Study on heavy metals toxicity biomarkers in Aspergillus niger

Aspergillus niger has shown production of metal chelating compounds mainly oxalic acid and citric acid. Production of oxalic acid by Aspergillus niger was found maximum in presence of Pb, followed by Cu+Pb and Cu. With increase in concentration of Pb to 50, 100 and 250 mg/L, the production of oxalic acid was increased. Whereas increase in concentration of Cu+Pb and Cu, resulted in decreased production of oxalic acid. Except Cu+Pb, the production of citric acid was increased with increase in Pb and Cu concentration. Increased synthesis of proline, malondialdehyde and catalase enzymes by metal treated A. niger indicates its significance in heavy metals detoxification. Catalase activity increased with increase in metal concentration up to 100 mg/L. Synthesis of malondialdehyde (MDA) was increased up to 100 mg/L metal concentration after 96 hr of growth period. Increased proline content was observed in A. niger treated with Pb compared to Cu and Cu+Pb.