Genetic and functional characterization of Lactobacillus panis levansucrase
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ORIGINAL PAPER
Genetic and functional characterization of Lactobacillus panis levansucrase Florian W. Waldherr · Daniel Meissner · Rudi F. Vogel
Received: 19 March 2008 / Revised: 30 May 2008 / Accepted: 25 June 2008 / Published online: 8 July 2008 © Springer-Verlag 2008
Abstract Exopolysaccharides (EPS) can aVect the rheological properties of foods, act as stabilizers or stimulate preferential growth of biWdobacteria in the gut and therefore function as prebiotics. The latter is referred to fructans, which are synthesized from sucrose by fructosyl transferases (FTFs). In this work, the FTF enzyme of Lactobacillus panis TMW1.648 isolated from sourdough was characterized. The coding gene was identiWed, sequenced and expressed heterologously in E. coli. Enzyme activity was maximal at pH 4.0–4.6, 45°C and a substrate concentration of 300 mmol l¡1. It produced free fructose, a high molecular fructan and the oligosaccharide kestose from sucrose. Calcium ions proved to be essential for the enzymatic activity. In comparison to published data of other FTF enzymes of lactobacilli the described enzyme showed signiWcant diVerences. Keywords Levansucrase · Fructosyltransferase · Exopolysaccharide · Fructan · Lactobacillus panis
Introduction Bacterial exopolysaccharides, like fructans and glucans, are increasingly employed in the food industry. They provide an alternative to chemical additives as stabilizer, anti-staling or water binding-agent and can aVect the rheological
Communicated by Erko Stackebrandt. F. W. Waldherr · D. Meissner (&) · R. F. Vogel Technische Mikrobiologie, Technische Universität München, Weihenstephaner Steig 16, 85350 Freising, Germany e-mail: [email protected]
properties of food such as milk products and bread. In addition, fructans and fructo-oligosaccharides (FOS) exhibit prebiotic features due to their abilities to pass the gastrointestinal tract undigested and stimulate preferential growth of beneWcial gut bacteria (Salminen et al. 1996; Bello et al. 2001; Delzenne and Kok 2001; Korakli et al. 2002). Many lactic acid bacteria secrete fructosyltransferases (FTFs) (commonly named fructansucrases) for the synthesis of high molecular fructans or low molecular FOS. These FTFs catalyze the transfer of the fructosyl residue from sucrose to various acceptor molecules. The use of raYnose as fructose donor has been described as well (Tieking et al. 2005b). Three diVerent transfer reactions can be distinguished depending on the acceptor molecule: (1) hydrolysis of sucrose, when water is used as acceptor, (2) transfer reaction, when sucrose or gluco- and fructosaccharides are used as acceptor (FOS synthesis) and (3) polymerization, when the growing fructan chain is used as acceptor (fructan synthesis). The ratio of the products (FOS or fructan) of FTFs diVers signiWcantly from enzyme to enzyme. The levansucrase of Bacillus subtilis produces only a high molecular levan and no FOS (Hernandez et al. 1995), whereas the levansucrase of Lactobacillus sanfranciscensis mainly synthesizes 1-kestose, a FOS,
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