Novel D-Galactose Isomerases from Lactobacillus Strains Isolated from the Sweet Sap of Agave atrovirens

Abstract

D-tagatose is a natural monosaccharide used as a low-calorie sugar substitute in food, beverage and pharmaceutical products. Although it is a rare sugar, it can manufacture by enzymatic isomerization of D-galactose Isomerase (D-GI). In this study, a screening was carried out to search microorganism producing D-GI in aguamiel. A rich selective medium was used in arabinose extracted from gum arabic. From 98 isolates obtained aguamiel of agave pulquero (Agave atrovirens), it was obtained 4 strains of Lactobacillus that producing D-GI and 2 strains of Bacillus sp. The Podi-20 strain was identified as Lactobacillus diolivorans based on 16S rRNA analysis, biological and biochemical characteristics. Furthermore, the gene encoding D-GI from L. diolivorans Podi-20 strain. Analysis of sequence revealed that the Open Reading Frame (ORF) of the araA gene consist of 1,428 pb that encodes a protein of 476 amino acid residues. The bioconversion yield of D-galactose to D-tagatose by the purified D-GI after 14 h at 60°C was 31.4%. D-tagatose can manufacture by enzymatic isomerization. This study contributes to new knowledge on D-GI from Lactobacillus strains, in particular those isolated from artisanal functional foods from Agave.