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Background: stevia and D-tagatose have shown a reduction in total calorie and carbohydrate intake as a substitute for sucrose, demonstrating a stabilizing effect on pH and bacterial proliferation. Objective: to evaluate the effect of D-tagatose, stevia and sucrose on salivary pH and bacterial activity in odontology students. Methodology: a controlled study of parallel and randomized groups with a single blind, whose sample considered three groups subjected to a mouthwash of D-tagatose (n = 10), stevia (n = 10) and sucrose (n = 10). These solutions were administered over 1 minute in a single 6.4 % concentrated dose. Data collection and analysis considered the recording of salivary pH 5 min before exposure to the sweetener, immediately after expulsion of the mouthwash and 15 min later, 30 min, 45 min and 48 hours. The counting of the final number of colony-forming units per mL (CFU/mL) was counted using the salivary samples obtained immediately after exposure of the sweetener together with the sample obtained 30 minutes later, with the cultures performed on agar plates. Results: D-tagatose, stevia and sucrose presented significant differences in total CFU/mL at 30 minutes (p < 0.001), while salivary pH showed significant differences at 48 hours after administration (p < 0.001). Conclusion: D-tagatose, stevia and sucrose present significant differences in total CFU/mL and salivary pH, these findings being a possible indication of a partial inhibitory effect on bacterial metabolism. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian Polytechnic University is the property of Journal of Dalian Polytechnic University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

L-Arabinose isomerase (L-AI) has been commonly used as an efficient biocatalyst to produce D-tagatose via the isomerization of D-galactose. However, it remains a significant challenge to efficiently synthesize D-tagatose using the native (wild type) L-AI at an industrial scale. Hence, it is extremely urgent to redesign L-AI to improve its catalytic efficiency towards D-galactose, and herein a structure-based molecular modification of Lactobacillus plantarum CY6 L-AI (LpAI) was performed. Among the engineered LpAI, both F118M and F279I mutants showed an increased D-galactose isomerization activity. Particularly, the specific activity of double mutant F118M/F279I towards D-galactose was increased by 210.1% compared to that of the wild type LpAI (WT). Besides the catalytic activity, the substrate preference of F118M/F279I was also largely changed from L-arabinose to D-galactose. In the enzymatic production of D-tagatose, the yield and conversion ratio of F118M/F279I were increased by 81.2% and 79.6%, respectively, compared to that of WT. Furthermore, the D-tagatose production of whole cells expressing F118M/F279I displayed about 2-fold higher than that of WT cell. These results revealed that the designed site-directed mutagenesis is useful for improving the catalytic efficiency of LpAI towards D-galactose. [ABSTRACT FROM AUTHOR]

D-allulose, D-sorbose and D-tagatose are D-fructose isomers that are called rare sugars. These rare sugars have been studied intensively in terms of biological production and food application as well as physiological effects. There are limited papers with regard to the transporters mediating the intestinal absorption of these rare sugars. We examined whether these rare sugars are absorbed via sodium-dependent glucose cotransporter 1 (SGLT1) as well as via GLUT type 5 (GLUT5) using rats. High-fructose diet fed rats, which express more intestinal GLUT5, exhibited significantly higher peripheral concentrations, Cmax and AUC0–180 min when D-allulose, D-sorbose and D-tagatose were orally administrated. KGA-2727, a selective SGLT1 inhibitor, did not affect the peripheral and portal vein concentrations and pharmacokinetic parameters of these rare sugars. The results suggest that D-allulose, D-sorbose and D-tagatose are likely transported via GLUT5 but not SGLT1 in rat small intestine. [ABSTRACT FROM AUTHOR]

Copyright of Modern Food Science & Technology is the property of Editorial Office of Modern Food Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

L-Arabinose isomerase (L-AI) has been commonly used as an efficient biocatalyst to produce D-tagatose via the isomerization of D-galactose. However, it remains a significant challenge to efficiently synthesize D-tagatose using the native (wild type) L-AI at an industrial scale. Hence, it is extremely urgent to redesign L-AI to improve its catalytic efficiency towards D-galactose, and herein a structure-based molecular modification of Lactobacillus plantarum CY6 L-AI (LpAI) was performed. Among the engineered LpAI, both F118M and F279I mutants showed an increased D-galactose isomerization activity. Particularly, the specific activity of double mutant F118M/F279I towards D-galactose was increased by 210.1% compared to that of the wild type LpAI (WT). Besides the catalytic activity, the substrate preference of F118M/F279I was also largely changed from L-arabinose to D-galactose. In the enzymatic production of D-tagatose, the yield and conversion ratio of F118M/F279I were increased by 81.2% and 79.6%, respectively, compared to that of WT. Furthermore, the D-tagatose production of whole cells expressing F118M/F279I displayed about 2-fold higher than that of WT cell. These results revealed that the designed site-directed mutagenesis is useful for improving the catalytic efficiency of LpAI towards D-galactose.

A one-pot extraction-assisted d-galactose-to-d-tagatose isomerization strategy was proposed based on the selective extraction of d-tagatose by phenylborate anions. 4-Vinylphenylboronic acid was selected with high extraction efficiency and selectivity towards d-tagatose. The extracted sugars could be desorbed through a two-staged stripping process with the purity of d-tagatose significantly increased. In-situ extraction-assisted d-galactose-to-d-tagatose isomerization was implemented for the first time ever reported, and the effect of boron-to-sugar ratio (boron: sugar) was investigated. The conversion yield of d-tagatose at 60 °C increased from ∼ 39 % (boron: sugar = 0.5) to ∼ 56 % (boron: sugar = 1) but then decreased to ∼ 44 % (boron: sugar = 1.5). With temperature increased to 70 °C, the conversion yield of d-tagatose was further improved to ∼ 61 % (boron: sugar = 1.5), with the minimized formation of byproducts. Moreover, high purity (∼83 %) and concentrated d-tagatose solution (∼40 g/L) was obtained after sequential desorption. The proposed extraction-assisted isomerization strategy achieved improving the yield and purity of d-tagatose, proving its feasibility in industrial applications.

