Structural studies on exopolysaccharides produced by three different propionibacteria strains

Area of Science:

• Microbiology
• Biochemistry
• Polymer Science

Background:

• Propionibacteria are known for producing various metabolites.
• Exopolysaccharides (EPS) are crucial for bacterial cell interactions and biofilm formation.
• Whey is a byproduct of cheese production, offering a sustainable medium for microbial fermentation.

Purpose of the Study:

• To characterize the exopolysaccharides produced by specific Propionibacteria strains grown on whey.
• To elucidate the structural composition and repeating unit of these bacterial exopolysaccharides.

Main Methods:

• Cultivation of Propionibacterium freudenreichii 109, P. freudenreichii 111, and P. thoenii 126 on whey-based media.
• Chemical analysis including methylation analysis, mass spectrometry, and partial acid hydrolysis.
• Advanced spectroscopic studies using 1D/2D NMR (1H and 13C) for structural elucidation.

Main Results:

• The exopolysaccharides are charged heteropolymers composed of D-glucose, D-mannose, and D-glucuronic acid.
• A consistent molar ratio of 2:2:1 (D-glucose:D-mannose:D-glucuronic acid) was observed across all strains.
• Structural determination revealed a common branched pentasaccharide repeating unit for all three exopolysaccharides.

Conclusions:

• The studied Propionibacteria strains produce structurally conserved exopolysaccharides on whey-based media.
• The identified pentasaccharide repeating unit provides insights into the biosynthesis and potential functions of these bacterial EPS.
• This research contributes to understanding bacterial polysaccharide structures and their production using sustainable resources.