Tailor-made polysaccharides containing uniformly distributed repeating units based on the xanthan gum skeleton

Area of Science:

• Biochemistry
• Materials Science
• Microbiology

Background:

• Xanthan gum is a microbial polysaccharide with structure-dependent physicochemical properties.
• Current production methods involving wild-type strains are complex and labor-intensive.
• Understanding the structure-property relationship is key to developing advanced xanthan-based materials.

Purpose of the Study:

• To design and produce novel xanthan gum variants with specific rheological properties.
• To investigate the impact of structural modifications on xanthan gum's properties.
• To establish a foundation for creating xanthan-containing block copolymers.

Main Methods:

• Utilized marker-less gene knockout and overexpression in *Xanthomonas campestris* CGMCC 15155.
• Designed eight polysaccharides with uniformly distributed repeating units based on the natural xanthan skeleton.
• Analyzed the relationship between primary structure, secondary structure, and rheological properties.

Main Results:

• Generated eight xanthan variants with distinct homogeneous primary structures and rheological behaviors.
• Identified key structural elements influencing properties: terminal mannose, pyruvyl, and acetyl groups.
• Demonstrated that absence of terminal mannose reduced viscosity and modulus.
• Showed internal acetyl groups stabilize helix structure, while pyruvyl groups destabilize it.

Conclusions:

• The engineered xanthan variants exhibit tailored rheological properties based on their specific structures.
• These findings provide a theoretical basis for further structure-activity relationship studies of xanthan.
• The developed variants facilitate the construction of xanthan-containing block copolymers.