Copyright of Journal of Dalian Polytechnic University is the property of Journal of Dalian Polytechnic University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Brewing is the property of China Brewing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Chocolate is a popular and widely consumed product in different ages, however, the demand of consumers has increased for healthy chocolate with free or low sugar in recent years. The objective of present research is to substitute the sucrose of chocolate with D-tagatose and lemon essential oil for improving biological functions. The seven formulations of chocolate included distinct percentages of D-tagatose (0, 13, 29 and 47 %) and lemon essential oil (0, 0.1 and 0.2 %). Afterwards, the tests were performed on chocolate treatments such as moisture level, fat, sugar content before and after hydrolysis, color perception, hardness, antioxidant, microbial and sensory evaluations. The results demonstrated that moisture of treatments (except CTL5 containing 47.80 % D-tagatose and 0.1 % lemon essential oil) was noticeably different from the control. A significant difference was observed between the average sugars of treatments before hydrolysis, however, there was no considerable difference in fat levels (33.39 to 33.41 %). The essential oil has led to a reduction in hardness, so CTL6 (including 47.90 % D-tagatose and 0.2 % lemon essential oil) with higher essential oil had a lower hardness (16.61 N). D-tagatose and lemon essential oil had an influence on color features, but antioxidant functions were affected only by essential oil and all treatments were within the standard range in terms of microbial load. In sensory assessment, the overall acceptance score was given to the control (4.96) and CTL5 (4.92). The conclusion of present research introduced CTL5 as the most suitable treatment for production of healthy chocolate. [ABSTRACT FROM AUTHOR]

β-galactosidase is an enzyme capable of hydrolysing lactose, used in various branches of industry, mainly the food industry. As the efficient industrial use of enzymes depends on their reuse, it is necessary to find an effective method for immobilisation, maintaining high activity and stability. The present work proposes cross-linked magnetic cross-linked enzyme aggregates (mCLEAs) to prepare heterogeneous biocatalysts of β-galactosidase. Different concentrations of glutaraldehyde (0.6%, 1.0%, 1.5%), used as a cross-linking agent, were studied. The use of dextran-aldehyde as an alternative cross-linking agent was also evaluated. The mCLEAs presented increased recovered activity directly related to the concentration of glutaraldehyde. Modifications to the protocol to prepare mCLEAs with glutaraldehyde, adding a competitive inhibitor or polymer coating, have not been effective in increasing the recovered activity of the heterogeneous biocatalysts or its thermal stability. The biocatalyst prepared using dextran-aldehyde presented 73.6% recovered activity, aside from substrate affinity equivalent to the free enzyme. The thermal stability at 60 °C was higher for the biocatalyst prepared with glutaraldehyde (mCLEA-GLU-1.5) than the one produced with dextran-aldehyde (mCLEA-DEX), and the opposite happened at 50 °C. Results obtained for lactose hydrolysis, the use of its product to produce a rare sugar (D-tagatose) and operational and storage stability indicate that heterogeneous biocatalysts have adequate characteristics for industrial use. [ABSTRACT FROM AUTHOR]

Abstract As a rare low‐calorie sugar with special medicinal value, d‐tagatose is widely used in the field of food, beverages, medicine, and cosmetics. However, enzymatic d‐tagatose production in vitro is commonly limited to low conversion efficiency and poor thermo‐stability. Herein, taking advantage of the self‐assembling property of protein scaffold EutM (ethanolamine bacterial microcompartments), Spy and Snoop peptide pairs was used to drive the linkage between the EutM and cargo proteins, β‐galactosidase (BagB), and l‐arabinose isomerase (TMAI) to construct a dual‐enzymes cascade and realize the d‐tagatose production from lactose. The optimal conditions of the cascade were shown to be pH of 8.0, temperature of 60°C, 100 g/L lactose as substrate with supplementing 5 mM Mn2+. When the ratio of immobilized enzymes to EutM scaffold reached 1:6, the d‐tagatose productivity of the dual‐enzymes cascade could reach 1.03 g/L/h, which was 1.24‐fold higher than free enzymes. In addition, the EutM‐based scaffold could efficiently improve the stability of immobilized enzymes, in which 45% of the activity remained after 12 h, 2.14‐fold higher than the free one. Overall, an attractive EutM‐based self‐assembling platform immobilizing BagB and TMAI was developed, showing enhanced catalysis efficiency and enzyme thermo‐stability for d‐tagatose production.

Rare sugar was defined as a sugar that occurs in very small quantities in nature. Among them, l -ribose and d -tagatose were of high added value and useful as pharmaceutical intermediate for anti-HBV drugs or low calorie sweetener in food industry. Bio-production of the two rare sugar from biomass waste has not been investigated. Hence, development of a feasible and efficient co-production method was of practical usage. However, lack of suitable biocatalyst has become a bottleneck. By sequence alignment and analysis, a C-terminal α-helix from l -arabinose isomerase (L-AI) family was selected as a tool for protein engineering. This α-helix was ligated to C-terminal of Lactobacillus fermentum L-AI (LFAI) and significantly enhanced its thermostability and robustness for both l -arabinose and galactose catalysis. The mutant LFAI-C4 enzyme was immobilized by alginate and antimicrobial peptide poly- l -lysine, and was used to convert pretreated corncob acid hydrolysate (PCAH) into l -ribulose and d -tagatose in the presence of boric acid. In addition, we identified and immobilized a novel thermostable mannose-6-phosphate isomerase from Bacillus subtilis (BsMPI-2) which was efficient in catalyzing retaining l -ribulose into l -ribose and showing no activity on d -tagatose. The dual immobilized enzymes (LFAI-C4 and BsMPI-2) system co-produced 191.9 g/L l -ribose and 80.1 g/L d -tagatose, respectively. Showing a total yield of 46.6% from l -arabinose to l -ribose, which was the highest among reported. The dual immobilized enzymes system preserved 82% activity after 40 batches reaction, showing excellent potentials for industrial use. This study presents a promising alternative for rare sugar production from low-value raw material and showed satisfied conversion rate, product concentration, and operation stability. • An α-helix ligated to l -arabinose isomerase significantly enhanced thermostability and robustness. • The modified L-AI was used to convert pretreated corncob acid hydrolysate into l -ribulose and d -tagatose in high efficiency. • A novel thermostable mannose-6-phosphate isomerase from Bacillus subtilis was identified. • The dual L-AI and MPI immobilized enzymes system co-produced high concentrations of rare sugar. • The dual immobilized enzymes system preserved most activity after long term bio-reaction. [ABSTRACT FROM AUTHOR]

Diabetes mellitus is the most common metabolic disorder contributing to significant morbidity and mortality in humans. Different preventive and therapeutic agents, as well as various pharmacological strategies or non-pharmacological tools, improve the glycemic profile of diabetic patients. Isomaltulose, d-tagatose, and trehalose are naturally occurring, low glycemic sugars that are not synthesized by humans but widely used in food industries. Various studies have shown that these carbohydrates can regulate glucose metabolism and provide support in maintaining glucose homeostasis in patients with diabetes, but also can improve insulin response, subsequently leading to better control of hyperglycemia. In this review, we discussed the anti-hyperglycemic effects of isomaltulose, D-tagatose, and trehalose, comparing their properties with other known sweeteners, and highlighting their importance for the development of the pharmaceutical and food industries. [ABSTRACT FROM AUTHOR]

The application of agarose oligosaccharides has garnered great attention, with their biological activities varying among different structures. However, it still meets a great bottleneck for the targeted production of odd-numbered neoagarooligosaccharides (NAOSs), such as neoagarotriose (NA3), due to the lack of one-step hydrolases. In this work, the α-agarase AgaA33 and β-galactosidase BgaD were synergistically used to prepare NA3 with agarose as a substrate. Additionally, an l-arabinose isomerase CaLAI from Clostridium acetobutylicum was characterized to valorize low-value byproducts (d-galactose) by forming d-tagatose, which exhibited good thermal stability without the need for additional metal ions. Under the optimal reaction conditions, the production of NA3 and d-galactose catalyzed by these three enzymes was 0.40 and 0.15 g/L, respectively. The artificial three-enzyme-based cascade transformation system not only achieved the highest production of NA3 until now but also allowed for the valorization of d-galactose, providing a wiser application route for agarose utilization.

