Volatilization mercury (II) into mercury (0) using crude enzyme produced by a mercury-resistant Azotobacteria
Mercury was poisonous and hazardous heavy metal, even one genus bacteria of Azotobacter was able to grow in a mercury contaminated habitat. This research aim was to select potential mercury resistant Azotobacter which was able to produce an extracellular mercury reductase for reducing toxic ion Hg2+ into a volatile less toxic ion Hg0. The isolates were A1a, A5 and A9 from an urban farming soil in ITS. Their viability under mercury stress was tested individually in an Azotobacter-selective agar each containing 0.1; and 5 mg/L HgCl2. The 24-hours bacterial growth was spectrophotometrically determined at λ600 nm each hour. The crude extracellular mercury reductase produced under 5mg/L dan 10mg/L HgCl2 stress was then extracted followed general method. The enzyme activity was spectrophotometrically measured at 340 nm to detect soluble oxidized NADH in a defined medium for a mercury reductase assay after 12 hours incubation. The viability test showed that those 3 isolates had a similar growth curve pattern; all of them were growing under 0.1; and 5 mg/L HgCl2, even after 12 hours incubation time they were start dying. Anyhow isolate A1a was the slowest growing Azotobacter under particular mercury stress. Enzyme activity tended to decrease over time; isolates A5 and A9 showed a greater enzyme activity than isolate A1a. Under 5mg/L HgCl2 stress, after 30, 60 and 120 minutes, isolate A5 and A9 produced 2.50U, 1.15U and 0.60U enzyme respectively, while under 10mg/L HgCl2 they were 2.70U, 1.44U and 0.7U.
Keywords: Azotobacter, HgCl2, mercuric reductase, reduction
Enny Zulaika, Anjar Lulu Sakinah, Kusnul Khotimah, Nengah Dwianita Kuswytasari, Nurhidayatul Alami, Nita Citrasari, Langkah Sembiring, Maya Shovitri. Volatilization mercury (II) into mercury (0) using crude enzyme produced by a mercury-resistant Azotobacteria. Acta Scientiae et Intellectus, 2(3)2016, 29-36.
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