**Metabolism of** *Lactobacillus sakei* **Chr82 in the Presence of Di**ff**erent Amounts of Fermentable Sugars**

**Federica Barbieri 1, Luca Laghi 1,2 , Fausto Gardini 1,2, Chiara Montanari 2,\* and Giulia Tabanelli 2,3**


Received: 26 March 2020; Accepted: 27 May 2020; Published: 2 June 2020

**Abstract:** *Lactobacillus sakei* is widely used as a starter culture in fermented sausages since it is well adapted to meat environments and able to maintain high viability thanks to secondary pathways activated when hexoses are depleted (i.e., metabolism of pentoses and amino acids). In this study, a commercial strain of *L. sakei* was inoculated in a defined medium with ribose or glucose as the carbon source, at optimal or reduced concentrations, to evaluate its different physiological and metabolic responses in relation to different growth conditions. The results obtained with different approaches (HPLC, 1H-NMR, flow cytometry) evidenced different growth performances, amino acid consumptions and physiological states of cells in relation to the carbon source as an active response to harsh conditions. As expected, higher concentrations of sugars induced higher growth performances and the accumulation of organic acids. The low sugars amount induced the presence of dead cells, while injured cells increased with ribose. Arginine was the main amino acid depleted, especially in the presence of higher ribose, and resulted in the production of ornithine. Moreover, the 1H-NMR analysis evidenced a higher consumption of serine at the optimal sugars concentration (pyruvate production). This information can be helpful to optimize the use of these species in the industrial production of fermented sausages.

**Keywords:** *Lactobacillus sakei*; sugar metabolism; amino acid metabolism; 1H-NMR; flow cytometry