Background and Purpose: 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., Materials and Methods: 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., Results: 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., Conclusion: Oral EGCG may be a promising strategy for preventing RIII clinically, and warrant further investigation in prospective randomized phase III trials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

As a rare sugar, D-Tagatose is regarded as an excellent low-energy food sweetener. It is especially beneficial for physical health, such as inhibiting hyperglycemia, improving intestinal flora, and avoiding caries. It is broadly employed in food, medicine, cosmetics, and other fields. Acquiring D-Tagatose solubility is vital to develop D-Tagatose crystallization process to obtain high-quality D-Tagatose production. In this study, the solubility of D-Tagatose in seven pure solvents (methanol, ethanol, n-propanol, water, N, N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone), three binary solvents (ethanol-water mixtures, ethanol-methanol mixtures, and n-propanol-water mixtures) was determined by HPLC method at temperatures from 293.15 K to 323.15 K. Then, the Van't Hoff equation, Apelblat equation, λh equation, NRTL equation, CNIBS/Redlich-Kister model and modified Jouyban-Acree-van't Hoff model were used to correlate the solubility. The correlated solubility accounted for suitable compatibility with the experimental results (ARD

Acute respiratory distress syndrome (ARDS) is characterized by disruption of the alveolar-capillary barrier, resulting in severe alveolar edema and inflammation. D-tagatose (TAG) is a low-calorie fructose isomer with diverse biological activities whose role in ARDS has never been explored. We found that TAG protects lung tissues from injury in the oleic acid-induced rat model of ARDS. Seventeen male Sprague-Dawley rats were randomly assigned to 3 groups: Sham (n = 5), ARDS (n = 6), and TAG + ARDS (n = 6). The treatment groups were injected with oleic acid to induce ARDS, and the TAG + ARDS group was given TAG 3 days before the induction. After the treatments, the effect of TAG was evaluated by blood gas analysis and observing the gross and histological structure of the lung. The results showed that TAG significantly improved the oxygenation function, reduced the respiratory acidosis and the inflammatory response. TAG also improved the vascular permeability in ARDS rats and promoted the differentiation of alveolar type II cells, maintaining the stability of the alveolar structure. This protective effect of TAG on the lung may be achieved by activating the PTEN/PI3K/AKT pathway. Thus, TAG protects against oleic acid-induced ARDS in rats, suggesting a new clinical strategy for treating the condition. [ABSTRACT FROM AUTHOR]

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]

• The D-tagaturonate epimerase (UxaE), which has a C4 epimerization function, catalyzes the synthesis of d -tagatose. • Semi-rational design has optimized UxaE to a 10.8-fold increase in efficiency. • Reshaping the substrate-binding pocket can effectively enhance the 4 epimerization function of the epimerase. d -tagatose, a rare sugar with broad applications in the food and pharmaceutical industries, can be synthesized from d -fructose by epimerases, an approach with significant biosynthesis potential. However, so far there has been only one attempt to engineer tagatose 4‑epimerase through random mutagenesis. The lack of exploration has severely restricted the application of epimerases in the industrial production of d -tagatose. The previous research primarily focused on enhancing the catalytic activity of epimerases through random mutagenesis, with limited understanding of how substrate-adjacent residues affect enzyme efficiency, which was hence the subject of this study. First, using a semi-rational design approach, after three rounds of mutagenesis and screening, the mutant (S125D/S268A/Q124E) of D-tagaturonate epimerase (UxaE) from Thermotoga neapolitana was obtained, which increased d -tagatose production efficiency by 10.8-fold compared to the wild type, with a specific activity of 1505.6 U/g, representing the highest specific activity reported for a UxaE mutant to date. Molecular dynamics simulations showed that the substitution of Ser to Asp-125 enhanced substrate-enzyme interactions, while the substitution of Glu to Gln-124 reinforced the hydrogen bond network around the catalytic residue Glu-128, further reshaping the substrate-binding pocket and enhancing catalytic activity. This study for the first time explored the enhancement of the C4 epimerization function of epimerases by reshaping their substrate-binding pockets, thereby providing a feasible route for the industrial biosynthesis of d -tagatose. [Display omitted] [ABSTRACT FROM AUTHOR]

Purpose: D-tagatose is an alternative sweetener with superior properties for reducing overall sugar absorption, which is especially important in the diabetic population. Large-scale production of D-tagatose remains costly, thereby limiting its commercialization. Introducing the unit operation of spray-drying may reduce some of these costs. However, D-tagatose is challenging to spray-dry due to its hydrophilic nature and low glass transition temperature (Tg). An appropriate spray-drying feed solution may offer an alternative approach if the material produced is glassy in nature, thus avoiding stickiness issues associated with Tgs less than the outlet temperature of the spray-dryer. Proof-of-concept formulations and processing conditions are presented in this study. Methods: D-tagatose was formulated with several excipients and screened for a sufficiently high Tg as characterized by differential scanning calorimetry (DSC). The spray-dry formulations were further characterized using attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM), and several viable options were identified. Results: D-tagatose formulated with HPMCAS and K90 both raised the Tg mix ( T g mix ) to within the processing range of spray-drying. These formulations were found to be sufficiently soluble in acetone/water cosolvent systems allowing for the production of processable powder. Specifically, SEM results confirm that both D-tagatose-HPMCAS and D-tagatose-K90 formulations result in particle formation using a small-scale dryer. Large-scale spray-drying is expected to allow for a greater processing range in comparison to small scale, suggesting that this approach will help commercialization. ATR-FTIR and PXRD results suggested that spray-dried D-tagatose-K90 composites lacked crystallinity, unlike the D-tagatose-HPMCAS composites. Conclusions: The addition of functional excipients allowed D-tagatose composites to be harvested using a typical laboratory-scale spray-dryer equipped with a bi-fluid nozzle. D-tagatose-K90 lacks crystallinity, while crystallinity is present in D-tagatose-HPMCAS composites. Crystallinity may not be a critical factor (depending on the future application) given the high aqueous solubility and high loading of the sugar. Both composites retained a sweet taste, suggesting that this spray-drying method may be worth further development. Other polymers with high Tg may be feasible as composites as well—as long as the amorphous phase or the residual amorphous phase has a Tg greater than, or about equal to, the outlet temperature of the spray-dryer. [ABSTRACT FROM AUTHOR]

