Abstract
The purpose of this study was to find the optimum growth cultural composition for the production of the microbial exopolysaccharide, gellan, by the bacteria Sphingomonas paucimobilis using batch cultural method in laboratory media. The study included the effect of the type and concentration of organic compounds as a sole carbon source, type and concentration of organic and non-organic nitrogen source, as well as, the effect of adding of some amino acids and non-ionic surfactants to the gellan production basal medium. The physical cultural conditions were fixed, and the production was carried for 48hrs incubation period, 10% inoculums volume, initial pH of 7.0, incubation temperature at 30oc and agitation speed of 250 rpm in an orbital shaker incubator. Results indicated that the best organic source was glucose at a concentration of 2% as it resulted in 4.44g of gellan/l of production medium, and the best organic nitrogen source was yeast extract at 0.05% and the best non-organic nitrogen source was ammonium chloride at 0.1% concentration, as they gave 4.27 and 4.41 g/l, respectively. On the other hand, the amino acid threonine at 0.05% was the best among other amino acids, and the non-ionic surfactant Triton X-100 at 0.1% was the best and they produced 5029 and 5.59 g of gellan/l of the medium.
