Molecular characterization of xanthan gum producing Xanthomonas Campestris isolated from dark rot spotted leaves in Keffi, Nasarawa State, Nigeria

Background: Despite the wide application of Xanthan gum, its commercial production remains a global challenge. In recent years, considerable research has been carried out using agro-industrial wastes, which are renewable and abundantly available to produce value-added products. The present study was set out for molecular identification of Xanthomonas campestris from leaves of four different plants with indications of dark rot spots and evaluation of their xanthan gum production capacity. Methods: Twenty-five (25) samples of leaves from four different plants with indications of dark rot spots were collected from the study area and isolated for Xanthomonas campestris following standard microbiological methods. Cultural, morphological and biochemical tests were conducted to confirm the organism. Results: The results revealed that of the total 100 samples taken, 6 leaves (24%) were infected with Xanthomonas species in mint, 3(12%) were infected in mango, 1(4%) were infected in rice and 2(8%) were infected in pepper. Further molecular identification of the isolates was carried out to reveal Xanthomonas campestris pv. vesicatoria strain 85-10 and Xanthomonas perforans strain 91-118. These were further used for the production of xanthan gum using sugar cane molasses substrates extracted from sugar cane, which was used as fermentation medium for the production. Isolates from plants varying ability in Xanthan gum production, with the mint plant having the highest Xanthan gum production (0.10 ± 0.02 to 0.9 ± 0.00 g/l). Conclusion: The present study confirmed the high xanthan gum production capacity of Xanthomonas campestris from dark rot spots containing mint leaves and should be considered during local and industrial production of the xanthan gum