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D-tagatose, a low-calorie rare sugar, has significant potential in food, medicine, cosmetics, and other industries owing to its high application value and market potential. In this study, Escherichia coli BL21 was used as the starting strain to express the β-galactosidase (β-Gal) gene—BgaB—derived from Bacillus stearothermophilus and the L-arabinose isomerase (L-AI) gene—araA—derived from Thermus sp., yielding the genetically engineered strains E. coli BL21-pET28a-BgaB and E. coli BL21-pET28a-araA. These strains synthesized D-tagatose using β-Gal and L-AI with a conversion rate of 23.73%. Based on this, we constructed a multienzyme cascade pathway comprising β-Gal, L-AI, glucose isomerase (GI), fructose kinase (FK), D-tagatose-bisphosphate aldolase (GatZ), polyphosphate kinase (PPK), and phosphatase (PGP), further enhancing D-tagatose biosynthesis. This multienzyme approach improved the conversion of the intermediate product D-glucose to D-tagatose by 3.84% compared with the dual-enzyme system. Thus, our study provides a theoretical basis and technical support for the industrial production of D-tagatose. [ABSTRACT FROM AUTHOR]

D-tagatose is a rare, naturally occurring low-calorie hexose, with a sweetness of 92% sucrose but only 1/3 of the calories. It has beneficial functions in lowering blood sugar, controlling obesity, preventing dental caries, and improving intestinal flora. In recent years, biotechnological routes to D-tagatose production from renewable raw materials have been regarded as very promising approaches. In this review, we provide an overview of the properties and applications of D-tagatose, with a focus on the current developments in the production of D-tagatose using enzymatic transformation and whole-cell catalytic synthesis. The biosynthetic pathways and the types and characteristics of the catalytic enzymes involved have been summarized, providing a reference for the design of D-tagatose synthesis pathways. We also expect that rapid developments in the fields of systems biology and synthetic biology will accelerate protein and metabolic engineering for microbial D-tagatose production in the future. [ABSTRACT FROM AUTHOR]

D-tagatose is a valuable rare sugar with potential health benefits such as antiobesity, low-calorie, prebiotic, and anticancer. However, its production is mainly depending on chemical or enzymatic catalysis. Herein, a cobalt-based metal–organic framework (MOF) was developed at room temperature in an aqueous system using a self-assembly method. The L-arabinose isomerase (L-AI) was immobilized into this unique MOF by an in situ encapsulation process. The morphology and structural aspects of the MOF preparations were characterized by different analytical techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FT-IR), and X-Ray diffraction (XRD). Moreover, thermogravimetric analysis (TGA) suggested the high thermal stability of the L-AI@MOF. Significantly, the immobilized catalyst exhibited enhanced catalytic efficiency (kcat/Km) of 3.22 mM−1 s−1 and improved turnover number (kcat) of 57.32 s−1. The L-AI@MOF efficiently catalyzes the synthesis of D-tagatose from D-galactose up to the equilibrium level (~ 50%) of isomerization in heterogeneous catalysis. Interestingly, L-AI@MOF was found stable and reusable for more than five cycles without the requirement of additional metal ions during catalysis. Thus, L-AI stabilized in the MOF system demonstrated a higher catalytic activity and potential guidance for the sustainable synthesis of rare sugar D-tagatose. [ABSTRACT FROM AUTHOR]

D-tagatose is a rare, naturally occurring low-calorie hexose, with a sweetness of 92% sucrose but only 1/3 of the calories. It has beneficial functions in lowering blood sugar, controlling obesity, preventing dental caries, and improving intestinal flora. In recent years, biotechnological routes to D-tagatose production from renewable raw materials have been regarded as very promising approaches. In this review, we provide an overview of the properties and applications of D-tagatose, with a focus on the current developments in the production of D-tagatose using enzymatic transformation and whole-cell catalytic synthesis. The biosynthetic pathways and the types and characteristics of the catalytic enzymes involved have been summarized, providing a reference for the design of D-tagatose synthesis pathways. We also expect that rapid developments in the fields of systems biology and synthetic biology will accelerate protein and metabolic engineering for microbial D-tagatose production in the future.

To improve the performance of whey protein isolates (WPI) as an encapsulation agent in the food industry, we investigated the formation mechanism of WPI and D-tagatose (DT) conjugates using simultaneous rheological and Fourier-Transform infrared spectroscopy (FTIR) techniques, and analysed its effects in encapsulating quercetin (Que). The degree of glycosylation of the conjugates increased to 18 % after heating treatment, whereas particle size and potential decreased to 64 nm and −39 mV, with WPI/D10 showing the lowest value. Simultaneous rheological and Fourier transform infrared analyses showed that the structure of the WPI/DT complexes changed, and the gel properties were much better than those of WPI. Several new peaks appeared at 2961, 1525, 1450, 1392, and 1236 cm-1, indicating that adding DT affected the structure of WPI. DT promoted secondary structural changes in WPI by increasing the degree of hydrocarbon chain, O-H group vibration, and C-O stretching. The WPI/DT conjugates increased the solubility of Que to 60.74 % and ABTS clearance to 73.98 %. The study may offer a theoretical foundation for using WPI/DT-encapsulated Que in food industry. [Display omitted] • WPI/DT Maillard reaction product was used as the embedding material. • DT improved the structural, physical, and antioxidant properties of WPI/DT conjugate. • WPI/DT conjugates structure was tested by the simultaneous rheology-FTIR technology. • The technology indicated that the gel properties of WPI/DT conjugate were improved. • The conjugates improve the bio-accessibility and antioxidant properties of Que. [ABSTRACT FROM AUTHOR]

