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A biomembrane's role is to be a barrier for interior cytosol from an exterior environment to execute the cell's normal biological functions. However, a water-soluble peptide called cell-penetrating peptide (CPP) has been known for its ability to directly penetrate through the biomembranes into cells (cytolysis) without perturbating cell viability and expected to be a promising drug delivery vector. Examples of CPP include peptides with multiple arginine units with strong cationic properties, which is the key to cytolysis. Here we show the conclusive evidence to support the mechanism of CPP’s cytolysis and way to control it. The mechanism we proposed is attributed to biomembrane’s physicochemical nature as lamellar liquid crystal (Lα). Cytolysis occurs as the temporal and local dynamic phase transitions from Lα to an undulated lamellar with pores called Mesh1. We have shown this phase transfer of Lα composed of dioleoyl-phosphatidylcholine (DOPC) with water by adding oligo-arginine (Rx) as CPP at the equilibrium. Using giant unilamellar vesicle composed of DOPC as a single cell model, we could control the level of cytolysis of CPP (FITC-R8) by changing the curvature of the membrane through osmotic pressure modulation. The cytolysis of CPP utilizes biomembrane's inherent topological and functional flexibility corresponding to the stimuli.

In this study, an N-heterocyclic carbene (NHC)-based metal coordinate surfactant (MCS), NHC-Au-MCS, in which the NHC framework afforded the bonding of the Au(I) at the linkage of the hydrophilic and hydrophobic moieties, was synthesized. The structure of NHC-Au-MCS was confirmed by 1H and 13C NMR spectroscopic measurements together with elemental analysis. Matrix-assisted laser desorption/ionization (MALDI), laser desorption/ionization (LDI), and electrospray ionization mass spectrometry (ESI-MS) indicated the distinct reactivity of NHC-Au-MCS, such as the exchange of Br to Cl and the formation of a cationic Au complex, where the two NHC ligands were coordinated to an Au(I) center upon laser activation. The surface tension and dynamic light scattering (DLS) measurements revealed that the coordination of Au(I) to NHC reduced the critical micelle concentration (CMC) of NHC-Au-MCS (1.3×10-5 M), which resulted in the formation of micelles at concentrations higher than the CMC in water. We also confirmed that the surface-active Au(I) complex of NHC-Au-MCS catalyzed the hydration of 1-dodecyne to 2-dodecanone in water in the absence of an organic solvent. On the basis of the detailed mechanistic investigations regarding the reactivity of NHC-Au-MCS, we revealed that NHC-Au-MCS partially translated into Au nanoparticles (AuNPs), which facilitated alkyne hydration. These mechanistic studies were supported by UV-vis measurements, transmission electron microscopy (TEM), and LDI-MS.

The Cover Feature shows the conversion of furfuryl alcohol, which can be obtained from biomass, to 1,2‐pentanediol. 1,2‐Pentanediol is used as an antimicrobial agent and as a moisturizing ingredient in cosmetics. We found that hydrogenolysis of furfuryl alcohol over Ru/MgO at 463 K in water afforded 1,2‐pentanediol with 42% selectivity. More information can be found in the Full Paper by Aritomo Yamaguchi et al.[Image: see text]

Hydrogenolysis of the furan rings of furfural and furfuryl alcohol, which can be obtained from biomass, has attracted attention as a method for obtaining valuable chemicals such as 1,2‐pentanediol. In this study, we examined the hydrogenolysis of furfuryl alcohol to 1,2‐pentanediol over Pd/C, Pt/C, Rh/C, and various supported Ru catalysts in several solvents. In particular, we investigated the effects of combinations of solvents and supports on the reaction outcome. Of all the tested combinations, Ru/MgO in water gave the best selectivity for 1,2‐pentanediol: with this catalyst, 42 % selectivity for 1,2‐pentanediol was achieved upon hydrogenolysis of furfuryl alcohol for 1 h at 463 K. In contrast, reaction in water in the presence of Ru/Al2O3 afforded cyclopentanone and cyclopentanol by means of hydrogenation and rearrangement reactions., The hydrogenolysis of furfuryl alcohol to 1,2‐pentanediol over Pd/C, Pt/C, Rh/C, and various supported Ru catalysts in several solvents has been investigated. In particular, we investigated the effects of combinations of solvents and supports on the reaction outcome. The highest selectivity was obtained when the reaction was carried out with Ru/MgO catalyst in water.

A total of 100 environmental samples were investigated for their ability to degrade 1 g/L surfactin as a substrate. Among them, two enrichment cultures, which exhibited microbial growth as well as surfactin degradation, were selected and further investigated. After several successive cultivations, nanopore sequencing of full-length 16S rRNA genes with MinIONTM was used to analyze the bacterial species in the enrichment cultures. Variovorax spp., Caulobacter spp., Sphingopyxis spp., and Pseudomonas spp. were found to be dominant in these surfactin-degrading mixed cultures. Finally, one strain of Pseudomonas putida was isolated as a surfactin-degrading bacterium. This strain degraded 1 g/L surfactin below a detectable level within 14 days, and C13 surfactin was degraded faster than C15 surfactin.

