Improved xanthan gum production by a newly Xanthomonas melonis: A promising biopolymer for drilling fluids

This study investigates xanthan gum production using bacterial strains isolated from plants. Bacteria were screened from local plant sources, fermentation conditions were optimized, and the viscosity of the produced xanthan gum was evaluated for oil drilling applications. A total of 27 bacterial strains were isolated from yellow pumpkin leaves, wild grape leaves, and the bark resin of the red water guava tree. Four strains with high gum viscosity were identified: Xanthomonas melonis LBU-4, X. melonis LBU-8, X. sacchari AGR-5, and Sphingomonas panni LBU-7. Shaken flask fermentation using different carbon sources showed that X. melonis LBU-4, grown in a sucrose-rich medium, produced the highest xanthan gum yield (22.8 g/l) with high viscosity after 120 hours of cultivation. FTIR spectroscopy confirmed the structural similarity between the produced xanthan gum and the commercial xanthan gum. Viscosity tests of the produced xanthan gum comply with American Petroleum Institute (API) 13A standards for drilling-grade xanthan gum. These findings highlight X. melonis LBU-4 as a promising candidate for industrial-scale xanthan gum production.