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Eur Food Res Technol (2013) 236:817826 DOI 10.1007/s00217-013-1938-5
ORIGINAL PAPER
Lactobacillus plantarum 70810 from Chinese paocai as a potential source of b-galactosidase for prebiotic galactooligosaccharides synthesis
Hongzhi Zhang Wei Li Xin Rui
Xingmin Sun Mingsheng Dong
Received: 2 December 2012 / Revised: 28 January 2013 / Accepted: 1 February 2013 / Published online: 5 March 2013 Springer-Verlag Berlin Heidelberg 2013
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.
Keywords Lactobacillus plantarum 70810
b-Galactosidase Chinese paocai Transgalactosylation
Galactooligosaccharides
Introduction
A prebiotic is dened as a nondigestible food ingredient that benecially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon and thus improves host health [1]. Generally, these food ingredients are specic types of dietary oligosaccharides. Galactooligosaccharides (GOS) together with fructooligosaccharides and lactulose are the few well-proven prebiotics in vitro and in vivo in human studies [2, 3]. GOS are known as the most promising functional food ingredients not only for their prebiotic effects but also for their other favorable characteristics such as the acid stability, low caloric value, excellent taste quality and relatively low sweetness [3, 4]. Usually, GOS are dened as a mixture of oligosaccharides comprising of two...