Cyanide-degrading enzymes for bioremediation

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Title: Cyanide-degrading enzymes for bioremediation
Author: Basile, Lacy Jamel
Abstract: Cyanide -containing waste is an increasingly prevalent problem in today's society . There are many applications that utilize cyanide , such as gold mining and electroplating , and these processes produce cyanide waste with varying conditions . Remediation of this waste is necessary to prevent contamination of soils and water . While there are a variety of processes being used , bioremediation is potentially a more cost effective alternative . A variety of fungal species are known to degrade cyanide through the action of cyanide hydratases , a specialized subset of nitrilases which hydrolyze cyanide to formamide . Here I report on previously unknown and uncharacterized nitrilases from Neurospora crassa , Gibberella zeae , and Aspergillus nidulans . Recombinant forms of four cyanide hydratases from N . crassa , A . nidulans , G . zeae , and Gloeocercospora sorghi were prepared after their genes were cloned with N -terminal hexahistidine purification tags , expressed in Escherichia coli and purified using immobilized metal affinity chromatography . These enzymes were compared according to their relative specific activity , pH activity profiles , thermal stability , and ability to degrade cyanide in the presence of high concentrations of copper and silver . Although all four were relatively similar , the N . crassa cyanide hydratase (CHT ) has the greatest thermal stability and widest pH range where activity remained above 50 % . N . crassa also demonstrated the highest rate of cyanide degradation in the presence of both metals tested . The CHT of A . nidulans and N . crassa have the highest reaction rate of the four fungal nitrilases evaluated in this work . These data help determine optimization conditions for the possible use of these enzymes in the bioremediation of cyanide -containing waste . Similar to known plant pathogenic fungi , in vivo expression of CHT in both N . crassa and A . nidulans were induced by growth in the presence of KCN (potassium cyanide ) .
URI: http : / /hdl .handle .net /1969 .1 /86035
Date: 2008-10-10

Citation

Cyanide-degrading enzymes for bioremediation. Available electronically from http : / /hdl .handle .net /1969 .1 /86035 .

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