Gellan gum

For decades microbial exopolysaccharides have been invaluable ingredients i n the food industry, as well as having many attractive pharmaceutical and c hemical applications. Gellan gum is a comparatively new gum elaborated by t he Gram-negative bacterium Sphingomonas paucimobilis. Although its physico- chemical properties have been well characterized, the ecology and physiolog y of Sphingomonas, and the factors influencing the fermentation process for production of this gum have received much less attention. This review focu ses on the metabolism and the enzymic activity of this bacterium, as well a s the factors that influence gellan production, including process temperatu re, pH, stirring rate, oxygen transfer, and composition of the production m edium. Potential strategies for improving the production process are discus sed in the context of processes for the production of other microbial biopo lymers, particularly exopolysaccharides. In addition, the importance and po tential utility of gellan lyases in modification of gellan and in other app lications is critically evaluated.