Production of riboflavin by L. plantarum CRL725 in soymilk. Influence of environmental pH conditions

M. JUAREZ DEL VALLE; J.E. LAIÑO; G. SAVOY DE GIORI; J.G. LEBLANC

San Miguel de Tucumán

Simposio; IV Simposio Internacional de Bacterias Lácticas: Alimentos, Salud y Aplicaciones; 2013

Centro de Referencia para Lactobacilos (CERELA-CONICET)

Soymilk, the water extract of soybean, is a rich source of high quality proteins, amino acids, unsaturated fatty acids and isoflavones. Soymilk contains sucrose as the main carbohydrate source, which makes it a good alternative from milk for lactose-intolerant people. However, soymilk contains low concentrations of B-group vitamins such as riboflavin. Riboflavin (vitamin B2) is important water-soluble vitamin available only through food intake, because humans lack the ability to synthesize it. Vitamin B2 is the precursor of two co-enzymes: flavin mononucleotide (FAD) and flavin adenin dinucleotide (FMN) that regulate the activity of many different metabolic enzymes of the redox pathways associated with energy production. Although riboflavin is found in a wide variety of foods, subclinical deficiency of riboflavin is common in many parts of the world, even in highly industrialized countries. Some lactic acid bacteria (LAB) have ability to produce riboflavin but it production depends on the strain used and the culture conditions. The ability of riboflavin production by 180 strains of LAB, belonging to CERELA culture collection, was evaluated using a commercial riboflavin-free growth medium. Only 43 strains were able to grow in this broth without the exogenous addition of riboflavin, and the vitamin production was evaluated by a microbiological method using Lactobacillus (L.) rhamnosus ATCC7469 as the indicator strain. L. plantarum CRL 725 was able to grow and increase 2.3 times the riboflavin concentration in soymilk (300ng/ml). In this study, the influence of controlled and uncontrolled pH conditions on riboflavin production by L. plantarum CRL 725 during soymilk fermentation was evaluated. The highest riboflavin production (900ngB2/mL) was achieved after 8 h of incubation under controlled pH (pH 6.0) whereas lower values were obtained during fermentation both at controlled pH of 5.0 or uncontrolled pH. These results showed that the ability of L. plantarum CRL 725 to produce riboflavin in soymilk is influenced by the environmental pH conditions. This strain could be used to obtain soy foods enriched in riboflavin, taking into account the growth conditions of this substrate.