In a one-step fermentation system of vitamin C production with Gluconobacter oxydans and Ketogulonicigenium vulgare, a functional module of α-lipoic acid biosynthesis was constructed in G. oxydans. The engineered G. oxydans was co-cultured with K. vulgare to enhance the growth and 2-keto-L-gulonic acid (2-KGA) production of K. vulgare. This one-step fermentation system alleviated the growth inhibition during the mono-culture of K. vulgare and strengthened the interaction between the two bacteria. Moreover, the yield of vitamin C precursor (2-KGA) increased to 73.34 g/L (the control group was 59.09 g/L), and the conversion of D-sorbitol to 2-KGA increased to 86.0%. This study provides a new idea for further optimizing the one-step fermentation system of vitamin C production.
Ascorbic Acid ; Fermentation ; Gluconobacter oxydans ; Rhodobacteraceae ; Thioctic Acid ; biosynthesis

Vitamin C is an essential vitamin for human beings. It has a huge market in the fields of food and pharmaceuticals. 2-keto-L-gulonic acid is an important precursor to produce vitamin C by microbial fermentation in industrial. In microbial fermentations, the L-sorbose pathway and the D-gluconate pathway have been the focus of research because of high yield. This article aims at stating recent research progress in dehydrogenases related to biosynthesis of vitamin C in the L-sorbose pathway and the D-gluconate pathway. The properties of dehydrogenase in terms of localization, substrate specificity, cofactors, and electron transport carrier are elaborated. And then, the main problems and strategies are reviewed in the L-sorbose pathway and in the D-gluconate pathway. Finally, future research on the dehydrogenases in the biosynthesis of vitamin C through L-sorbose pathway and D-gluconate pathway is discussed.
Ascorbic Acid/biosynthesis* ; Fermentation ; Gluconates ; Oxidoreductases/metabolism* ; Sorbose

Biological synthesis of L-Ascorbyl Palmitate in organic system were studied in this text. The contradiction between conversion of vitamin C and concentration of L-Ascorbyl Palmitate were resolved. High conversion of vitamin C and concentration of L-Ascorbyl Palmitate were obtained by Novo435. A series of solvents(log P from -0.24 to 3.5 )were investigated for the reaction,and acetone was found to be the most suitable from the standpoint of the enzyme activity and solubility of L-ascorbic. And the equilibrium of the reaction was affected by the addition of the molecular sieves and temperature. Reaction carried out at 60 degrees C and with 20% 0.4nm molecular sieves is good for the enzyme to keep its activity and for making the equilibrium go to the product. With 1.094 g palmitic acid, 0.107 g vitamin C and 0.020 g Novo435, rotate rate of 200 r/min, the conversion of ascorbic reached 80% and the concentration of L-ascorbyl palmitate is 20 g/L after 48 h. Furthermore, reaction batch of Novo435 and substrates recycle were observed, the result indicated that Novo435 may used 4-5 times continuously with high conversion. And 6-O-unsaturated acyl L-ascorbates were synthesized through Novo435 condensation of ascorbic acid and various unsaturated fatty acids with high conversion in this text.
Ascorbic Acid ; analogs & derivatives ; biosynthesis ; Catalysis ; Enzymes, Immobilized ; chemistry ; metabolism ; Lipase ; chemistry ; metabolism

OBJECTIVETo study the effects of ascorbic acid and citric acid on iron bioavailability using an in vitro digestion/Caco-2 cell culture model and evaluate the validity of this cell model.

METHODSThis model combined in vitro digestion technique with Fe uptake by Caco-2 cells by utilizing an inserted ring attached to a dialysis membrane to simulate the gastrointestinal environment to allow simultaneous food digestion and uptake processes. Ferritin formation in the Caco-2 cells was measured as the indicator of Fe uptake by exposing Caco-2 cells to the digests containing Fe plus ascorbic acid or citric acid.

RESULTSWhen Fe concentration in the digest was below 100 micromol/L, ferritin formation increased with the Fe concentration in the digest. The iron digest containing ascorbic acid exhibited a significant increase in ferritin formation relative to the iron digest containing citric acid. The model was more sensitive to lower iron concentrations when ascorbic acid was present in the digest, while wider range of iron concentration could be assessed by addition of citric acid.

CONCLUSIONSThe in vitro digestion/ Caco-2 cell culture model is a valuable tool for iron bioavailability assessment. Ascorbic acid has a stronger effect than citric acid in promoting iron bioavailability.

