2024-03-29T14:25:30Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/575072020-10-21T11:44:23Zcom_10261_86com_10261_1col_10261_339
Citrate metabolism and aroma compound production in lactic acid bacteria
García-Quintans, Nieves
Blancato, Víctor S.
Repizo, Guillermo D.
Magni, C.
López, Paloma
24 p.-8 fig.-1 tab.
The main activity of lactic acid bacteria (LAB)
during fermentation is the catabolism of sugars
present in food, producing lactic acid by homoor
heterofermentative pathways. In addition, these
microorganisms also have the capability to metabolize
other substrates, such as citrate. Citrate is present in
fruit juices, milk and vegetables and is also added as
a preservative to foods. Citrate fermentation by LAB
leads to the production of 4-carbon compounds, mainly diacetyl, acetoin and butanediol, which have aromatic properties. One of these
compounds, diacetyl is responsible for the buttery aroma of dairy products
such as butter, acid cream and cottage cheese. In addition, it is an important
component of the flavour of different kinds of chesses and yoghurt. Moreover,
the CO2 produced as a consequence of citrate metabolism contributes to the
formation of "eyes" (holes) in Gouda, Danbo and other cheeses. Thus, the
utilization of citrate in milk by LAB has a very positive effect on the quality of
the end products. Therefore, the interest of the dairy industry in controlling
citrate utilization by LAB has promoted research into the proteins and
effectors controlling its metabolic pathway. In this chapter we summarize the
current knowledge of citrate utilization by LAB. The transport of citrate and its
metabolism to pyruvate, as well as further conversion to aroma compounds, is
described and, the differences in the co-metabolism of citrate with glucose
between homo or heterofermentative bacteria is discussed. In addition, the
molecular mechanisms controlling expression of genes responsible for
transport and conversion of citrate into pyruvate are presented, as are their
correlation with the physiological function of citrate metabolism. To date, two
different models of regulation have been described which are unique to LAB.
In Lactococcus lactis, a specific transcriptional activation of the promoters
controlling the cit operons takes place at low pH to provide an adaptative
response to acidic stress. In Weissella paramesenteroides, the CitI
transcriptional regulator functions as a citrate-activated switch allowing the
cell to optimize the generation of metabolic energy. CitI, its operators and
citrate transport and metabolic operons are highly conserved in several LAB.
Therefore, this mechanism of sensing and response to citrate appears to have
been conserved and propogated during the evolution of LAB
2008-05
capítulo de libro
Molecular Aspects of Lactic Acid Bacteria for Traditional and New Applications, Chapter 3:65-88(2008)
978-81-308-0250-3
http://hdl.handle.net/10261/57507
eng
openAccess
Research Singpost (India)