Isolation of folate-producing Weissella spp. from Thai fermented fish (Plaa Som Fug)

Folate-producing lactic acid bacteria (LAB) have received a great deal of attention since they are generally used as starter cultures. When they produce folate, fermented products obtained are beneficial to health. This study sought to screen new metabolites from Weissella spp. isolated from Thai fermented fish (Plaa Som Fug). Among 52 lactic acid bacteria isolates, 11 strains were identified as Weissella spp. based on 16S rRNA gene sequences, six of which were W. confusa (SF2-1, SF2-3, SF4-4, SF5-1, SF6-2 and PL13-2); five of which were W. cibaria (SF1-1, SF1-2, SF4-3, PL 5-4 and PL17-3). All strains of Weissella produced lactic acid at a concentration of 8.75-32.30 mg mL(-1). Determination of folate by high-performance liquid chromatography (HPLC) revealed that these strains were also capable of producing folate in a folate-free medium, with a maximum concentration of 4.14 mu g mL(-1) yielded by W. ciboria PL17-3. The average folate concentration produced among the 11 strains was 2.47 ig mL(-1). This is the first study to report the isolation of folate-producing W cibaria. The discovery of folate-producing Weissella may help improve the nutrition of fermented food.