HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Goncalves, J. A. Articles by Castillo, F. J. Search for Related Content PubMed Articles by Goncalves, J. A. Articles by Castillo, F. J.

Partial Purification and Characterization of ß-D-Galactosidase from Kluyveromyces marxianus

Laboratorio de Fermentacion, Centro de Microbiologia y Biologia Celular, Instituto Venezolano de Investigaciones Cientificas, Apdo, 1827 Caracas 1010A, Venezuela

ABSTRACT

Optimal conditions for lactase extraction with 2% chloroform from the yeast Kluyveromyces marxianus NCYC 111 grown on whey included pH 6.8, 25°C, and 10 h of treatment. The enzyme was purified 11-fold after acetone and ammonium sulfate precipitations. The molecular weight was 280,000. Optimum pH and temperature for enzyme activity were 6.2 and 45 to 52°C. The enzyme was inactivated in 4 min at 56°C and retained 50% of its activity after 90 min at 50°C. Michaelis-Menten constants were 3.1 mM on o-nitrophenyl-ß-D-galac-topyranoside and 25 mM on lactose. Hydrolysis o-nitrophenyl-°-D-galactopy-ranoside was inhibited competitively by methyl-°-D-galactoside (inhibition constant 58 mM), galactose (110 mM), ribose (111 mM), and lactose (52 mM). P-chloromercuribenzoate inhibited non-competitively, and its activity was blocked by dithiothreitol, indicating sulphydryl groups in the enzyme and their possible involvement in lactase activity. The enzyme (at .59 mg protein/ml) hydrolyzed 50% of the lactose in milk and whey solutions at 6% of concentration in 5 h at 37°C. Kluyveromyces marxianus represents a potential source of lactase for reduction of lactose in milk and sweet whey.