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Abstract
Sphingomonas strains are known to produce extracellular biopolymers. S. paucimobilis ATCC 31461 synthesizes the exopolysaccharide (EPS) gellan gum, which hase a wide range of applications in the food, pharmaceutical, and other industries. The main objective of the present study is to improve the production of gellan gum -#102;-#114;-#111;-#109; different strains of S. paucimobilis. br Sixteen local S. paucimobilis strains were isolated -#102;-#114;-#111;-#109; different Egyptian geographical sites and subjected to identification and characterization using different microbiological, biochemical and molecular genetic techniques. Strain evaluation was carried out to compare polysaccharide productivity of the 16 local strains with the industrial strain S. paucimobilis ATCC 31461. Two protocols were applied in this study to improve S. paucimobilis polysaccharide productivity. The first was mutation induction using gamma irradiation and sodium azide. The second was utilize protoplast fusion technique for producing new genetic recombinants. Mutagenesis was more efficient in the improvement of S. paucimobilis polysaccharides productivity The mutant strain S. paucimobilis ATCC 31461gam1, which obtained after the exposure of the industrial strain to gamma radiation dose of 50 Gray, recorded the highest polysaccharides productivity (49 g/L), exceeding 8-folds the productivity of its original strain (6 g/L). This improved mutant was followed by the mutant S. p.G1gam1, which produces 46 g/L (2300% of the its original strain). Fusant F22 showed the highest efficiency of polysaccharide productivity (17.16 g/l) among all protoplast fusion products, followed by F13 (16.82 g/l) and F9 (16.3 g/l)