Enhancement of alpha- and beta-galactosidase activity in Lactobacillus reuteri by different metal ions

The hydrolysis of oligosaccharides and lactose is of great importance to the food industry. Normally, oligosaccharides like raffinose, stachyose, and verbascose which are rich in different plants like soy bean are considered indigestible by the human gut. Moreover, many humans suffer from lactose intolerance due to the absence of effective enzyme that can digest lactose. alpha-Galactosidase can digest oligosaccharides like raffinose, while beta-galactosidases can hydrolyze lactose. Therefore, selection of microorganisms safe for human use and capable of producing high levels of enzymes becomes an attractive task. The objective of this study was to investigate the enhancement of alpha- and beta-galactosidase activity in Lactobacillus reuteri by different metal ions. Ten millimolar of Na(+), K(+), Fe(2+), and Mg(2+) and 1 mM of Mn(2+) were added separately to the growth culture of six strains of L. reuteri (CF2-7F, DSM20016, MF14-C, MM2-3, MM7, and SD2112). Results showed that L. reuteri CF2-7F had the highest alpha- and beta-galactosidase activity when grown in the medium with added Mn(2+) ions (22.7 and 19.3 Gal U/ml, respectively). 0.0274% of Mn(2+) ions lead to 27, 18% enhancement of alpha- and beta-galactosidase activity over the control group, and therefore, it could be added to the growth culture of CF2-7F to produce enhanced levels of alpha- and beta-galactosidase activity. The addition of Fe(2+) led to a significant (P < 0.01) decrease in the activity of both enzymes for most strains. This study shows that modified culture medium with that 0.0274% Mn(2+) can be used to promote the production for alpha- and beta-galactosidase in L. reuteri CF2-7F, which may lead to enhancement of alpha- and beta-galactosidase activity and have a good potential to be used in the food industry.