• Green tea extract EGCG potently prevents RIII in mouse model. • Oral EGCG reduces acute RIII severity in pelvic cancer patients undergoing RT. • The radio-protective effect of EGCG on intestine could be transferred via SFF transplantation. • EGCG enriches gut microbiota-derived metabolite D-tagatose. • D-tagatose prevents RIII via activation of AMPK signalling. Radiation-induced intestinal injury (RIII) compromises the clinical utility of pelvic radiotherapy (RT). We aimed to explore the protective effect and underlying mechanism of (−)-epigallocatechin-3-gallate (EGCG) on RIII. We evaluated the protective effect of EGCG on intestine in RIII mouse model and pelvic cancer patients, while explored the underlying mechanism through (1) 16S rRNA sequencing, (2) metabolomic profiles, (3) fresh sterile fecal filtrate (SFF) transplantation, and (4) transcriptome sequencing. EGCG efficiently prevented RIII in mouse, as reflected by improved survival, alleviated intestinal structure damage, promoted intestinal regeneration, and ameliorated gut microbiota dysbiosis. Prophylactic EGCG intervention reduced the severity of RIII in patients receiving pelvic RT. Mechanistically, the protective effect of EGCG could be transferred to other mice by SFF transplantation. EGCG enriched gut microbiota-derived metabolite D-tagatose, and oral administration of D-tagatose reproduced the radio-protective effect of EGCG via activating AMPK. Oral EGCG may be a promising strategy for preventing RIII clinically, and warrant further investigation in prospective randomized phase III trials. [ABSTRACT FROM AUTHOR]

d-Tagatose, a rare low-calorie sweetener, is ideal for beverages due to its high solubility and low viscosity. Current enzymatic production methods from d-galactose or d-galactitol are limited by reaction reversibility, affecting the yield and purity. This study demonstrates that Escherichia coli harbors a thermodynamically favorable pathway for producing d-tagatose from d-glucose via phosphorylation-epimerization-dephosphorylation steps. GatZ and KbaZ, annotated as aldolase chaperones, exhibit C4 epimerization activity, converting d-fructose-6-phosphate to d-tagatose-6-phosphate. Structural analysis reveals active site differences between these enzymes and class II aldolases, indicating functional divergence. By exploiting the strains' inability to metabolize d-tagatose, carbon starvation was applied to remove sugar byproducts. The engineered strains converted 45 g L -1 d-glucose to d-tagatose, achieving a titer of 7.3 g L -1 and a productivity of 0.1 g L -1 h -1 under test tube conditions. This approach highlights E. coli as a promising host for efficient d-tagatose production.

D-Tagatose is a representative rare sugar with the physiochemical properties of low energy and high sweetness, as well as excellent physiological functions such as blood sugar regulation, enhancement of intestinal flora, and prevention of dental caries. At present, D-tagatose production involves lactose hydrolysis and D-galactose isomerization processes, resulting in high production costs that hinder its industrial advancement. Tagatose 4-epimerase (T4Ease) has the capability to directly convert d-fructose into D-tagatose through C-4 epimerization, providing a new approach for D-tagatose production. In this study, a hyperthermostable T4Ease from Infirmifilum uzonense (Inuz-TE4ase) was identified from the Foldseek clustered AlphaFold database and its biochemical properties were characterized in detail. Under the optimal reaction conditions of 90 °C and pH 8.5 (Tris-HCl) with the addition of 1 mM Ni 2+ , the maximum catalytic activity towards d-fructose was determined to be 0.680 U/mg. Inuz-TE4ase exhibited exceptional thermostability, with half-life (t 1/2 ) values of 19.3 h at 85 °C and 8.9 h at 90 °C, respectively. Inuz-TE4ase was strictly metal-dependent, and its stability could be enhanced by Ni 2+ with an increase in the melting temperature (T m ) value from 101.1 °C to 105.7 °C. When 100 g/L d-fructose was used as the substrate, Inuz-TE4ase could catalyze the production of 21.67 g/L D-tagatose, indicating its significant potential for D-tagatose bioproduction., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2025 Elsevier B.V. All rights reserved.)

d-Tagatose, a rare sugar endowed with a low-calorie property, superior taste quality, and probiotic functionality, has garnered significant research attention. However, the prevailing biological production methods relying on β-galactosidase and l-arabinose isomerase face challenges including high cost and suboptimal conversion efficiency. Consequently, it is of great research significance to find efficient alternative routes for d-tagatose synthesis. Previously, Thermotoga petrophila tagaturonate 3-epimerase was modified to function as tagatose 4-epimerase (T4E) enabling the direct conversion of d-fructose to d-tagatose. In this study, T4E was further engineered through directed evolution, specifically targeting the enhancement of its thermostability for application. This endeavor yielded promising T4E variants with superiority over those of the original enzyme. T4E I430P exhibits a half-life ( t 1/2 ) at 70 °C that is 1.83-fold that of T4E, with an increased melting temperature ( T m is 2.9 °C higher than T4E. Furthermore, whole-cell immobilization integrating these engineered T4E variants into a robust biocatalytic system was employed. This innovative approach not only underscores the practical feasibility of modifying enzymes through directed evolution but also establishes a foundation for the cost-effective, large-scale production of d-tagatose.t 1/2 was 1.69-fold that of T4E, and its T m is 2.9 °C higher than T4E. Furthermore, whole-cell immobilization integrating these engineered T4E variants into a robust biocatalytic system was employed. This innovative approach not only underscores the practical feasibility of modifying enzymes through directed evolution but also establishes a foundation for the cost-effective, large-scale production of d-tagatose.