d-Tagatose is a highly promising functional sweetener known for its various physiological functions. In this study, a novel tagatose 4-epimerase from Thermoprotei archaeon (Thar-T4Ease), with the ability to convert d-fructose to d-tagatose, was discovered through a combination of structure similarity search and sequence-based protein clustering. The recombinant Thar-T4Ease exhibited optimal activity at pH 8.5 and 85 °C, in the presence of 1 mM Ni 2+ . Its k cat and k cat / K m values toward d-fructose were measured to be 248.5 min -1 value of 198 h at 80 °C. Moreover, it achieved a conversion ratio of 18.9% using 100 g/L d-fructose as the substrate. Finally, based on sequence and structure analysis, crucial residues for the catalytic activity of Thar-T4Ease were identified by molecular docking and site-directed mutagenesis. This research expands the repertoire of enzymes with C4-epimerization activity and opens up new possibilities for the cost-effective production of d-tagatose from d-fructose.-1 ·min -1 , respectively. Notably, Thar-T4Ease exhibited remarkable thermostability, with a t 1/2 value of 198 h at 80 °C. Moreover, it achieved a conversion ratio of 18.9% using 100 g/L d-fructose as the substrate. Finally, based on sequence and structure analysis, crucial residues for the catalytic activity of Thar-T4Ease were identified by molecular docking and site-directed mutagenesis. This research expands the repertoire of enzymes with C4-epimerization activity and opens up new possibilities for the cost-effective production of d-tagatose from d-fructose.

Recent studies have shown phenotypic and metabolic heterogeneity in related species including Streptococcus oralis , a typical oral commensal bacterium, Streptococcus mutans , a cariogenic bacterium, and Streptococcus gordonii , which functions as an accessory pathogen in periodontopathic biofilm. In this study, metabolites characteristically contained in the saliva of individuals with good oral hygiene were determined, after which the effects of an identified prebiotic candidate, D-tagatose, on phenotype, gene expression, and metabolic profiles of those three key bacterial species were investigated. Examinations of the saliva metabolome of 18 systemically healthy volunteers identified salivary D-tagatose as associated with lower dental biofilm abundance in the oral cavity (Spearman's correlation coefficient; r = -0.603, p = 0.008), then the effects of D-tagatose on oral streptococci were analyzed in vitro. In chemically defined medium (CDM) containing D-tagatose as the sole carbohydrate source, S. mutans and S. gordonii each showed negligible biofilm formation, whereas significant biofilms were formed in cultures of S. oralis. Furthermore, even in the presence of glucose, S. mutans and S. gordonii showed growth suppression and decreases in the final viable cell count in a D-tagatose concentration-dependent manner. In contrast, no inhibitory effects of D-tagatose on the growth of S. oralis were observed. To investigate species-specific inhibition by D-tagatose, the metabolomic profiles of D-tagatose-treated S. mutans , S. gordonii , and S. oralis cells were examined. The intracellular amounts of pyruvate-derived amino acids in S. mutans and S. gordonii , but not in S. oralis , such as branched-chain amino acids and alanine, tended to decrease in the presence of D-tagatose. This phenomenon indicates that D-tagatose inhibits growth of those bacteria by affecting glycolysis and its downstream metabolism. In conclusion, the present study provides evidence that D-tagatose is abundant in saliva of individuals with good oral health. Additionally, experimental results demonstrated that D-tagatose selectively inhibits growth of the oral pathogens S. mutans and S. gordonii. In contrast, the oral commensal S. oralis seemed to be negligibly affected, thus highlighting the potential of administration of D-tagatose as an oral prebiotic for its ability to manipulate the metabolism of those targeted oral streptococci. [ABSTRACT FROM AUTHOR]

Phosphorylase is a type of enzyme-producing sugar phosphates through the reversible phosphorolysis reactions of glycosides, which makes it an important starting enzyme in multi-enzyme systems for rare sugar biomanufacturing. To investigate its application in d-tagatose biosynthesis from maltodextrin using in vitro multi-enzyme cascade biosystem, the α-glucan phosphorylase (αGP; EC 2.4.1.1) from the thermophile D. turgidum DSM 6724 was prepared and characterized. It exhibited the specific activity of 30.28 U/mg at its optimal temperature of 70 °C. Thermostability results revealed that DituαGP could maintain more than 25% of initial activity for 4 h, even at 90 °C. The highest activity was observed at pH 5.5, and most divalent metal ions deactivated the enzyme. DituαGP exhibited great application potential in the multi-enzyme system that about 3.919 g/L of d-tagatose was produced from 150 g/L of maltodextrin within 36 h. DituαGP has played an important role in this biosystem and will also be applied in the synthesis of other rare sugars from maltodextrin. [ABSTRACT FROM AUTHOR]

D-Galactose is an abundant carbohydrate monomer in nature and widely exists in macroalgae, plants, and dairy wastes. D-Galactose is useful as a raw material for biomass fuel production or low-calorie sweetener production, attracting increased attention. This article summarizes the studies on biotechnological processes for galactose utilization. Two main research directions of microbial fermentation and enzyme-catalyzed conversion from galactose-rich biomass are extensively reviewed. The review provides the recent discoveries for biofuel production from macroalgae, including the innovative methods in the pretreatment process and technological development in the fermentation process. As modern people pay more attention to health, enzyme technologies for low-calorie sweetener production are more urgently needed. D-Tagatose is a promising low-calorie alternative to sugar. We discuss the recent studies on characterization and genetic modification of L-arabinose isomerase to improve the bioconversion of D-galactose to D-tagatose. In addition, the trends and critical challenges in both research directions are outlined at the end. Key points: • The value and significance of galactose utilization are highlighted. • Biofuel production from galactose-rich biomass is accomplished by fermentation. • L-arabinose isomerase is a tool for bioconversion of D-galactose to D-tagatose. [ABSTRACT FROM AUTHOR]

