Purification and properties of a milk-clotting enzyme produced by Penicillium oxalicum

• Published in: Bioresource technology Vol. 75; no. 3; pp. 219 - 222
• Main Author: Hashem, Amal M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2000; Elsevier Science
• Subjects: Acetone; ascorbic acid; Biological and medical sciences; Cellulose; Chlorine compounds; chromatography; cobalt; Column chromatography; copper; culture filtrates; cysteine; cystine; EDTA (chelating agent); enzyme activity; Enzyme properties; enzymes; Ethanol; Food industries; Food microbiology; Fundamental and applied biological sciences. Psychology; magnesium; Methanol; Milk and cheese industries. Ice creams; milk clotting; Milk-clotting enzyme; Penicillium oxalicum; Penicillium sp; pH effects; Precipitation (chemical); proteolysis; Purification; sodium; Sodium compounds; sulfates; Milk-clotting enzyme; Penicillium sp; Purification; Enzyme properties; Enzyme; Clotting time; Chymosin; Temperature effect; Enzyme inhibitor; Penicillium oxalicum; Fungi; Peptidases; Enzymatic activity; Dairy industry; pH; Hydrolases; Aspartic endopeptidases; Fungi Imperfecti; Thallophyta
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/S0960-8524(00)00055-9

Partial purification of milk-clotting and caseinase enzymes, produced by Penicillium oxalicum, was achieved by fractional precipitation with acetone, ethanol and methanol. Of the fractions obtained by three precipitants, the 60–70% ethanol fraction was the most promising enzyme fraction and possessed the highest milk-clotting activity, which reached about ninefold that of the culture filtrate. Purification of the milk-clotting enzyme by DEAE-cellulose column chromatography afforded a rennin-like enzyme component that showed no proteolytic activity. The enzyme activity was maximum at pH 4.0–5.0 and 65°C. In absence of substrate and up to 50°C, the enzyme showed good stability and retained 80% of its original activity after 20 min. Cu 2+, Co 2+ and Mg 2+ had stimulating effects on enzyme activity. Ascorbic acid, sodium lauryl sulphate, cysteine hydrochloride, cystine and EDTA had partial inhibitory effects on the enzyme.