Folate production by Streptococcus thermophilus CRL803 in controlled and non-controlled pH conditions

J.E. LAIÑO; M. JUAREZ DEL VALLE; 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)

Folates play a key role in many metabolic pathways such as DNA and RNA synthesis. Folate deficiency is very frequent, reason for which many countries have adopted mandatory fortification programs; however, high intakes of folic acid (the synthetic form of folate used in fortification) can mask vitamin B12 deficiency, and alter the activity of the hepatic dihydrofolate reductase enzyme. These adverse health effects do not occurs with natural folates. In this study, the folate production by Streptococcus thermophilus CRL803 in low-folate culture medium was investigated during batch fermentations with uncontrolled pH and constant pH (6.0 and 5.0). This medium was based in LAPTg culture medium without yeast extract (the main source of folate). The temperature was maintained at 37ºC and the pH was kept automatically at 6.0 and 5.0 with 3 M NaOH. Samples were aseptically withdrawn at 0, 2, 4, 6, 8, 10, 12 and 24 h of incubation from the fermentation vessel and immediately cooled on ice to determine folate production (µg/L) and cell viability (log cfu/mL). Folate levels were estimated by the microbiological assay using Lactobacillus rhamnosus NCIMB 10463 as the indicator strain. The results showed that folate production and yields were higher under constant pH condition compared to fermentations at free pH. The highest folate production was reached at 8 h of incubation at pH 6.0 (168.4±7.3 µg/L) compared to pH 5.0 (35.1±3.6 µg/L) or even at uncontrolled pH conditions (84.9±2.7 µg/L). Also, at pH 6.0, the highest values of viability were observed, being 19 times higher (log cfu/mL 8.8±0.1) than at pH 5.0 (log cfu/mL 6.2±0.2) or at uncontrolled pH (log cfu/mL 7.9±0.1). In conclusion, Streptococcus thermophilus CRL803 grown at pH 6.0 was able to increase about 167% the folate levels, being a promising low cost strategy for the obtaining biofortified products without the need to add costly additives.