SCREENING OF β-GALACTOSIDASE ACTIVITY OF ARGENTINIAN LACTIC ACID BACTERIA FOR SYNTHESIS OF PREBIOTIC OLIGOSACCHARIDES FROM LACTOSE (GOS) AND LACTULOSE (OsLu)

SABATER, C.; MONTILLA, A.; CORZO, N.; ZÁRATE G.; REQUENA, T.

San Miguel de Tucumán

Simposio; V Simposio Internacional de Bacterias Lácticas SIBAL 2016; 2016

CERELA-CONICET

The development of functional foods has received great attention from industry due to the high demand of healthy foods by consumers around the world. Among functional ingredients, probiotic microorganisms and prebiotic compounds have gained increasing interest by researchers. In this respect, β-D-galactosidase enzyme possesses a relevant technological value allowing hydrolysis of lactose in dairy products for intolerant population. Also, β-D-galactosidases are used to synthesize prebiotic galactooligosacharides (GOS) by transgalactosylation reactions. GOS are non-digestible carbohydrates that modulate the colonic microflora in a healthy manner and also have application as functional ingredients. However, depending on the origin of the enzyme and reaction conditions different amounts of GOS and linkages between D-galactose units may be formed which in turn could affect their properties and prebiotic potential. Then, in the present work we screened the β-D-galactosidase activity of 36 strains of potential probiotic lactic acid bacteria (LAB) isolated from Argentinean foods in order to select the most appropriate strains for GOS and oligosaccharides derived from lactulose (OsLu) synthesis. As a first step, strains were grown in media with lactose as sole carbon source in order to determine the presence or induction of the enzyme in different microorganisms. Then, suspensions of LAB that showed growth were mechanically disrupted and cell free extracts were assayed for specific enzyme activity by a colorimetric method with ONPG as substrate. Synthesized GOS and OsLu were determined by GC-FID and HPLC-RID. According to the results obtained, 28 strains (78%) were able to grow on lactose medium and were assayed for their β-D-galactosidase activity which ranged from 0.01 to 2.55 U/mg protein. Three Lactobacillus strains (L. delbrueckii subsp. bulgaricus CRL 450, L. paracasei CRL 200 and L. plantarum GS30) with the highest activities were selected to assess their ability to synthesize the oligosaccharides from 30% (w/v) lactose or lactulose solutions at pH 6.5, 45 °C, for 48 h of incubation. All microorganisms were able to produce GOS and OsLu (di-, tri- and tetrasaccharides) in the range of 23-38% from lactose and 16-24% from lactulose in relation to the total sugars present in reaction mixtures. L. delbrueckii subsp. bulgaricus CRL 450 and L. paracasei CRL 200 were the most efficient strains producing 38% of GOS and 24% of OsLu, respectively, showing higher β-D-galactosidase activity than Lactozym (commercial enzyme of Kluyveromyces lactis) used as control. Our results show by the first time production of GOS and OsLu by L. delbrueckii subsp. bulgaricus and L paracasei and encourage further studies on the optimization of synthesis and structure characterization of the oligosaccharides obtained.