Structures and properties of gellan polymers produced by Sphingomonas paucimobilis ATCC 31461 from lactase compared with those produced from glucose and from cheese whey

The dairy industry produces large quantities of whey as a by-product of che ese production and is increasingly looking for new ways to utilize this was te product. Gellan gum is reliably produced by Sphingomonas paucimobilis in growth media containing lactose, a significant component of cheese,whey, a s a carbon source. We studied and compared polysaccharide biosynthesis by S . paucimobilis ATCC 31461 in media containing glucose, lactose (5 to 30 g/l iter), and sweet cheese whey. We found that altering the growth medium can markedly affect the polysaccharide yield, acyl substitution level, polymer rheological properties, and susceptibility to degradation. Depression of ge llan production from lactose compared with gellan production from glucose ( approximately 30%) did not appear to occur at the level of synthesis of sug ar nucleotides, which are the donors of monomers used for biosynthesis of t he repetitive tetrasaccharide unit of gellan. The lactose-derived biopolyme r had the highest total acyl content; the glucose- and whey-derived gellans had similar total acyl contents but differed markedly in their acetate and glycerate levels. Rheological studies revealed how the functionality of a gellan polysaccharide is affected by changes in the acyl substitution.