Abstract

Aspergillus repens isolated from cultivated soils released pectinmethylesterase (PME) into the liquid culture medium during growth. The enzyme preparation was partially purified by ammonium sulphate precipitation and dialysed. The ammonium sulphate-dialysate fraction of the enzyme was separated by molecular exclusion and ion exchange chromatography. The molecular weight of the enzyme was found to be 141,300 daltons. The optimum temperature for PME activity was 30^oC and most active at pH 6.5. The activity of the enzyme was stimulated by Na⁺, K⁺, Ca²⁺, Mg²⁺ and Zn²⁺, while EDTA, PbCl₂, HgCl₂ and IAA inhibited enzyme activity. The activity of the enzyme increased with increase in substrate concentration reaching maximum at 4 mg/ml. The Lineweaver-Burk plot for the hydrolysis of pectin indicated approximately 1.3 mg/ml. These qualities could be explored during the industrial applications of this enzyme.

Key words: Cultivated soils, pectimethylesterase, temperature, enzyme, fraction.