Abstract
Two Pantoea anthophila bacterial strains were isolated from “tejuino”, a traditional Mexican beverage, and studied as β-galactosidase producers for galactooligosaccharides synthesis. Using 400 g/L of lactose, 50 °C, and 15 U/mL of β-galactosidase activity with ethanol-permeabilized cells, the maximum galactooligosaccharides (GOS) yield determined by High performance anion exchange chromatography with pulse amperometric detection (HPAEC-PAD) was 136 g/L (34% w/w of total sugars) at 96% of lactose conversion for Bac 55.2 and 145 g/L (36% w/w of total sugars) at 94% of lactose conversion for Bac 69.1. The main synthesized products were the disaccharides allolactose [Gal-β(1 → 6)-Glc] and 6-galactobiose [Gal-β(1 → 6)-Gal], as well as the trisaccharides 3′-galactosyl-lactose [Gal-β(1 → 3)-Gal-β(1 → 4)-Glc], 6-galactotriose [Gal-β(1 → 6)-Gal-β(1 → 6)-Gal], 3′-galactosyl-allolactose [Gal-β(1 → 3)-Gal-β(1 → 6)-Glc], and 6′-galactosyl-lactose [Gal-β(1 → 6)-Gal-β(1 → 4)-Glc]. The β-galactosidases present in both strains showed a high transgalactosylation activity and formed principally β(1 → 3) and β(1 → 6) linkages. Considering the stability and bifidogenic properties of GOS containing such types of bonds, P. anthophila strains Bac 55.2 and Bac 69.1 possess a high potential as novel biocatalysts for prebiotic industrial production.
Highlights
A growing interest has been observed in β-galactosidases with transgalactosylation activity for the commercially available production of galactooligosaccharides (GOS), which are added-value lactose derivatives [1]
The enzyme β-galactosidase (EC 3.2.1.23) hydrolyze the terminal non-reducing β-D-galactose in β-D-galactosides. This enzyme can perform the transgalactosylation reaction in which the donor is transferred to a nucleophilic acceptor different than water; almost any sugar present in the reaction medium can act as an acceptor of galactose, resulting in its elongation to a higher degree of polymerization, forming different
In this type of spontaneous fermentations, it has been isolated a wide variety of microorganisms such as lactic acid bacteria (LAB) and non-LAB fungi and yeasts [29]
Summary
A growing interest has been observed in β-galactosidases with transgalactosylation activity for the commercially available production of galactooligosaccharides (GOS), which are added-value lactose derivatives [1]. Traditional corn fermentations could be a source of these enzymes, such as the case of Tejuino, which is a traditional Mexican beverage produced from the 2–3 days fermentation of natural nixtamal (maize dough obtained by milling heat treated maize with lime), mixed with water and brown sugar cane [28]. In this type of spontaneous fermentations, it has been isolated a wide variety of microorganisms such as lactic acid bacteria (LAB) and non-LAB fungi and yeasts [29]. Since the reaction mixtures typically contain numerous oligosaccharides varying in DP and glycosidic linkages, a kinetic study of the transgalactosylation reaction was carried out and the structure of synthesized GOS was analyzed
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