Characterization and optimization of gellan gum production by natural Sphingomonas sp. SM2

Gellan is one of the most important industrial microbial exopolysaccharides used for a wide range of applications in food, pharmaceutical, and oil. In this study, a native strain of Sphingomonas producing gellan gum was identified from rice roots. Various factors, including carbon and nitrogen sources, pH levels, fermentation duration, and aeration, were investigated to enhance the production of gellan by Sphingomonas sp. SM2. The highest efficiency in gum production was achieved by a medium composed of 30 g/L glucose. When the carbon-to-nitrogen ratio was 30, organic nitrogen caused this increase. By incorporating all relevant factors, the optimized fermentation process can yield a gum concentration of 8.64±0.34 g/L. The total carbohydrate content of the native gum was found to be 52.62±0.52%. The existence of mucilage surrounding the bacterial cells was verified by scanning electron microscopy images. The extracted gellan gum was characterized using FTIR, 1H NMR, and HPLC analyses. The structure of the gum was confirmed by comparing it with the standard gellan gum. The production of gellan gum by Sphingomonas sp. SM2 using the utilization of diverse carbon sources suggests its immense potential as a gellan producer.