A genome-scale metabolic network of the aroma bacterium Leuconostoc mesenteroides subsp. cremoris

Emrah Özcan, S. Selvin Selvi, Emrah Nikerel, Bas Teusink, Ebru Toksoy Öner, Tunahan Çakır*

*Corresponding author for this work

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Abstract

Leuconostoc mesenteroides subsp. cremoris is an obligate heterolactic fermentative lactic acid bacterium that is mostly used in industrial dairy fermentations. The phosphoketolase pathway (PKP) is a unique feature of the obligate heterolactic fermentation, which leads to the production of lactate, ethanol, and/or acetate, and the final product profile of PKP highly depends on the energetics and redox state of the organism. Another characteristic of the L. mesenteroides subsp. cremoris is the production of aroma compounds in dairy fermentation, such as in cheese production, through the utilization of citrate. Considering its importance in dairy fermentation, a detailed metabolic characterization of the organism is necessary for its more efficient use in the industry. To this aim, a genome-scale metabolic model of dairy-origin L. mesenteroides subsp. cremoris ATCC 19254 (iLM.c559) was reconstructed to explain the energetics and redox state mechanisms of the organism in full detail. The model includes 559 genes governing 1088 reactions between 1129 metabolites, and the reactions cover citrate utilization and citrate-related flavor metabolism. The model was validated by simulating co-metabolism of glucose and citrate and comparing the in silico results to our experimental results. Model simulations further showed that, in co-metabolism of citrate and glucose, no flavor compounds were produced when citrate could stimulate the formation of biomass. Significant amounts of flavor metabolites (e.g., diacetyl and acetoin) were only produced when citrate could not enhance growth, which suggests that flavor formation only occurs under carbon and ATP excess. The effects of aerobic conditions and different carbon sources on product profiles and growth were also investigated using the reconstructed model. The analyses provided further insights for the growth stimulation and flavor formation mechanisms of the organism.

Original languageEnglish
Pages (from-to)3153-3165
Number of pages13
JournalApplied Microbiology and Biotechnology
Volume103
Early online date2 Feb 2019
DOIs
Publication statusPublished - 1 Apr 2019

Funding

Funding information This work received financial support from The Scientific and Technological Research Council of Turkey through TUBITAK 2214-A program and the Marmara University Scientific Research Project Fund through Project No: FEN-C-DRP-091116-0498. Burcu Şirin (Yeditepe University) and Sebastián N. Mendoza (VU Amsterdam) are acknowledged for their help in HPLC analyses and reorganizing the SBML file, respectively.

FundersFunder number
Marmara University Scientific Research Project FundFEN-C-DRP-091116-0498
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu
Yeditepe Üniversitesi

    Keywords

    • Flavor metabolism
    • Flux balance analysis
    • Genome-scale metabolic model
    • Heterolactic fermentation
    • Lactic acid bacteria
    • Leuconostoc mesenteroides subsp. cremoris

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