Isovaleric acid is mainly produced by Propionibacterium freudenreichii in Swiss cheese

ABSTRACT Several branched-chain volatile compounds are involved in the flavor of Swiss cheese. These compounds are probably produced by enzymatic conversion of branched-chain amino acids, but the flora and the pathways involved remain hypothetical. Our aim was to determine the ability of Propionibacterium freudenreichii, which is one of the main components of the secondary flora of Swiss cheese, to produce flavor compounds during leucine catabolism. Cell extracts and resting cells of two strains were incubated in the presence of l-leucine, α-ketoglutaric acid, and cofactors, and the metabolites produced were determined by high-performance liquid chromatography and gas chromatography. The first step of leucine catabolism was a transamination that produced α-ketoisocaproic acid, which was enzymatically converted to isovaleric acid. Both reactions were faster at pH 8.0 than at acidic pHs. Cell extracts catalyzed only the transamination step under our experimental conditions. Small amounts of 3-methylbutanol were also produced by resting cells, but neither 3-methylbutanal norα-hydroxyisocaproic acid was detected. l-Isoleucine and l-valine were also converted to the corresponding acids and alcohols. Isovaleric acid was produced by both strains during growth in a complex medium, even under conditions simulating Swiss cheese conditions (2.1% NaCl, pH 5.4, 24Ã¯Â¿Â½C). Our results show that P. frendenreichii could play a significant role in the formation of isovaleric acid during ripening.

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Autolysis of Lactobacillus helveticus and Propionibacterium freudenreichii in Swiss cheeses: first evidence by using species-specific lysis markers

Journal of Dairy Research ◽

10.1017/s0022029998003021 ◽

1998 ◽

Vol 65 (4) ◽

pp. 609-620 ◽

Cited By ~ 40

Author(s):

FLORENCE VALENCE ◽

ROMAIN RICHOUX ◽

ANNE THIERRY ◽

AIRI PALVA ◽

SYLVIE LORTAL

Keyword(s):

Coenzyme A ◽

Streptococcus Thermophilus ◽

Lactobacillus Helveticus ◽

Propionibacterium Freudenreichii ◽

Swiss Cheese ◽

Specific Lysis ◽

Cold Room ◽

Sds Page ◽

Intracellular Proteins ◽

Species Specific

Lactobacillus helveticus and Propionibacterium freudenreichii are essential starters in Swiss cheesemaking and the release of their intracellular enzymes through autolysis could significantly influence ripening. To provide evidence of this lysis, cheese made from microfiltered thermized milk inoculated with Lb. helveticus ITGLH77, Prop. freudenreichii ITGP23 and a commercial Streptococcus thermophilus was assayed. Starter viability was determined and lysis was monitored during ripening by protein analysis with SDS-PAGE of aqueous cheese extracts and by immunoblot detection of intracellular proteins: dipeptidase (PepD) for Lb. helveticus and methylmalonyl coenzyme A mutase for Prop. freudenreichii. We verified that the species specificity of these lysis markers was towards the cytoplasms of all the species currently used in Swiss cheese. Lb. helveticus exhibited an almost complete loss of viability (99·9%) from the beginning of ripening in the cold room; concomitantly PepD appeared in the cheese extracts and was detected until the end of ripening. Damaged Lb. helveticus cells were also visualized by scanning electron microscopy. In addition, free PepD was also successfully detected in commercial Swiss-related cheeses. All these results clearly demonstrated the autolysis of Lb. helveticus in Swiss cheese. Prop. freudenreichii ITGP23 grew during warm room ripening and no loss of viability was detected after maximal growth (109 cfu/g cheese). Free methylmalonyl-coenzyme A mutase was detected at the end of ripening during cold storage, when the cheese extracts were concentrated 20-fold, demonstrating that the autolysis of Prop. freudenreichii was tardy and limited.

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Propionibacterium freudenreichii strains quantitatively affect production of volatile compounds in Swiss cheese

Dairy Science & Technology ◽

10.1051/lait:2004036 ◽

2005 ◽

Vol 85 (1-2) ◽

pp. 57-74 ◽

Cited By ~ 47

Author(s):

Anne Thierry ◽

Marie-Bernadette Maillard ◽

Romain Richoux ◽

Jean-Ren� Kerjean ◽

Sylvie Lortal

Keyword(s):

Volatile Compounds ◽

Propionibacterium Freudenreichii ◽

Swiss Cheese

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The Secreted Esterase of Propionibacterium freudenreichii Has a Major Role in Cheese Lipolysis

Applied and Environmental Microbiology ◽

10.1128/aem.03640-13 ◽

2013 ◽

Vol 80 (2) ◽

pp. 751-756 ◽

Cited By ~ 15

Author(s):

María Claudia Abeijón Mukdsi ◽

Hélène Falentin ◽

Marie-Bernadette Maillard ◽

Victoria Chuat ◽

Roxana Beatriz Medina ◽

...

Keyword(s):

Fatty Acids ◽

Type Strain ◽

Wild Type Strain ◽

Lipolytic Activity ◽

Premature Stop Codon ◽

Propionibacterium Freudenreichii ◽

Wild Type ◽

Swiss Cheese ◽

Content Type ◽

Type Strains

ABSTRACTFree fatty acids are important flavor compounds in cheese.Propionibacterium freudenreichiiis the main agent of their release through lipolysis in Swiss cheese. Our aim was to identify the esterase(s) involved in lipolysis byP. freudenreichii. We targeted two previously identified esterases: one secreted esterase, PF#279, and one putative cell wall-anchored esterase, PF#774. To evaluate their role in lipolysis, we constructed overexpression and knockout mutants ofP. freudenreichiiCIRM-BIA1Tfor each corresponding gene. The sequences of both genes were also compared in 21 wild-type strains. All strains were assessed for their lipolytic activity on milk fat. The lipolytic activity observed matched data previously reported in cheese, thus validating the relevance of the method used. The mutants overexpressing PF#279 or PF#774 released four times more fatty acids than the wild-type strain, demonstrating that both enzymes are lipolytic esterases. However, inactivation of thepf279gene induced a 75% reduction in the lipolytic activity compared to that of the wild-type strain, whereas inactivation of thepf774gene did not modify the phenotype. Two of the 21 wild-type strains tested did not display any detectable lipolytic activity. Interestingly, these two strains exhibited the same single-nucleotide deletion at the beginning of thepf279gene sequence, leading to a premature stop codon, whereas they harbored apf774gene highly similar to that of the other strains. Taken together, these results clearly demonstrate that PF#279 is the main lipolytic esterase inP. freudenreichiiand a key agent of Swiss cheese lipolysis.

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