Recent studies have shown phenotypic and metabolic heterogeneity in related species including Streptococcus oralis, a typical oral commensal bacterium, Streptococcus mutans, a cariogenic bacterium, and Streptococcus gordonii, which functions as an accessory pathogen in periodontopathic biofilm. In this study, metabolites characteristically contained in the saliva of individuals with good oral hygiene were determined, after which the effects of an identified prebiotic candidate, D-tagatose, on phenotype, gene expression, and metabolic profiles of those three key bacterial species were investigated. Examinations of the saliva metabolome of 18 systemically healthy volunteers identified salivary D-tagatose as associated with lower dental biofilm abundance in the oral cavity (Spearman’s correlation coefficient; r = -0.603, p = 0.008), then the effects of D-tagatose on oral streptococci were analyzed in vitro. In chemically defined medium (CDM) containing D-tagatose as the sole carbohydrate source, S. mutans and S. gordonii each showed negligible biofilm formation, whereas significant biofilms were formed in cultures of S. oralis. Furthermore, even in the presence of glucose, S. mutans and S. gordonii showed growth suppression and decreases in the final viable cell count in a D-tagatose concentration-dependent manner. In contrast, no inhibitory effects of D-tagatose on the growth of S. oralis were observed. To investigate species-specific inhibition by D-tagatose, the metabolomic profiles of D-tagatose-treated S. mutans, S. gordonii, and S. oralis cells were examined. The intracellular amounts of pyruvate-derived amino acids in S. mutans and S. gordonii, but not in S. oralis, such as branched-chain amino acids and alanine, tended to decrease in the presence of D-tagatose. This phenomenon indicates that D-tagatose inhibits growth of those bacteria by affecting glycolysis and its downstream metabolism. In conclusion, the present study provides evidence that D-tagatose is abundant in saliva of individuals with good oral health. Additionally, experimental results demonstrated that D-tagatose selectively inhibits growth of the oral pathogens S. mutans and S. gordonii. In contrast, the oral commensal S. oralis seemed to be negligibly affected, thus highlighting the potential of administration of D-tagatose as an oral prebiotic for its ability to manipulate the metabolism of those targeted oral streptococci.

It is known that fructose may contribute to myocardial vulnerability to ischemia/reperfusion (I/R) injury. D-tagatose is a fructose isomer with less caloric value and used as low-calorie sweetener. Here we compared the metabolic impact of fructose or D-tagatose enriched diets on potential exacerbation of myocardial I/R injury. Wistar rats were randomizedly allocated in the experimental groups and fed with one of the following diets: control (CTRL), 30% fructose-enriched (FRU 30%) or 30% D-tagatose-enriched (TAG 30%). After 24 weeks of dietary manipulation, rats underwent myocardial injury caused by 30 min ligature of the left anterior descending (LAD) coronary artery followed by 24 h′ reperfusion. Fructose consumption resulted in body weight increase (49%) as well as altered glucose, insulin and lipid profiles. These effects were associated with increased I/R-induced myocardial damage, oxidative stress (36.5%) and inflammation marker expression. TAG 30%-fed rats showed lower oxidative stress (21%) and inflammation in comparison with FRU-fed rats. Besides, TAG diet significantly reduced plasmatic inflammatory cytokines and GDF8 expression (50%), while increased myocardial endothelial nitric oxide synthase (eNOS) expression (59%). Overall, we demonstrated that D-tagatose represents an interesting sugar alternative when compared to its isomer fructose with reduced deleterious impact not only on the metabolic profile but also on the related heart susceptibility to I/R injury.

D‐Tagatose is a rare natural sugar, which is promising alternative for popular dietary sweeteners. To optimize and make D‐tagatose production more cost‐effective, a portable (bio)sensor would be beneficial for D‐tagatose quantification in bioreactor media during D‐tagatose (bio)synthesis. In this study, a pilot study of D‐tagatose quantification by a bioamperometric system is reported. A key feature of the system is usage of fructose dehydrogenase from Gluconobacter japonicus, widely known as a highly fructose‐specific enzyme, and 2‐arylamino‐1,4‐benzoquinone derivatives, as electron transfer mediators from the enzyme to carbon electrodes. The system has been validated as biosensor for D‐tagatose quantification in the fermentation medium. [ABSTRACT FROM AUTHOR]

Summary: The study aimed to investigate the utilisation of prebiotic D‐tagatose by probiotic lactobacilli (L. rhamnosus GG, L. casei, L. acidophilus and L. fermentum) and enteric pathogens (E. coli and S. typhimurium) to determine synbiotic potential of D‐tagatose and lactobacilli combination. The antimicrobial efficacy of the synbiotic preparations (D‐tagatose with lactobacillus) was assessed against selected pathogens in co‐culture assays. Evidently, D‐tagatose supported growth of selected lactobacilli, especially the L. rhamnosus GG and L. casei, but not the enteric pathogens. The tested synbiotic preparations completely inhibited growth of both the pathogens, even in the presence of D‐glucose in co‐cultures. The well‐diffusion assay demonstrated the presence of antimicrobial activity as recorded by drop of culture pH. The study substantiated that D‐tagatose could be an effective prebiotic component for formulation of potential synbiotic combinations with L. rhamnosus GG or L. casei that can be used as an alternative to antibiotics against enteric pathogens. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian Polytechnic University is the property of Journal of Dalian Polytechnic University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study reports an alternative strategy for the expression of a recombinant l-AI from Enterococcus faecium DBFIQ E36 by auto-induction using glucose and glycerol as carbon sources and residual whey lactose as inducer agent. Commercial lactose and isopropyl β-d-1-thiogalactopyranoside (IPTG) were also evaluated as inducers for comparison of enzyme expression levels. The enzymatic extracts were purified by affinity chromatography, characterized, and applied in the bioconversion of d-galactose into d-tagatose. l-AI presented a catalytic activity of 1.67 ± 0.14, 1.52 ± 0.01, and 0.7 ± 0.04 U/mL, when expressed using commercial lactose, lactose from whey, and IPTG, respectively. Higher activities could be obtained by changing the protocol of enzyme extraction and, for instance, the enzymatic extract produced with whey presented a catalytic activity of 3.8 U/mL. The specific activity of the enzyme extracts produced using lactose (commercial or residual whey) after enzyme purification was also higher when compared to the enzyme expressed with IPTG. Best results were achieved when enzyme expression was conducted using 4 g/L of residual whey lactose for 11 h. These results proved the efficacy of an alternative and economic protocol for the effective expression of a recombinant l-AI aiming its high-scale production. [ABSTRACT FROM AUTHOR]

d-Tagatose, a functional sweetener, is converted from d-galactose by l-arabinose isomerase, which catalyzes the conversion of l-arabinose to l-ribulose. In this study, the araA gene encoding l-arabinose isomerase from Klebsiella pneumoniae was cloned and expressed in Escherichia coli, and the expressed enzyme was purified and characterized. The purified l-arabinose isomerase, a soluble protein with 11.6-fold purification and a 22% final yield, displayed a specific activity of 1.8 U/mg for d-galactose and existed as a homohexamer of 336 kDa. The enzyme exhibited maximum activity at pH 8.0 and 40 °C in the presence of Mn2+ and relative activity for pentoses and hexoses in the order l-arabinose > d-galactose > l-ribulose > d-xylulose > d-xylose > d-tagatose > d-glucose. The thermal stability of recombinant E. coli cells expressing l-arabinose isomerase from K. pneumoniae was higher than that of the enzyme. Thus, the reaction conditions of the recombinant cells were optimized to pH 8.0, 50 °C, and 4 g/L cell concentration using 100 g/L d-galactose with 1 mM Mn2+. Under these conditions, 33.5 g/L d-tagatose was produced from d-galactose with 33.5% molar yield and 67 g/L/h productivity. Our findings will help produce d-tagatose using whole-cell reactions, extending its industrial application.

