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Towards enhanced galactose utilization by Lactococcus lactis.

Ana R Neves1, Wietske A Pool, Ana Solopova

  • 1Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República (EAN), 2780-157 Oeiras, Portugal. arn@itqb.unl.pt

Applied and Environmental Microbiology
|September 7, 2010
PubMed
Summary
This summary is machine-generated.

Lactic acid bacteria engineered to consume galactose improve dairy product quality and safety for galactosemia patients. Enhancing the Leloir pathway and phosphotransferase system boosts galactose metabolism by up to 50%.

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Area of Science:

  • Microbiology and Genetic Engineering
  • Biochemistry and Metabolic Pathways
  • Food Science and Technology

Background:

  • Partial lactose fermentation by lactic acid bacteria leads to galactose accumulation in dairy products, reducing quality and posing risks for individuals with galactosemia.
  • Understanding galactose metabolism in Lactococcus lactis is crucial for developing strains that efficiently consume galactose.

Purpose of the Study:

  • To investigate galactose utilization pathways in Lactococcus lactis, specifically the Leloir (gal genes) and tagatose 6-phosphate (Tag6P) (lac genes) pathways.
  • To identify key enzymes and transporters involved in galactose metabolism to enhance galactose consumption in engineered strains.

Main Methods:

  • Utilized directed genetic engineering of Lactococcus lactis strain NZ9000 to examine the roles of chromosomal gal genes and plasmid-encoded lac genes.
  • Assessed the necessity of galactose permease (GalP) and galactokinase (GalK) for galactose utilization.
  • Investigated the function of the lactose phosphotransferase system (PTS) (lacFE) and identified an alternative galactose dissimilation route.

Main Results:

  • Galactokinase (GalK) is essential for growth on galactose, and an alternative galactose phosphotransferase system (PTS) pathway was discovered.
  • The lactose PTS (lacFE) is implicated in galactose uptake, with both PTS transporters showing low affinity for galactose, while GalP has high affinity.
  • Overexpression of galPMKT revealed a bottleneck at α-phosphoglucomutase; subsequent overexpression of this enzyme enhanced galactose consumption rates by up to 50%.

Conclusions:

  • The GalP/Leloir pathway exhibits the highest galactose consumption rate, but bottlenecks exist.
  • Engineering α-phosphoglucomutase activity is a key strategy for significantly improving galactose metabolism in Lactococcus lactis.
  • These findings provide a foundation for developing robust strains for enhanced galactose consumption, benefiting dairy production and galactosemia patient diets.