Sugar fatty acid ester surfactants: Biodegradation pathways

Abstract

In previous work, we found that the presence of a sulfonyl or alkyl group adjacent to the ester bond of sugar ester surfactants is associated with a dramatic reduction in the rate of biodegradation relative to that of unsubstituted esters. In this study, we investigated the pathways followed during the biodegradation of sucrose laurate, sucrose α-sulfonyl laurate, and sucrose α-ethyl laurate to determine the reasons for their different biodegradation rates. Through the use of high-performance liquid chromatography and proton nuclear magnetic resonance spectroscopy, the nature of the intermediates formed during the biodegradation of these three key sugar esters was determined. It was found that sucrose laurate biodegradation occurs via initial ester hydrolysis. In contrast, sucrose α-sulfonyl laurate degrades by initial alkyl chain oxidation. This indicates that the ester hydrolysis pathway is blocked by the sulfonyl group adjacent to the ester bond so that biodegradation is forced to proceed via the slower alkyl chain oxidation pathway. Sucrose α-ethyl laurate was degraded at least in part by alkyl chain oxidation, indicating that ester hydrolysis was also inhibited by the presence of an ethyl group. It is therefore concluded that previously observed relationships between structure and biodegradability arise because of the influence that different structural elements have on the pathways followed during biodegradation.Paper no. S1141 in JSD 3, 13-27 (January 2000).KEY WORDS: Biodegradation, ester, fatty acid, high-performance liquid chromatography, laurate, nuclear magnetic resonance, pathway, sucrose, sulfonyl, surfactant.As discussed in our previous paper (1), sucrose fatty acid esters are known to be rapidly biodegradable (2-8). However, relationships between biodegradability and the chemical structure of these surfactants have not been studied. Understanding these relationships would facilitate a targeted design of sugar ester surfactants for use in consumer products, while retaining a high degree of biodegradability.In our previous paper, we reported the ultimate biodegradabilities of an array of sugar ester surfactants whose structures were systematically varied. This revealed that a sulfonyl or alkyl group adjacent to the ester bond is associated with a reduction in the biodegradation rate. The biodegradation of sucrose laurate was complete within 12 h, while that of sucrose α-sulfonyl laurate occurred more slowly, reaching about 85% in 25 d. Biodegradation of sucrose α-ethyl laurate occurred at a rate that was between those of sucrose laurate and sucrose α-sulfonyl laurate, reaching completion in 4 d. In contrast, other structural modifications, including variations in the sugar head group size and the length and number of alkyl chains, did not have a significant effect on biodegradability. In order to establish reasons behind these relationships between structure and biodegradability, the chemical pathways followed during biodegradation of three key sugar esters were investigated. The three surfactants c...

Sugar fatty acid ester surfactants: Structure and ultimate aerobic biodegradability

“…When α-ethyl or αmethyl groups were attached, the inhibitory effect was weaker, but nonetheless significant. Further studies, described in separate publications (39,40), indicated that these structural changes affect biodegradability of this class of surfactants through their effects on the pathways followed during biodegradation. The biodegradation rate of sulfonated sugar esters was similar to that of the soft anionic standard, linear alkylbenzene sulfonate.…”

“…The different electronic properties of these subtsituents may also affect biodegradability. Reasons for biodegradability differences were the subject of considerable further investigation described in separate publications (39,40).…”

Synthesis ofD-Allose Fatty Acid EstersviaLipase-Catalyzed Regioselective Transesterification

“…7) From the point of view of more efficient and practical applications, we expected that the D-allose fatty acid esters might have a higher biological activity than Dallose itself because the hydrophobic carbon chains of the D-allose esters could improve the surface activity 8,9) and membrane permeability. They are also non-ionic and biodegradable 10) and, therefore, could be used in the food, cosmetic, and pharmaceutical industries. Although the chemical esterification of a monosaccharide with a fatty acid affords a mixture of the regioisomers of monoesters and diesters, the enzymatic acylation of a monosaccharide using porcine pancreatic lipase (PPL) and 2,2,2-trichloroethyl carboxylate has been reported to proceed with high regioselectivity by Klibanove et al 11) Since then, the enzymatic productions of monosaccharide esters using various lipases and such acylating agents as a fatty acid, 12) oxime ester, 13) and vinyl ester 14) have been reported.…”

Synthesis and Performance Properties of Cationic Fabric Softeners Derived from Free Fatty Acid of Tallow Fat

“…Esterquat cationic surfactant is one of the biodegradable fabric softener due to the presence of ester linkage 3 . Specialty of cationic surfactant is environmental friendly, non toxic and biodegradable properties 4 . Quats have been proven to be useful in variety of application, including the following as fabric conditioner, antistatic agent, biocides, emulsifiers in cosmetics, antibacterial agent, corrosion inhibiters and foam dispersant 5 .…”