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ABSTRACT: The Indian leather industry, crucial for the economy, relies on chrome tanning, using 69,000 tons of chromium annually, with 39% ending up as hazardous waste. The non-biodegradable and toxic nature of released chromium poses health risks and contributes to soil contamination. Exploring extremophiles, especially thermophiles, for metal reduction shows promise for efficient bioremediation. The study aims to isolate and identify microorganisms efficient in hexavalent Cr (Cr6+) bioremediation, encountering two Cr6+ resistant thermotolerant isolates, MW50 and TJ100. The isolates MW50 and TJ100 could tolerate up to 700ppm and 600ppm of Cr6+ respectively. Atomic absorption spectroscopy (AAS) revealed MW50 to reduce 97.58% of 200ppm Cr6+, and TJ100 to reduce 90.26% 200ppm Cr6+. Also, the isolates were resistant to multiple heavy metals and antibiotics. The 16Sr RNA studies identified MW50 as Ochrobactrum anthropi and TJ100 as Bacillus aerius. MW50 showed extracellular chromate reductase activity. Crude form of the enzyme was extracted and studied for bioremediation. The enzyme was partially purified by ammonium sulphate precipitation, dialysis and, ion exchange chromatography, and its molecular weight was found to be 72 kDa by SDS PAGE. The DNA samples isolated from both the isolates showed the presence of chrA gene responsible for Cr bioremediation.
Manoranjitham et al. (Mon,) studied this question.