Discovery of a Thermostable Tagatose 4-Epimerase Powered by Structure- and Sequence-Based Protein Clustering.

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 Ni2+. Its kcat and kcat/Km values toward d-fructose were measured to be 248.5 min-1 and 2.117 mM-1·min-1, respectively. Notably, Thar-T4Ease exhibited remarkable thermostability, with a t1/2 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.

Development and Characterization of a Tunable Metal-Organic Framework (MOF) for the Synthesis of a Rare Sugar D-Tagatose.

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.

L-arabinose isomerase from Lactobacillus fermentum C6: Enzymatic characteristics and its recombinant Bacillus subtilis whole cells achieving a significantly increased production of D-tagatose.

L-arabinose isomerase (L-AI) is a functional enzyme for the isomerizing of D-galactose to produce D-tagatose. In this study, L-AI-C6-encoding gene from the probiotic Lactobacillus fermentum C6 was cloned and expressed in Bacillus subtilis WB600 for investigating enzymatic characteristics and bioconverting D-tagatose by means of whole-cell catalysis. Results showed that the engineered B. subtilis WB600-pMA5-LAI achieved a maximum specific activity of L-AI-C6 (232.65 ± 15.54 U/mg protein) under cultivation in LB medium at 28 °C for 40 h. The recombinant L-AI-C6 was purified, and enzymatic characteristics test showed its optimum reaction temperature and pH at 60 °C and 8.0, respectively. In addition, L-AI-C6 exhibited good stability within the pH range of 5.5-9.0. By using B. subtilis WB600-pMA5-LAI cells as whole-cell catalyst, the highest D-tagatose yield reached 42.91 ± 0.28 % with D-galactose as substrate, which was 2.41 times that of L. fermentum C6 (17.79 ± 0.11 %). This suggested that the cloning and heterologous expression of L-AI-C6 was an effective strategy for improving D-tagatose conversion by whole-cell catalysis. In brief, the present study demonstrated that the reaction temperature, pH, and stability of L-AI-C6 from L. fermentum C6 meet the demands of industrial application, and the constructed B. subtilis WB600-pMA5-LAI shows promising potential for the whole-cell biotransformation of D-tagatose.

Improving Catalytic Efficiency of L-Arabinose Isomerase from Lactobacillus plantarum CY6 towards D-Galactose by Molecular Modification.

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.

Exploiting the biocatalytic potential of co-expressed l-fucose isomerase and d-tagatose 3-epimerase for the biosynthesis of 6-deoxy-l-sorbose.

6-Deoxy-l-sorbose (6-DLS) is an imperative rare sugar employed in food, agriculture, pharmaceutical and cosmetic industeries. However, it is a synthetic and very expensive rare sugars, previously synthesized by chemo-enzymatic methods through a long chain of chemical processes. Recently, enzymatic synthesis of rare sugars has attracted a lot of attention due to its advantages over synthetic methods. In this work, a promising approach for the synthesis of 6-DLS from an inexpensive sugar l-fucose was identified. The genes for l-fucose isomerase from Paenibacillus rhizosphaerae (Pr-LFI) and genes for d-tagatose-3-epimerase from Caballeronia fortuita (Cf-DTE) have been used for cloning and co-expression in Escherichia coli, developed a recombinant plasmid harboring pANY1-Pr-LFI/Cf-DTE vector. The recombinant co-expression system exhibited an optimum activity at 50 °C of temperature and pH 6.5 in the presence of Co2+ metal ion which inflated the catalytic activity by 6.8 folds as compared to control group with no metal ions. The recombinant co-expressed system was stable up to more than 50 % relative activity after 12 h and revealed a melting temperature (Tm) of 63.38 °C exhibiting half-life of 13.17 h at 50 °C. The co-expression system exhibited, 4.93, 11.41 and 16.21 g/L of 6-DLS production from initial l-fucose concentration of 30, 70 and 100 g/L, which equates to conversion yield of 16.44 %, 16.30 % and 16.21 % respectively. Generally, this study offers a promising strategy for the biological production of 6-DLS from an inexpensive substrate l-fucose in slightly acidic conditions with the aid of co-expression system harboring Pr-LFI and CF-DTE genes.

