How is vitamin C produced?

Chemical synthesis is currently the main production method for vitamin C, for both pharmaceutical and cosmetic applications. It largely relies on the Reichstein process, developed in the 1930s and still employed in optimized forms at an industrial scale. This process enables the conversion of D-glucose, most often derived from corn starch, into L-ascorbic acid, the biologically active form of vitamin C.

Synthetic vitamin C is strictly identical, in chemical and biological terms, to the vitamin C naturally present in plants.

Several successive steps are required, combining organic chemistry and biotechnology, in order to obtain the correct stereoisomer. First, glucose is hydrogenated to D-sorbitol using a Raney nickel catalyst. This sorbitol is then oxidized by microbial fermentation to yield L-sorbose, a key step that ensures the correct stereochemical configuration of the molecule. The hydroxyl groups of L-sorbose are then protected by forming acetals in the presence of acetone and sulfuric acid at low temperature, before a chemical oxidation is performed conventionally with potassium permanganate under alkaline conditions.

The final step involves closing the lactone ring to form ascorbic acid. It can be achieved either by heating in an aqueous medium or by esterification followed by treatment with sodium methoxide and a final acidification. More modern variations of the process also include direct oxidation in the presence of oxygen and a platinum catalyst, aimed at improving yields.

At Typology, we use stable derivatives of vitamin C obtained from D-glucose by the Reichstein-Grüssner process, combining chemical steps with a microbiological step.

Bacterial fermentation is an attractive alternative to chemical synthesis for the industrial production of vitamin C. In most cases, it does not directly yield ascorbic acid but instead produces its immediate precursor, 2-keto-L-gulonic acid (2-KGA), which is subsequently chemically converted into vitamin C. For this purpose, complementary microorganisms must be used, such as Gluconobacter oxydans, Ketogulonicigenium vulgare and various species of Bacillus.

In fact, K. vulgare can produce 2-KGA, but this bacterium functions optimally only in the presence of auxiliary strains, such as Bacillus. These provide essential metabolites and siderophores that enhance iron uptake and help mitigate the oxidative stress to which K. vulgare is highly sensitive. Proteomic and metabolomic analyses have shown that sporulation (i.e., spore formation) and the partial lysis of Bacillus release nutrients essential for the growth and metabolic activity of K. vulgare, thereby improving 2-KGA production yields.

This process is recognized for its efficiency, but it presents significant industrial constraints, such as long fermentation times and additional sterilization phases.

More recently, advances in metabolic engineering have enabled the streamlining of this scheme by developing fermentations based on better-controlled synthetic microbial consortia. For example, the genetic modification of G. oxydans to limit its consumption of sorbitol reduces competition with K. vulgare and strengthens their mutualism. Other studies have also demonstrated that it is possible to produce vitamin C directly from glucose using genetically modified bacteria, such as Escherichia coli expressing plant biosynthesis genes, although yields remain insufficient for industrial application.

Finally, vitamin C can be obtained by extraction from natural sources such as fruits, vegetables, certain leaves, or even algae. Historically, this route relied primarily on conventional aqueous or acidic extractions—effective but sometimes time-consuming, energy-intensive, and poorly selective. In recent years, the development of so-called "green" extraction techniques has renewed interest in this approach, seeking to reconcile yield, environmental sustainability, and preservation of this molecule particularly sensitive to oxidation and heat.

Among these innovative methods are ultrasound-assisted extraction, microwave-assisted extraction, pressurized liquid extraction, and supercritical fluid extraction. They rely on the use of mild conditions and eco-compatible solvents, such as water or mildly acidified solutions. Several studies illustrate the effectiveness of these approaches. For example, the extraction of vitamin C from camu-camu, a fruit naturally rich in ascorbic acid, showed that acid extraction reached high yields, while pressurized liquid extraction offered a cleaner, more controlled alternative. Similarly, optimizing microwave-assisted extraction, particularly using citric acid–based solutions, achieved high extraction rates from vegetables like bok choy while limiting vitamin C oxidation.

Although natural extraction is more difficult to standardize on a large scale than chemical synthesis, it presents a promising avenue that warrants future exploration for food, pharmaceutical, and cosmetic applications.

• SALVADOR A. & al. Environmentally friendly LC for the simultaneous determination of ascorbic acid and its derivatives in skin-whitening cosmetics. Journal of Separation Science (2008).

• VAID F. & al. Formulation and stability of ascorbic acid in topical preparations. Systematic Reviews in Pharmacy (2011).

• TELANG P. Vitamin C in dermatology. Indian Dermatology Online Journal (2013).

• YUAN Y.-J. & al. Reorganization of a synthetic microbial consortium for one-step vitamin C fermentation. Microbial Cell Factories (2016).

• PISANO R. & al. Advances in ascorbic acid (vitamin C) manufacturing: Green extraction techniques from natural sources. Processes (2023).

• CUI X. & al. Impact of anaerobic fermentation liquid on bok choy and mechanism of combined vitamin C from bok choy and allicin in treatment of DSS colitis. Foods (2025).