Abstract
Streptococcus thermophilus, an extensively used lactic starter, is generally produced in yeast extract-based media containing a complex mixture of peptides whose exact composition remains elusive. In this work, we aimed at investigating the peptide content of a commercial yeast extract (YE) and identifying dynamics of peptide utilization during the growth of the industrial S. thermophilus N4L strain, cultivated in 1 l bioreactors under pH-regulation. To reach that goal, we set up a complete analytical workflow based on mass spectrometry (peptidomics). About 4,600 different oligopeptides ranging from 6 to more than 30 amino acids in length were identified during the time-course of the experiment. Due to the low spectral abundance of individual peptides, we performed a clustering approach to decipher the rules of peptide utilization during fermentation. The physicochemical characteristics of consumed peptides perfectly matched the known affinities of the oligopeptide transport system of S. thermophilus. Moreover, by analyzing such a large number of peptides, we were able to establish that peptide net charge is the major factor for oligopeptide transport in S. thermophilus N4L.
Highlights
Lactic acid bacteria (LAB) are a group of microorganisms displaying a wide range of properties making them suitable for various applications in fields such as health (Hill et al, 2017), chemistry (Othman et al, 2017; Sauer et al, 2017), or cosmetics (Izawa and Sone, 2014)
Production media usually contain complex substrates such as cell or protein hydrolysates that notably include yeast extracts (YEs), which are widely used for LAB industrial production
S. thermophilus N4L was cultivated in a YE-based medium in 1 l bioreactors
Summary
Lactic acid bacteria (LAB) are a group of microorganisms displaying a wide range of properties making them suitable for various applications in fields such as health (Hill et al, 2017), chemistry (Othman et al, 2017; Sauer et al, 2017), or cosmetics (Izawa and Sone, 2014). They have been historically used for food production (Salque et al, 2013), and it still remains their main outcome, in particular for dairy starters.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have