High yield production of levan-type fructans by Gluconobacter japonicus LMG 1417

Levan, a β-2,6-glycosidic linked fructan, is a promising alternative for the inulin dominated fructan market. Although levan is already used in some cosmetic products, the commercial availability of the fructan is still limited. Here we show that Gluconobacter japonicus LMG 1417 is a potent levan-forming organism and a promising platform for the industrial production of levan. The levansucrase LevS1417, which is produced by G. japonicus LMG 1417 and secreted by a signal-peptide-independent pathway, exhibited extraordinary high activity (4726 ± 821 U mg^-1 at 50 °C). A cell-free levan production based on the supernatant of the investigated strain led to a final levan yield of 157.9 ± 7.6 g L^-1. The amount of secreted levansucrase was more than doubled by plasmid-mediated homologous overproduction of LevS1417 in G. japonicus LMG 1417. Accordingly, the space-time yield of cell-free levan production was doubled using the plasmid-bearing mutant.