Levan is a fructan polymer that offers a variety of applications in the chemical, health, cosmetic and food industries. Most of the levan applications depend on levan molecular weight, which in turn depends on the source of the synthesizing enzyme and/or on reaction conditions. Here we demonstrate that in the particular case of levansucrase from Bacillus subtilis 168, enzyme concentration is also a factor defining the molecular weight levan distribution. While a bimodal distribution has been reported at the usual enzyme concentrations (1U/ml equivalent to 0.1μM levansucrase) we found that a low molecular weight normal distribution is solely obtained al high enzyme concentrations (>5U/ml equivalent to 0.5μM levansucrase) while a high normal molecular weight distribution is synthesized at low enzyme doses (0.1U/ml equivalent to 0.01μM of levansucrase).