Properties and Applications of Anionic Amino Acid Surfactants

Anionic amino acid surfactants (AAS), represented by N-acyl amino acids and their salts, exhibit excellent surface activity and superior performance. Due to their low irritation, non-toxicity, and biodegradability, anionic amino acid surfactants find widespread applications in various fields, especially daily chemicals, food, and biomedicine. This article briefly overviews the physicochemical properties of anionic amino acid surfactants and extends to their applications.

Properties of Anionic Amino Acid Surfactants

As mentioned in related articles (found below), anionic amino acid surfactants are typically acylation products of fatty acid chlorides and amino acids. In cleaning and daily chemical products, the most widely used anionic AAS on the market include N-lauroyl alanine sodium (SLA), N-lauroyl sarcosine sodium (SLS), N-lauroyl glutamate sodium (ULS), and N-lauroyl glycine sodium (YLS). Various research institutions and corporate labs have tested these amino acid surfactants for surface activity and detergency. Surface activity is generally assessed by measuring surface tension, contact angle, and wetting ability, while detergency is characterized by changes in soil whiteness. Additionally, emulsification capability and freezing point are important product characteristics.

Surface Properties

Test data from these institutions show that SLA, SLS, ULS, and YLS have surface tensions between 20-30 mN/m. The wetting critical tension for general synthetic fibers is above 30 mN/m, such as 44 mN/m for acrylic fibers, indicating these four AAS can effectively wet common fabrics. This is supported by contact angle data; ULS has a contact angle of only 47.8°, signifying strong wetting ability—a 0.2% mass fraction ULS solution wets canvas in just 3.52 s. Even SLA, the poorest performer among the four, requires only 7.06 s. These data demonstrate the high surface activity of anionic amino acid surfactants.

Foaming Properties

Different surfactants require varying foaming abilities and foam stability. Amino acid surfactants generally feature low foaming, noteworthy as foaming ability does not directly correlate with detergency in detergents. Thus, low-foaming amino acid surfactants can formulate low-foam detergent products, which are easy to rinse and water-saving.

Detergency

Compared to strongly alkaline soap-based surfactants, amino acid surfactants are significantly milder, though this results in inferior detergency.

Overall, these N-fatty acyl amino acid salts exhibit good surface activity and low foaming, making them ideal for low-foam surfactants. Notably, these anionic AAS have very low freezing points, allowing use at lower temperatures.

Applications of Anionic Amino Acid Surfactants

Due to low human irritation, low toxicity, and good biodegradability, amino acid surfactants primarily apply in daily chemicals, but also have specialized uses in medicine, food, industry, and agriculture.

Daily Chemicals

Over the years, amino acid surfactants in cleansers, hand sanitizers, shampoos, and toothpastes have permeated daily life. Their pH typically ranges from 5.5-7, weakly acidic like human skin, ensuring no irritation. Amide bonds form special associations with chelating and antioxidant functions, good surface penetration, and inhibition of irritants like sodium ions penetrating skin, preventing roughness post-use. N-lauroyl sarcosine sodium exhibits good antibacterial activity against Gram-positive bacteria and some filamentous fungi. Experiments show 0.25% N-lauroyl sarcosine sodium effectively inhibits bacterial growth in human saliva; 0.5% kills 90% bacteria in 5 min, adsorbing firmly to dental plaque with prolonged activity. Compared to traditional sodium lauryl sulfate, adding N-lauroyl sarcosine sodium to oral care reduces irritation while providing antibacterial properties.

Biomedical Field

Though current production for biomedical amino acid surfactants is far less than for daily chemicals, research is extensive, with domestic firms like Changsha Puji having pharmaceutical-grade lines. Overseas, Chin Y.C. found N-acyl amino acids significantly improve vitamin E solubility in water. Tomohiro Hikima et al. developed a novel Gemini sodium lysinate surfactant, aiding ascorbyl-2-glucoside skin penetration.

Studies also show adding small amounts of N-lauroyl sarcosine sodium to eye drops enhances safety, stability, and antibacterial ability. In sympathetic nerve drugs, minor N-acyl amino acids or salts reduce skin allergic reactions. Anionic amino acid surfactants are widely used in immunology.

Food Industry

N-lauroyl sarcosine sodium has low toxicity; adding to vegetable oil or cocoa powder coatings retains aromas longer with anti-mold effects, useful for food storage. As additives, it inhibits acidic fermentation residues from carbohydrates on caries, protecting teeth.

Anionic amino acid surfactants also offer antistatic and anti-fog functions for food packaging.

Industry

Chen Shangbing et al. proposed N-lauroyl sarcosine’s hydrophobic chain covers metal surfaces, forming barriers to reduce carbon steel corrosion rates—non-toxic and cost-effective, making anionic amino acid surfactants excellent water treatment and metal corrosion inhibitors.

Research shows adding minor anionic amino acid surfactants to lubricants improves biodegradability with good rust prevention, wear resistance, and anti-wear. They apply broadly in metal processing and oil extraction.

Agriculture

Studies indicate adding N-acyl amino acids to pesticides enhances active ingredient efficacy while reducing toxicity and irritation.

Current Status of Anionic AAS Industry

As of 2025, the global amino acid surfactants market is estimated around USD 1.72 billion, up from USD 1.28 billion in 2021, with ongoing growth driven by demand for eco-friendly products. Leading producers include Ajinomoto, Sino Lion, and Changsha Puji, accounting for about 40% of the market. China remains the largest market, comprising around 60% globally. By the end of 2024, domestic firms like Nanjing Huashi and Changsha Puji have anionic AAS production lines, with demand for amino acid daily chemicals surging alongside improved living standards. However, compared to traditional anionic surfactants, green anionic amino acid surfactants remain niche functional products.

Technically, amino acid surfactants face purification challenges; pharmaceutical, food, and cosmetic industries require high purity for human safety. Economically, production involves high-cost biotechnology, so technological innovation remains the industry’s priority.

For more on related products, visit Surfactants. Questions? Contact us. In summary, anionic amino acid surfactants continue to expand in sustainable applications due to their superior properties and versatility as eco-friendly surfactants and biodegradable surfactants.

Synthesis, Properties, and Industrial Applications of Amino Acid Surfactants