초록
<P>The ability of an inulosucrase (IS) from <I>Lactobacillus gasseri</I> DSM 20604 to synthesize fructooligosaccharides (FOS) and maltosylfructosides (MFOS) in the presence of sucrose and sucrose-maltose mixtures was investigated after optimization of synthesis conditions, including enzyme concentration, temperature, pH, and reaction time. The maximum formation of FOS, which consist of β-2,1-linked fructose to sucrose, was 45% (in weight with respect to the initial amount of sucrose) and was obtained after 24 h of reaction at 55°C in the presence of sucrose (300 g liter<SUP>−1</SUP>) and 1.6 U ml<SUP>−1</SUP> of IS–25 mM sodium acetate buffer–1 mM CaCl<SUB>2</SUB> (pH 5.2). The production of MFOS was also studied as a function of the initial ratios of sucrose to maltose (10:50, 20:40, 30:30, and 40:20, expressed in g 100 ml<SUP>−1</SUP>). The highest yield in total MFOS was attained after 24 to 32 h of reaction time and ranged from 13% (10:50 sucrose/maltose) to 52% (30:30 sucrose/maltose) in weight with respect to the initial amount of maltose. Nuclear magnetic resonance (NMR) structural characterization indicated that IS from <I>L. gasseri</I> specifically transferred fructose moieties of sucrose to either C-1 of the reducing end or C-6 of the nonreducing end of maltose. Thus, the trisaccharide erlose [α-<SMALL>d</SMALL>-glucopyranosyl-(1→4)-α-<SMALL>d</SMALL>-glucopyranosyl-(1→2)-β-<SMALL>d</SMALL>-fructofuranoside] was the main synthesized MFOS followed by neo-erlose [β-<SMALL>d</SMALL>-fructofuranosyl-(2→6)-α-<SMALL>d</SMALL>-glucopyranosyl-(1→4)-α-<SMALL>d</SMALL>-glucopyranose]. The formation of MFOS with a higher degree of polymerization was also demonstrated by the transfer of additional fructose residues to C-1 of either the β-2,1-linked fructose or the β-2,6-linked fructose to maltose, revealing the capacity of MFOS to serve as acceptors.</P>