Hydrolysis of Lactose and Transglycosylation of Selected Sugar Alcohols by LacA β-Galactosidase from Lactobacillus plantarum WCFS1

Abstract

The production, biochemical characterization and carbohydrate specificity of LacA βgalactosidase (locus lp_3469) belonging to the Glycoside Hydrolase family 42 from the probiotic organism Lactobacillus plantarum WCFS1 is addressed. The β-Dgalactosidase activity was maximal in the pH range of 4.0-7.0 and 30-37 ºC. High hydrolysis capacity towards the β (1 → 4) linkages between galactose and glucose (lactose) or fructose (lactulose) was found. High efficiency towards galactosylderivatives formation was observed when lactose and glycerol, xylitol or erythritol were used. Galactosyl-derivatives of xylitol were characterized for the first time as 3-O-β-Dgalactopyranosyl-xylitol and 1-O-β-D-galactopyranosyl-xylitol displaying the great preference of LacA β-galactosidase for the transfer of galactosyl residues from lactose to the C1 or C3 hydroxyl group of xylitol. These results indicate the feasibility of using LacA β-galactosidase for the synthesis of different galactosyl-polyols, which could be promising candidates for beneficial and appealing functional and technological applications such as novel prebiotics or hypocaloric sweeteners.

Production and Digestibility Studies of β-Galactosyl Xylitol Derivatives Using Heterogeneous Catalysts of LacA β-Galactosidase from Lactobacillus Plantarum WCFS1

“…The synthesis of β-galactosyl xylitol derivatives was done using the optimal derivative (agarose-IDA-Zn-CHO) compared to the soluble enzyme. The chromatographic profile shows the production of different compounds derived from lactose and xylitol as starting materials (Figure 3) as was previously optimized for the soluble enzyme [16], demonstrating the production of galactosyl-derivatives from xylitol (peaks 5 and 6) apart from the lower presence of GOS di-(peaks 8) and trisaccharides (peaks 9) derived from lactose. The obtained derivatives of LacA β-galactosidase from the impure protein extracts had the same properties (activity and stability) as those immobilized using the previously purified enzyme.…”

“…As it has already been mentioned, in addition to lactose hydrolysis, yielding glucose and galactose, transgalactosylation takes place giving rise to new oligosaccharides derived from xylitol due to its capacity to accept galactose units. Two main compounds were obtained corresponding to the previously characterized structures of 3-O-β-D-galactopyranosyl-xylitol (galactosyl xylitol 1, peaks 5) and (2R) and (2S))-1-O-β-galactopyranosyl-xylitol (galactosyl xylitol 2, peaks 6) [16] at concentrations of 13.7 and 44.8 g/L for the soluble enzyme, and 14.1 and 53.6 for the immobilized derivative (Table 1). Considering that xylitol is five times in excess, the yields considering galactopyranosyl-xylitol derivatives was 32 and 37% using the soluble and immobilized enzyme, respectively.…”

“…Synthesis of β-galactosyl xylitol derivatives was performed using the soluble and immobilized enzyme in a final volume of 2 mL, according to the optimal conditions obtained from previous studies [16]. Briefly, reactions were carried out for 48 h using lactose as donor (200 g L −1 ) and xylitol as acceptor (450 g L −1 ) using 1 mL of β-galactosidase (A = 4.32 U mL −1 of enzyme), in 50 mM sodium phosphate buffer (pH 6.5).…”

“…This transgalactosylation process results in the formation of different compounds with a β-configuration, which gives them certain prebiotic properties of food or nutritional interest. Recently, the production of β-galactosyl xylitol derivatives has been described using a soluble LacA β-galactosidase from a microorganism from human microbiota such as Lactobacillus plantarum WCFS1 [16].…”

Galactosyldiacylglycerols: From a Photosynthesis-Associated Apparatus to Structure-Defined In Vitro Assembling

“…(2) Engineering of glucosidase/galactosidase or glucosyltransferase/galactosyltransferase for in vitro assembling of MGDG and DGDG: In this respect, our joint research 143 and other research groups 142,148,149 are progressing in identifying new enzymes and engineering them for glycosylation and transgalactosylation.…”