Candidate Acetic Acid Bacteria Strains for Levan Production.

In this study, twelve strains of acetic acid bacteria (AAB) belonging to five different genera were tested for their ability to produce levan, at 70 and 250 g/L of sucrose concentration, respectively. The fructan produced by the bacterial strains was characterized as levan by NMR spectroscopy. Most of the strains produced levan, highlighting intra- and inter-species variability. High yield was observed for NBRC 101099 , DSM 14400 and DSM 9533 at 70 g/L of sucrose. A 12-fold increase was observed for NBRC 101099 at 250 g/L of sucrose concentration. Levan production was found to be affected by glucose accumulation and pH reduction, especially in DSM 14400 . All the strains showed a negative correlation with the increase in sucrose concentration. Among strains of genus, no clear effect of sucrose on levan yield was found. Results obtained in this study highlighted the differences in levan yield among AAB strains and showed interdependence between culture conditions, carbon source utilization, and time of incubation. On the contrary, the levan yield was not always related to the sucrose concentration.