We report the synthesis of bolaamphiphilic alkenyl phosphonic acid (BPC12) through the olefin crossmetathesis reaction of vinylphosphonic acid with 1,11-dodecadiene in the presence of a Ru-carbene catalyst. BPC12 possesses two trans-P-C=C moieties and is thus readily soluble in water up to 3.4 g L-1, as confirmed by 1H nuclear magnetic resonance (NMR) measurements. Surface tension measurements revealed that BPC12 reduced the surface tension of water from 72.0 to 47.0 mN m‒1. The occupied area per molecule at the air/water interface (A) of BPC12 (216 A2) was ten times larger than that of dodecenyl phosphonic acid PC12 (23 A2). Moreover, dynamic light scattering measurement of an aqueous BPC12 solution (5 mM) revealed the formation of large aggregates with an average diameter of 81.8±27.0 nm.

Bacillus subtilis RB14 produces the lipopeptide antibiotic iturin A by submerged and biofilm fermentation. In this study, we optimized the conditions for iturin A production in a jar fermentor. The maximum yield of iturin A was 932 mg L-1 after 120 h. The surface tension of water decreased from 72.0 to 39.0 mN m-1 as the concentrations of C14 iturin A increased, indicating that C14 iturin A behaves as a surfactant in water. The critical micellar concentration obtained from the intersection of two fitted lines was 1.2 × 10-4 M. Moreover, the surface tension of water decreased as the length of the alkyl chain of iturin A increased.

We report the synthesis of amphiphilic dodecenyl phosphonic acid PC12 from vinylphosphonic acid, a reactive phosphonic acid intermediate. The trans-P-C=C moiety enabled PC12 to disperse well in water. Surface tension and dynamic light scattering measurements revealed that PC12 exhibited high surface activity and reduced the surface tension of water from 72.0 to 23.6 mN/m, thereby resulting in the spontaneous formation of aggregates even in a dilute aqueous solution (critical aggregation concentration (CAC) = 4.8 × 10-4 M). In contrast to modern lipids with double-tailed structures, the PC12 of simple singletailed structure spontaneously formed bilayered vesicles, without an external energy supply. Compared with the strength of hydrogen bonds formed by the long, saturated alkyl chain of dodecyl phosphonic acid (DPA), the strength of PC12 intermolecular hydrogen bonds was weaker. The melting point of PC12 was approximately 20°C lower than that of DPA. These results indicate that the trans-P-C=C moiety was considerably important for spontaneous vesicle formation in water. Preliminary modeling of the morphological transitions of the closed bilayer structures in the vesicles was then conducted, by varying the pH and adding an α-helical peptide scaffold.

We discovered that Candida floricola ZM1502 is capable of selectively producing the promising hydrophilic biosurfactants, acid-form sophorolipids (SLs), from glycerol. However, productivity was very low (approximately 3.5 g L-1) under the initial culture conditions. Here, we describe the design of culture medium for abundant production of acid-form SLs by C. floricola ZM1502 using waste glycerol and hydrophobic substrates in order to develop a method for SL production and disposal of waste glycerol produced by oleo-chemical industries. Urea provided the best nitrogen source for acid-form SL production from glycerol among four nitrogen sources tested [urea, NaNO3, NH4NO3, and (NH4)2SO4]. Among carbon sources we compared, hydrophobic substrates (soybean oil and oleic acid) led to productivities of approximately 20 g L-1, indicating that hydrophobic substrates provided fatty acid moieties for SL production. Addition of olive oil and oleic acid to waste glycerol enhanced acid-form SL production to 42.1 ± 0.9 and 37.5 ± 3.4 g L-1, respectively. To develop a potential industrial process, we explored other suitable hydrophobic substrates for SL production, which were obtained on site from oleo-chemical industries. Alkyl C18 esters (Pastell M-182), along with waste glycerol, increased acid-form SL production to 48.0 ± 3.4 g L-1 over a 7-d period. Furthermore, we demonstrated abundant production of acidic SLs at the mini-jar fermenter scale, obtaining 169 g L-1 over 180 h using a fed-batch cultivation technique. Efficient acid-form SL production by C. floricola could have a great impact on the development of bio-industrial processes using waste glycerol as a substrate.

A new species of fluorinated polymer surfactant was developed by three component polycondensation analogous to Ugi four-component condensation. The surfactant exhibited unique surface properties, which made cellulose-based materials hydrophobic and decreased the surface tension of CHCl3. It turned out that the polymer forms micelles in CHCl3.

