Turanose

Physicochemical properties of turanose and its potential applications as a sucrose substitute

Among the structural isomers of sucrose, turanose has been considered as one of good candidates as novel sweetener due to its mild taste, low calorie, and anti-cariogenicity. Here, various physicochemical properties of turanose, such as solubility, temperature and pH stabilities, viscosity, non-enzymatic browning reaction, and dynamic vapor sorption, were investigated by comparing them to those of other commercial sugars. Turanose did not significantly hydrolyze through the simulated digestion tract overall but in the artificial small intestinal environment specifically, turanose degraded by only 18% when sucrose was hydrolyzed by 36% after 4 h. In addition, physicochemical properties of turanose confirmed that it had a potential to replace sucrose due to similar or better product qualities as a food ingredient than other types of sugars with similar chemical structure. Thus, our study suggests that turanose can be applied as a functional sweetener or bulking agent in food processing.

Cryoprotective effect of turanose on lyophilized Lactobacillus paracasei subsp. paracasei, L. casei 431

The lyophilization process is the most convenient and successful method to preserve probiotics, although microorganisms are exposed to conditions of extremely low freezing temperatures as well as dehydration. In this study, we evaluated the cryoprotective effect of turanose on Lactobacillus paracasei subsp. paracasei, L. casei 431 (L. casei 431) as a method to increase survival rate by improving cell viability. The results indicated that the viability of L. casei 431 was 9.6% without the cryoprotective agent, whereas bacterial cell viability was increased to 67.1% with the addition of 12% turanose. When turanose-treated freeze-dried cells were stored at 4 °C for 30 days, the survival rate decreased from 67.1 to 53.4%. Furthermore, cell viability significantly decreased by 50% after 30 days when stored at 25 °C with the same amount of turanose. Overall, turanose may be used as an effective cryoprotectant to preserve probiotics against the freeze-drying process and for extended storage at 4 °C.

CRYSTALLINE TURANOSE

Site-Directed Mutagenic Engineering of a Bifidobacterium Amylosucrase toward Greater Efficiency of Turanose Synthesis

The aim of this study was to establish one of the most efficient biocatalytic processes for turanose production by applying a robust Bifidobacterium thermophilum (BtAS) mutant developed through site-directed mutagenesis. A gene encoding the amylosucrase of B. thermophilum (BtAS) was cloned and used as a mutagenesis template. Among the BtAS variants generated by the site-directed point mutation, four different single-point mutants (P200R, V202I, Y265F, and Y414F) were selected to create double-point mutants, among which BtAS_Y414F/P200R displayed the greatest turanose productivity without losing the thermostability of native BtAS. The turanose yield of BtAS_Y414F/P200R reached 89.3% at 50 °C after 6 h with 1.0 M sucrose + 1.0 M fructose. BtAS_Y414F/P200R produced significantly more turanose than BtAS-wild type (WT) by 2 times and completed the reaction faster by another 2 times. Thus, turanose productivity (82.0 g/(L h)) by BtAS_Y414F/P200R was highly improved from 28.1 g/(L h) of BtAS-WT with 2.0 M sucrose + 0.75 M fructose.

Regulation of Inflammation by Sucrose Isomer, Turanose, in Raw 264.7 Cells

Increased sugar consumption has been proposed to be a risk factor for obesity-related metabolic disorders. The objective of this study was to investigate the anti-inflammatory effect of turanose in Raw 264.7 macrophages. Turanose (3-O-α-D-glucosyl-D-fructose), an isomer of sucrose, naturally exists in honey. For these studies, macrophages were treated with total glucose (Glu), 50% Glu/50% turanose (T50), 25% Glu/75% turanose (T75), and 100% turanose (T100), each with a total concentration of 25 mM in cell media. Expressions of inflammatory enzymes and cytokines were analyzed. Cell viability was not affected in the turanose treated groups compared to the Glu group. Lipopolysaccharide and glucose-induced nitric oxide production, protein expression of inducible nitric oxide synthase, COX-2, and superoxide dismutase 2, and mRNA expression levels of interleukin (IL)-1β and IL-18 were significantly suppressed by turanose treatment. These results demonstrate that turanose exerts anti-inflammatory effects in vitro, and possesses potential to serve therapeutic functional sweetener for testing in vivo and in clinical trials.