Diversity of L-leucine catabolism in various microorganisms involved in dairy fermentations, and identification of the rate-controlling step in the formation of the potent flavour component 3-methylbutanal

Appl Microbiol Biotechnol. 2004 Apr;64(3):396-402. doi: 10.1007/s00253-003-1447-8. Epub 2003 Nov 18.


Various microorganisms, belonging to the genera Lactococcus, Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium, Propionibacterium, Brevibacterium, Corynebacterium and Arthrobacter, used in dairy fermentations such as cheese making, were analysed for their potential to convert leucine into flavour components, most notably 3-methylbutanal. A large variation between and within species was observed for various enzyme activities involved in the conversion pathway, e.g. transaminases, alpha-hydroxy acid dehydrogenase and alpha-keto acid decarboxylase. In particular, alpha-keto acid decarboxylase activity-leading to 3-methylbutanal-was found to be present in only two of the strains tested. It is proposed that this activity is rate-controlling in the conversion pathway leading to the flavour compound 3-methylbutanal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / metabolism
  • Alcohol Oxidoreductases / metabolism
  • Aldehydes / metabolism*
  • Arthrobacter / metabolism
  • Bacteria / metabolism*
  • Bifidobacterium / metabolism
  • Biotransformation
  • Brevibacterium / metabolism
  • Cheese / microbiology*
  • Corynebacterium / metabolism
  • Fermentation
  • Flavoring Agents*
  • Food Microbiology
  • Lactobacillus / metabolism
  • Lactococcus / metabolism
  • Leucine / metabolism*
  • Leuconostoc / metabolism
  • Propionibacterium / metabolism
  • Streptococcus / metabolism
  • Transaminases / metabolism


  • Aldehydes
  • Flavoring Agents
  • isovalerylaldehyde
  • Alcohol Oxidoreductases
  • D-2-hydroxyacid dehydrogenase
  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
  • Transaminases
  • Leucine