In this study, an N-heterocyclic carbene (NHC)-based metallosurfactant (MS), NHC-PdMS, was synthesized, where Pd(II) was bound to the NHC framework via a robust Pd-carbene bond with NEt3 as a co-ligand. Surface tension measurements revealed that the critical micelle concentration (CMC) of NHC-PdMS (1.8×10-4 M) was one order of magnitude lower than that of its MS precursor (imidazolium bromide). Coordination of the MS precursor and NEt3 to Pd(II) also influenced micelle size; the hydrodynamic diameters of NHC-PdMS and the MS precursor were observed to be 25.8±5.6 nm and 2.5±0.3 nm, respectively. Furthermore, small angle X-ray scattering measurements indicated that NHC-PdMS exhibited liquid crystalline behavior above 26 wt%, with a spacing ratio of 1:2:3 for the first, second, and third Bragg peaks. To understand the role of the reactive interface, NHC-PdMS was also applied to aqueous catalytic reactions. Owing to its low CMC value, a catalytic amount of NHC-PdMS (3 mol%) provided the reactive interface, which facilitated the aqueous Mizoroki-Heck reaction of various aryl iodides and styrene in good yields (72-95%). These results suggest that MS formation results in a drastic change in selfassembling properties, which are important for the development of highly reactive chemical interfaces in water.

Nanodiscs are self-assembled discoidal nanoparticles composed of amphiphilic α-helical scaffold proteins or peptides that accumulate around the circumference of a lipid bilayer. In this study, Pxt-5, which is an antimicrobial peptide isolated from the skin of Xenopus tropicalis, and its modified peptide (Modify-Pxt-5) were synthesized by solid-phase peptide synthesis (SPPS).Their surface properties, which are an important factor in inducing nanodisc formation, were investigated by circular dichroism (CD) spectroscopy, surface tension measurement, phospholipid vesicle clearance assay, and negative-staining transmission electron microscopy (NS-TEM). The α-helicity of Pxt-5 (8.4%) improved drastically to 45.6% by four amino-acid substitutions (Modify-Pxt-5). Both the peptides, having hydrophobic and hydrophilic faces, behaved like general surfactants, and the surface activity of Modify-Pxt-5 (CAC: 9.5×10-5 M, γCAC: 30.3 mN·m-1) was much higher than that of Pxt-5 (CAC: 7.9×10-5 M, γCAC: 38.1 mN·m-1). A turbid L-α-dimyristoylphosphatidylcholine (DMPC) vesicle solution (T = 0.3%) quickly turned transparent upon addition of Pxt-5 or Modify-Pxt-5. After twelve hours, the transmittance of vesicle solution with Modify-Pxt-5 (T = 96.2%) was found to be higher than that of vesicle solution with Pxt-5 (T = 83.5%), and then the micro-solubilized solutions were observed by NS-TEM. Interestingly, nanodisc structures were found in the vicinity of DMPC vesicles in both the images, and the average diameter of the nanodiscs was 11.2 ± 6.0 nm for those containing Pxt-5 and 10.8 ± 5.8 nm for those containing Modify-Pxt-5. It was also found that Modify-Pxt-5 effectively self-assembles into nanodiscs compared to Pxt-5 without any substitutions.

The cyclic lipopeptide surfactin (SF), an anionic biosurfactant that gaining interest because of its unique characteristics and promising applications, forms various self-assembled structures in solution. Although counter-cations are known to affect the surface properties and self-assembly of anionic surfactants, the influence of counter-cations on the behaviour of SF requires further investigation. Here, we report the self-assembly properties of SF with different organic and inorganic counter-cations including potassium (SF-K), monoethanolamine (SF-MEA), diethanolamine (SF-DEA), and triethanolamine (SF-TEA). We studied the influence of these counter-cations on the surface properties of SF as compared to the SF sodium salt (SF-Na) using the Wilhelmy plate method. The critical aggregation concentrations (CACs) of SF-K, SF-DEA, SF-TEA, and SF-MEA were 2.8–4 times higher than that of SF-Na (2.7 × 10−5 M). Furthermore, the CACs increased as the organic counter-cations became less hydrophobic (SF-TEA (8.7 × 10−5 M)

The cyclic lipopeptide surfactin (SF) is one of the promising environmental friendly biosurfactants abundantly produced by microorganisms such as Bacillus subtilis. SF shows excellent surface properties at various pH, together with lower toxicity and higher biodegradability than commonly used petroleum-based surfactants. However, the effect of the dissociation degree of SF on self-assembly is still incompletely understood, even though two acidic amino acid residues (Asp and Glu) are known to influence eventual surface and biological functions. Here, we report changes in the secondary structure of SF induced by increased pH, and the effect on protease activity. We found that the β-sheet and β-turn formation of SF are significantly enhanced through increased dissociation of Asp and Glu as revealed by a titration experiment of SF solution to estimate apparent pK1 and pK2 values together with circular dichroism spectroscopy. We also studied the activity of the common detergent enzyme subtilisin in SF solution at above its pK2 (pH 7.6) to understand the role of the dissociation degree in the interaction with the protein. The mixing of SF having a unique cyclic topological feature with subtilisin suppressed the decrease in protease activity observed in the presence of synthetic surfactants such as sodium dodecyl sulfate and polyoxyethylene alkyl ether. Thus, SF has great potential for use in laundry detergent formulations, to improve the stability and reliability of detergent enzymes.

