Production of extracellular fructans by Gluconobacter nephelii P1464.

Abstract

Bacterial extracellular fructans, known as levans, have potential applications in food, pharmaceutical and cosmetic industries and high fructan producing strains could contribute into the cost reduction and more extensive commercial usage of them. An acetic acid bacteria (AAB) isolate P1464 was obtained from the Microbial Strain Collection of Institute of Microbiology and Biotechnology, University of Latvia and identified as Gluconobacter nephelii by DNA-DNA hybridization and the formation of extracellular fructans by this strain was confirmed. Isolated extracellular fructose polymers were characterized using FT-IR spectroscopy and the structural features of fructan appeared as similar to the reference sample of bacterial levan. Molecular mass estimates showed that the isolated G.nephelii P1464 fructose polymer has a relatively small molecular weight (Mw 1122·939±153·453kDa) and a sizeable polydispersity (Mw/Mn=21·57±1·60), as compared with other AAB, which could promote their physiological activity, including the prebiotic effects. Obtained at different cultivation conditions characteristics of fructan production, including the biotechnological indices such as the productivity (Qp) and yield (Yp/s) ranging from 0·774 to 1·244gl(-1) h and from 0·181 to 0·436gg(-1) , respectively, confirmed, that G.nephelii P1464 could be used as promising strain for commercial production of levan. Bacterial fructans, known as levans, have extensive options for practical usage, however, actually limited due to high production costs. Therefore, the searches for efficient producer strains should be an urgent task to reduce costs. This study is the first report on the formation of fructans by a novel strain of acetic acid bacteria (AAB) Gluconobacter nephelii P1464. Characteristics obtained at different cultivation conditions confirmed the operation of a competitive and perspective producer strain. Isolated extracellular fructans are characterized by a lower molecular weight as compared with other AAB which could promote their physiological activity, including the prebiotic effects.