Evaluation of a quantitative screening method for hydrogen sulfide production by cheese-ripening microorganisms: the first step towards l-cysteine catabolism.
A practical adaptation of the methylene blue reaction for hydrogen sulfide quantification was developed to perform microbial selection. Closed plate flasks containing a zinc-agar layer above the liquid microbial culture are proposed as a trap system where the H(2)S can be retained and then quantified by the methylene blue reaction. Using this quantitative method, the ability to produce H(2)S was studied in several cheese-ripening microorganisms. Our aim was to select strains that produce the highest quantities of H(2)S as the main product of L-cysteine catabolism. Thirty seven yeast and bacteria strains were cultivated with or without L-cysteine. The separation between the growth medium and the H(2)S trapping layer displayed good performance: all the studied strains grew efficiently and only negligible loss of H(2)S was observed during culturing. The strains displayed large differences in their H(2)S production capabilities: yeast strains were greater producers of H(2)S than bacteria with production strain-related in both cases. Furthermore, the relationship between H(2)S production and L-cysteine consumption was analyzed, which made it possible for us to select microorganisms with high capacity in L-cysteine degradation. The production of volatile sulfur compounds was also studied and the possible effect of culture pH and metabolic differences between strains are discussed.
Lopez del Castillo Lozano
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Institut National de la Recherche Agronomique, Institut National Agronomique Paris-Grignon, Unité Mixte de Recherche Génie et Microbiologie des Procédés Alimentaires, CBAI-rue Lucien Brétignère, 78 850 Thiverval Grignon, France.
Tâche
R
R
Bonnarme
P
P
Landaud
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S
D002611:Cheese / Q000382:microbiology*; D003545:Cysteine / Q000378:metabolism*; D006862:Hydrogen Sulfide / Q000378:metabolism*; D008751:Methylene Blue / Q000378:metabolism; D008828:Microbiological Techniques / Q000379:methods*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013457:Sulfur Compounds / Q000378:metabolism; D014835:Volatilization
D013457:Sulfur Compounds; D003545:Cysteine; D008751:Methylene Blue; D006862:Hydrogen Sulfide