Factors stimulating riboflavin produced by Lactobacillus plantarum CRL 725 grown in a semi-defined medium.

Riboflavin (vitamin B2 ) is one of the B-group water-soluble vitamins and is essential for energy metabolism of the cell. The aim of this study was to determine factors that affect riboflavin production by Lactobacillus (L.) plantarum CRL 725 grown in a semi defined medium and evaluate the expression of its rib genes. The factors found to enhance riboflavin production in this medium were incubation at 30 °C, and the addition of specific medium constituents, such as casamino acids (10 g L-1 ), guanosine (0.04 g L-1 ), and sucrose as carbon source (20 g L-1 ). In these conditions, higher riboflavin concentrations were directly associated with significant increases in the expression of ribA, ribB, and ribC genes. The culture conditions defined in this work and its application to a roseoflavin resistant mutant of L. plantarum allowed for a sixfold increase in riboflavin concentrations in our semi-defined medium which were also significantly higher than those obtained previously using the same strain to ferment soymilk. These conditions should thus be evaluated to increase vitamin production in fermented foods.

Relationships between the genome and some phenotypical properties of Lactobacillus fermentum CECT 5716, a probiotic strain isolated from human milk.

Lactobacillus fermentum CECT 5716, isolated from human milk, has immunomodulatory, anti-inflammatory, and anti-infectious properties, as revealed by several in vitro and in vivo assays, which suggests a strong potential as a probiotic strain. In this work, some phenotypic properties of L. fermentum CECT 5716 were evaluated, and the genetic basis for the obtained results was searched for in the strain genome. L. fermentum CECT 5716 does not contain plasmids and showed neither bacteriocin nor biogenic amine biosynthesis ability but was able to produce organic acids, glutathione, riboflavin, and folates and to moderately stimulate the maturation of mouse dendritic cells. No prophages could be induced, and the strain was sensitive to all antibiotics proposed by European Food Safety Authority (EFSA) standards, while no transmissible genes potentially involved in antibiotic resistance were detected in its genome. Globally, there was an agreement between the phenotype properties of L. fermentum CECT 5716 and the genetic information contained in its genome.

Applicability of a Lactobacillus amylovorus strain as co-culture for natural folate bio-enrichment of fermented milk.

The ability of 55 strains from different Lactobacillus species to produce folate was investigated. In order to evaluate folic acid productivity, lactobacilli were cultivated in the folate-free culture medium (FACM). Most of the tested strains needed folate for growth. The production and the extent of vitamin accumulation were distinctive features of individual strains. Lactobacillus amylovorus CRL887 was selected for further studies because of its ability to produce significantly higher concentrations of vitamin (81.2 ± 5.4 µg/L). The safety of this newly identified folate producing strain was evaluated through healthy experimental mice. No bacterial translocation was detected in liver and spleen after consumption of CRL887 during 7 days and no undesirable side effects were observed in the animals that received this strain. This strain in co-culture with previously selected folate producing starter cultures (Lactobacillus bulgaricus CRL871, and Streptococcus thermophilus CRL803 and CRL415) yielded a yogurt containing high folate concentrations (263.1 ± 2.4 µg/L); a single portion of which would provide 15% of the recommended dietary allowance. This is the first report where a Lactobacillus amylovorus strain was successfully used as co-culture for natural folate bio-enrichment of fermented milk.