title: Effect of Formic Acid on Exopolysaccharide Production in Skim Milk Fermentation by Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1.
abstract: In yogurt, the formation of formate by Streptococcus thermophilus stimulates the activity of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). However, there have been no reports how formic acid acts on the exopolysaccharide (EPS) production of L. bulgaricus. Here, the effect of formate on the EPS production in skim milk by L. bulgaricus OLL1073R-1 was investigated. After incubation for 24 hr with 100 mg/l formate, cell proliferation and lactic acid production were accelerated. The viable and total cell numbers were increased about ten- and four-fold, respectively. The amount of EPS in culture with formate (~116 µg/ml) was also four-fold greater than that of the control (~27 µg/ml). Although elongation of cells was observed at 6 hr of cultivation in both cultures, cells cultivated with formate returned to a normal shape after incubation for 24 hr. The sensitivity to cell wall hydrolase and composition of surface layer proteins, as well as the cell membrane fatty acid composition of L. bulgaricus OLL1073R-1, were not influenced by formate. However, differences were observed in intracellular fatty acid compositions and sensitivity to antibiotics. Cell length and surface damage returned to normal in cultures with formate. These observations suggest that formic acid is necessary for normal cell growth of L. bulgaricus OLL1073R-1 and higher EPS production.
authors.affiliation: Laboratory of Animal Products Chemistry, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aobaku, Sendai 981-8555, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Nishimura
authors.affiliation: Laboratory of Animal Products Chemistry, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aobaku, Sendai 981-8555, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawai
authors.affiliation: Laboratory of Animal Products Chemistry, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aobaku, Sendai 981-8555, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Aritomo
authors.affiliation: Food Science Institute, Meiji Co., Ltd., 540 Naruda, Odawara, Kanagawa 250-0862, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Food Science Institute, Meiji Co., Ltd., 540 Naruda, Odawara, Kanagawa 250-0862, Japan.
authors.forename: Seiya
authors.initials: S
authors.lastname: Makino
authors.affiliation: Food Science Institute, Meiji Co., Ltd., 540 Naruda, Odawara, Kanagawa 250-0862, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Ikegami
authors.affiliation: Laboratory of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aobaku, Sendai 981-8555, Japan.
authors.forename: Emiko
authors.initials: E
authors.lastname: Isogai
authors.affiliation: Laboratory of Animal Products Chemistry, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aobaku, Sendai 981-8555, Japan.
authors.forename: Tadao
authors.initials: T
authors.lastname: Saito
keywords: Lactobacillus delbrueckii subsp. bulgaricus; cell division; exopolysaccharide; formic acid