Molecular and biochemical characteristics of inulosucrase InuBK from Alkalihalobacillus krulwichiae JCM 11691.

Information about the inulosucrase of nonlactic acid bacteria is scarce. We found a gene encoding inulosucrase (inuBK) in the genome of the Gram-positive bacterium Alkalihalobacillus krulwichiae JCM 11691. The inuBK open reading frame encoded a protein comprising 456 amino acids. We expressed His-tagged InuBK in culture medium using a Brevibacillus system. The optimal pH and temperature of purified InuBK were 7.0-9.0 and 50-55 °C, respectively. The findings of high-performance anion-exchange chromatography, nuclear magnetic resonance spectroscopy, and high-performance size-exclusion chromatography with multiangle laser light scattering showed that the polysaccharide produced by InuBK was an inulin with a molecular weight of 3806, a polydispersity index (PI) of 1.047, and fructosyl chain lengths with 3-27 degrees of polymerization. The size of InuBK was smaller than commercial inulins, and the PI of the inulin that it produced was lower.

Production of Functional Inulin-Type Fructooligosaccharides by an Enzyme from Penicillium citrinum.

We report the production of functional inulin-type fructooligosaccharides such as trisaccharide 1-kestose, O-ß-D-fructofuranosyl-(2→1)-ß-D-fructofuranosyl α-D-glucopyranoside, and tetrasaccharide nystose, O-ß-D-fructofuranosyl-(2→1)-ß-D-fructofuranosyl-(2→1)-ß-D-fructofuranosyl α-D-glucopyranoside, from sucrose by an enzyme from Penicillium citrinum. Sucrose acted as a fructosyl donor and acceptor for the enzyme. The optimum pH and temperature for the enzymatic reaction were 5 and 50 °C, respectively. The enzyme was stable in the pH range of 4.5-7 and at 50 °C. The maximum concentration of 1-kestose obtained was 110 mg/ml, and the maximum production efficiency was 37.3% after a 48-h reaction. The maximum efficiency of combined fructooligosaccharide (1-kestose and nystose) production was 47.1% after a 72-h reaction. Fructooligosaccharides were therefore successfully produced via a fructosyl transfer reaction catalyzed by an enzyme from P. citrinum.