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Glutathione reductase from Lactobacillus sanfranciscensis DSM20451T: contribution to oxygen tolerance and thiol exchange reactions in wheat sourdoughs.

ABSTRACT: The effect of the glutathione reductase (GshR) activity of Lactobacillus sanfranciscensis DSM20451(T) on the thiol levels in fermented sourdoughs was determined, and the oxygen tolerance of the strain was also determined. The gshR gene coding for a putative GshR was sequenced and inactivated by single-crossover integration to yield strain L. sanfranciscensis DSM20451(T)DeltagshR. The gene disruption was verified by sequencing the truncated gshR and surrounding regions on the chromosome. The gshR activity of L. sanfranciscensis DSM20451(T)DeltagshR was strongly reduced compared to that of the wild-type strain, demonstrating that gshR indeed encodes an active GshR enzyme. The thiol levels in wheat doughs fermented with L. sanfranciscensis DSM20451 increased from 9 microM to 10.5 microM sulfhydryl/g of dough during a 24-h sourdough fermentation, but in sourdoughs fermented with L. sanfranciscensis DSM20451(T)DeltagshR and in chemically acidified doughs, the thiol levels decreased to 6.5 to 6.8 microM sulfhydryl/g of dough. Remarkably, the GshR-negative strains Lactobacillus pontis LTH2587 and Lactobacillus reuteri BR11 exerted effects on thiol levels in dough comparable to those of L. sanfranciscensis. In addition to the effect on thiol levels in sourdough, the loss of GshR activity in L. sanfranciscensis DSM20451(T)DeltagshR resulted in a loss of oxygen tolerance. The gshR mutant strain exhibited a strongly decreased aerobic growth rate on modified MRS medium compared to either the growth rate under anaerobic conditions or that of the wild-type strain, and aerobic growth was restored by the addition of cysteine. Moreover, the gshR mutant strain was more sensitive to the superoxide-generating agent paraquat.

SUBMITTER: Jansch A

PROVIDER: S-EPMC1932818 | biostudies-literature | 2007 Jul

REPOSITORIES: biostudies-literature

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Glutathione reductase from Lactobacillus sanfranciscensis DSM20451T: contribution to oxygen tolerance and thiol exchange reactions in wheat sourdoughs.

Jänsch André A Korakli Maher M Vogel Rudi F RF Gänzle Michael G MG

Applied and environmental microbiology 20070511 14

The effect of the glutathione reductase (GshR) activity of Lactobacillus sanfranciscensis DSM20451(T) on the thiol levels in fermented sourdoughs was determined, and the oxygen tolerance of the strain was also determined. The gshR gene coding for a putative GshR was sequenced and inactivated by single-crossover integration to yield strain L. sanfranciscensis DSM20451(T)DeltagshR. The gene disruption was verified by sequencing the truncated gshR and surrounding regions on the chromosome. The gshR ...[more]

PMID: 17496130

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Project description:The structure and stability of the dominant lactic acid bacterium population were assessed during wheat flour sourdough type I propagation by using singly nine strains of Lactobacillus sanfranciscensis. Under back-slopping propagation with wheat flour type 0 F114, cell numbers of presumptive lactic acid bacteria varied slightly between and within starters. As determined by randomly amplified polymorphic DNA-PCR and restriction endonuclease analysis-pulsed-field gel electrophoresis analyses, only three (LS8, LS14, and LS44) starters dominated throughout 10 days of propagation. The others progressively decreased to less than 3 log CFU g(-1). Partial sequence analysis of the 16S rRNA and recA genes and PCR-denaturating gradient gel electrophoresis analysis using the rpoB gene allowed identification of Weissella confusa, Lactobacillus sanfranciscensis, Lactobacillus plantarum, Lactobacillus rossiae, Lactobacillus brevis, Lactococcus lactis subsp. lactis, Pediococcus pentosaceus, and Lactobacillus spp. as the dominant species of the raw wheat flour. At the end of propagation, one autochthonous strain of L. sanfranciscensis was found in all the sourdoughs. Except for L. brevis, strains of the above species were variously found in the mature sourdoughs. Persistent starters were found in association with other biotypes of L. sanfranciscensis and with W. confusa or L. plantarum. Sourdoughs were characterized for acidification, quotient of fermentation, free amino acids, and community-level catabolic profiles by USING Biolog 96-well Eco microplates. In particular, catabolic profiles of sourdoughs containing persistent starters behaved similarly and were clearly differentiated from the others. The three persistent starters were further used for the production of sourdoughs and propagated by using another wheat flour whose lactic acid bacterium population in part differed from the previous one. Also, in this case all three starter strains persisted during propagation.

Dataset Information

Glutathione reductase from Lactobacillus sanfranciscensis DSM20451T: contribution to oxygen tolerance and thiol exchange reactions in wheat sourdoughs.

Publications

Glutathione reductase from Lactobacillus sanfranciscensis DSM20451T: contribution to oxygen tolerance and thiol exchange reactions in wheat sourdoughs.

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