Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Abstract

Maltose long-chain fatty acid esters (MFAE), esterified at the 6 and 6′ position, were synthesized with stearic, palmitic, myristic, and oleic groups. Synthesis yields were 15-20% based on initial maltose present, and structural confirmation was obtained using plasma desorption mass spectrometry and nuclear magnetic resonance spectroscopy. These surfactants have surface tensions in the range of 34-36 dyn/cm at their critical micelle concentrations (CMC) of approximately 10 −5 -10 −6 mol/L. The increased chain lengths have a marked effect, reducing CMC values for MFAE by approximately three orders of magnitude over similar carbohydrate-based dodecyl chain sources. Within chain lengths between 14 and 18 carbons, the rate of change in CMC is significant and decreases with increasing chain length for MFAE. The melting points of MFAE are approximately 40°C, and the heat capacities range from 1.6 to 1.9 J/g·K. These numbers are comparable to those of sucrose esters, indicating their applicability in similar uses. However, because MFAE, unlike sucrose, possess an anomeric carbohydrate carbon position, these surfactants maintain their reducing nature and are susceptible to further derivatization. They are also synthesized from renewable, economical carbohydrates and lipids and may provide an excellent alternative to petrochemical-derived products.Paper no. S1273 in JSD 5, 245-255 (July 2002).KEY WORDS: Biosurfactants, carbohydrate esters, nonionic surfactants, sugar esters.Carbohydrate polysaccharides, produced naturally in plants, account for approximately 75% of the dry weight of the biological world and nearly 80% of the human caloric diet (1). Currently, corn, potatoes, tapioca, and wheat plants are all processed to provide common sources of starch. Carbohydrates are of interest because of the number of reactive hydroxyl groups they contain. Condensation of one of the reactive groups of a saccharide with a fatty acid produces a surface-active agent. Carbohydrate-based surfactants have been used primarily in the cosmetic, detergent, food, and pharmaceutical industries (2) because they are physiologically, dermatologically, and biologically acceptable (3). Because they are odorless, tasteless, nonionic, and biodegradable, they compare well in overall performance (i.e., emulsification, detergency, foam power, wettability, and other related properties) with other surface-active compounds (4). To date, several major types of carbohydratebased surfactants are commonly used worldwide, including sorbitan esters, sucrose esters, alkyl glycosides, and glucoseamide derivatives (5-8).There are three significant limitations with a majority of the existing petroleum-based surfactants. First, they are monofunctional, (i.e., can contribute only one desired property to a formulation). Therefore, several surfactants must be combined to achieve all desired properties.Second, many surfactants are incompatible and cannot function effectively with other surfactants. Cationic and anionic surfactants neutralize each other if they are combin...

PFGSE–NMR study of the self-diffusion of sucrose fatty acid monoesters in water

“…For longer chains, intermolecular distances obtained in the thermotropic mesophases tend to be smaller than those obtained for lyotropic phases (micelles), probably illustrating the increasing effect of the hydration sphere for the longer chains and a tighter packing of the chains in the neat state [17,23]. Simple modelization with the Tanford formula, by taking, for the extended chain length, L = 1.50 + 1.265 × N c (N c = number of -CH 2 -: 7,9,11,13,15,17) and by taking 10 Å for the sugar head [51,52], is reported in Table 5 for comparison. The difference between the calculated length and the micelle hydrodynamic radius measured by PFGSE-NMR could probably illustrate the increasing size of the hydration sphere with micelle size, such a phenomenon being already demonstrated.…”

“…They are prepared on an industrial scale by transesterification of fatty acid methyl esters, such as methyl stearate, methyl palmitate, or methyl laurate, by unprotected sucrose, leading to technical mixtures with different substitution degrees and regioisomers. The practical properties of these compounds, used directly as blends, were investigated early, directed toward applications in food and cosmetics [5][6][7][8][9][10][11][12][13]. The physicochemical properties of sucrose fatty acid esters at the molecular level have not been extensively studied compared to those of other kinds of nonionic surfactants such as polyoxyethylenic surfactants or alkylpolyglucosides.…”

Comparative Study of the Emulsifying Properties of a Homologous Series of Long-Chain 6′-O-Acylmaltose Esters

“…Corn-derived maltose is an inexpensive and sustainably produced disaccharide comprised of two 1′,4linked glucose residues and so embodying just two primary hydroxyl groups (there are three in sucrose). A previous study 27 suggests that esters derived from reducing sugars such as maltose cannot be readily obtained by conventional chemical methods. Accordingly, most efforts to prepare maltose fatty acid esters have focused on enzymatic approaches.…”

Surfactants produced from carbohydrate derivatives: A review of the biobased building blocks used in their synthesis

“…In fact, it is not surprising that a variety of commercial surfactants are direct derivatives of sugars and oligosaccharides. These can be biocompatible, readily biodegradable, and present low toxicity for pharmaceutical, food, and personal hygiene applications (Allen & Tao, 1999, 2002; Hayes et al, 2019). In this context, it is evident that difunctional or polyfunctional heteroatomic compounds are especially useful for constituting the hydrophilic part of surfactants (Le Guenic et al, 2019).…”