title: Food-grade controlled lysis of Lactococcus lactis for accelerated cheese ripening.
abstract: An attractive approach to accelerate cheese ripening is to induce lysis of Lactococcus lactis starter strains for facilitated release of intracellular enzymes involvement in flavor formation. Controlled expression of the lytic genes lytA and lytH, which encode the lysin and the holin proteins of the lactococcal bacteriophage phi US3, respectively, was accomplished by application of a food-grade nisin-inducible expression system. Simultaneous production of lysin and holin is essential to obtain efficient lysis and concomitant release of intracellular enzymes as exemplified by complete release of the debittering intracellular aminopeptidase N. Production of holin alone leads to partial lysis of the host cells, whereas production of lysin alone does not cause significant lysis. Model cheese experiments in which the inducible holinlysin overproducing strain was used showed a fourfold increase in release of L-Lactate dehydrogenase activity into the curd relative to the control strain and the holin-overproducing strain, demonstrating the suitability of the system for cheese applications.
authors.affiliation: Department of Biophysical Chemistry, NIZO, Ede, The Netherlands.
authors.forename: P G
authors.initials: PG
authors.lastname: de Ruyter
authors.forename: O P
authors.initials: OP
authors.lastname: Kuipers
authors.forename: W C
authors.initials: WC
authors.lastname: Meijer
authors.forename: W M
authors.initials: WM
authors.lastname: de Vos
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis; D001435:Bacteriophages / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D002611:Cheese / Q000382:microbiology*; D003001:Cloning, Molecular; D004798:Enzymes / Q000096:biosynthesis; D005285:Fermentation / Q000187:drug effects; D005520:Food Preservatives / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D007770:L-Lactate Dehydrogenase / Q000096:biosynthesis; D013294:Lactococcus lactis / Q000235:genetics* / Q000378:metabolism / Q000821:virology; D009238:N-Acetylmuramoyl-L-alanine Amidase; D009561:Nisin / Q000494:pharmacology*; D010957:Plasmids; D016133:Polymerase Chain Reaction
chemical_list: D001426:Bacterial Proteins; D004798:Enzymes; D005520:Food Preservatives; D009561:Nisin; D007770:L-Lactate Dehydrogenase; C108616:LytH protein, Staphylococcus aureus; D009238:N-Acetylmuramoyl-L-alanine Amidase