Production of D -tagatose, bioethanol, and microbial protein from the dairy industry by-product whey powder using an integrated bioprocess.

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.

Exploring an l-arabinose isomerase from cryophile bacteria Arthrobacter psychrolactophilus B7 for d-tagatose production.

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 (kcat/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.

Highly efficient production and simultaneous purification of d-tagatose through one-pot extraction-assisted isomerization of 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 âˆ¼ 39 % (boron: sugar = 0.5) to âˆ¼ 56 % (boron: sugar = 1) but then decreased to âˆ¼ 44 % (boron: sugar = 1.5). With temperature increased to 70 °C, the conversion yield of d-tagatose was further improved to âˆ¼ 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.

Rewiring Bacillus subtilis and bioprocess optimization for oxidoreductive reaction-mediated biosynthesis of D-tagatose.

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.

Production of d-aldotetrose from l-erythrulose using various isomerases.

d-Aldotetroses are rare sugars that are obtained via chemical synthesis in low yield. In this study, we demonstrated that d-aldotetroses could be produced using 3 isomerases. First, l-erythrulose was epimerized using d-tagatose 3-epimerase from Pseudomonas cichorii ST-24. The specific optical rotation of the reaction solution gradually decreased to zero, indicating that approximately 50% of the l-erythrulose was converted to d-erythrulose. d, l-Erythrulose mixture was isomerized with d-arabinose isomerase from Klebsiella pneumoniae 40bXX to produce d-threose, resulting in a conversion rate of 9.35%. d-Erythrose production using l-rhamnose isomerase from Pseudomonas stutzeri LL172 resulted in a conversion rate of 12.9%. Because of the low purity of the purchased d-erythrose, the product was reduced by the Raney nickel catalyst compared with authentic erythritol. We confirmed the products using HPLC and 13C-NMR spectra. This is the first report of d-aldotetrose production using an enzymatic reaction.

[Rational design of L-arabinose isomerase from Lactobacillus fermentum and its application in D-tagatose production].

L-arabinose isomerase (L-AI) is the key enzyme that isomerizes D-galactose to D-tagatose. In this study, to improve the activity of L-arabinose isomerase on D-galactose and its conversion rate in biotransformation, an L-arabinose isomerase from Lactobacillus fermentum CGMCC2921 was recombinantly expressed and applied in biotransformation. Moreover, its substrate binding pocket was rationally designed to improve the affinity and catalytic activity on D-galactose. We show that the conversion of D-galactose by variant F279I was increased 1.4 times that of the wild-type enzyme. The Km and kcat values of the double mutant M185A/F279I obtained by superimposed mutation were 530.8 mmol/L and 19.9 s-1, respectively, and the catalytic efficiency was increased 8.2 times that of the wild type. When 400 g/L lactose was used as the substrate, the conversion rate of M185A/F279I reached a high level of 22.8%, which shows great application potential for the enzymatic production of tagatose from lactose.

Efficient production of d-tagatose via DNA scaffold mediated oxidoreductases assembly in vivo from whey powder.

