Two different pathways for D-xylose metabolism and the effect of xylose concentration on the yield coefficient of L-lactate in mixed-acid fermentation by the lactic acid bacterium Lactococcus lactis IO-1

K. Tanaka, A. Komiyama, Kenji Sonomoto, A. Ishizaki, S. Hall, P. Stanbury

Research output: Contribution to journalArticle

107 Citations (Scopus)

Abstract

In lactic acid bacteria, pentoses are metabolized via the phosphoketolase pathway, which catalyzes the cleavage of D-xylulose-5-phosphate to equimolar amounts of glyceraldehyde 3-phosphate and acetylphosphate. Hence the yield coefficient of lactate from pentose does not exceed 1.0 mol/mol, while that of Lactococcus lactis IO-1(JCM7638) at high D-xylose concentrations often exceeds the theoretical value. This suggests that, in addition to the phosphoketolase pathway, L. lactis IO-1 may possess another metabolic pathway that produces only lactic acid from xylose. In the present study, the metabolism of xylose in L. lactis IO-1 was deduced from the product formation and enzyme activities of L. lactis IO-1 in batch culture and continuous culture. During cultivation with xylose concentrations above ca. 50 g/l, the yield coefficient of L-lactate exceeded 1.0 mol/mol while those of acetate, formate and ethanol were very low. At xylose concentrations less than 5 g/l, acetate, formate and ethanol were produced with yield coefficients of about 1.0 mol/mol, while L-lactate was scarcely produced. In cells grown at high xylose concentrations, a marked decrease in the specific activities of phosphoketolase and pyruvate formate lyase (PFL), and an increase in those of transketolase and transaldolase were observed. These results indicate that in L. lactis IO-1 xylose may be catabolized by two different pathways, the phosphoketolase pathway yielding acetate, formate and ethanol, and the pentose phosphate (PP)/glycolytic pathway which converts xylose to L-lactate only. Furthermore, it was deduced that the change in the xylose concentration in the culture medium shifts xylulose 5-phosphate metabolism between the phosphoketolase pathway and the PP/glycolytic pathway in L. lactis IO-1, and pyruvate metabolism between cleavage to acetyl-CoA and formic acid by PFL and the reduction to L-lactate by lactate dehydrogenase.

Original languageEnglish
Pages (from-to)160-167
Number of pages8
JournalApplied Microbiology and Biotechnology
Volume60
Issue number1-2
DOIs
Publication statusPublished - Oct 1 2002

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phosphoketolase
Lactococcus lactis
Xylose
formic acid
Fermentation
Lactic Acid
Bacteria
Acids
formate C-acetyltransferase
Pentoses
Pentose Phosphate Pathway
Acetates
Ethanol
Transaldolase
Glyceraldehyde 3-Phosphate
Transketolase
Acetyl Coenzyme A
Batch Cell Culture Techniques
Metabolic Networks and Pathways
Pyruvic Acid

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Applied Microbiology and Biotechnology

Cite this

Two different pathways for D-xylose metabolism and the effect of xylose concentration on the yield coefficient of L-lactate in mixed-acid fermentation by the lactic acid bacterium Lactococcus lactis IO-1. / Tanaka, K.; Komiyama, A.; Sonomoto, Kenji; Ishizaki, A.; Hall, S.; Stanbury, P.

In: Applied Microbiology and Biotechnology, Vol. 60, No. 1-2, 01.10.2002, p. 160-167.

Research output: Contribution to journalArticle

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AU - Stanbury, P.

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