Andean tubers fermentation with potentially probiotic folate-producing lactic acid bacteria

Abstract

Folate is a B-group vitamin that cannot be synthesized by humans and must be obtained exogenously. It is known that certain strains of lactic acid bacteria (LAB) can produce natural folates that, unlike the chemically synthesized form folic acid, is not associated with certain unwanted side effects. Fermentation of vegetables with selected potentially probiotic cultures can confer health benefits to the host since these could produce beneficial metabolites such as folates. The aim of the current study was to evaluate the tolerance in simulated gastrointestinal (SGIC) conditions of folate-producing LAB strains and use these LABB to ferment Andean tubers in order to obtain potentially probiotic products with elevated folate levels. Five strains of LAB -Lactobacillus (Lb.) sakei 2T2MM10 and 2T3MS8, Lb. fermentum T3M3, Lb. paracasei 3T3M3 and 3T3MS2- originally isolated from a traditional Andean fermented potato product named Tocosh and characterized as being folate producers were examined to test their tolerance to SGIC. The in vitro tests determined that the five strains could survive in gastric juice (2.5h, pH 2.5, containing 0.3% of pepsin) without any reduction in cell counts. However, they showed lower resistance to intestinal conditions (2.5h, pH 8.0, containing 0.3% of bile salts and 0.03% of pancreatin) with the exception of Lb. parakasei parakasei 3T3MS2 whose survivability was not affected. These strains were used toferment three Andean tubers (Solanum tuberosum ssp andigena Collareja potato variety, Oxalis tuberosa purple variety and Ullucus tuberosum pink variety). Sterile cooked purees were inoculated and samples were collected at 0, 6, 24 hours and 28 days to determine cell growth, pH and total folate content. Although all five strains were able to grow and produce folates in the three tubers, L. sakei 2T2MM10 showed the highest increase after 24h incubation in oca and papalisa, with folate concentrations of 1656±148 and 735±62 ng/g respectively, which represents a two and threefold increase compared to the unfermented tubers. Folate concentration in Collareja potato fermented for 24h with L. sakei 2T3MS8 strain was 792 ng/g, representngs a 265% increase with respect with the unfermented potato. Viable cell counts of all strains remain stable (>log 8 UFC/g) among 28 days of storage at 4°C. Conclusion: The adequate selection of LAB could be used to produce new tuber-based products with elevated folate concentrations.