Physiological role of beta-phosphoglucomutase in Lactococcus lactis.

Area of Science:

• Microbiology
• Biochemistry
• Metabolic Engineering

Background:

• Lactococcus lactis is a key lactic acid bacterium used in food fermentation.
• Beta-phosphoglucomutase (beta-PGM) is an enzyme involved in carbohydrate metabolism.
• Understanding its role is crucial for optimizing industrial applications and metabolic engineering.

Purpose of the Study:

• To investigate the function of beta-PGM in Lactococcus lactis.
• To elucidate the impact of beta-PGM on carbohydrate catabolism and anabolism.
• To characterize trehalose metabolism in L. lactis.

Main Methods:

• Construction of a beta-PGM deletion mutant using double-crossover recombination.
• Cultivation of wild-type and mutant strains under controlled conditions with various sugars (glucose, lactose, maltose, trehalose).
• Analysis of growth rates, product formation, cell composition, and enzyme activity.

Main Results:

• The beta-PGM mutant exhibited significantly reduced growth rates on maltose (0.05 h⁻¹) and no growth on trehalose, compared to the wild-type (0.5 h⁻¹).
• Mutant growth on maltose led to altered fermentation products (less lactate, more formate, acetate, ethanol) and accumulation of polysaccharides.
• A novel enzymatic pathway for trehalose metabolism, distinct from maltose metabolism, was identified, involving trehalose 6-phosphate.
• The mutant accumulated more polysaccharides than the wild-type, especially at lower growth rates.

Conclusions:

• Beta-PGM is essential for efficient growth of Lactococcus lactis on maltose and trehalose.
• The enzyme plays a critical role in directing carbon flux during growth on specific sugars.
• Lactococcus lactis possesses a unique pathway for trehalose breakdown, independent of maltose metabolism.