Bacillus subtilis RB14 produces the lipopeptide antibiotic iturin A by submerged and biofilm fermentation. In this study, we optimized the conditions for iturin A production in a jar fermentor. The maximum yield of iturin A was 932 mg L

Biosurfactants (BSs) are produced in abundance from various feedstocks by diverse microorganisms, and are used in various applications. In this paper, we describe a new yeast isolate that produces glycolipid-BSs from glycerol, with the aim of enhancing the utilization of the surplus glycerol produced by the oleo-chemical industry. As a result of the screening, strain ZM1502 was obtained as a potential producer of BS from glycerol. Based on TLC analysis, the strain produced glycolipid BSs. According to structural analyses (NMR, MALDI-TOF MS, and GC-MS), the main component of the glycolipids was 6',6"-di-O-acetylated acid-form sophorolipid (SL). Interestingly, the strain produced only acid-form SL, without lactone-form SLs, although the conventional SL-producing yeast, Starmerella bombicola, produces lactone-form SLs with small amounts of the acid-form. Based on taxonomy, the strain was identified as Candida floricola. It produced 3.5 g L-1 of acid-form SLs in 20% (w/v) glycerol. In addition, C. floricola CBS7290 and NBRC10700T also produced only acid-form SLs from glycerol. These results suggest that C. floricola would enhance the utilization of waste glycerol as a fermentation feedstock and facilitate a broad range of applications for SLs.

The cyclization of amphiphiles has emerged as an attractive strategy for inducing remarkable properties in these materials without changing their chemical composition. In this study, we successfully synthesized three cyclic polyoxyethylene dodecyl ethers (c-POEC12's) with different ring sizes and explored the effects of their topology on their surface and self-assembly properties related to their function, comparing them with those of their linear counterparts (l-POEC12's). The surface activity of the c-POEC12's remained almost constant despite the change in their hydrophobic and hydrophilic balance (HLB) value, while that of the l-POEC12's decreased with an increase in the HLB value as general surfactants. In contrast to the normal micelles seen in the case of the l-POEC12's (3.4-9.7 nm), the cyclization of the POEC12's resulted in the formation of large spherical structures 72.8-256.8 nm in size. It also led to a dramatic decrease of 28 °C in the cloud point temperature. Furthermore, the cyclization of the POEC12's markedly suppressed the rate of protease hydrolysis caused by the surfactants. The initial rate of reduction of a detergent enzyme from Bacillus licheniformis was increased by more than 40% in the case of c-POE600C12 and c-POE1000C12, even though they exhibited surface activities almost equal to or higher than those of their linear counterparts. These results suggest that cyclization induces unusual aqueous behaviors in POEC12, making the surfactant milder with respect to detergent enzymes while ensuring it exhibits increased surface activity.

A surface-active N-heterocyclic carbene (NHC) ligand with an octaethylene glycol monomethyl ether and n-dodecyl chain was synthesized. The NHC and its Pd complex behaved as a general surfactant, and hydrophobic oily substrates such as iodobenzene and styrene were emulsified in water, resulting in the acceleration of the Mizoroki–Heck reaction under heterogeneous conditions. Our results demonstrated that the reactive emulsion interface rendered by the surface-active NHC is effective for the aqueous Mizoroki–Heck reaction.

Zeolitic imidazolate framework-7-III (ZIF-7-III), a well-known metal–organic framework (MOF), has attracted attention as gas separation membrane material. For practical realization, it is necessary to adjust the aspect ratio of ZIF-7-III particles because it can affect the gas separation performance. In this study, we demonstrate the control of the aspect ratio by changing the synthesis condition using microemulsion prepared from n-alkyltrimethylammonium bromide as a surfactant, 1-hexanol as a co-surfactant, heptane as a continuous phase, and water as a dispersed phase. When cetyltrimethylammonium bromide (CTAB) was used as surfactant, ZIF-7-III particles with particle sizes of 10–20 μm were prepared by changing the water and CTAB concentration. In synthesis using four types of surfactants, the particle size of the resultant ZIF-7-III particles increased from 7 μm to 26 μm, and the aspect ratio increased from 4.9 to 11 with an increase in the hydrophobic chain length from C12 to C18. The control of the morphology is attributed to the adsorption of surfactants on hydrophobic (001) facets of ZIF-7-III, which is currently hypothesized to be monolayer or bilayer. The supply of the reactants could be hindered further with the increase of the hydrophobic chain length of the surfactants in either cases. ZIF-7-III particles obtained in this study can be exfoliated into nanosheets, which will accelerate the development of ZIF-7-III-based molecular–sieve gas separation membranes.