As a substitute sweetener for sucrose, d‐tagatose is widely used in products, such as health drinks, yogurt, fruit juices, baked goods, confectionery, and pharmaceutical preparations. In the fermentation process of l‐AI produced by Lactobacillus plantarum, d‐tagatose is produced through biotransformation and this study was based on the fermentation process of Lactobacillus plantarum WU14 producing l‐AI to further research the biotransformation and separation process of d‐tagatose. The kinetics of cell growth, substrate consumption, and l‐arabinose isomerase formation were established by nonlinear fitting, and the fitting degrees were 0.996, 0.994, and 0.991, respectively, which could better reflect the change rule of d‐tagatose biotransformation in the fermentation process of L. plantarum WU14. The separation process of d‐tagatose was identified by decolorization, protein removal, desalination, and freeze drying, initially. Finally, the volume ratio of whole cell catalysts, d‐galactose, and borate was 5:1:2 at 60°C, pH 7.17 through borate complexation; then, after 24 hr of conversion, the yield of d‐tagatose was 58 g/L. [ABSTRACT FROM AUTHOR]

d -tagatose is regarded as one of the most valuable rare sugars in the current market and its biotechnological ways of production is a very hot topic as of today. As a ketohexose, d -tagatose having low-caloric value and 90% of sweetness with sucrose is a rare monosaccharide that exists extremely in low quantities in nature. Owing to distinct properties and beneficial functions on human health it has received a great interest and attained Generally Recognised as Safe (GRAS) status by the U.S. Food and Drug Administration (USFDA) in 2010. Due to scarcity in nature, production of d -tagatose either by chemical or biological methods is of utmost importance. In order to overcome the challenges that occur in chemical production, recently, biological process by using l -arabinose isomerase (L -AIs) for converting d -galactose to d -tagatose has allured researchers to find out more new ways to synthesize it in a cheap and eco-friendly manner. Herein, a brief summary on the scope of enzyme engineering methods like rational, semi-rational and directed evolution approaches to generate tailored L -AIs for improving d -tagatose yield and its function under harsh conditions are summarized. In addition, comparison of biochemical parameters and structural key aspects are also highlighted in this paper. Till date, L -AIs from various microbial sources are identified and characterized. Elucidating crystal structures and catalytic mechanism has elevated the researcher's interest to modify the L -AIs at molecular level and demonstrate its potential that is suited for industrial settings. However, works to produce d -tagatose from cheap renewable feedstocks and methods like immobilization and cell-surface display of L -AIs for efficient uptake and biotransformation of d -galactose are scarcely reported. In future, by employing the aforementioned strategies, the research studies must be focused more on shaping L -AIs as powerful biocatalysts to produce d -tagatose at industrial scale that necessitates for the human welfare. • Scope and importance of l -arabinose isomerase (L -AI) for biological production of d -tagatose is reviewed. • Engineering L -AI by various protein engineering methods is comprehensively discussed. • Feasibility of using renewable sources and industrial by-products wastes for d -tagatose synthesis are highlighted. • Importance of immobilization and other cellular engineering for enhancing d -tagatose yield or efficient substrate utilization are discussed. • Use of unnatural amino acid mutagenesis and downstream processing research needs are highlighted in future research area. [ABSTRACT FROM AUTHOR]

D-Galactose-specific L-arabinose isomerase (L-AI) would have much potential for the enzymatic conversion of D-Galactose into D-tagatose, while most of the reported L-AIs are L-arabinose specific. This study explored a highly D-Galactose-specific L-AI from Bifidobacterium adolescentis (BAAI) for the production of D-tagatose. In the comparative protein-substrate docking for D-Galactose and L-arabinose, BAAI showed higher numbers of hydrogen bonds in D-Galactose-BAAI bonding site than those found in L-arabinose-BAAI bonding site. The activity of BAAI was 24.47 U/mg, and it showed good stability at temperatures up to 65°C and a pH range 6.0–7.5. The Km, Vmax, and Kcat/Km of BAAI were found to be 22.4 mM, 489 U/mg and 9.3 mM–1 min–1, respectively for D-Galactose, while the respective values for L-arabinose were 40.2 mM, 275.1 U/mg, and 8.6 mM–1 min–1. Enzymatic conversion of D-Galactose into D-tagatose by BAAI showed 56.7% conversion efficiency at 55°C and pH 6.5 after 10 h.

Downy mildew caused by the oomycete Plasmopara viticola represents one of the most devastating diseases in vineyards. Current ways to control this disease rely mainly on fungicide applications, but agro-ecological concerns have raised interest in sustainable alternative methods. Certain rare sugars, like D-tagatose, have shown efficacy in reducing various plant diseases, including grapevine downy mildew. However, the mechanism of action of D-tagatose against grapevine downy mildew is not understood. The aim of this study was to characterize the efficacy and mechanism of action of a D-tagatose-based formulated product (IFP48) against grapevine downy mildew and compare it with the correspondent active molecule, pure D-tagatose (TAG). Whereas IFP48 root treatment provided scarce protection, the leaf treatment was the most efficient, especially at the dosage of 5 g/L. In particular, IFP48 treatment directly inhibited P. viticola sporangia germination, upregulated the expression of defense-related genes, and increased the content of stilbene phytoalexins. Conversely, the expression of defense-related genes and the content of stilbene phytoalexins were only slightly affected by TAG, suggesting that the formulation possibly improved D-tagatose effects against downy mildew in grapevine.

