Fermentation characteristics of levansucrase mutants of Zymomonas mobilis

Two mutants, Ls1 and Ls2, of Zymomonas mobilis B-806 unable to produce levan were isolated. With native gel electrophoresis and zymogram analysis it was confirmed that the mutants did not synthesize active levansucrase (E2). However, they produced intracellular sucrase (E1) and extracellular invertase (E3). Comparison of these mutants with the parent strain for alcohol production on glucose, fructose and sucrose (100 g/l each) media revealed that the final ethanol concentration achieved in sucrose medium was only about 5 g/l higher with the mutants than with the wild type. The ethanol yield of the mutants increased from 0.48 g/g to 0.50 g/g on sucrose medium.