Mannosylerythritol Lipids: Production and Applications 2018-04-02آ  Mannosylerythritol lipids J. Oleo

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    Journal of Oleo Science Copyright ©2015 by Japan Oil Chemists’ Society doi : 10.5650/jos.ess14185 J. Oleo Sci. 64, (2) 133-141 (2015)

    Mannosylerythritol Lipids: Production and Applications Tomotake Morita* , Tokuma Fukuoka, Tomohiro Imura and Dai Kitamoto Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5-2, Higashi 1-1-1, Tsukuba, Ibaraki 305-8565, JAPAN

    1 MANNOSYLERYTHRITOL LIPIDS(MELs) MELs are long chain fatty acids that contain either 4-O-

    β - D - m a n n o p y r a n o s y l - e r y t h r i t o l o r 1 - O - β - D - mannopyranosylerythritol as the hydrophilic head group, which is attached to a variety of fatty acids as the hydro- phobic chain(Fig. 1). These compounds are known to act as functional glycolipids, and are produced almost exclu- sively by yeast strains of the genus Pseudozyma1-3). MELs exhibit excellent interfacial properties4), as well as a variety of other biochemical functions, including the induction of differentiation in mammalian cells and the binding of various classes of immunoglobulins5). As with many lipids, differences in chemical structure directly affect their bio- logical activity; for example, MEL-A, a diacetylated MEL, has been shown to strongly increase the efficiency of gene transfection using cationic liposomes6, 7). Furthermore, certain MELs have been shown to possess anti-inflammato- ry properties, such as inhibiting the secretion of inflamma- tory mediators from mast cells8-12). When combined with their high biodegradability and relative ease of production,

    *Correspondence to: Tomotake Morita, Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5-2, Higashi 1-1-1, Tsukuba, Ibaraki 305-8565, JAPAN E-mail: morita-tomotake@aist.go.jp Accepted September 3, 2014 (received for review August 22, 2014) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/  http://mc.manusriptcentral.com/jjocs This is the review by the winner of 48th Award for Prominent Studies, The Japan Oil Chemists’ Society (JOCS).

    these compounds hold tremendous promise for use in a wide range of applications, including food production, cos- metics, and pharmaceuticals5, 13).

    Here, we provide a brief summary highlighting recent advances in MEL research, including the identification of MEL-producing fungi, structural characterizations of MELs, the use of alternative compounds as a primary carbon source, and the use of MELs in cosmetic applica- tions.

    2 IDENTIFICATION OF MEL-PRODUCING FUNGI To identify a wide variety of MEL structures, we first

    sought to develop a rapid and efficient method for detect- ing MEL production on the basis of decreasing surface tension in cultures containing biosurfactants. The surface tension of each culture was assessed by evaluating the di- ameter of droplets on the surface of a hydrophobic film (Fig. 2)14). MELs were then detected by thin-layer chroma-

    Abstract: Mannosylerythritol lipids (MELs) are a glycolipid class of biosurfactants produced by a variety yeast and fungal strains that exhibit excellent interfacial and biochemical properties. MEL-producing fungi were identified using an efficient screening method for the glycolipid production and taxonomical classification on the basis of ribosomal RNA sequences. MEL production is limited primarily to the genus Pseudozyma, with significant variability among the MEL structures produced by each species. Outside of Pseudozyma, one recently isolated strain, Ustilago scitaminea, has been shown to exhibit abundant MEL-B production from sugarcane juice. Structural analyses of these compounds suggest a role for MELs in numerous cosmetic applications. MELs act as effective topical moisturizers and can repair damaged hair. Furthermore, these compounds have been shown to exhibit both protective and healing activities, to activate fibroblasts and papilla cells, and to act as natural antioxidants. In this review, we provide a brief summary of MEL research over the past few decades, focusing on the identification of MEL-producing fungi, the structural characterization of MELs, the use of alternative compounds as a primary carbon source, and the use of these compounds in cosmetic applications.

    Key words: glycolipid, biosurfactant, mannosylerythritol lipid, yeast, sugarcane, cosmetics

    REVIEW

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    Fig. 1 �Chemical structure of glycolipids produced by yeast strains of the genus Pseudozyma. (a) Tri-acylated MEL. (b) di-acylated MEL. (c) mono-acylated MEL. (d) diastereomer type of MEL. (e) mono-acylated and tri-acetylated MEL. (f) mannosyl-mannitol lipid. (g) mannosyl-arabitol lipid. (h) mannosyl-ribitol lipid. MEL-A: R1=Ac, R2=Ac; MEL-B: R1=Ac, R2=H; MEL-C: R1=H, R2=Ac; MEL-D: R1=H, R2=H; n = 4-16; m = 6-16.

