Pectin lyase and polygalacturonase of Aspergillus niger pathogenic for yam tubers (Diascorea rotundata) |
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Authors: | S.K.C. Obi N.A. Moneke |
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Affiliation: | Department of Microbiology, University of Nigeria, Nsukka, Nigeria |
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Abstract: | Polygalacturonase and pectin lyase of Aspergillus niger partially purified by ethanol, ammonium sulphate precipitation, DEAE-cellulose and Sephadex G-150 column chromatography were characterized. Polygalacturonase gave optimum activity at pH 4–5, and at 35°C. It was stable at pH 3–7 and at 20–50°C. The molecular weight was 38020. For pectin lyase optimum activity occurred at pH 5 and 45°C. The enzyme was stable at pH 3–4 and at 40–50°C. The molecular weight was 30 900. Yam tissue was optimally macerated at pH 4–5 by the enzymes. At pH 4.5, potassium sorbate (0.6 mg/ml), benzoic acid (0.8 mg/ml) and sodium benzoate (1.0 mg/ml) caused complete inhibition of polygalacturonase activity. With pectin lyase, this effect was achieved with potassium sorbate and benzoic acid each at 0.9 mg/ml, but not with sodium benzoate. |
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Keywords: | Pectin lyase Polygalacturonase Yam tubers |
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