Biosurfactants (BS) are surface-active compounds abundantly produced by microorganisms from a variety of renewable resources. They have been receiving great attention due to their unique properties, including higher biodegradability, lower toxicity, and versatile biological functions, compared to typical synthetic surfactants. In this review, we focus on three kinds of promising glycolipid BS such as mannosylerythritol lipid (MEL), sophorose lipid (SL), and cellobiose lipid (CL).
The structural variety of MELs was considerably expanded, and the excellent properties lead to their cosmetic application, i.e., moisturization of dry skin and repair of damaged hair. Recently, SL production from non-edible vegetable oils including jatropha and mahua oils was succeeded, and the yield was reached 122 gL^–1 for jatropha oil after 9 days. CL found its new application as a low molecular weight gelator (LMWG), and it can gelates 6 out of 26 solvent by forming 3D supramolecular structures with an entangled fibrous network. These features of glycolipid BS would broaden its applications in new advanced technologies. The current status of research and development on glycolipid BS, especially their production and potential applications, is discussed.

Alkylglucosides are biomass-based nonionic surfactants which have sugar structures as their hydrophilic groups. Alkylglucosides showed much higher foaming performances than ethyleneoxide added type nonionic surfactants, and their foaming performances are probably caused by the orientation controlled by their sugar structures. Alkylglucosides are mild for protein and skin, and they also show high compatibility with water environment. Therefore, they are one of the remarkable surfactants in future for the requirement of safety of chemicals and a low environmental impact. In this paper, we describe the physical properties and characteristic performances of alkylglucosides.

Sugar surfactants are derived from renewable resources, and have biocompatible and biodegradable properties. Moreover, sugar surfactants exhibit good solubilization and dispersion. Since sucrose fatty acid esters and alkyl glucosides stably form reverse micelles in organic solvents, metal nanoparticles can be synthesized by using their reverse micelles as reaction fields. This paper introduces the size-controlled synthesis of metal nanoparticles by selecting the molecular shape of sugar surfactants, and the one-pot method of synthesizing metal nanoparticles at high concentrations.

Protein is one of the substances that are indispensable in the food and pharmaceutical industries and, however, is apt to lose its native conformation and consequently bioactivity under nonphysiological conditions. Hence, to date, the methodologies to protect proteins against denaturation have been investigated and various substances including sugars, amino acids, and certain types of polymers have been known to serve to maintain the protein conformation under different conditions. On the other hand, the sugar surfactants that are frequently used as food additives have been found to stabilize protein in various situations. Herein, the effectiveness of sugar surfactant as a protein stabilizing agent against denaturation in aqueous solution, freezing step, and freeze-drying are demonstrated as well as the denaturation pathways of proteins. Particularly, this review focuses on the differences among the protein stabilizing effects of various sugar surfactants in freezing and freeze-drying. The impacts on the protein stabilizing characteristics by alkyl chain length, sugar head group structure, and ester/ether bondings of sugar surfactant are discussed as well as the possible stabilizing mechanism.