Catabolism of volatile sulfur compounds precursors by Brevibacterium linens and Geotrichum candidum, two microorganisms of the cheese ecosystem.
Two Brevibacterium linens strains and the cheese-ripening yeast Geotrichum candidum were compared with regard to their ability to produce volatile sulfur compounds (VSCs) from three different precursors namely L-methionine, 4-methylthio-2-oxobutyric acid (KMBA) and 4-methylthio-2-hydroxybutyric acid (HMBA). All microorganisms were able to convert these precursors to VSCs. However, although all were able to produce VSCs from L-methionine, only G. candidum accumulated KMBA when cultivated on this amino acid, contrary to B. linens suggesting that the transamination pathway is not active in this microorganism. Conversely, a L-methionine gamma-lyase activity--which catalyses the one step L-methionine to methanethiol (MTL) degradation route--was only found in B. linens strains. Several other enzymatic activities involved in the catabolism of the precursors tested were investigated. KMBA transiently accumulated in G. candidum cultures, and was then reduced to HMBA by a KMBA dehydrogenase (KDH) activity. This activity was not detected in B. linens. Despite no HMBA dehydrogenase (HDH) was found in G. candidum, a strong HMBA oxidase (HOX) activity was measured in this microorganism. This latter activity was weakly active in B. linens. KMBA and HMBA demethiolating activities were found in all the microorganisms. Our results illustrate the metabolic diversity between cheese-ripening microorganisms of the cheese ecosystem.
Arfi
Kenza
K
Department of Food and Fermentation Engineering, Institut National de la Recherche Agronomique, LGMPA, CBAI, 78850 Thiverval-Grignon, France.
Amárita
Felix
F
Spinnler
Henry-Eric
HE
Bonnarme
Pascal
P
D001951:Brevibacterium / Q000254:growth & development / Q000378:metabolism*; D002611:Cheese / Q000382:microbiology*; D005516:Food Microbiology; D005848:Geotrichum / Q000254:growth & development / Q000378:metabolism*; D008715:Methionine / Q000031:analogs & derivatives* / Q000378:metabolism; D013457:Sulfur Compounds / Q000378:metabolism*; D014835:Volatilization
D013457:Sulfur Compounds; C008391:alpha-hydroxy-gamma-methylmercaptobutyric acid; C014632:2-keto-4-methylthiobutyric acid; D008715:Methionine