topic: Biotechnology · Difficulty: Medium

## Question

A major organism used in commercial bioleaching for copper recovery is

## Options

- **A.** Pseudomonas aeruginosa
- **B.** Aspergillus niger
- **C.** Desulfovibrio desulfuricans
- **D.** Thiobacillus ferrooxidans

## Answer

Option D

## Explanation

Acidithiobacillus ferrooxidans (previously Thiobacillus ferrooxidans) is a chemolithoautotrophic Gram-negative bacterium central to commercial bioleaching. It oxidises: (1) $\text{Fe}^{2+} \rightarrow \text{Fe}^{3+}$ (iron oxidation); (2) Reduced sulfur compounds ( $\text{S}^0, \text{S}_2\text{O}_3^{2-}$ ) → $\text{SO}_4^{2-}$ (sulfur oxidation), generating $\text{H}_2\text{SO}_4$ . $\text{Fe}^{3+}$ oxidises metal sulfides (e.g. $\text{CuFeS}_2$ ) releasing $\text{Cu}^{2+}$ into solution for downstream extraction. This process is used industrially at mine tailings and low-grade ore deposits. A. ferrooxidans thrives at pH 1–2 and 30–40°C — conditions created by its own acid production.

Source: https://mypyqbuddy.com/questions/a-major-organism-used-in-commercial-bioleaching-for-6a05a8a02adafec470293225