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KMID : 1094720080130020210
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Biotechnology and Bioprocess Engineering
2008 Volume.13 No. 2 p.210 ~ p.216
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Enzymatic detection of heavy metal ions in aqueous solution from vegetable wastes by immobilizing pumpkin ( Cucumis melo ) urease in calcium alginate beads
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Prakash Om
Talat Mahe
Hasan S. H.
Pandey Rajesh K.
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Abstract
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Enzyme urease is extracted from the discarded seeds of pumpkin. Urease was purified to apparent homogeneity (5.2 fold) by heat treatment at 48 ± 1°C and gel filtration through Sephadex G-200. Effect of model metal ions on the activity of the homogeneous enzyme preparation (sp. activity 353 U/mg protein, A280/A260 = 1.12) of soluble as well as immobilized enzyme was investigated. The soluble and immobilized urease has been used for the quantitative estimation of general water pollution with heavy metal ions like Hg2+, Cu2+, Cd2+, and Co2+. The measurements of the urease residual activity have been carried out in tris-acetate buffer after pre-incubation of model metal salt. The inhibition was found to be biphasic with an initial rapid loss of activity and remainder in slow phase of 10∼15 min. The immobilization was done in 3.5% alginate beads leading to 86% of entrapment. There was no leaching of the enzyme over a period of 15 days at 4°C. The beads were fairly stable up to 50°C and exhibited activity even at ?10°C. The inhibition by these ions was non-competitive and irreversible, hence could not be restored by dialysis. Based on the values of inhibition constant Ki the heavy-metal ions were found to inhibit urease in the following order Hg2+ > Cu2+ > Cd2+ > Co2+.
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KEYWORD
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urease, pumpkin, Cucumis melo, immobilization, calcium alginate, inhibition
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