Content area
Abstract
A novel food-grade strain Lactobacillus plan-tarum 70810 producing b-galactosidase with high transgalactosylation activity was isolated from Chinese paocai. The galactooligosaccharides (GOS) were synthesized by using this enzyme with a maximum yield of 44.3 % (w/w) from 400 g/L lactose at 45 C for 10 h. The b-galactosidase from this strain was puried to homogeneity by ammonium sul-fate precipitation, anion exchange chromatography and gel ltration chromatography. It was a heterodimer arrangement of approximately 105 kDa composed of two subunits of 35 and 72 kDa. The optimal pH of the puried b-galactosidase was 8.0 for both o-nitrophenyl-b-D-galactopyranoside (oNPG) and lactose hydrolysis, and optimal temperature was 60 C and 55 C, respectively. Its Km and Vmax values for oNPG and lactose were 0.89 0.05 mM, 194 3.0 lmoL/min/mg protein, and 9.88 0.16 mM, 15.88 0.21 lmoL/min/mg protein, respectively. This enzyme was slightly inhibited by the hydrolysis products, that is, glucose and galactose. Since the b-galactosidase from L. plantarum 70810 exhibited higher transgalactosylation activity, strong afnity for lactose and low end-product inhibition, it was suggested to be a potential candidate for the synthesis of prebiotic GOS. [PUBLICATION ABSTRACT]