Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
β-Galactosidase is an enzyme that catalyzes the hydrolysis of lactose. It has potential importance due to various applications in the food and dairy industries, involving lactose-reduced ingredients. The properties of two β-galactosidase enzymes, crude and purified, from different sources, Kluyveromyces marxianus CCT 7082 and Kluyveromyces marxianus ATCC 16045, were analyzed. The pH and temperature optima, deactivation energy, thermal stability and kinetic and thermodynamic parameters were determined, as well as the ability to hydrolyze lactose and produce galactooligosaccharides. Purification process improved the properties of the enzymes, and the results showed that purified enzymes from both strains had a higher optimum temperature, and lower values of Km, thus showing greater affinity for o-nitrophenyl-β-D-galactopiranoside than the crude enzymes. The production of galactooligosaccharides was also greater when using purified enzymes, increasing the synthesis by more than 30 % by both strains.β-Galaktozidaza je enzim koji katalizira hidrolizu laktoze. Primjenjuje se u prehrambenoj i mliječnoj industriji za dobivanje proizvoda sa smanjenim udjelom laktoze. U ovom su radu ispitana svojstva dvaju enzima, sirove i pročišćene β-galaktozidaze, dobivenih iz sojeva kvasca Kluyveromyces marxianus CCT 7082 i Kluyveromyces marxianus ATCC 16045. Određeni su sljedeći parametri: optimalna pH-vrijednost i temperatura, energija deaktivacije, termička stabilnost, kinetički i termodinamički parametri, te sposobnost enzima da hidrolizira laktozu i proizvede galaktooligosaharide. Pročišćavanjem su poboljšana svojstva enzima, što je vidljivo iz rezultata; pročišćeni enzimi iz oba soja imali su višu optimalnu temperaturu i niže vrijednosti Km, te veću specifičnost prema o-nitrofenil-β-D-galaktopiranozidu od sirovih enzima. Također je povećana proizvodnja galaktooligosaharida, i to za 30 % pomoću oba soja
