Abstract
Microbial levan, a natural polymer of fructose, was produced and purified by alcohol precipitation from culture supernatants of Bacillus megaterium type 1 grown in an optimized liquid sucrose medium. GPC analysis showed that the yield of the major fraction of levan having molecular weight ~5000D increased with increase in sucrose concentration in the broth. Levan subjected to 60Co-gamma radiation as well as acid hydrolysis was investigated by rheometry, UV–visible spectrophotometry and gel permeation chromatography (GPC) techniques. Unlike most of the polysaccharides, levan powder exhibited good radiation degradation stability up to 150kGy. Gamma irradiation of 10% levan aqueous solution at 250kGy yielded 63.0% fructo-oligosaccharide (FOS) with an average molecular weight of 1250D. Acid hydrolysis of levan using 0.5N HCl for 60min treatment time gave rise to the desired FOS with lower yield (23.1%) as compared to that obtained in gamma radiolysis process.
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