RESUMO
Mandatory fortification of foods with folic acid is being questioned by many scientists principally because of the potential adverse secondary effects associated with their excessive consumption. It has been shown that selected strains of lactic acid bacteria (LAB) are able to produce natural forms of folate and these could be included in foods to prevent deficiencies without causing adverse effects. The aim of this study was to evaluate folate production and fol gene expression by Streptococcus gallolyticus subsp. macedonicus (S. macedonicus) CRL415 under different growth conditions in vitro and to assess its potential probiotic application. Results showed that glucose as the principal carbon source, and incubation at 42⯰C under controlled pH conditions (6.0) increased folate production, fol gene expression, and growth of S. macedonicus CRL415. This strain was able to produce elevated folate concentrations during milk fermentation without the need of prolonged incubation times and was able to resist conditions simulating the gastrointestinal tract. In addition, S. macedonicus was susceptible to all required antibiotics, and had a good adhesion level to intestinal cells in vitro, making it a promising candidate for biotechnological application as functional starter cultures in the dairy industry.
Assuntos
Ácido Fólico/biossíntese , Probióticos/metabolismo , Streptococcus/metabolismo , Ácido 4-Aminobenzoico/metabolismo , Animais , Antibacterianos/farmacologia , Aderência Bacteriana , Bile , Células CACO-2 , Produtos Fermentados do Leite/análise , Produtos Fermentados do Leite/microbiologia , Ácido Fólico/genética , Suco Gástrico , Regulação Bacteriana da Expressão Gênica , Glucose/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Streptococcus/genética , Streptococcus/crescimento & desenvolvimento , TemperaturaRESUMO
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.
Assuntos
Genes Bacterianos , Lactobacillus plantarum/genética , Lactobacillus plantarum/metabolismo , Riboflavina/biossíntese , Aminoácidos/metabolismo , Proteínas de Bactérias/genética , Meios de Cultura/química , Fermentação , Guanosina/metabolismo , Lactobacillus plantarum/efeitos dos fármacos , Mutação , Nucleotidiltransferases/genética , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Leite de Soja/metabolismo , Sacarose/metabolismoRESUMO
Lactobacillus delbrueckii subsp. bulgaricus CRL871 is the first strain of L. delbrueckii subsp. bulgaricus reported as a folate-producing strain. We report the draft genome sequence of L. delbrueckii subsp. bulgaricus CRL871 (2,063,981 bp, G+C content of 49.1%). This strain is of great biotechnological importance to the dairy industry because it constitutes an alternative to folic acid fortification.
RESUMO
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.
Assuntos
Ácido Fólico/biossíntese , Microbiologia de Alimentos , Lactobacillus/metabolismo , Iogurte/microbiologia , Animais , Técnicas de Cocultura , Fermentação , Ácido Fólico/análise , Lactobacillus/crescimento & desenvolvimento , Camundongos , Leite/microbiologia , Streptococcus thermophilus/metabolismo , Iogurte/análiseRESUMO
Folate is a B-group vitamin that cannot be synthesized by humans and must be obtained exogenously. Although some species of lactic acid bacteria (LAB) can produce folates, little is known about the production of this vitamin by yogurt starter cultures. Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were isolated from artisanal Argentinean yogurts and were grown in folate-free culture medium (FACM) and nonfat milk after which intracellular and extracellular folate production were evaluated. From the initial 92 isolated LAB strains, 4 L. delbrueckii subsp. bulgaricus and 32 S. thermophilus were able to grow in the absence of folate. Lactobacillus delbrueckii subsp. bulgaricus CRL 863 and S. thermophilus CRL 415 and CRL 803 produced the highest extracellular folate levels (from 22.3 to 135 µg/L) in FACM. In nonfat milk, these strains were able to increase the initial folate concentrations by almost 190%. This is the first report where native strains of L. delbrueckii subsp. bulgaricus were shown to produce natural folate. The LAB strains identified in this study could be used in developing novel fermented products bio-enriched in natural folates that could in turn be used as an alternative to fortification with the controversial synthetic chemical folic acid.