The N-terminally- and domain V truncated enzyme GtfB of Lactobacillus reuteri strain 121 converts malto-oligosaccharides and starch in multiple carbohydrate structures. The products formed by the 4,6-glucanotransferase are elongated isomalto-/malto-oligosaccharides (IMMO) and isomalto-/malto-polymers (IMMPs). The enzyme GtfB-ΔN-ΔV converts maltoheptaose with a degree of polymerization (DP) of 7 in linear carbohydrates with DPs ranging from 2 to 35. Size-exclusion chromatography with BioGel P-2 is used to monitor the separated compounds. The glucans of DP > 35 contain 85 % α(1→6), and 15 % α(1→4) glycosidic linkages. Instead, when using amylose V as starting material the product mixture mainly consists of IMMPs. The modified starch products formed by the GtfB enzyme are derived soluble dietary fibers, which are potentially useful in the food industry.

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