Production of extracellular fructans by Gluconobacter nephelii P1464

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 1122939153453kDa) and a sizeable polydispersity (Mw/Mn=2157 +/- 160), 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 0774 to 1244gl(-1)h and from 0181 to 0436gg(-1), respectively, confirmed, that G.nephelii P1464 could be used as promising strain for commercial production of levan. Significance and Impact of the StudyBacterial 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

Cellulose synthesis by Komagataeibacter rhaeticus strain P 1463 isolated from Kombucha

Isolate B17 from Kombucha was estimated to be an efficient producer of bacterial cellulose (BC). The isolate was deposited under the number P 1463 and identified as Komagataeibacter rhaeticus by comparing a generated amplified fragment length polymorphism (AFLP (TM)) DNA fingerprint against a reference database. Static cultivation of the K. rhaeticus strain P 1463 in Hestrin and Schramm (HS) medium resulted in 4.40 +/- 0.22 g/L BC being produced, corresponding to a BC yield from glucose of 25.30 +/- 1.78 %, when the inoculum was made with a modified HS medium containing 10 g/L glucose. Fermentations for 5 days using media containing apple juice with analogous carbon source concentrations resulted in 4.77 +/- 0.24 g/L BC being synthesised, corresponding to a yield from the consumed sugars (glucose, fructose and sucrose) of 37.00 +/- 2.61 %. The capacity of K. rhaeticus strain P 1463 to synthesise BC was found to be much higher than that of two reference strains for cellulose production, Komagataeibacter xylinus DSM 46604 and Komagataeibacter hansenii DSM 5602(T), and was also considerably higher than that of K. hansenii strain B22, isolated from another Kombucha sample. The BC synthesised by K. rhaeticus strain P 1463 after 40 days of cultivation in HS medium with additional glucose supplemented to the cell culture during cultivation was shown to have a degree of polymerization of 3300.0 +/- 122.1 glucose units, a tensile strength of 65.50 +/- 3.27 MPa and a length at break of 16.50 +/- 0.83 km. For the other strains, these properties did not exceed 25.60 +/- 1.28 MPa and 15.20 +/- 0.76 km