Fig. 5

Molecular weight distribution of levan with different treatments. a Levan from 72-h cultivation sample; b 72-h cultivation sample centrifuged, filtered through a 0.22-μm membrane, and incubated for 120 h; c 72-h cultivation sample centrifuged, filtered through a 0.22-μm membrane, pH-adjusted to 7.0, boiled, pH-adjusted to 4.0, and incubated for 120 h; d control