The Production, Purification and Properties of the Biopolymer Levan Produced by the Bacterium Erwinia Herbicola

Abstract : The optimized conditions for the production of levan by Erwinia herbicola were determined to be pH (6.0-7.5), incubation time (72 hours), culture media (K2HPO4, 3.0g; NaC1, 2.0g; Urea, 0.3g; MgSO4.7H2O, 0.4g; FeSO47H2O, 0.10g, 5% sucrose per liter), and polymer purification (sodium dodecyl sulfate treatment, dilution with H2O, dialysis, and methanol precipitation). While continuous culture fer;mentation at pH 7.2 produced the highest yield of polymer, molecular weight determinations of the isolated polymer could not be made with certainty because of laven behavior in aqueous solution. In addition, the yields of polymer were low (below 25%) when compared to other biopolymers studied (i.e., pullulan, elsinan). The physical properties of clear films produced from this polymer could not be adequately evaluated due to brittleness, which could not be overcome with the addition of glycerol as a plasticizer. Keywords: Biopolymer, Levan, Fermentation, Molecular weight, Properties, Processing/purification.