The biopolymer gellan belongs to the family of microbial polysaccharides having a wide range of industrial applications. Attempts were made to produce gellan gum in submerged fermentation (SmF) using Sphingomonas paucimobilis ATCC 31461. Studies on the nutritional requirements for optimal exopolysaccharide production in a salt based synthetic medium revealed soluble starch (20 g/l) as the best carbon source and tryptone (0.5 w/v%) as the best nitrogen source. Supplementation of L-threonine (5 g/l) to the production medium slightly enhanced the formation of gellan. A maximum of 35.7 g/l gellan was produced under optimized conditions, which included 20-h old inoculum of 10% (v/v) size. Deacetylated gellan was also recovered successfully from the fermentation broth. (C) 2002 Elsevier Science Ltd. All rights reserved.