Characterization of xanthan gum-metal complexes biosynthesized using a medium containing produced water and cassava processing residues.

The use of residues from petroleum and crop industries is a feasible and sustainable alternative approach for the production of xanthan gum (XG). This study aimed to evaluate the biosynthesis of XG and the resulting final product obtained using Xanthomonas axonopodis pv. manihotis 1182 in a medium containing produced water (PW) and cassava processing residues. The combined use of PW and cassava crop residues was beneficial for XG production, achieving a product yield of 6.80 g L^-1. The micrographs of recovered XG revealed the presence of elongated fiber-like microstructures rather than large agglomerates. The X-ray diffraction profiles of recovered xanthan comprised well-defined peaks rather than an amorphous halo. The thermogravimetry profiles revealed the presence of approximately 60 % of remaining solids in recovered xanthan, in contrast to 30 % in the commercial sample. All the samples demonstrated a pseudoplastic behavior; however, the consistency indices of the recovered samples were approximately 50-times lower than those of commercial XG. The emulsification indices of the recovered XG were > 50 % and comparable to those of commercial xanthan. In this study, for the first time, we obtained a complex XG-metal structure possessing a high emulsification capacity and low viscosity.