In-depth rheological characterization of genetically modified xanthan-variants.

Xanthan is an extensively studied viscosifying agent discovered in 1961. Acetylation and pyruvylation have a major influence on its rheological properties and the effect of these groups on the conformation and rheological properties of xanthan have been studied for decades. However, these studies rely mainly on chemical modifications and therefore the degree of pyruvylation and acetylation as well as regioselectivity of deacetylation cannot be controlled. Here, we present an in-depth rheological characterization of natural xanthan and seven xanthan-variants, with defined acetylation and pyruvylation patterns created via genetic modification of Xanthomonas campestris LMG 8031. By that approach xanthan-variants with defined acetylation and pyruvylation patterns in their most natural state due to the mild production conditions were obtained. It was possible to link the defined substituent patterns to their corresponding rheological properties to give novel structure-function relationship insights of xanthan-variants in salt-free environments and in the presence of mono- and divalent cations.