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Citrate Metabolism by Pediococcus halophilus

C Kanbe1, K Uchida

  • 1Soy Sauce Research Laboratories, Kikkoman Corporation, Noda-shi, Chiba-ken 278, Japan.

Applied and Environmental Microbiology
|June 1, 1987
PubMed

Insights

Soy pediococci that cannot metabolize citrate lack citrate lyase activity. Pediococcus halophilus utilizes citrate lyase to produce acetate and formate, with glucose reducing formate production.

Area of Science:

  • Microbiology
  • Food Science
  • Biochemistry

Background:

  • Soy sauce fermentation involves Pediococcus halophilus.
  • Some strains of P. halophilus do not metabolize citrate.
  • Citrate metabolism in these bacteria is not fully understood.

Purpose of the Study:

  • Investigate factors controlling citrate metabolism in soy pediococci.
  • Characterize the enzyme responsible for citrate decomposition.
  • Elucidate the metabolic pathway of citrate in P. halophilus.

Main Methods:

  • Enzyme assays for citrate lyase activity.
  • pH optima determination for citrate lyase.
  • Analysis of metabolic products from citrate using P. halophilus 7117 (Cit).

Main Results:

  • Non-citrate-metabolizing strains lacked citrate lyase activity.
  • Citrate lyase in P. halophilus is an inducible enzyme with optimal activity at pH 7.0.
  • P. halophilus converts citrate to acetate and formate, lacking acetoin/diacetyl production; glucose inhibits formate production.

Conclusions:

  • Citrate lyase is essential for citrate decomposition in P. halophilus.
  • The citrate metabolism pathway in P. halophilus differs from lactic streptococci.
  • P. halophilus 7117 (Cit) possesses all necessary enzymes for converting citrate to acetate and formate.

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