Optimization of levansucrase/endo-inulinase bi-enzymatic system for the production of fructooligosaccharides and oligolevans from sucrose

Abstract

A bi-enzymatic system based on the combined use of levansucrase (LS) from Bacillus amyloliquefaciens and endo-inulinase from Aspergillus niger in a one-step reaction was investigated for the synthesis of fructooligosaccharides (FOSs) and oligolevans using sucrose as the sole substrate. Sucrose concentration was the most important independent variable, whilst LS to endo-inulinase ratio exhibited significant effects on the end-product profiles. The interaction between sucrose concentration and reaction time exhibited significant effect on all responses. At the initial stage of time course, short chain FOSs (scFOSs, 1-kestose, nystose, 1F-fructosylnystose) were the major products, whilst 6-kestose, medium chain fructooligosaccharides (mcFOSs, levanohexaose, levanopentaose) and oligolevans became the dominant ones at the late stage. The optimal conditions leading to a high yield of scFOSs (1:1 ratio, 0.5h, 0.6M) were different from those resulting in a high yield of mcFOSs and oligolevans (1.85:1 ratio, 1.77h, 0.6M). The bi-enzymatic system has a great potential for the production of FOSs and oligolevans at a large scale because of its high yield (57–65%, w/w) and productivity (65.8–266.8g/Lh), and its uses of low temperature (35°C) and low concentration of sucrose. To the best of our knowledge, this is the first study on the optimization of a LS/endo-inulinase bi-enzymatic system.