Amino acid surfactants biodegradability

Hocker et al. [137] synthesized anionic A-acylated L-amino acids, oligopeptides, and protein hydrolysates and studied the adsorption on wool. Increased bath exhaustion and a more intense coloration of wool were obtained during dying of wool by the addition of the studied amino acid surfactants. These surfactants exhibited good biodegradabilities with 68-78% BOD5/COD. 

Being amino acid derivatives, the iminodipropionate surfactants are quite biodegradable and they are compatible with most other surfactants used. 

Kamimura [100], Shida et al. [101,102], and Kubo et al. [103] conducted extensive studies on biodegradability and found that A-acylamino acids are readily biodegradable through decomposition into amino acid and fatty acid. Thus they are desirable surfactants compatible with the environment [Fig. 22],... 

Naturally occurring amino acids have been of particular interest in the field of environmentally friendly surfactants. Surfactant molecules from renewable raw materials that mimic natural lipoamino adds are one of the preferred choices for food, pharmaceutical, and cosmetic applications. Given their natural and simple structure they show low toxicity and quick biodegradation. 

Contrarily to fatty add salts (i.e., sodium laurate soap), the long-chain iV -acyl amino adds have excellent water solubility (due to the presence of additional CO-NH linkages), quick biodegradability and good lime resistance (i.e., caldum ion tolerance) [11]. The surfactant properties of pure sodium salts of iV -acyl amino acids (anionic surfactants) with different alkyl chains (saturated and unsaturated with 10-18 carbon atoms) and amino acid residues have been described and compared with those of sodium lauryl sulfate (SLS) and sodium laurate [11-14]. The authors showed that the critical micelle concentration (CMQ of the amino acid-based surfactants was lower than that of the SLS but higher than that of sodium laurate. The surface activity increased and the CMC decreased by raising the alkyl chain... 

One important milestone in our research is the design and development of new amino acid-based surfactants with antimicrobial properties, which mimic natural amphiphilic cationic peptides [42,43]. To this end, Lys and Arg derivatives of long-chain A -acyl, COO-ester, and A-alkyl amide have been prepared. In particular, the A -acylarginine methyl ester derivatives series 1 (Scheme 1) have turned out to be an important class of cationic surface active compounds with a wide bactericidal activity, high biodegradability, and low toxicity profile. We have shown that essential structural factors for their antimicrobial activity include both the length of the fatty residue (akin with their solubility and surface activity) and the presence of the protonated guanidine function [43,44]. 

In addition to ammonium quaternary salts, other surfactants are also mentioned in the literature as an organomodifler in organoclays. Nonionic surfactants, which are linear alcohol ethoxylate, with low toxicity and potential for biodegradation are used to prepare organomontmorillonite (Shen, 2001). Furthermore, clays can also be modified with biomolecules, such as proteins, enzymes, amino acids, peptides, and so forth. 

Proteins are versatile materials, which combine many characteristics relevant for technical applications. The protein properties depend on both the source (amino acid composition) and the modifications that have been performed to improve specific features. The interest in non-food use of protein is increasing over the last two decades because of their renewability and biodegradability. Proteins have thus been used for the fabrication of materials such as edible films, films and coating, adhesives, thermoplastics and surfactants [196,197,198]. 

Biocompatible cationic surfactants from the amino acid lysine (hydrochloride salts of A -lauroyl-lysine methyl ester, IV -miristoyl-lysine methyl ester and A -palmitoyl-lysine methyl ester) show moderate antimicrobial activity against the Gram-positive bacteria. The haemolytic activity of these compounds is considerably lower than those reported for other cationic Ai -acyl amino acid analogues [64]. Taking into account the high biodegradation level and the low haemolytic activity, these compounds could be considered safe surfactants in relation to the cell of the human body. These properties make them suitable candidates for biological and medical applications [65]. 

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