Biosurfactants (BS) produced by various microorganisms show unique properties (e.g., mild production conditions, lower toxicity, higher biodegradability and environmental compatibility) compared to their chemical counterparts. The numerous advantages of BS have prompted applications not only in the food, cosmetic, and pharmaceutical industries but in environmental protection and energy-saving technology as well. Glycolipid BS are the most promising, due to high productivity from renewable resources and versatile biochemical properties. Mannosylerythritol lipids (MEL), which are glycolipid BS produced by a yeast Candida antarctrica, exhibit not only excellent interfacial properties but also remarkable differentiation-inducing activities against human leukemia cells. MEL also show a potential anti-agglomeration effect on ice particles in ice slurry used for cold thermal storage. Recently, the cationic liposome bearing MEL has been demonstrated to increase dramatically the efficiency of gene transfection into mammalian cells. These features of BS should broaden its applications in new advanced technologies. The current status of research and development on glycolipid BS, especially their function and potential applications, is discussed.
A yeast strain, isolated from the exudate of a tree, accumulated biosurfactants abundantly when grownon soybean oil as the sole carbon source. Thebiosurfactants were found to be a mixture of 4 mannosylerythritol lipids, including two new mannosylerythritol lipids as major components. The major components, which amounted to about 80 % of the total lipids, were determined to be 4-0-(di-0-acetyl-di-O-alkanoyl-/?-D-mannopyranosyl)-erythritol and 4-0-(mono-0-acetyl-di-0-alkanoyl-/?-D-mannopyranosyl)-erythritol. The yeast strain was identified as Candida antarctica (Goto et al.) Kurtzman et al. Wepreviously reported that Candida sp. B-7 produced a mannosylerythritol lipid (MEL), that is, 4-O-(2/,6/-di-O-alkanoyl-^-D-mannopyranosyl)-erythritol (designated as MEL-B7), from /7-alkanes or vegetable oils in high concentrations (about 30g/l).1 2) We again tried to screen microorganisms accumulating biosurfactants and succeeded in obtaining some strains by using a selective medium containing soybean oil as a renewable resource. A yeast strain, T-34, was found to extracellularly accumulate anthrone-positive biosurfactants, which were a mixture of MELs showing different Rfvalues from that of MEL-B7 on thin-layer chromatography. This paper describes the screening for microorganisms accumulating biosurfactants, identification of the isolated yeast and characterization of the biosurfactants accumulated by the yeast. Materials and Methods Microorganisms. Strain T-34 used in this study was isolated from the exudate of a tree on Mt. Tsukuba.
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