T I G O T É C

alternatives. A wide range of substances, viz. Carrageenans[9], Gelrite®[5], sago and isubgol[10], and xyloglucan[11], have been tried as substitute or partial substitute for agar. Other polymers, such as galactomannans (GMs), also occur in large amounts in plant seeds. They essentially consist of 1-4 linked β-D-mannopyranosyl backbone partially substituted at O-6 with D-galactopyranosyl side groups[12]. Two GMs are produced commercially in great amounts: guar gum from Cyamopsis tetragonolobus and locust bean gum from carob (Ceratonia siliqua)[13]. The first has a polysaccharide structure characterized by Man/ Gal ratio near to 2:1 and the second near to 4:1. To compete with the great demand for gums, a native tree of Brazil has been investigated for GM production. Cassia fastuosa, a Caesalpiniaceae, also known as Cassia, Maripixuma, Parica, contains a legume with 40-50 seeds with total mass of 8-10g, and from which seeds the GM used in this work was extracted. To evaluate the physical properties of agar/ galactomannan mixture in the culture media rheological techniques and diffusion tests were applied. The viscoelastic behaviour of polysaccharide blends in the media was compared with the individual components, using oscillatory measurements. Furthermore, was investigated the in vitro effect of partial substitution of agar by galactomannans fro