Biocatalytic conversion of inulin and sucrose into short chain oligosaccharides for potential pharmaceutical applications

Abstract

The production of fructooligosaccharides (FOS) and inulooligosaccharides (IOS) of varying degrees of polymerization (DP) was optimized by orthogonal experimental designs using central composite design (CCD) and response surface methodology (RSM). The FOS produced were quantified and maximal GF2, GF3 and GF4 were 211.09 mM, 156.06 mM and 43.99mM respectively at pH 5.6 and 60 °C. Maximal IOS produced were quantified and F3, F4 and F5 were 70.3 mM, 38.8 mM and 12.43 mM respectively at pH 6.0 and 60 °C. The detection and quantification of oligosaccharides of specific chain length from inulin hydrolysis and sucrose elongation were carried out using high performance liquid chromatography with refractive index (HPLC-RI) detection, thin layer chromatography (TLC) and mass spectrometry with electrospray ionization (MS-ESI). FOS and IOS were ionized and detected in the positive ion mode using 1 mM LiCl, [M+Li]⁺. The FOS produced by the action of fructosyltransferases were monosaccharides (m/z=187.98), disaccharides (m/z=349.19), 1-kestose (GF2; m/z=511.25), nystose (GF3; m/z=673.27) and fructofuranosyl nystose (GF4; m/z=835.45). IOS produced were identified as fructose (F; m/z=187.01), inulobiose (F2; m/z=349.22) inulotrioses (F3; m/z=511.23), inulotetraoses (F4; m/z=673.29) and inulopentaoses (F5; m/z=835.22).