Among the emerging sweeteners, d-tagatose occupies a significant niche due to its low calorific value, antidiabetic property and growth promoting effects on intestinal probiotics. Recently, the main approach for d-tagatose biosynthesis is l-arabinose isomerase-based isomerization reaction from galactose, which shows relatively low conversion rate because of unfavorable thermodynamic equilibria. Herein, oxidoreductases, d-xylose reductase and galactitol dehydrogenase, together with endogenous ß-galactosidase were employed to catalyze the biosynthesis of d-tagatose from lactose with a yield of 0.282 g/g in Escherichia coli. Then, a deactivated CRISPR-associated (Cas) proteins-based DNA scaffold system was developed, which were proved to be efficient for assembling the oxidoreductases in vivo and got a 1.44-folds increase in d-tagatose titer and yield. Further, by employing d-xylose reductase with higher galactose affinity and activity, as well as overexpressing pntAB genes, the d-tagatose yield from lactose (0.484 g/g) increased to 92.0 % of the theoretical value, 1.72-times as that of original strain. Finally, whey powder, a lactose-rich food by-product, was bifunctionally utilized as an inducer and substrate. In the 5 L bioreactor, d-tagatose titer reached 32.3 g/L with little galactose detected, and the yield from lactose approached 0.402 g/g, which was the highest from waste biomass in the literature. The strategies used here might provide new insights into the biosynthesis of d-tagatose in future.

Safety evaluation of the food enzyme d-tagatose 3-epimerase from the genetically modified Escherichia coli strain PS-Sav-001.

The food enzyme d-tagatose 3-epimerase (EC 5.1.3.31) is produced with the genetically modified Escherichia coli strain PS-Sav-001 by SAVANNA Ingredients GmbH. The genetic modifications do not give rise to safety concerns. The food enzyme is considered free from viable cells of the production organism and its DNA. The food enzyme is used while retained inside a membrane reactor to convert d-fructose into the speciality carbohydrate d-allulose (syn. d-psicose). Since residual amounts of total organic solids (TOS) are removed by the purification steps applied during the production of d-allulose, dietary exposure was not calculated and toxicological studies were not considered necessary. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no match was found. The Panel considered that under the intended conditions of use, the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

A Retro-Aldol Reaction Prompted the Evolvability of a Phosphotransferase System for the Utilization of a Rare Sugar.

The evolution of the bacterial phosphotransferase system (PTS) linked to glycolysis is dependent on the availability of naturally occurring sugars. Although bacteria exhibit sugar specificities based on carbon catabolite repression, the acquisition and evolvability of the cellular sugar preference under conditions that are suboptimal for growth (e.g., environments rich in a rare sugar) are poorly understood. Here, we generated Escherichia coli mutants via a retro-aldol reaction to obtain progeny that can utilize the rare sugar d-tagatose. We detected a minimal set of adaptive mutations in the d-fructose-specific PTS to render E. coli capable of d-tagatose utilization. These E. coli mutant strains lost the tight regulation of both the d-fructose and N-acetyl-galactosamine PTS following deletions in the binding site of the catabolite repressor/activator protein (Cra) upstream from the fruBKA operon and in the agaR gene, encoding the N-acetylgalactosamine (GalNAc) repressor, respectively. Acquired d-tagatose catabolic pathways then underwent fine-tuned adaptation via an additional mutation in 1-phosphofructose kinase to adjust metabolic fluxes. We determined the evolutionary trajectory at the molecular level, providing insights into the mechanism by which enteric bacteria evolved a substrate preference for the rare sugar d-tagatose. Furthermore, the engineered E. coli mutant strain could serve as an in vivo high-throughput screening platform for engineering non-phosphosugar isomerases to produce rare sugars. IMPORTANCE Microorganisms generate energy through glycolysis, which might have preceded a rapid burst of evolution, including the evolution of cellular respiration in the primordial biosphere. However, little is known about the evolvability of cellular sugar preferences. Here, we generated Escherichia coli mutants via a retro-aldol reaction to obtain progeny that can utilize the rare sugar d-tagatose. Consequently, we identified mutational hot spots and determined the evolutionary trajectory at the molecular level. This provided insights into the mechanism by which enteric bacteria evolved substrate preferences for various sugars, accounting for the widespread occurrence of these taxa. Furthermore, the adaptive laboratory evolution-induced cellular chassis could serve as an in vivo high-throughput screening platform for engineering tailor-made non-phosphorylated sugar isomerases to produce low-calorigenic rare sugars showing antidiabetic, antihyperglycemic, and antitumor activities.

