Improved yields of cyclic nigerosylnigerose from starch by pretreatment with a thermostable branching enzyme
2010
Aga, H., Hayashibara Biochemical Labs. Inc., Okayama (Japan) | Okamoto, I. | Taniguchi, M. | Kawashima, A. | Abe, H. | Chaen, H. | Fukuda, S.
Cyclic nigerosylnigerose (CNN) is produced enzymatically from starch by the combined action of 6-alpha-glucosyltransferase and 3-alpha-isomaltosyltransferase. In our previous study, alpha-1,6-branching chains found in the structure of amylopectin and glycogen were shown to be favorable for CNN formation by the two enzymes. Therefore, we examined whether the introduction of alpha-l,6-branch points into starch using the action of branching enzyme (BE) could improve the yield of CNN from starch. Thermostable BE from Geobacillus stearothermophilus TC-9l was prepared as a purified recombinant protein. Pretreatment of amylose with BE considerably increased the CNN yield from 5% to 38%. When BE acted on tapioca starch, the CNN yield was elevated from 47% to 60%. Conversely, BE treatment of waxy corn starch containing very little amylose resulted in a negligible increase in CNN yield. In addition, BE exerted a beneficial effect when starch with a lower degree of hydrolysis was used as a substrate. The present results indicate that the addition of alpha-l,6-glucosidic linkages to starch using BE is an effective strategy to improve the yield of CNN from starch.
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