The surface and interfacial properties of casein-hydrolyzed peptides were evaluated using measurement of surface and interfacial tensions, surface viscosity, dynamic light scattering (DLS), and freeze-fracture transmission electron microscopy (FF-TEM). In this study, high internal oil phase emulsion (HIPE) gels were successfully prepared, using the surface and interfacial properties of casein peptides. The casein peptides exhibited surface and interfacial activities. The estimated critical micelle concentration (CMC) and γCMC values were 3.0 mg/mL and 47.8 mN/m, and the average size of casein peptide micelles was 13.2 ± 1.7 nm. The surface shear viscosity of an aqueous casein peptide solution at 10 mg/mL was 1603 µPa ms, which is fifteen times larger than that of sodium dodecyl sulfate (SDS, 106 µPa ms). The larger surface viscosity of casein peptide adsorbed layer could stabilize emulsions and prevent flocculation and coalescence. High internal oil phase gel emulsions were then prepared by slowly adding oil and polyisobutene into an aqueous casein peptide solution/glycerol mixture with different compositions. Based on the pseudo ternary 15 wt% aqueous casein peptide solution/polyisobutene/glycerol phase diagram, the HIPE containing the maximum 88.1 wt% (91.5 vol%) of oil is obtained by the addition of 0.36 wt% of casein peptides. The use of only a small amount of protein-hydrolyzed peptides instead of the commonly used synthetic surfactants for HIPE preparation has great advantages for the widespread application of HIPE technology.

Bacillus licheniformis NBRC 104464 produces a cyclic lipopeptide different from surfactin. After we performed liquid chromatography fractionation and purification, we used structural analyses to identify the cyclic lipopeptide as lichenysin. Surface tension measurements of lichenysin sodium salt in water yielded a critical micelle concentration (CMC) of 1.0×10

Nanodiscs are self-assembled discoidal nanoparticles composed of amphiphilic α-helical scaffold proteins or peptides that accumulate around the circumference of a lipid bilayer. In this study, Pxt-5, which is an antimicrobial peptide isolated from the skin of Xenopus tropicalis, and its modified peptide (Modify-Pxt-5) were synthesized by solid-phase peptide synthesis (SPPS).Their surface properties, which are an important factor in inducing nanodisc formation, were investigated by circular dichroism (CD) spectroscopy, surface tension measurement, phospholipid vesicle clearance assay, and negative-staining transmission electron microscopy (NS-TEM). The α-helicity of Pxt-5 (8.4%) improved drastically to 45.6% by four amino-acid substitutions (Modify-Pxt-5). Both the peptides, having hydrophobic and hydrophilic faces, behaved like general surfactants, and the surface activity of Modify-Pxt-5 (CAC: 9.5×10

We discovered that Candida floricola ZM1502 is capable of selectively producing the promising hydrophilic biosurfactants, acid-form sophorolipids (SLs), from glycerol. However, productivity was very low (approximately 3.5 g L

Cyclic peptide of surfactin (SF) is one of the promising environment-friendly biosurfactants abundantly produced by microorganisms such as Bacillus subtilis. SF is also known to act as an ionophore, wherein alkali metal ions can be trapped in the cyclic peptide. Especially, SF is expected to show high affinity for Cs(+) because of the distinctive cavity size and coordination number. In this study, we reported the specific interaction between SF and Cs(+) and succeeded in the highly efficient removal of Cs(+) from water using giant SF micelles as a natural sorbent. The specific interaction between SF and Cs(+) to form their inclusion complex was revealed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy. We found that SF micelles selectively encapsulate Cs(+), which was suggested by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). A highly effective separation of Cs(+) immobilized on the surface of the SF micelles was also achieved through facile centrifugal ultrafiltration in 91% even in coexisting with other alkali metal ions such as Na(+) and K(+). Thus, the use of the giant micellar system of SF with its high Cs(+) affinity and distinctive assembling properties would be a new approach for the treatment of contaminated soil and water.

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.

In this study, the effects of the degree of hydrolysis on the interfacial and emulsifying properties of soybean peptides were evaluated based on surface and interfacial tension, dynamic light scattering (DLS), and freeze-fracture transmission electron microscopy (FF-TEM) analyses. Of the five evaluated soybean peptides (SP95, SP87, SP75, SP49, and SP23), those with higher degrees of hydrolysis (SP95 and SP87) did not exhibit noticeable surface-active properties in water, whereas those with relatively low degrees of hydrolysis (SP75, SP49, and SP23) exhibited remarkable surface tension-lowering activity. The latter set (SP75, SP49, and SP23) also formed giant associates with average sizes ranging from 64.5 nm to 82.6 nm above their critical association concentration (CAC). Moreover, SP23 with the lowest degree of hydrolysis exhibited excellent emulsifying activity for soybean oil, and FF-TEM analysis demonstrated that the emulsions were stabilized by a lamella-like multilayer peptide structure on the oil droplets that prevented coagulation. The peptide with the lowest degree of hydrolysis (SP23) was effective not only for soybean oil emulsification, but also for the emulsification of liquid paraffin and silicon oil that are generally difficult to emulsify.

