27. Developments in Thermostable Gellan Lyase

Thermostable carbohydrate-degrading enzymes are of special interest for many industrial applications as the solubility of carbohydrates at elevated temperatures sharply increases. Gellan is among the microbial exopolysaccharides found recently extensive use in food, microbial cultivation media, and pharmaceutical industries. Enzyme modification of gellan could change its molecular weight, hardness of its gel, and its elasticity and in such a way might broaden its current spectrum of application. As gellan is soluble at temperatures higher than 60°C, an industrial need in a thermostable gellan lyase is clearly outlined. Several reports on mesophilic bacterial strains producing gellan lyases are known, and only one thermophilic bacterial producer, Geobacillus stearothermophilus 98, was reported up to now. In this chapter, the source microorganism and properties of the thermostable gellan lyase are discussed in relation to those of mesophilic producers. Even though the accumulated knowledge on the structural and catalytic properties of the gellan lyase is still very limited, the results obtained clearly demonstrate that it is a new enzyme with interesting characteristics, which could add to the commercial value of gellan as an emulsifier, stabilizer, gel agent, thickener and suspending agent, and application in the future are also suggested.