| Abstrakt: |
Streptomyces albusATCC 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°C 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 2,4-dichlorophenol (2,4-DCP) assay was 53°C, 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°C, with a half-life of 224 min, while at higher temperatures the stability and activity was reduced such that at 50°C and 70°C 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. |
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