Sixty Bacillus subtilis strains were investigated for their ability to produce cyclic lipopeptides (CLPs). Among them, B. subtilis NBRC 109107 produced at least three types of CLPs by high-performance liquid chromatography (HPLC) analysis, and these CLPs were thought to be surfactin, iturin A, and fengycin by polymerase chain reaction amplification of respective CLP synthetase-encoding genes. However, after HPLC fractionation and purification, structural analysis of the CLPs revealed that these were surfactin homologues, iturin A, and unknown CLPs, whose surface-tension-lowering activities were 29.4, 56.7, and 48.6 mN/m, respectively. By contrast, fengycin was not detected.

Background Mass spectrometry-guided venom peptide profiling is a powerful tool to explore novel substances from venomous animals in a highly sensitive manner. In this study, this peptide profiling approach is successfully applied to explore the venom peptides of a Japanese solitary carpenter bee, Xylocopa appendiculata (Hymenoptera: Apoidea: Apidae: Anthophila: Xylocopinae: Xylocopini). Although interesting biological effects of the crude venom of carpenter bees have been reported, the structure and biological function of the venom peptides have not been elucidated yet. Methods The venom peptide profiling of the crude venom of X. appendiculata was performed by matrix-assisted laser desorption/ionization-time of flight mass spectroscopy. The venom was purified by a reverse-phase HPLC. The purified peptides were subjected to the Edman degradation, MS/MS analysis, and/or molecular cloning methods for peptide sequencing. Biological and functional characterization was performed by circular dichroism analysis, liposome leakage assay, and antimicrobial, histamine releasing and hemolytic activity tests. Results Three novel peptides with m/z 16508, 1939.3, and 1900.3 were isolated from the venom of X. appendiculata. The peptide with m/z 16508 was characterized as a secretory phospholipase A2 (PLA2) homolog in which the characteristic cysteine residues as well as the active site residues found in bee PLA2s are highly conserved. Two novel peptides with m/z 1939.3 and m/z 1900.3 were named as Xac-1 and Xac-2, respectively. These peptides are found to be amphiphilic and displayed antimicrobial and hemolytic activities. The potency was almost the same as that of mastoparan isolated from the wasp venom. Conclusion We found three novel biologically active peptides in the venom of X. appendiculata and analyzed their molecular functions, and compared their sequential homology to discuss their molecular diversity. Highly sensitive mass analysis plays an important role in this study. Electronic supplementary material The online version of this article (doi:10.1186/s40409-017-0119-6) contains supplementary material, which is available to authorized users.

Nanodiscs are a relatively new class of nanoparticles composed of amphiphilic α-helical scaffold peptides and a phospholipid bilayer, and find potential applications in various fields. In order to identify the minimum number of amino acid residues of an amphiphilic α-helical peptide that leads to nanodisc formation, seven peptides differing in lengths (22-, 18-, 14-, 12-, 10-, 8-, and 6-mers) that mimic and modify the C-terminal domain of apoA-I (residues 220-241) were synthesized. At a concentration of 0.3 mM, the 6- and 8-mer peptides did not present any surface activity. In case of the 10-mer peptide, the aqueous surface tension initially decreased and reached a constant value of 51.9 mN/m with the 14-, 18-, and 22-mer peptides. Moreover, upon mixing the surface-active peptides (14-, 18-, and 22-mers) with dipalmitoylphosphatidylcholine (DMPC) liposomes (2.5:1, peptide : DMPC), the turbid DMPC liposome solution rapidly became transparent. Further analysis of this solution by negative-stain transmission electron microscopy (NS-TEM) indicated the presence of disk-like nanostructures. The average diameter of the nanodiscs formed was 9.5 ± 2.7 nm for the 22-mer, 8.1 ± 2.7 nm for the 18-mer, and 25.5 ± 8.5 nm for the 14-mer peptides. These results clearly demonstrate that the surface properties of peptides play a critical role in nanodisc formation. Furthermore, the minimum length of an amphiphilic peptide from the C-terminal of apoA-I protein that can lead to nanodisc formation is 14 amino acid residues.

