Engineering microbial exopolysaccharides for food applications.

Microbial exopolysaccharides for direct food applications remain rare due to significant financial and regulatory hurdles. However, exopolysaccharides without direct food approval have recently been employed in various indirect food-related uses. This review highlights microbial exopolysaccharides with strong potential for both direct and indirect food applications and outlines engineering strategies to optimize their biotechnological production. For sucrase-based polysaccharides, enzyme engineering aimed at controlling molecular weight has shown strong potential for generating novel functional properties. In the case of synthase-based polysaccharides, leveraging epimerases or exploiting the natural promiscuity of the synthase enzyme emerges as a particularly promising approach. For heteropolysaccharides, this review presents some rare examples of successful engineering and heterologous expression in chassis organisms, while also identifying key challenges that still limit efficient optimization.