Sustainable Copper Extraction Using Synthetic Biology

Copper extraction from low-grade ores such as chalcopyrite is becoming increasingly important owing to the high demand of copper, rising cost of metals, and evasive high-grade ores. Bioleaching of chalcopyrite by Iron and Sulfur oxidizing consortia addresses many problems in these regard. However, the mesoacidic conditions conducive for these consortia bestows a development of passivation layer that prevents further leaching from the ore. A proprietary catalyst developed by participating company aids in the removal of this passivation layer. Interestingly, however, the microbial activity and thus the leaching rate is reduced in the presence of this catalyst. This study investigates the shift in the microbial community as well as a global meta-transcriptomic response following exposure to catalysts in sub-toxic dosages using 16S rRNA experiment and whole genome meta-transciptomic sequencing. A mixed culture consisting of Acidithiobacillus ferroxidans, Leptospirillum ferroxidans and Thiobacillus thiooxidans are first cultured in 9k media with and without the catalyst and harvested following exponential growth. The 16S rRNA and meta-transcriptomic sequencing is performed on the microbial community and its result is used to track the active microbial community as well as the differential gene expression following exposure to the catalyst. Our results suggest that 16S rRNA can be actively used to monitor population differentiation during growth with the catalyst and that different genes were differentially expressed during exposure to the catalyst. Some of these candidate genes can form basis for future genetic manipulation that will ultimately increase tolerance of microbes to the catalyst. The catalyst along with increased information of its impact on these 3 mixed microbial community could possibly be a game-changer for copper extraction in mining community.