Dechlorination of chlorophenols using extracellular peroxidases produced by Streptomyces albus ATCC 3005

Streptomyces albus ATCC 3005 was found to produce higher levels of extracellular peroxidase activity (3.420 U mg(-1)) than previously reported for any other actinomycete. Maximum peroxidase activity was obtained after 72 h of incubation at a temperature of 30 degreesC in a liquid medium (pH 7.6) containing (in w/v) 0.8% to 0.9% oat spelts xylan and 0.6% yeast extract, corresponding to a C:N ratio of around 8.4:1. Characterization of the peroxidases revealed that the optimal temperature for peroxidase activity, using the standard 2,3-dichlorophenol (2,4-DCP) assay was 53 degreesC, when the enzyme reaction was performed at pH 7.2. A study of the effect of temperature on the stability of peroxidase over time, showed that the enzyme was stable at 40 degreesC, with a half-life of 224 min, while at higher temperatures the stability and activity was reduced such that at 50 degreesC and 70 degreesC the half-life of the enzyme was 50 min and 9 min respectively. The optimum pH for the activity of the enzyme occurred between pH 8.1 and 10.4. In terms of substrate specificity, the peroxidase was able to catalyze a broad range of substrates including 2,4-DCP, L-3,4-dihydroxyphenylalanine (L-DOPA), 2,4,5-trichlorophenol and other chlorophenols in the presence of hydrogen peroxide. Ion exchange chromatography was used to confirm that the enzyme was able to release chloride ions from a range of chlorophenols. (C) 2001 Elsevier Science Inc. All rights reserved.