The present work was devoted to investigations of the fructooligosaccharide (FOS) and levan forming activity of ethanol producing bacteria Zymomonas mobilis and their extracellular levansucrase. After cell separation the culture liquid was treated with ethanol to precipitate levan together with extracellular levansucrase. Levan-levansucrase sediment can be used as biocatalyst for fructooligosaccharide (FOS) production in sucrose syrup and levan sediment as soluble fibre source. The dynamics of sucrose conversion and glucose, fructose, and FOS formation by extracellular levansucrase showed that the fructose content increased only during the first 6 h, while the glucose content continued to increase during all 24 h of incubation. The glucose content exceeded the fructose approximately four times. I-Kestose, 6-kestose, neokestose and nystose, as well as other non identified fructooligosaccharides, was found in fructan syrup. Native or lyophilized Z. mobilis biomass added to levan-levansucrase sediment showed small changes in the activity of the biocatalyst. Z. mobilis biomass sedimented by ethanol together with levan and used as biocatalyst together with levansucrase did not increase the FOS forming activity of the biocatalyst. The presence of ethanol (7.0%) in sucrose syrup decreased the enzyme FOS forming activity on 24% during the first 24 h of incubation. Fructan syrup obtained from sucrose syrup by levan-levansucrase sediment as biocatalyst had a satisfactory taste, reduced energetic value and can be used as source of prebiotics-fructooligosaccharides and soluble fibre-levan as cholesterol lowering factor. (C) 2002 Elsevier Science Ltd. All rights reserved.