To promote the effective use of raw glycerol (a by-product of biodiesel production), 110 yeast strains that produce D-arabitol from glycerol were isolated from environmental samples. Among them, strain 17-2A was an effective D-arabitol producer in the presence of 250 g/l glycerol and was identified as Candida quercitrusa based on morphological, physicochemical, and phylogenetic analyses. C. quercitrusa type strain NBRC1022 produced the greatest quantity of D-arabitol (41.7 g/l) when the ability to produce D-arabitol from raw glycerol was compared among C. quercitrusa 17-2A and its phylogenetically related strains in flask culture. Under optimized culture conditions, strain NBRC1022 produced D-arabitol at a concentration of 58.2 g/l after a 7-day cultivation in 250 g/l glycerol, 6 g/l yeast extract, and 2 g/l CaCl2. The culture conditions were further investigated with raw glycerol using a jar fermenter; the concentration of D-arabitol reached 67.1 g/l after 7 days and 85.1 g/l after 10 days, respectively, which corresponded to 0.40 g/g of glycerol. To our knowledge, the present D-arabitol yield from glycerol is higher than reported previously using microbial production.

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants abundantly produced by different basidiomycetous yeasts such as Pseudozyma, and show not only excellent interfacial properties but also versatile biochemical actions. These features of MELs make their application in new technology areas possible. Recently, the structural and functional variety of MELs was considerably expanded by advanced microbial screening methods. Different types of MELs bearing different hydrophilic and hydrophobic parts have been reported. The genes responsible for MEL biosynthesis were identified, and their genetic study is now in progress, aiming to control the chemical structure. The excellent properties leading to practical cosmetic ingredients, i.e., moisturization of dry skin, repair of damaged hair, activation of fibroblast and papilla cells and antioxidant and protective effects in skin cells, have been demonstrated on the yeast glycolipid biosurfactants. In this review, the current status of research and development on MELs, particularly the commercial application in cosmetics, is described.

To facilitate the development of bio-based chemicals from renewable and inexpensive natural resources, we sought to produce biosurfactants using non-edible jatropha oil. Twenty yeasts known to produce biosurfactants were tested in this study, and Stamerella bombicola NBRC 10243 was found to use jatropha oil efficiently to produce sophorolipids (SLs) as a mixture of lactone-form SL (L-SL) and acid-form SL (A-SL). Under culture conditions using rice bran as the source of organic nutrients, the yield of SLs reached 122.6 g/L in 5-L jar fermentors after 9 d in culture. HPLC analysis of the culture medium showed that the levels of phorbol esters (PEs), major toxic components of the oil, decreased markedly with an increase in culture time, suggesting that the yeast degrades PEs. Although the SLs obtained by solvent extraction of the culture medium contained a small amount of PEs, the sodium salt of A-SL (A-SL-Na) obtained by alkaline treatment (5N NaOH, 80°C) showed no PE peaks upon HPLC analysis. A-SL-Na had excellent surface activity with low CMC (9.0×10⁻⁴ M) and γ(CMC) (29.6 mN/m), which are lower than that of sodium dodecyl sulfate (SDS). The solubilizing ability of A-SL-Na toward for octanoic acid ([octanoic acid]/[A-SL-Na]) was found to be 2.0, which is half that of SDS. Our findings should help improve SL production from non-edible feedstock and broaden the use of promising bio-based surfactants.

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by various yeasts belonging to the genus Pseudozyma, which exhibit excellent surface activities as well as versatile biochemical activities. A study on P. tsukubaensis NBRC1940 as a mono-acetylated MEL (MEL-B) producer revealed that the yeast accumulated a novel glycolipid from castor oil at a yield of 22 g/L. Its main chemical structure was identified as 1-O-β-(2'-O-alka(e)noyl-3'-O-hydroxyalka(e)noyl-6'-O-acetyl-D-mannopyranosyl)-D-erythritol designated as "new MEL-B." The new MEL-B, comprising a hydroxy fatty acid had a reduced surface tension of 28.5 mN/m at a critical micelle concentration (CMC) of 2.2×10⁻⁵ M in water. The observed CMC was 5-fold higher than that of conventional MEL-B. When conventional MEL-B was dispersed in water, it self-assembled to form the lamellar (L(α)) phase at a wide range of concentrations. In contrast, new MEL-B formed spherical oily droplets similar to the sponge (L₃) phase, which is observed in aqueous solutions of di-acetylated MEL (MEL-A). The data suggest that the newly identified MEL-B is likely to have a different structure and interfacial properties compared to the conventional MELs, and could facilitate an increase in the application of glycolipid biosurfactants.

The title agent and its Pd complex act as a general surfactant: hydrophobic oily substrates are emulsified in water and thus, an acceleration of the reaction becomes possible under heterogeneous conditions.

