Abstract

ARAUJO, Karelen et al. Effect of lactose concentration on the grow kinetics of Kluyveromyces marxianus var. marxianus and production of b-D-galactosidase (E.C. 3.2.1.23). Rev. Téc. Ing. Univ. Zulia [online]. 2007, vol.30, n.1, pp.64-73. ISSN 0254-0770.

Abstract The effect of lactose concentration on the kinetics of growth of Kluyveromyces marxianus var. marxianus ATCC 8554 and production of enzyme b-D-galactosidase in cheese whey previously deproteinized was studied. The assays were carried out to lactose concentrations of 4.72%, 8.5%, 12.6% and to pH of 5 and temperature of 35°C, in a bioreactor Bioflo 4000 with a volume work of 3 liters. The enzymatic activity was determined evaluating hydrolysis of o-nitrophenil-b-D-galactopiranoside (ONPG) and the extraction of the enzyme from the cell was realized through ultrasound treatment. The maximum activity, 384.42 ± 13.11 µmol ONP/L/5minutos was obtained in the non concentrated cheese whey (4.72%). The greater concentration of biomass and the highest specific speeds of growth were obtained in the non concentrated cheese whey (4.72%), and were 19.68 ± 0.004 kg/m³ and 0.29 h^-1 ± 0,006 respectively. The results showed a decrease in enzyme activity at high concentration of lactose, despite the fact that this carbohydrate is normally used for induction of b-D-galactosidase activity

Keywords : Lactose; b-D-galactosidase; grow kinetics of Kluyveromyces marxianus var; marxianus.