Producción de galactooligosacáridos potencialmente prebióticos por bacterias grado alimentario

ZÁRATE G.; FARA, A.; SABATER, C.; SÁEZ G.; MONTILLA, A.

IDITEC

EDUSPT

Lugar: San Pablo; Año: 2019 vol. 8 p. 3 - 17

2525-1597

Prebiotics are functional ingredients that enhance the growth and activity of beneficial bacteria in the gut, improving in this way the consumer?s health. Among them, non-digestible carbohydrates (NDC) and particularly galactooligosaccharides (GOS) have received special attention due to their biotechnological properties. GOS are mainly synthesized from lactose by a tranglycosilation reaction catalyzed by the β-galactosidase (β-gal) enzyme. Their monomers composition and linkages have influence on their selectivity and bioactivity so that the selection of the suitable enzymes is relevant. In the present work, we assessed the β-gal activity of a panel of lactic acid bacteria (LAB) and propionibacteria (PAB) from food in order to select the microorganisms with tranglycosidase activity for the synthesis of GOS with potential prebiotic effects. With this aim, the enzymes were extracted from the cultures grown at expense of lactose (ELC) and their hydrolytic activity was quantified by a colorimetric method with ONPG as substrate. P. acidipropionici LET 120 y L. bulgaricus CRL 450 displayed the highest specific activities (2.55±0.15 y 1.07±0.13 U/mg, respectively) and their β-gal were incubated with 300 g/L of lactose at pH 6.5 and 45 °C for 24 h and the oligosaccharides produced were quantified by HPLC-RID and GC-FID. Different environmental conditions (pH 5.0 to 7.0; 40 to 60 ºC, 1 to 2.5 U/mL and 0.5 to 10.5 h of reaction) were tested in order to optimize the synthesis. β-gal of L. bulgaricus CRL 450 synthesized 38,1- 48,4 % GOS and the double allolactose and 3?galactosyl-lactose concentration than the β-gal of P. acidipropionici LET 120, whereas this enzyme produced 23.8-26.8 % of GOS, higher concentration of 6-galactobiose and was the only one that synthesized 4´galactosyl-lactose. GOS were purified by adsorption on active charcoal followed by yeasts fermentation and were then used as carbon source for the growth of probiotic strains for assessing their prebiotic activity. LET 120-GOS were prebiotic for intestinal Bifidobacterium y Lactobacillus probiotic strains which encourage further studies about their structural characterization and physiological effect in the complex gut ecosystem.