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Phenotypic Diversity of
Chiara Montanari1, Federica Barbieri1, Michael Magnani2
1Interdepartmental Center for Industrial Agri-Food Research, University of Bologna, Cesena, Italy.
Frontiers in Microbiology
|September 14, 2018
Summary
Lactobacillus sakei, a key starter culture in fermented sausages, utilizes amino acids for energy when sugars are low. This study reveals its metabolic diversity and adaptability to meat environments.
Area of Science:
- Food Microbiology
- Bacteriology
- Metabolic Engineering
Background:
- Lactobacillus sakei (L. sakei) is a lactic acid bacteria (LAB) species adapted to meat environments.
- Selected L. sakei strains are vital starter cultures for fermented sausages, particularly in Mediterranean regions.
- This species dominates fermented sausages and maintains viability throughout long ripening periods, utilizing energy pathways active even without sugars.
Purpose of the Study:
- To investigate the metabolic responses of six L. sakei strains in a synthetic medium with amino acids.
- To understand the influence of temperature and NaCl concentration on L. sakei metabolism.
- To explore the impact of pre-growth conditions (glucose vs. ribose) on cellular activities.
Main Methods:
- Cultivation of six L. sakei strains in a defined synthetic medium (DM) with amino acids.
- Exposure to varying temperatures and NaCl concentrations.
- Analysis of amino acid uptake, organic acid accumulation, and diacetyl/acetoin production.
- Testing of cells pre-grown on glucose or ribose.
Main Results:
- Arginine uptake was efficient across most strains, except DSMZ 20017t.
- Serine, asparagine, cysteine, and methionine were metabolized via pyruvate-dependent energetic pathways, evident from organic acid accumulation.
- Excess pyruvate from amino acids led to diacetyl and acetoin production when sugars were present.
- Significant phenotypic variability was observed among the L. sakei strains.
Conclusions:
- L. sakei exhibits diverse metabolic strategies for survival and growth in restrictive conditions like fermented sausages.
- Understanding these metabolic pathways, particularly amino acid utilization, is crucial for optimizing starter culture applications.
- The study enhances comprehension of L. sakei's adaptability, informing improved starter culture selection and fermentation processes.
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