The use of natural bio-based compounds becomes an eco-friendly strategy to control plant diseases. Rare sugars would be promising compounds as inducers of plant “sweet immunity”. The present study aimed to investigate the induced resistance of grapevine leaves against Plasmopara viticola and Botrytis cinerea by a rare sugar-based product (IFP48) and its active ingredient D-tagatose (TAG), in order to elucidate molecular mechanism involved in defense-related metabolic regulations before and after pathogen challenge. Data showed that spraying leaves with IFP48 and TAG lead to a significant reduction of downy mildew, but not of gray mold disease. The induced protection against P. viticola relies on IFP48’s and to a lesser extent TAG’s ability to potentiate the activation of salicylic acid- and jasmonic acid/ethylene-responsive genes and stilbene phytoalexin accumulation. Most of defense responses remained upregulated in IFP48-treated plants after infection with P. viticola, but inconsistent following challenge with B. cinerea. The beneficial effects of IFP48 were associated with an enhanced accumulation of tagatose inside leaf tissues compared to TAG treatment. Meanwhile, the amounts of sugars, glucose, fructose, maltose, galactose and trehalose remained unchanged or decreased in IFP48-treated leaves after P. viticola infection, although only a few genes involved in sugar transport and metabolism showed transcriptional regulation. This suggests a contribution of sugar homeostasis to the IFP48-induced sweet immune response and priming plants for enhanced resistance to P. viticola, but not to B. cinerea.

The one-pot production of tagatose from lactose using recombinant l -arabinose isomerase (L-AI) from Thermotoga maritima and commercial β-galactosidase (β-gal) from Aspergillus oryzae was evaluated. The β-gal and L-AI ratio (R β-gal/L-AI), initial lactose concentration and temperature were chosen as study variables. Maximum values of tagatose yield (Y Tag), specific tagatose productivity (π Tag) and sugars ratio (R Tag/Gal) obtained were 23 %, 0.202 ± 0.03 mmol Tag/(g prot⋅h) and 1, respectively. The composition of the product on a dry basis was as follows (g/g): 0.23 tagatose, 0.232 galactose, 0.454 glucose, 0.043 fructose, 0.029 lactose and 0.012 GOS. The one-pot production was superior compared with a sequential operation, where values of 16.5 %, 0.11 mmol Tag/(g prot⋅h) and 0.59 were obtained for Y Tag , π Tag and R Tag/Gal , respectively. • Tagatose was produced in one-pot operation with A. oryzae βgal and T. maritima L-AI. • Higher yield and specific productivity were achieved in one-pot operation. • Thermodynamically and kinetically controlled reaction are involved in one-pot operation. [ABSTRACT FROM AUTHOR]

A novel l -arabinose isomerase (L-AI) from Arthrobacter psychrolactophilus (Ap L-AI) was successfully cloned and characterized. The enzyme catalyzes the isomerization of d -galactose into a rare sugar d -tagatose. The recombinant Ap L-AI had an approximate molecular weight of about 258 kDa, suggesting it was an aggregate of five 58 kDa monomers and became the first record as a homo-pentamer L-AI. The catalytic efficiency (k cat /Km) and Km for d -galactose were 0.32 mM−1 min−1 and 51.43 mM, respectively, while for l -arabinose, were 0.64 mM−1 min−1 and 23.41 mM, respectively. It had the highest activity at pH 7.0–7.5 and 60 °C in the presence of 0.250 mM Mn2+. Ap L-AI was discovered to be an outstanding thermostable enzyme that only lost its half-life value at 60 °C for >1000 min. These findings suggest that l -arabinose isomerase from Arthrobacter psychrolactophilus is a promising candidate for d -tagatose mass-production due to its industrially competitive temperature. • Sequence of L-AI retrieved from the genome of Arthrobacter psychrolactophilus B7 • Gene cloning and overexpression in E. coli host using pET-28a(+) • Enzyme activity characterization indicated high thermal stability. [ABSTRACT FROM AUTHOR]

d-tagatose is a popular functional monosaccharide produced from lactose by β-galactosidase and arabinose isomerase. In this study, two d-alanine-deficient heterologous gene expression systems were constructed, B. subtilis 168 D1 and B. subtilis 168 D2, using overlapping extension PCR and the CRE/loxP system. The lacZ gene for β-galactosidase was integrated into a specific locus of the chassis B. subtilis 168 D2. A mutually complementary plasmid pMA5 with the alanine racemase gene alrA attached to it was constructed and used to assemble recombinant plasmids overexpressing β-galactosidase and arabinose isomerase. Afterward, an integrated recombinant was constructed by the plasmid expressing the arabinose isomerase gene araA of E. coli transform-competent B. subtilis 168 D2 cells. The co-expressing plasmids were introduced into alanine racemase knockout B. subtilis 168 D1. Whole-cell bioconversion was performed using the integrated recombinant with a maximum yield of 96.8 g/L d-tagatose from 500 g/L lactose, and the highest molar conversions were 57.2%. B. subtilis 168 D1/pMA5-alrA-araA-lacZ is capable of single-cell one-step production of d-tagatose. This study provides a new approach to the production of functional sugars.

As electrode nanomaterials, thermally reduced graphene oxide (TRGO) and modified gold nanoparticles (AuNPs) were used to design bioelectrocatalytic systems for reliable D-tagatose monitoring in a long-acting bioreactor where the valuable sweetener D-tagatose was enzymatically produced from a dairy by-product D-galactose. For this goal D-fructose dehydrogenase (FDH) from Gluconobacter industrius immobilized on these electrode nanomaterials by forming three amperometric biosensors: AuNPs coated with 4-mercaptobenzoic acid (AuNP/4-MBA/FDH) or AuNPs coated with 4-aminothiophenol (AuNP/PATP/FDH) monolayer, and a layer of TRGO on graphite (TRGO/FDH) were created. The immobilized FDH due to changes in conformation and spatial orientation onto proposed electrode surfaces catalyzes a direct D-tagatose oxidation reaction. The highest sensitivity for D-tagatose of 0.03 ± 0.002 μA mM−1cm−2 was achieved using TRGO/FDH. The TRGO/FDH was applied in a prototype bioreactor for the quantitative evaluation of bioconversion of D-galactose into D-tagatose by L-arabinose isomerase. The correlation coefficient between two independent analyses of the bioconversion mixture: spectrophotometric and by the biosensor was 0.9974. The investigation of selectivity showed that the biosensor was not active towards D-galactose as a substrate. Operational stability of the biosensor indicated that detection of D-tagatose could be performed during six hours without loss of sensitivity.

We designed and constructed a green and sustainable bioprocess to efficiently coproduce D -tagatose, bioethanol, and microbial protein from whey powder. First, a one-pot biosynthesis process involving lactose hydrolysis and D -galactose redox reactions for D -tagatose production was established in vitro via a three-enzyme cascade. Second, a nicotinamide adenine dinucleotide phosphate-dependent galactitol dehydrogenase mutant, D36A/I37R, based on the nicotinamide adenine dinucleotide-dependent polyol dehydrogenase from Paracoccus denitrificans was created through rational design and screening. Moreover, an NADPH recycling module was created in the oxidoreductive pathway, and the tagatose yield increased by 3.35-fold compared with that achieved through the pathway without the cofactor cycle. The reaction process was accelerated using an enzyme assembly with a glycine-serine linker, and the tagatose production rate was 9.28-fold higher than the initial yield. Finally, Saccharomyces cerevisiae was introduced into the reaction solution, and 266.5 g of D -tagatose, 162.6 g of bioethanol, and 215.4 g of dry yeast (including 38% protein) were obtained from 1 kg of whey powder (including 810 g lactose). This study provides a promising sustainable process for functional food ( D -tagatose) production. Moreover, this process fully utilized whey powder, demonstrating good atom economy., (© 2024 Wiley-VCH GmbH.)