Synthesis of a Healthy Sweetener d-Tagatose from Starch Catalyzed by Semiartificial Cell Factories.

d-Tagatose is one of the several healthy sweeteners that can be a substitute for sucrose and fructose in our daily life. Whole cell-catalyzed phosphorylation and dephosphorylation previously reported by our group afford a thermodynamic-driven strategy to achieve tagatose production directly from starch with high product yields. Nonetheless, the poor structural stability of cells and difficulty in biocatalyst recycling restrict its practical application. Herein, an efficient and stable semiartificial cell factory (SACF) was developed by constructing an organosilica network (OSN) artificial shell on the cells bearing five thermophilic enzymes to produce tagatose. The OSN artificial shell, the thickness of which can be regulated by changing the tetraethyl silicate concentration, exhibited tunable permeability and superior mechanical strength. In contrast with cells, SACFs showed a relative activity of 99.5% and an extended half-life from 33.3 to 57.8 h. Over 50% of initial activity was retained after 20 reuses. The SACFs can catalyze seven consecutive reactions with tagatose yields of over 40.7% in field applications.

Rational design of L-arabinose isomerase from Lactobacillus fermentum and its application in D-tagatose production / 生物工程学报

L-arabinose isomerase (L-AI) is the key enzyme that isomerizes D-galactose to D-tagatose. In this study, to improve the activity of L-arabinose isomerase on D-galactose and its conversion rate in biotransformation, an L-arabinose isomerase from Lactobacillus fermentum CGMCC2921 was recombinantly expressed and applied in biotransformation. Moreover, its substrate binding pocket was rationally designed to improve the affinity and catalytic activity on D-galactose. We show that the conversion of D-galactose by variant F279I was increased 1.4 times that of the wild-type enzyme. The Km and kcat values of the double mutant M185A/F279I obtained by superimposed mutation were 530.8 mmol/L and 19.9 s-1, respectively, and the catalytic efficiency was increased 8.2 times that of the wild type. When 400 g/L lactose was used as the substrate, the conversion rate of M185A/F279I reached a high level of 22.8%, which shows great application potential for the enzymatic production of tagatose from lactose.

Intestinal absorption of D-fructose isomers, D-allulose, D-sorbose and D-tagatose, via glucose transporter type 5 (GLUT5) but not sodium-dependent glucose cotransporter 1 (SGLT1) in rats.

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 AUC0­180 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.

Improved thermostability and robustness of L-arabinose isomerase by C-terminal elongation and its application in rare sugar 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.

D-tagatose protects against oleic acid-induced acute respiratory distress syndrome in rats by activating PTEN/PI3K/AKT pathway.

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.

Uncovering the role of impurity sugars on the crystallization of d-tagatose crystal: Experiments and molecular dynamics simulations.

Impurity sugars produced in upstream process of functional sugars are significantly impacting the product quality. In this work, the effect of congeners (d-maltose (d-MAL), d-fructose (d-FRU), d-glucose (d-GLU)) on primary and secondary nucleation of d-tagatose (d-TAG) crystals was investigated. The impurity sugars showed an inhibition on primary nucleation of d-TAG crystals, while a promotion on the secondary nucleation of d-TAG. Interestingly, the impact of impurity sugars on d-TAG crystal growth was similar to that on primary nucleation. The diffusion ability, hydrogen bonding forming ability, interaction energy of d-TAG crystal surfaces and impurity sugars were evaluated by molecular dynamics (MD) simulations to reveal the nucleation and growth behavior. Based on the above findings, we designed the d-TAG crystallization experiments, and obtained d-TAG crystals with uniform particle size distribution and regular morphology. This study helps to understand the influence of impurity sugars on crystallization, guiding the industrial manufacturing of functional sugars.