Sugar fatty acid ester surfactants: Structure and ultimate aerobic biodegradability

Ultimate aerobic biodegradabilities of an array of sugar ester surfactants were determined by International Standards Organisation method 7827, "Water Quality-Evaluation in an Aqueous Medium of the Aerobic Biodegradability of Organic Compounds, Method by Dissolved Organic Carbon" (1984). The surfact ants were nonionic sugar esters with different-sized sugar head groups (for med from glucose, sucrose, or raffinose) and different lengths and numbers of alkyl chains [formed from lauric (C-12) or palmitic (C-16) acid]. Analog ous anionic sugar ester surfactants, formed by attaching an alpha-sulfonyl group adjacent to the ester bond, and sugar esters with alpha-alkyl substit uents were also studied. It was found that variations in sugar head group s ize or in alkyl chain length and number do not significantly affect biodegr adability. In contrast, the biodegradation rate of sugar esters with alpha- sulfonyl or alpha-alkyl groups, although sufficient for them to be classifi ed as readily biodegradable, was dramatically reduced compared to that of t he unsubstituted sugar esters. An understanding of the relationship between structure and biodegradability provided by the results of this study will aid the targeted design of readily biodegradable sugar ester surfactants fo r use in consumer products.