An α-selective glycosidation reaction of d -tagatofuranose was successfully achieved using 3,4- O -isopropylidene-protected d -tagatofuranose as a glycosyl donor. A variety of glycosyl acceptors, including primary, secondary, and β-amino alcohols, and carbohydrates, can be used for this d -tagatofuranosidation reaction with complete α-selectivities and good yields (57–83%). The stereochemistries at the anomeric positions were determined by nuclear Overhauser effect spectroscopic correlations, as well as comparison of the chemical shifts in the 13C NMR spectra. Image 1 [ABSTRACT FROM AUTHOR]

Copyright of Iraq Journal of Market Research & Consumer Protection / Al-Mağallaẗ al-ʿIrāqiyyaẗ li-Buḥūṯ al-Sūq wa-Ḥimāyaẗ al-Mustahlik is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

d-Tagatose is a ketohexose, which presents unique properties as a low-calorie functional sweetener possessing a sweet flavor profile similar to d-sucrose and having no aftertaste. Considered a generally recognized as safe (GRAS) substance by FAO/WHO, d-tagatose can be used as an intermediate for the synthesis of other optically active compounds as well as an additive in detergent, cosmetic, and pharmaceutical formulations. This study reports important features for l-arabinose isomerase (EC 5.3.1.4) (L-AI) use in industry. We describe arabinose (araA) gene virulence analysis, gene isolation, sequencing, cloning, and heterologous overexpression of L-AI from the food-grade GRAS bacterium Enterococcus faecium DBFIQ E36 in Escherichia coli and assess biochemical properties of this recombinant enzyme. Recombinant L-AI (rL-AI) was one-step purified to homogeneity by Ni2+-agarose resin affinity chromatography and biochemical characterization revealed low identity with both thermophilic and mesophilic L-AIs but high degree of conservation in residues involved in substrate recognition. Optimal conditions for rL-AI activity were 50 °C, pH 5.5, and 0.3 mM Mn2+, exhibiting a low cofactor concentration requirement and an acidic optimum pH. Half-life at 45 °C and 50 °C were 1427 h and 11 h, respectively, and 21.5 h and 39.5 h at pH 4.5 and 5.6, respectively, showing the high stability of the enzyme in the presence of a metallic cofactor. Bioconversion yield for d-tagatose biosynthesis was 45% at 50 °C after 48 h. These properties highlight the technological potential of E. faecium rL-AI as biocatalyst for d-tagatose production. [ABSTRACT FROM AUTHOR]

A recombinant l-arabinose isomerase from Enterococcus faecium DBFIQ E36 was immobilized onto multifunctional epoxide supports by chemical adsorption and onto a chelate-activated support via polyhistidine-tag, located on the N-terminal (N-His-L-AI) or on the C-terminal (C-His-L-AI) sequence, followed by covalent bonding between the enzyme and the support. The results were compared to reversible L-AI immobilization by adsorption onto charged agarose supports with improved stability. All the derivatives presented immobilization yields of above 75%. The ionic interaction established between agarose gels containing monoaminoethyl-N-aminoethyl structures (MANAE) and the enzyme was the most suitable strategy for L-AI immobilization in comparison to the chelate-activated agarose. In addition, the immobilized biocatalysts by ionic interaction in MANAE showed to be the most stable, retaining up to 100% of enzyme activity for 60 min at 60 °C and with Km values of 28 and 218 mM for MANAE-N-His-L-AI and MANAE-C-His-L-AI, respectively. [ABSTRACT FROM AUTHOR]

L-arabinose isomerase (L-AI) (EC 5. 3. 1. 4. L-AI) that mediates the isomerization of D-galactose to D-tagatose was isolated from Lactobacillus brevis (MF 465792), and was further purified and characterized. Pure enzyme with molecular weight of 60.1 kDa was successfully obtained after the purification using Native-PAGE gel extraction method, which was a monomer in solution. The L-AI was found to be stable at 45-75 °C, and at pH 7.0-9.0. Its optimum temperature and pH was determined as 65 °C and 7.0, respectively. Besides, we found that Ca2+, Cu2+, and Ba2+ ions inhibited the enzyme activity, whereas the enzyme activity was significantly enhanced in the presence of Mg2+, Mn2+, or Co2+ ions. The optimum concentration of Mn2+ and Co2+ was determined to be 1 mM. Furthermore, we characterized the kinetic parameters for L-AI and determined the Km (129 mM) and the Vmax (0.045 mM min− 1) values. Notably, L. brevisL-AI exhibited a high bioconversion yield of 43% from D-galactose to D-tagatose under the optimal condition, and appeared to be a more efficient catalyst compared with other L-AIs from various organisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-performance galactitol dehydrogenase was identified and charactered. • Redox pathway was constructed in Bacillus subtilis for D-tagatose production from D-galactose. • Fine-tuned promoter and cofactor regeneration provided 6.75-fold higher D-tagatose. • Optimum fermentation conditions and medium composition produced 39.57 g/L D-tagatose, providing a potential approach for D-tagatose production. D-tagatose holds significant importance as a functional monosaccharide with diverse applications in food, medicine, and other fields. This study aimed to explore the oxidoreductive pathway for D-tagatose production, surpassing the contemporary isomerization-mediated biosynthesis approach in order to enhance the thermodynamic equilibrium of the reactions. Initially, a novel galactitol dehydrogenase was discovered through biochemical and bioinformatics analyses. By co-expressing the galactitol dehydrogenase and xylose reductase, the oxidoreductive pathway for D-tagatose synthesis was successfully established in Bacillus subtilis. Subsequently, pathway fine-tuning was achieved via promoter regulation and dehydrogenase-mediated cofactor regeneration, resulting in 6.75-fold higher D-tagatose compared to that produced by the strain containing the unmodified promoter. Finally, optimization of fermentation conditions and medium composition produced 39.57 g/L D-tagatose in a fed-batch experiment, with a productivity of 0.33 g/L/h and a yield of 0.55 mol/mol D-galactose. These findings highlight the potential of the constructed redox pathway as an effective approach for D-tagatose production. [ABSTRACT FROM AUTHOR]