Structural and property characterization of low-molecular-weight novel reuterans synthesized from pea starch by Limosilactobacillus reuteri N1 GtfB with 4,6-α-glucanotransferase II activity.

Promising novel α-glucanotransferases with starch-converting activity have recently emerged from the CAZy GH70 GtfB subfamily. In this study, we thoroughly investigated and elucidated the impact of the newly characterized 4,6-α-glucanotransferase II Limosilactobacillus reuteri N1 GtfB (LrN1 GtfB), which was capable of synthesizing linear (α1 → 6) and branched (α1 → 4,6) linkages, on the fine structure, rheology, and retrogradation properties of pea starch (PS). The results revealed that as the reaction time increased, the total (α1 → 6) linkages in linear chains and branching points of PS increased from 5.6 % to 18.7 %, the molecular weight decreased from 7.3 × 10 g/mol to 7.4 × 10 g/mol, and the percentage of short chains (DP ≤ 12) increased from 47.4 % to 92.7 %, thereby producing low-molecular-weight, short-clustered novel reuterans with new (α1 → 6) linkages in both linear chains and branches. Additionally, LrN1 GtfB-modified PS exhibited lower storage/loss modulus and weaker creep property, indicating a significant attenuation of the strength and rigidity of the modified gel structure. Moreover, products derived from pea starch and LrN1 GtfB exhibited notably low retrogradation properties. These findings provide insights into the potential application of GtfB-type α-glucanotransferases in starch-based products, thereby producing unique-structured α-glucans with versatile properties from starch.