Levan from Azotobacter vinelandii as a Component of Biosorbents for Heavy Metals and Radionuclides

Cultivation of Azotobacter vinelandii D-08 in media with molasses and distillery waste was shown to increase levansaccharase activity and levan biosynthesis. Levansaccharase also exhibited maximal activity when grown in a molasses medium, which correlated with the highest level of the polysaccharide synthesis. An additional fraction of high molecular weight levan (more than 1000 kDa) with a modified molecular structure (reduced contribution of double bond oscillations and decreased molecule hydration) was synthesized by bacteria, which resulted in a higher capacity for the binding of Na, Mg, S, Ca, and Fe in the cultivation medium. Cryogels based on polyvinyl alcohol and levan were capable of efficient maximal absorption of different ions at different times: copper (1 h), zinc (24 h), and cadmium (10 min), radioactive plutonium (4 h), and uranium (168 h). This suggests that they can be used as sorbents for wastewater treatment to eliminate heavy metals and radionuclides.