In order to develop novel glycolipid biosurfactants, Pseudozyma parantarctica JCM 11752(T), which is known as a producer of mannosylerythritol lipids (MEL), was cultivated using different sugar alcohols with the presence of vegetable oil. When cultivated in a medium containing 4 % (w/v) olive oil and 4 % D-ribitol or D-arabitol, the yeast strain provided different glycolipids, compared to the case of no sugar alcohol. On TLC, both of the extracted glycolipid fractions gave two major spots corresponding to MEL-A (di-acetylated MEL) and MEL-B (mono-acetylated MEL). Based on (1)H NMR analysis, one glycolipid was identified as MEL-A, but the other was not MEL-B. On high-performance liquid chromatography after acid hydrolysis, the unknown glycolipid from the D-ribitol culture provided mainly two peaks identical to D-mannose and D-ribitol, and the other unknown glycolipid from the D-arabitol culture did two peaks identical to D-mannose and D-arabitol. Accordingly, the two unknown glycolipids were identified as mannosylribitol lipid (MRL) and mannosylarabitol lipid (MAL), respectively. The observed critical micelle concentration (CMC) and surface tension at CMC of MRL were 1.6 × 10(-6) M and 23.7 mN/m, and those of MAL were 1.5 × 10(-6) M and 24.2 mN/m, respectively. These surface-tension-lowering activities were significantly higher compared to conventional MEL. Furthermore, on a water-penetration scan, MRL and MAL efficiently formed not only the lamella phase (L(α)) but also the myelins at a wide range of concentrations, indicating their excellent self-assembling properties and high hydrophilicity. The present two glycolipids should thus facilitate the application of biosurfactants as new functional materials.

Glycolipid biosurfactants, such as mannosylerythritol lipids (MELs), are produced by different yeasts belonging to the genus Pseudozyma and have been attracting much attention as new cosmetic ingredients owing to their unique liquid-crystal-forming and moisturizing properties. In this study, the effects of different MEL derivatives on the skin were evaluated in detail using a three-dimensional cultured human skin model and an in vivo human study. The skin cells were cultured and treated with sodium dodecyl sulfate (SDS), and the effects of different lipids on the SDS-damaged cells were evaluated on the basis of cell viability. Most MEL derivatives efficiently recovered the viability of the cells and showed high recovery rates (over 80%) comparable with that of natural ceramide. It is interesting that the recovery rate with MEL-A prepared from olive oil was significantly higher than that of MEL-A prepared from soybean oil. The water retention properties of MEL-B were further investigated on human forearm skin in a preliminary study. Compared with the control, the aqueous solution of MEL-B (5 wt%) was estimated to considerably increase the stratum corneum water content in the skin. Moreover, perspiration on the skin surface was clearly suppressed by treatment with the MEL-B solution. These results suggest that MELs are likely to exhibit a high moisturizing action, by assisting the barrier function of the skin. Accordingly, the yeast glycolipids have a strong potential as a new ingredient for skin care products.

An ustilaginomycetous anamorphic yeast species isolated from the leaves of Saccharum officinarum (sugarcane) in Okinawa, Japan, was identified as a novel Pseudozyma species based on morphological and physiological aspects and molecular taxonomic analysis using the D1/D2 domains of the large subunit (26S) rRNA gene and the internal transcribed spacer 1 (ITS1)-5.8S-ITS2 regions. The name Pseudozyma churashimaensis sp. nov. was proposed for the novel species, with JCM 16988(T) as the type strain. Interestingly, P. churashimaensis was found to produce glycolipid biosurfactants, a mixture of mannosylerythritol lipids (MELs), including a novel tri-acetylated derivative (MEL-A2), from glucose. The observed critical micelle concentration (CMC) and the surface tension at CMC of MEL-A2 were 1.7 × 10⁻⁶ M and 29.2 mN/m, respectively. Moreover, on a water-penetration scan, MEL-A2 efficiently formed different lyotropic liquid crystalline phases, including the lamella phase at a wide range of concentrations, indicating its excellent surface-active and self-assembling properties. The novel strain of the genus Pseudozyma should thus facilitate the application of glycolipid biosurfactants in combination with other MEL producers.

We improved the culture conditions for a biosurfactant producing yeast, Pseudozyma hubeiensis SY62. We found that yeast extract greatly stimulates MEL production. Furthermore, we demonstrated a highly efficient production of MELs in the improved medium by fed-batch cultivation. The final concentration of MELs reached 129 ± 8.2 g/l for one week.

Biosurfactants (BS) are produced by a variety of microorganisms from renewable resources, and have unique properties compared to chemical surfactants. In order to attain efficient production of BS from low-cost materials, we focused our attention on the use of sugarcane molasses. Fifteen yeast strains that are known as BS producers were examined for BS productivity from a culture medium consisting of only molasses and water. Among the strains tested, only Starmerella bombicola NBRC 10243 produced sophorolipids (SL), which are glycolipid BS. The culture conditions for the yeast were then investigated in a shake-flask culture. SL production was significantly affected by the pH of the medium and was highly accelerated at pH 6. Under the optimum conditions, the amount of SL reached 14.4 g/L after 120 h from a medium containing 150 g/L of total sugars. We tried to improve the production of SL further by feeding the molasses using a jar fermentor. Interestingly, the amount of SL increased up to 22.8 g/L after 120 h; the production rate was 1.6-fold higher than that in the shake-flask culture. These results suggest that the present yeast should have great potential for the low-cost production of SL, and facilitate the application of BS in various fields.