Starch-acting α-glucanotransferase enzymes are of great interest for applications in the food industry. In previous work, we have characterized various 4,6- and 4,3-α-glucanotransferases of the glycosyl hydrolase (GH) family 70 (subfamily GtfB), synthesizing linear or branched α-glucans. Thus far, GtfB enzymes have only been identified in mesophilic Lactobacilli. Database searches showed that related GtfC enzymes occur in Gram-positive bacteria of the genera Exiguobacterium, Bacillus, and Geobacillus, adapted to growth at more extreme temperatures. Here, we report characteristics of the Geobacillus sp. 12AMOR1 GtfC enzyme, with an optimal reaction temperature of 60 °C and a melting temperature of 68 °C, allowing starch conversions at relatively high temperatures. This thermostable 4,6-α-glucanotransferase has a novel product specificity, cleaving off predominantly maltose units from amylose, attaching them with an (α1 → 6)-linkage to acceptor substrates. In fact, this GtfC represents a novel maltogenic α-amylase. Detailed structural characterization of its starch-derived α-glucan products revealed that it yielded a unique polymer with alternating (α1 → 6)/(α1 → 4)-linked glucose units but without branches. Notably, this Geobacillus sp. 12AMOR1 GtfC enzyme showed clear antistaling effects in bread bakery products.

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ObjectiveTo determine whether a gum-containing thickener maintains its viscosity better during oral processing than a completely starch-based thickener.MethodsThirty-five healthy volunteers participated in a double-blind, cross-over study. Artificial tap water was thickened to honey-like consistency (effective viscosity of 1,300±100 mPa·s at a shear rate of 50 per second at 20℃) with a starch-based thickener (SB) or a gum-containing thickener (GC). Bolus viscosity was determined after standardized oral processing of the thickened water by the subjects for 10 and 20 seconds. Significant effects were determined by ANOVA analysis and pairwise comparisons.ResultsBoth thickeners were susceptible to breakdown during oral processing. However, GC-thickened water retained its viscosity significantly better than SB-thickened water.ConclusionThe presence of gums has a protective effect on the starch hydrolysis by salivary amylase in thickened drinks, which may facilitate safer swallowing.

Scope Resistant starches (RSs) are classically considered to elicit health benefits through fermentation. However, it is recently shown that RSs can also support health by direct immune interactions. Therefore, it has been hypothesized that the structural traits of RSs might impact the health benefits associated with their consumption. Methods and results Effects of crystallinity, molecular weight, and chain length distribution of RSs are determined on immune Toll‐like receptors (TLRs), dendritic cells (DCs), and T‐cell cytokines production. To this end, four type‐3 RSs (RS3) are compared, namely Paselli WFR, JD150, debranched Etenia, and Amylose fraction V, which are extracted from potatoes and enzymatically modified. Dextrose equivalent seems to be the most important feature influencing immune signaling via activation of TLRs. TLR2 and TLR4 are most strongly stimulated. Especially Paselli WFR is a potent activator of multiple receptors. Moreover, the presence of amylose, even to residual levels, enhances DC and T‐cell cytokine responses. Paselli WFR and Amylose fraction V influence T‐cell polarization. Conclusions It has been shown here that chain length and particularly dextrose equivalent are critical features for immune activation. This knowledge might lead to tailoring and design of immune‐active RS formulations.

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