A Comprehensive Overview of Bio-based Surfactants

Bio-based surfactants are a class of green, environmentally friendly, and human-safe surfactants that have garnered significant attention from enterprises and research institutions for continuous innovation. Starting now, we’ll guide you through this novel type of surfactant.

Overview of Bio-based Surfactants

In the 1960s, a new type of surfactant emerged, distinct from traditional chemical products. This surfactant is prepared from biomass as raw materials, making it renewable, with fast degradation after use and minimal pollution. As a result, it quickly became a hot topic in research upon its introduction. This is the bio-based surfactant. (Note: Bio-based surfactants and biosurfactants are two different concepts. Bio-based surfactants are substances prepared from biomass with fixed hydrophilic and lipophilic groups that can align directionally on the surface of solutions and significantly reduce surface tension. Biosurfactants are amphiphilic compounds secreted by microorganisms or plants during metabolism under certain conditions, integrating hydrophilic and hydrophobic structures in one molecule, such as glycolipids, polysaccharides, lipopeptides, or neutral lipid derivatives.)

In the decades following the emergence of bio-based surfactants, dozens of products were developed abroad, all prepared from biomass. In China, surfactant research started late, with independent development beginning in 1957, so bio-based surfactant products were scarce until the 21st century. However, in recent years, many universities and enterprises have caught up. Compared to foreign counterparts, China’s bio-based surfactants face some severe issues, such as:

1. Lack of variety in green surfactants, missing high-efficiency, environmentally friendly new varieties developed from biomass resources.
2. Although China’s surfactant intermediates and production processes have made significant progress in recent years, they still lag behind advanced international levels.

Traditional surfactants rely on petroleum products, and international crude oil prices fluctuate frequently. China lacks abundant crude oil resources, so petroleum is like the Sword of Damocles hanging over our heads. However, China is vast and rich in resources, spanning 49 degrees of latitude across temperate, subtropical, and tropical zones, boasting extremely diverse biological species. Additionally, the bio-based surfactant market is expanding rapidly, with the global market expected to reach $2.8 billion by 2023. In summary, developing affordable, renewable new bio-based surfactants and reforming and innovating production processes should be prioritized on the agenda of researchers and enterprises.

What Are Bio-based Surfactants?

Bio-based surfactants, as the name suggests, are surfactants synthesized from biomass as raw materials. Their hydrophobic parts mainly come from vegetable oils (castor oil, palm oil, coconut oil, and even used cooking oil), animal fats (including oils produced by some bacteria), phospholipids, etc. The hydrophilic parts from biological sources include polysaccharides, amino acids (from proteins), glycerol (a cheap and underutilized byproduct of biodiesel production), and citric acid. Of course, some natural biological products inherently possess excellent surface activity, known as “biosurfactants.” The European Committee for Standardization (Comité Européen de Normalisation, abbreviated as CEN) classifies products based on whether the carbon atoms in bio-based surfactants come from renewable resources: fully bio-based (>95%), mostly bio-based (50%–94%), minority bio-based (5%–49%), and non-bio-based (<5%) [2]. Figures 1-5 illustrate the structures of several types of bio-based surfactants.

Figure 1 shows several well-researched bio-based surfactants, among which methyl ester sulfonate (MES) is likely the most widely used anionic bio-based surfactant currently, especially in Asia, often formulated into detergent products. Ester quaternary ammonium salts are common cationic bio-based surfactants with antistatic and antibacterial properties, making them suitable as fabric antistatic agents and swimming pool disinfectants. Betaines are widely present in animals and plants, with chemical structures similar to amino acids, belonging to quaternary ammonium bases, commonly used in cleaning daily chemical products.

Figure 2 illustrates several currently well-researched amino acid-based surfactants. The most widely used amino acid surfactants are N-acyl amino acids made from glutamic acid, sarcosine, alanine, etc., essentially a class of anionic surfactants. There are also cationic surfactants made from arginine. Depending on the structure, amino acid surfactants can be divided into Bola-type, linear-type, Gemini-type, etc. Our public account article “A Comprehensive Guide to Amino Acid Surfactants” provides a more detailed explanation of different types of amino acids and synthesis processes.

Figure 3 shows several non-ionic bio-based surfactants. Among them, alkyl polyglucosides (APG) are a new type of green non-ionic surfactant, formed by dehydration of sugar’s hemiacetal hydroxyl and alcohol hydroxyl under catalyst action. APG has unique properties not found in traditional surfactants, such as low surface tension, strong detergency, high solubility even in high electrolyte concentrations, and an LD50 exceeding 5 g/kg, indicating very low toxicity. APG also has thickening functions, especially monosaccharides, with thickening ability comparable to common thickeners like alkanolamides.

Figure 4 illustrates several glycolipid compounds, which are generally biosurfactants, meaning they are directly synthesized by organisms. Sugar esters can serve as emulsifiers, commonly used in the food and pharmaceutical industries. Sophorolipids and rhamnolipids are products fermented by microorganisms under certain conditions. The former has a larger molecular weight and is a low-foam surfactant, while the latter, rhamnolipid, has various structures and is the longest-researched biosurfactant, already industrialized. The team of Xia Wenjie at Nankai University cultivated a Pseudomonas strain that can generate dirhamnolipids and lipopeptides under carbon dioxide ; Haloi Saura et al. cultivated TMB1, a Chromobacterium that produces rhamnolipids, which can be used in oil recovery. Additionally, previous knowledge points are available in the blog on this website.

Lipopeptide biosurfactants are surface-active lipopeptide compounds secreted by microorganisms during metabolism under certain conditions. These active substances have unique amphiphilic molecular structures, with polar hydrophilic peptide bonds and non-polar hydrophobic groups composed of fatty hydrocarbon chains, possessing special functions. Microorganisms reported to produce lipopeptides include at least 10 strains from genera such as Bacillus, Clostridium, and Pseudomonas. The produced lipopeptides include cyclic lipopeptides like surfactin and linear lipopeptides like Dragonamide. Lipopeptide bio-based surfactants are also a type of biosurfactant directly produced by organisms .

Characteristics of Bio-based Surfactants

In the above introduction, we have already provided some structures and features of bio-based surfactants. Here, we briefly summarize: Compared to conventional surfactants, bio-based surfactants have the following advantages:

1. Bio-based surfactants mostly have biodegradability, making them more environmentally friendly.
2. Bio-based surfactants have low allergenicity and are digestible, so they can be used in cosmetics and food additives.
3. Some bio-based surfactants have stronger surface activity.
4. Bio-based surfactants have diverse structures.
5. Bio-based surfactants often have complex and bulky structures, occupying large spaces, with low critical micelle concentrations.
6. Many bio-based surfactants are prepared by enzymes or organisms, rather than traditional chemical equipment.

Future Prospects

Due to consumer demand for green and environmentally friendly products, as well as the superior performance and special functions of bio-based surfactants that traditional surfactants cannot achieve, we can foresee that bio-based surfactants have great development prospects in the coming period. They will gradually replace non-degradable or human-harmful traditional surfactants in some fields.

For more information on our range of bio-based surfactants and related products, visit Book Chem’s Surfactant Products. As leaders in sustainable chemistry, Book Chem is committed to advancing bio-based surfactants for a greener future.

Synthesis, Properties, and Industrial Applications of Amino Acid Surfactants