Gluconate is a salt or ester derived from gluconic acid, which is a natural organic acid produced by the oxidation of glucose. The most common form of gluconate used in various industries is sodium gluconate, although it can also appear as other salts, such as calcium gluconate, magnesium gluconate, and potassium gluconate. Gluconates are widely used in cosmetics, pharmaceuticals, food, and industrial applications.

Chemical Composition and Structure

Gluconate is the conjugate base of gluconic acid. The chemical structure of gluconic acid is characterized by a six-carbon chain with a carboxyl group (-COOH) at one end and a hydroxyl group (-OH) at the other end. When gluconic acid reacts with a base, such as sodium hydroxide, it forms a salt known as sodium gluconate or other forms depending on the counter-ion used.

The general chemical structure of gluconate salts is:

• C₆H₁₁O₇⁻ (glucose backbone with the carboxyl group ionized)

Physical Properties

• Appearance: Gluconates, particularly sodium gluconate, are usually white, crystalline solids.

• Solubility: Gluconates are highly soluble in water, making them effective for use in aqueous solutions.

• Odor: Gluconates typically have little to no odor.

• Stability: They are generally stable and do not easily degrade under normal conditions, though exposure to heat and light for extended periods may cause some degradation.

Benefits and Functions

• Chelating Agent: Gluconates, especially sodium gluconate, are often used as chelating agents in cosmetics, cleaning products, and water treatment. They help bind and remove metal ions that could interfere with formulations or processes.

• Emulsifying and Stabilizing: In cosmetics, gluconates are used to stabilize emulsions, preventing the separation of water and oil-based ingredients.

• Skin Conditioning: In personal care products, gluconates may help condition the skin and improve the texture and feel of the product.

• Antimicrobial: Certain gluconate salts, such as calcium gluconate, are sometimes used for their mild antimicrobial properties.

• Mineral Supplementation: Gluconates like calcium gluconate and magnesium gluconate are used in pharmaceutical and dietary applications to provide these essential minerals to the body.

Applications

Cosmetics and Personal Care

• Shampoos and conditioners: Gluconates are used in hair care products to improve the stability of emulsions and enhance the texture of formulations.

• Lotions and creams: Gluconates are commonly included in skin care products, providing moisturization and improving product spreadability.

• Cleansers: Due to their ability to chelate metal ions, gluconates are used in cleansing products to enhance performance.

Pharmaceuticals

• Mineral supplementation: Calcium gluconate and magnesium gluconate are used in intravenous or oral formulations to treat or prevent mineral deficiencies.

• Topical treatments: Some gluconates are used in topical formulations to aid in wound healing or to provide soothing effects.

Food Industry

• Food additives: Sodium gluconate and calcium gluconate are sometimes used as food additives to enhance flavor or serve as mineral supplements.

• Preservative: Certain gluconates can be used as preservatives in processed food products.

Industrial Applications

• Cleaning products: Gluconates are used in industrial cleaners to remove scale, rust, and other metal ions from surfaces.

• Water treatment: They are used in water treatment processes to prevent scale buildup in pipes and equipment.

Environmental and Safety Considerations

• Biodegradability: Gluconates are biodegradable and generally considered environmentally friendly, making them a safer alternative to synthetic chelating agents.

• Safety: Gluconates are generally recognized as safe for use in cosmetics and food products. However, high concentrations in pharmaceutical products or large amounts ingested could lead to side effects, especially with specific mineral gluconates (e.g., calcium gluconate).

• Sustainability: The production of gluconates from glucose-based sources (like corn or sugar) can be considered a renewable resource, though it is important to consider the environmental impact of the raw materials and production processes.

References_____________________________________________________________________

Kornecki, J.F., Carballares, D., Tardioli, P.W., Rodrigues, R.C., Berenguer-Murcia, Á., Alcantara, A.R. and Fernandez-Lafuente, R., 2020. Enzyme production of D-gluconic acid and glucose oxidase: successful tales of cascade reactions. Catalysis Science & Technology, 10(17), pp.5740-5771.