Ascorbic Acid ; pharmacology ; Biological Availability ; Caco-2 Cells ; metabolism ; Citric Acid ; pharmacology ; Ferritins ; biosynthesis ; Ferrous Compounds ; pharmacokinetics ; Humans ; Iron ; pharmacokinetics ; Models, Biological

PURPOSE: This study investigated the role of ascorbic acid on the production of nitric oxide (NO) in the trabecular meshwork (TM) cells. METHODS: After primarily cultured human TM cells were exposed to 1, 10, and 100 micrometer of L-ascorbic acid (LAA), with or without co-administration of 1 mM sodium nitroprusside or 100 micrometer hydrogen peroxide for 48 hr, cellular survival and NO production were measured with MTT and Griess assay, respectively. RESULTS: LAA significantly potentiated NO production in a dose-dependent manner (p< 0.05) without affecting cell viability. LAA increased cell viability after hydrogen peroxide-induced oxidative stress in a dose-dependent manner. LAA enhanced NO production in TM cells and showed a cytoprotective effect against hydrogen peroxide-induced oxidative stress. CONCLUSIONS: LAA might be involved in the regulation of trabecular outflow by enhancing NO production in TM cells.
Trabecular Meshwork/cytology/*drug effects/*metabolism ; Nitric Oxide/*biosynthesis ; Humans ; Dose-Response Relationship, Drug ; Cells, Cultured ; Cell Survival/drug effects ; Ascorbic Acid/administration & dosage/*pharmacology

OBJECTIVE: To investigate the effects of high dose vitamin C (VC) on proliferation of breast cancer cells and to explore its mechanisms. METHODS: Human breast cancer cells Bcap37 and MDA-MB-453 were treated with VC at low dose (0.01 mmol/L), medium dose (0.10 mmol/L) and high dose (2.00 mmol/L). Cell proliferation was determined with CCK-8 assay, protein expression was evaluated by Western blot, and the secretion of lactic acid in tumor cells was detected by colorimetric method. Bcap37 cells were inoculated in nude mice, and tumor baring nude mice were intraperitoneally injected with high VC(4 g/kg, VC group, =5)or normal saline (control group, =5) for 24 d. Tumor weight and body weight were calculated. RESULTS: experiments demonstrated that high dose VC significantly inhibited cell proliferation in Bcap37 and MDA-MB-453 cells (all <0.01); the expressions of Glut1 and mTOR signaling pathway-related proteins were decreased (all <0.05); and the secretion of lactic acid was also markedly reduced (all <0.05). experiment showed that the tumor weight was decreased in mice treated with high-dose VC as compared with control group (<0.05), but no difference in body weights between two groups was observed. CONCLUSIONS High dose VC may inhibit proliferation of breast cancer cells both and through reducing glycolysis and protein synthesis.
Animals ; Ascorbic Acid ; pharmacology ; Breast Neoplasms ; drug therapy ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Glycolysis ; drug effects ; Humans ; Mice ; Mice, Nude ; Protein Biosynthesis ; drug effects

OBJECTIVETo study the effect of vitamin C on preventing oxidative modification of low density lipoprotein cholesterol (LDL) in vitro.

METHODSDifferent levels of vitamin C were added to two different systems of lipid peroxidation of LDL induced by either Cu(2+) or macrophage. The level of VC in systems induced by Cu(2+) were 10, 50, 100 and 200 micromol/L respectively and by macrophage were 50, 100, 200 micromol/L respectively. Vitamin E (200 micromol/L) and VC(0) (0 micromol/L) were served as positive and negative control respectively. The content of TBARS, Ox-LDL, fluorescent compounds, electrophoretic mobility of LDL and the lag-phage of oxidation of LDL were measured.

RESULTSIn the oxidative systems induced by Cu(2+), the groups with higher levels of VC (100, 200 micromol/L) reduced the levels of TBARS, Ox-LDL at 3, 6, and 9 hour after adding Cu(2+), but low dose groups (10, 50 micromol/L) had no the effects. In the macrophage systems, higher levels of VC (100, 200 micromol/L) significantly reduced levels of fluorescent compounds and TBARS, and also lowered electrophoretic mobility of LDL and increased the lag-phage of oxidation of LDL.

CONCLUSIONVitamin C has dual effect on oxidation of LDL. Low dose treatment enhanced oxidation of LDL, but high doses has anti-oxidative effects on LDL.

Animals ; Antioxidants ; metabolism ; pharmacology ; Ascorbic Acid ; metabolism ; pharmacology ; Cells, Cultured ; Copper ; Electrophoresis, Agar Gel ; methods ; Fluorescent Dyes ; Lipofuscin ; analysis ; Lipoproteins, LDL ; biosynthesis ; metabolism ; Macrophages, Peritoneal ; cytology ; drug effects ; metabolism ; Male ; Oxidation-Reduction ; Rats ; Rats, Sprague-Dawley ; Thiobarbituric Acid Reactive Substances ; metabolism