Role, mechanisms and control of lactic acid bacteria lysis in cheese

Lysis of dairy starters is a prerequisite for optimum cheese maturation, since intracellular starter enzymes, particularly peptidases, can then play their role. Here we describe the different methods used to detect starter lysis in situ and current knowledge concerning the impact of lysis on cheese ripening, particularly the increase of free amino acids due to early lysis and the reduction of bitterness by hydrolysis of large hydrophobic peptides. Recent results obtained on the impact of lysis on lipolysis and amino acid catabolism are also described. Then, we present current knowledge regarding the mechanisms involved, focussing mainly on the model most investigated: Lactococcus lactis. Recent advances concerning the molecular characterization of peptidoglycan hydrolases are summarized (sequence, structure, regulation) together with current knowledge of the relationship between lysogeny and lysis. Lastly, we review the different approaches proposed to control or induce lysis in situ. In conclusion, we point out unaddressed questions.