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.

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.

Alkoxycarbonyl elimination of 3-O-substituted glucose and fructose by heat treatment under neutral pH

3-O-Substituted reducing aldoses are commonly unstable under heat treatment at neutral and alkaline pH. In this study, to evaluate the decomposition products, nigerose (3-O-α-d-glucopyranosyl-d-glucose) and 3-O-methyl glucose were heated at 90 °C in 100 mM sodium phosphate buffer (pH 7.5). Decomposition via β-elimination was observed that formed a mixture of 3-deoxy-arabino-hexonic acid and 3-deoxy-ribo-hexonic acid; upon further acid treatment, it was converted to their γ-lactones. Similarly, turanose (3-O-α-d-glucopyranosyl-d-fructose), a ketose isomer of nigerose, decomposed more rapidly than nigerose under the same conditions, forming the same products. These findings indicate that 3-O-substituted reducing glucose and fructose decompose via the same 1,2-enediol intermediate. The alkoxycarbonyl elimination of 3-O-substituted reducing glucose and fructose occurs readily if an O-glycosidic bond is located on the carbon adjacent to the 1,2-enediol intermediate. Following these experiments, we proposed a kinetic model for the3- decomposition of nigerose and turanose by heat treatment under neutral pH conditions. The proposed model showed a good fit with the experimental data collected in this study. The rate constant of the decomposition for nigerose was (1.2 ± 0.1) × 10^-4 s^-1, whereas that for turanose [(2.6 ± 0.2) × 10^-4 s^-1] was about 2.2 times higher.

Versatile biotechnological applications of amylosucrase, a novel glucosyltransferase

Amylosucrase (AS; EC 2.4.1.4) is an enzyme that has great potential in the biotechnology and food industries, due to its multifunctional enzyme activities. It can synthesize α-1,4-glucans, like amylose, from sucrose as a sole substrate, but importantly, it can also utilize various other molecules as acceptors. In addition, AS produces sucrose isomers such as turanose and trehalulose. It also efficiently synthesizes modified starch with increased ratios of slow digestive starch and resistant starch, and glucosylated functional compounds with increased water solubility and stability. Furthermore, AS produces turnaose more efficiently than other carbohydrate-active enzymes. Amylose synthesized by AS forms microparticles and these can be utilized as biocompatible materials with various bio-applications, including drug delivery, chromatography, and bioanalytical sciences. This review not only compares the gene and enzyme characteristics of microbial AS, studied to date, but also focuses on the applications of AS in the biotechnology and food industries.

Sucrose isomers as alternative sweeteners: properties, production, and applications

In the daily diet, sweeteners play an indispensable role. Among them, sucrose, a widely occurring disaccharide in nature, is a commonly used sweetener. However, the intake of sucrose can cause a rapid increase in blood glucose, which leads to a number of health problems. Therefore, there is an urgent need for possible alternatives to sucrose. Currently, four naturally occurring sucrose isomers, trehalulose, turanose, leucrose, and isomaltulose are considered to be possible alternatives to sucrose due to their suitable sweetness, potential physiological benefits, and feasible production processes. This review covers the properties of these alternative sweeteners, including their structure, sweetness, hydrolysis rate, toxicology, and cariogenicity, and exhibits their potential applications in chronic diseases management, anti-inflammatory supplement, prebiotic dietary supplement, and stabilizing agent. The biosynthesis of these sucrose isomers using carbohydrate-active enzymes and their industrial production processes are also systematically summarized.

Characterization of a novel amylosucrase gene from the metagenome of a thermal aquatic habitat, and its use in turanose production from sucrose biomass

Turanose is a natural isomer of sucrose. It is an emerging functional sweetener of the next generation. Turanose is catalytically synthesized from the sucrose biomass by employing amylosucrase enzyme. In this study, a novel gene encoding amylosucrase (As_met) has been identified from the metagenome of a thermal aquatic habitat. As_met exhibits 37-55% identity at the protein level with the known amylosucrases characterized till date. As_met was cloned and expressed in Escherichia coli, followed by protein purification, and characterization. As_met protein exhibited the maximum total activity at 9.0 pH and 60 °C temperature, whereas, 8.0 pH and 50 °C temperature were found optimum for transglycosylation activity. As_met showed fairly high thermal tolerance at 50 °C. The conjugation of As_met protein with functionalized iron nanoparticles significantly improved its thermal tolerance, showing hardly any loss in the enzyme's activity even after 72 h of heat (50 °C) exposure. The turanose yield of about 47% was achieved from 1.5 M sucrose, containing 0.5 M fructose in the reaction. Turanose was purified (˜95%) via a bio-physical process, and characterized by TLC, HPLC, and NMR. The novel amylosucrase gene was demonstrated to be a potential candidate for turanose production, utilizing various sucrose containing feedstocks.

Sucrose-based biosynthetic process for chain-length-defined α-glucan and functional sweetener by Bifidobacterium amylosucrase

A unique thermostable amylosucrase from Bifidobacterium thermophilum was produced as a recombinant protein with the half-life of 577 h at 50 °C. By adding 1.0 M fructose, turanose yield was improved from 22.7% to 43.3% with 1.0 M sucrose, and from 23.7% to 39.4% with 1.5 M sucrose. Sucrose consumption rate was greatest at 55 °C, but the lowest amount of turanose was produced. Thus, turanose yield from sucrose biomass was inversely proportional to reaction temperature and was highly dependent on [fructose]. Meanwhile, insoluble α-glucan yield was clearly reduced as [fructose] increased. With 1.0 M fructose + 1.0 M sucrose, glucan byproduct yield significantly decreased from 29.4% to 1.1%. Molecular weights of linear glucans were almost identical among various [sucrose]s and were homogenous with very low polydispersity. This unique dual reaction patterns of amylosucrase enzyme would be very useful for massive productions of two different biomaterials simply by changing sucrose biomass concentration.

Elucidation of rheological, microstructural, water mobility, and noodle-making properties of rice flour affected by turanose

The effects of turanose on the physicochemical properties of rice flour systems (aqueous suspension, dough, and noodles) were investigated in terms of rheology, microstructure, and water mobility. Inclusion of turanose increased the pasting viscosities of rice flour by maintaining a closely-packed structure at high temperatures that was confirmed by the real-time microscopic measurements during heating. The elevated probability of intergranular interactions by turanose apparently raised both storage (G') and loss (G″) moduli of the rice flour pastes as well as their respective viscosities. NMR spin-spin relaxation times showed two distinct water populations in the turanose-rice flour samples. The Mixolab experiments demonstrated that the rice doughs with higher levels of turanose exhibited greater dough stability as well as higher degrees of starch gelatinization and retrogradation. Furthermore, the extruded rice noodles containing turanose exhibited a higher expansion ratio and a firmer texture that contributed to lowering the cooking loss by 24.5%.

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.