Abstract. This review mainly focuses on the use of glucose oxidase in the production of D-gluconic acid, which is a reactant of undoubtable interest in different industrial areas. The enzyme has been used in numerous instances as a model reaction to study the problems of oxygen supply in bioreactors. One of the main topics in this review is the problem of the generated side product, hydrogen peroxide, as it is an enzyme-inactivating reagent. Different ways to remove hydrogen peroxide have been used, such as metal catalysts and use of whole cells; however, the preferred method is the coupling glucose oxidase with catalase. The different possibilities of combining these enzymes have been discussed (use of free enzymes, independently immobilized enzymes or co-immobilized enzymes). Curiously, some studies propose the addition of hydrogen peroxide to this co-immobilized enzyme system to produce oxygen in situ. Other cascade reactions directed toward the production of gluconic acid from polymeric substrates will be presented; these will mainly involve the transformation of polysaccharides (amylases, cellulases, etc.) but will not be limited to those (e.g., gluconolactonase). In fact, glucose oxidase is perhaps one of most successful enzymes, and it is involved in a wide range of cascade reactions. Finally, other applications of the enzyme have been reviewed, always based on the production of D-gluconic acid, which produces a decrease in the pH, a decrease in the oxygen availability or the production of hydrogen peroxide; in many instances, cascade reactions are also utilized. Thus, this review presents many different cascade reactions and discusses the advantages/drawbacks of the use of co-immobilized enzymes.

Gomes, R.J., de Fatima Borges, M., de Freitas Rosa, M., Castro-Gómez, R.J.H. and Spinosa, W.A., 2018. Acetic acid bacteria in the food industry: systematics, characteristics and applications. Food technology and biotechnology, 56(2), p.139.

Abstract. The group of Gram-negative bacteria capable of oxidising ethanol to acetic acid is called acetic acid bacteria (AAB). They are widespread in nature and play an important role in the production of food and beverages, such as vinegar and kombucha. The ability to oxidise ethanol to acetic acid also allows the unwanted growth of AAB in other fermented beverages, such as wine, cider, beer and functional and soft beverages, causing an undesirable sour taste. These bacteria are also used in the production of other metabolic products, for example, gluconic acid, l-sorbose and bacterial cellulose, with potential applications in the food and biomedical industries. The classification of AAB into distinct genera has undergone several modifications over the last years, based on morphological, physiological and genetic characteristics. Therefore, this review focuses on the history of taxonomy, biochemical aspects and methods of isolation, identification and quantification of AAB, mainly related to those with important biotechnological applications.

Anastassiadis S, Morgunov IG. Gluconic acid production. Recent Pat Biotechnol. 2007;1(2):167-80. doi: 10.2174/187220807780809472.

Abstract. Gluconic acid, the oxidation product of glucose, is a mild neither caustic nor corrosive, non toxic and readily biodegradable organic acid of great interest for many applications. As a multifunctional carbonic acid belonging to the bulk chemicals and due to its physiological and chemical characteristics, gluconic acid itself, its salts (e.g. alkali metal salts, in especially sodium gluconate) and the gluconolactone form have found extensively versatile uses in the chemical, pharmaceutical, food, construction and other industries. Present review article presents the comprehensive information of patent bibliography for the production of gluconic acid and compares the advantages and disadvantages of known processes. Numerous manufacturing processes are described in the international bibliography and patent literature of the last 100 years for the production of gluconic acid from glucose, including chemical and electrochemical catalysis, enzymatic biocatalysis by free or immobilized enzymes in specialized enzyme bioreactors as well as discontinuous and continuous fermentation processes using free growing or immobilized cells of various microorganisms, including bacteria, yeast-like fungi and fungi. Alternatively, new superior fermentation processes have been developed and extensively described for the continuous and discontinuous production of gluconic acid by isolated strains of yeast-like mold Aureobasidium pullulans, offering numerous advantages over the traditional discontinuous fungi processes.