Enzymatic Production of Cellobiose from Starch and Its Reduction to Cellobiitol

Abstract

Cellobiose (528-50-7) was synthesized from starch using two phosphorylases. α-Glucan phosphorylase (EC 2.4.1.1) converted 39.6% of glucose residues in the starch mol. into glucose 1-phosphate in the presence of 1 M inorg. phosphate. Inorg. phosphate was selectively dialyzed out from the resultant reaction mixt. by electrodialysis equipped with an ion exchange membrane having a mol. wt. cut-off of 100. Thus glucose 1-phosphate soln. free from inorg. phosphate was obtained with 82.1% yield. Cellobiose phosphorylase (EC 2.4.1.20) converted 89.2% of added glucose 1-phosphate into cellobiose when the above G1P soln. was incubated with a roughly equimolar amt. of glucose in the presence of magnesium acetate under alk. conditions (pH 8.0). As a result of three successive steps using two phosphorylases, cellobiose was produced from starch with a 29.0% yield. Cellobiose was reduced under a sponge nickel catalyst (Raney nickel) and the obtained cellobiitol was crystd. with an 86.7% yield. The 1H- and 13C-NMR spectra of this compd. agreed well with those expected from 4-O-β-glucosyl-D-glucitol (cellobiitol, 535-94-4). The X-ray crystallog. anal. of the obtained cellobiitol crystal revealed it to be a monoclinic space group P21 (4), with the following unit-cell parameters: a = 1.0007, b = 0.8683, c = 2.3137 nm, β = 127.27°. From a thermo gravimetric-differential scanning calorimetric anal., the cellobiitol crystal was found to have a m.p. of 103.6°C and to be in the form of a monohydrate. Cellobiitol showed a relative sweetness of around 20, being less sweet than other sugar alcs. such as glucitol (sorbitol) and maltitol. Cellobiitol was found to be much less hygroscopic than sorbitol and maltitol. The median LD of cellobiitol in rats was detd. to be more than 5000 mg/kg body wt. All these properties of cellobiitol indicate it to be a promising compd. as a food ingredient. [on SciFinder(R)]