Screening of Bacterial Isolates from Plant Leaves for Xanthan Gum Producing Potential

Abstract

Xanthan gum is a microbial polysaccharide produced by the plant pathogen Xanthomonas campestris, it is of great commercial importance due to its rheological properties and water solubility and has been used in various industries as a thickening and stabilizing agent. This research was aimed at producing Xanthan gum using Xanthomonas campestris isolated from diverse sources (tomato, pepper, mango and banana leaves) in Niger State, Nigeria. Leaves with black rot spots were collected from the plants in selected farms within Minna metropolis and transported to the research laboratory. The leaves were washed in normal saline and tenfold dilutions were prepared. Aliquots (1ml) were plated on Nutrient agar and incubated at 37˚C for 48h. Colonies with yellow colour were gram stained. Gram negative rod bacteria were subjected to emulsification test. Isolates with yellow colonies, gram negative rods and exhibited stable emulsion in carbon enriched medium were regarded as potential xanthan gum producers. Eight (61.5%) of the isolates screened fulfilled these conditions. Biochemical tests on the isolates revealed that the organism were Xanthomonas campestris and were coded accordingly (PP02, MG03, PP04, BN06, BN07, TM08, TM09 and MG11). Maximum xanthan production (21.01g/l) was observed in TM09 (isolate from tomato leaves) While BN07 (isolate from banana leave) had the least (0.02g/l) gum produced. The results suggest that the strain of Xanthomonas that infects tomato produce more gum than those from pepper, mango and banana leaves.