    Fig. 2 �The shape of the culture supernatant containing MELs (modified from Morita et al., 2006)9). The surface tension of the culture medium of P. antarctica grown with glucose, glycerol, and soybean oil were visualized on the hy- drophobic surface of Parafilm M, reported previously.

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    tography(TLC). This novel screening method resulted in the identification of numerous MEL-producing fungi, as well as many previously undescribed MEL structures. For example, an MEL-producing species of the genus Pseudo- zyma, Pseudozyma churashimaensis, isolated from sug- arcane, was found to produce not only MEL-A as the major product, but also two novel compounds, monoactylated and triacetylated MELs, as the minor fraction(Fig. 1e)15). Alternatively, the smut fungus Ustilago scitaminea, also isolated from sugarcane, was found to produce MEL-B16). Other fungi shown to produce diastereomers of MEL-B include Pseudozyma tsukubaensis strains 1D9, 1D10, 1D11, and 1E5, all of which were isolated from Perilla fru- tescens leaves17). Fifteen additional strains of MEL-produc- ing fungi, representing a variety of Pseudozyma yeasts, were isolated from various vegetables and fruits using this new screening method18).

    3 TAXONOMY OF MEL-PRODUCING FUNGI The vast majority of MEL-producing fungi belong to the

    genus Pseudozyma. The first-known MEL producer, Pseu- dozyma antarctica T-34, was first identified over two decades ago; it produces mainly MEL-A, along with smaller amounts of MEL-B and MEL-C19). More recently identified MEL-producing fungi include Pseudozyma rugulosa, Pseudozyma aphidis, Pseudozyma parantarctica, P. tsukubaensis, Pseudozyma fusiformata, Pseudozyma graminicola, Pseudozyma shanxiensis, Pseudozyma siamensis, and Pseudozyma crassa2, 20-24), in addition to the smut fungus Ustilago cynodontis, which produces pri- marily MEL-C when grown in the presence of vegetable oil25). Not surprisingly, the taxonomic distribution of these fungi is strongly associated with MEL production(Fig. 3). Fungi that produce mainly MEL-A, including P. antarctica, P. aphidis, P. rugulosa, and P. parantarctica, are closely linked within a discrete branch of the phylogenetic tree. A producer of MEL-A diastereomers, P. crassa, also clustered closely with the MEL-A producers, albeit in a separate tax- onomic branch. The producer of a diastereomeric MEL-B,

    Fig. 3 �Molecular phylogenic tree constructed using ITS1, 5.8S rRNA gene, and ITS2 sequences of the genus Pseudo- zyma and Ustilago (from Morita et al., 2009)3). The DDBJ/GenBank/EMBL accession numbers are indicated in parentheses.

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    P. tsukubaensis, was independently positioned in the tree, while MEL-C-producing fungi were scattered throughout the tree, indicative of less conservation between these species. Additional genetic studies will be necessary to better characterize the structures of less common MEL variants, and to determine the relationship between the fungi that produce them.

    4 STRUCTURAL DIVERSITY OF MELs As described previously, P. antarctica, P. aphidis, P.

    rugulosa, and P. parantarctica are the largest producers of MELs, mainly MEL-A(a diacetylated MEL)along with smaller percentages of MEL-B and MEL-C(Fig. 1b)3, 13). These fungi can produce>100 g/L of MELs using vegetable oil as a substrate19, 21, 26-29). Pseudozyma tsukubaensis se- lectively produces a diastereomer of MEL-B. The sugar moiety found within this alternative MEL-B consists of 1-O- β-D-mannopyranosyl-erythritol(Fig. 1d), an isomer of the traditional 4-O-β-D-mannopyranosyl-erythritol found in other MELs30). Pseudozyma crassa produces diastereo- mers of MEL-A, MEL-B, and MEL-C, all of which are ste- reochemically distinct from conventional MELs20). Pseudo- zyma hubeiensis, P. graminicola, P. shanxiensis, and P. siamensis produce MEL-C exclusively23, 24, 31, 32). A synthet- ic MEL, MEL-D, has been also synthesized via the lipase- catalyzed hydrolysis of MEL-B33).

    The use of alternative substrates as the primary carbon source can be used to produce MELs with hydrophobic chains of different lengths, including triacylated MELs(Fig. 1a)34, 35), which are produced in the presence of excess soybean oil, or monoacylated MELs(Fig. 1c), which are produced using glucose as the sole carbon source36). The diastereomeric form of MEL-B containing a hydroxy fatty acid was produ