Effect of different nutrients on riboflavin production and gene expression. by Lactobacillus plantarum CRL 725

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

Córdoba

Congreso; XI Congreso Argentino de Microbiología General - SAMIGE; 2015

Sociedad Argentina de Microbiología General - SAMIGE

Riboflavin (vitamin B2) participates in a wide variety of metabolic reactions that are essential for human life. In blood, this vitamin is found as the cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which act as electron carriers in oxidation?reduction reactions performing as coenzymes for flavoproteins such as, FMN- or FAD-dependent enzymes. The aim of this work was to evaluate the influence of temperature and certain components of a chemically defined medium on riboflavin production and gene expression by L. plantarum CRL 725. Chemically defined media (CDM) were prepared from concentrated individual stock solutions which were stored at -4°C after sterilized by filtration through cellulose acetate membranes (0.22um. L. plantarum CRL 725 was exposed to different carbohydrates (sucrose, lactose and glucose), which were added individually to CDM at a final concentration of 20 g/L, and different concentrations of sodium acetate, casamino acids, asparagine and guanosine. The incubation was carried out at 30 and 37ºC. Growth parameters (OD600 and cell viability), riboflavin production and the expression of vitamin B2 genes were evaluated. The total riboflavin concentration was determined using a microbiological assay and these results were confirmed by HPLC analysis. In respect to the influence of carbohydrates, L. plantarum CRL725 showed higher viability and growth rates with glucose (log 8.68, μ 0,651h-1 ) or sucrose (log 8.73, μ 0.758h-1 ) than with lactose (log 6.56 at 12 h). The riboflavin production in presence of sucrose was higher than that observed with glucose. The omission of casamino acids, affected both the cell growth in CDM and the vitamin production. The addition of guanosine at different concentrations had not effect on strain growth while at a concentration of 0.04 g/L it enhanced the riboflavin production reaching values of 2588,5 ± 250 ng/. Based on all of these results, the optimum conditions for growth and riboflavin production by L. plantarum CRL 725 were defined using CDM containing sucrose 2% (w/v) and guanosine 0.04 (g/L) and an incubation temperature of 30ºC. In optimized conditions, L. plantarum CRL 725 was able to increase vitamin B2 production two fold respect to reference condition and this was directly associated with significant increases in riboflavin biosynthesis gene expression such as ribA, ribB and ribC (2.62; 2.36;2.28 fold increases, respectively). In this study, optimized parameters were defined that allow increased riboflavin production in a CDM. These observations could be employed to increase production of riboflavin not only in microbial growth media, but also in different food matrices.