Statistical approach to optimization of fermentative production of gellan gum from Sphingomonas paucimobilis ATCC 31461

Gellan gum, a high-molecular-weight anionic linear polysaccharide produced by pure-culture fermentation from Sphingomonas paucimobilis ATCC 31461, has elicited industrial interest in recent years as a high-viscosity biogum, a suspending agent, a gelling agent, and an agar substitute in microbial media. In this paper we report on the optimization of gellan gum production using a statistical approach. In the first step, the one factor-at-a-time method was used to investigate the effect of medium constituents such as carbon and nitrogen sources; subsequently, the intuitive analysis based on statistical calculations carried out using the L16-orthogonal array method. The design for the L16-orthogonal array was developed and analyzed using MINITAB 13.30 software. All the fermentation runs were carried out at 30±2°C on a rotary orbital shaker at 180 rpm for 48 h. In the second step, the effects of amino acids and gellan precursors such as uridine-5′-diphospate (UDP) and adenosine-5′-diphospate (ADP) on the fermentative production of gellan gum were studied. Media containing 4% soluble starch, 0.025% yeast extract, 1.0 mM ADP and 0.05% tryptophan gave a maximum yield of 43.6 g l−1 starch-free gellan gum, which was significantly higher than reported values in the literature.