TITLE:
The Citrate Metabolism in Homo- and Heterofermentative LAB: A Selective Means of Becoming Dominant over Other Microorganisms in Complex Ecosystems
AUTHORS:
Gemelas Laëtitia, Degraeve Pascal, Demarigny Yann
KEYWORDS:
Citrate Metabolism, Lactococcus lactis subsp. lactis biovar. diacetylactis, Leuconostoc spp., Complex Microbial Ecosystems, Homo- and Heterofermentative Lactic Acid Bacteria
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.5 No.10,
May
22,
2014
ABSTRACT:
The
citrate metabolism has been extensively studied in lactic acid bacteria (LAB)
for its aroma compound production. Among the 4-carbon (C4) by-products
obtained from citrate fermentation, diacetyl is one of the better known
products for its contribution to the buttery aroma of dairy products. A lot of
documents deal with ways to improve diacetyl concentration in food matrices.
Apart from these organoleptic advantages, in a microbial ecosystem, the citrate
metabolism gives selective advantages to citrate positive microorganisms.
Citrate metabolism allows the LAB to use another carbon source for their growth,
withstand acidic conditions and generate a “proton motive force” (PMF).
Moreover, the citrate/glucid co-metabolism leads to the fast release of organic
compounds known for having bacteriostatic effects. Under specific conditions,
the C4pathway liberates diacetyl which is bacteriostatic. In this
review we first describe the citrate metabolism and the enzymes involved in the
two homo- and heterofermentative LABLc
diacetylactisandLeuconostocspp.
Moreover, the way to shift the metabolic pathway toward the production of
aromatic compounds is discussed for both of these fermentative types of
bacteria. Finally, the selective advantages of citrate metabolism for LAB in
complex microbial ecosystems are delineated.