Klebsormidium flaccidum is a charophytic alga living in terrestrial and semiaquatic environments. K. flaccidum grows in various habitats, such as low-temperature areas and under desiccated conditions, because of its ability to tolerate harsh environments. Wax and cuticle polymers that contribute to the cuticle layer of plants are important for the survival of land plants, as they protect against those harsh environmental conditions and were probably critical for the transition from aquatic microorganism to land plants. Bryophytes, non-vascular land plants, have similar, but simpler, extracellular waxes and polyester backbones than those of vascular plants. The presence of waxes in terrestrial algae, especially in charophytes, which are the closest algae to land plants, could provide clues in elucidating the mechanism of land colonization by plants. Here, we compared genes involved in the lipid biosynthetic pathways of Arabidopsis thaliana to the K. flaccidum and the Chlamydomonas reinhardtii genomes, and identified wax-related genes in both algae. A simple and easy extraction method was developed for the recovery of the surface lipids from K. flaccidum and C. reinhardtii. Although these algae have wax components, their surface lipids were largely different from those of land plants. We also investigated aliphatic substances in the cell wall fraction of K. flaccidum and C. reinhardtii. Many of the fatty acids were determined to be lipophilic monomers in K. flaccidum, and a Fourier transform infrared spectroscopic analysis revealed that their possible binding mode was distinct from that of A. thaliana. Thus, we propose that K. flaccidum has a cuticle-like hydrophobic layer composed of lipids and glycoproteins, with a different composition from the cutin polymer typically found in land plant cuticles.

Wheat flour has an ability of forming dough by mixing with water, which exhibits a rheological property required for making bread. The major protein is gluten, which is a valuable protein material for food industry. In this study, gluten protein gels and films were formed with cysteine and sodium alginate. Adding cysteine improved gel and film properties (stress relaxation behavior, bending strength). The gel containing 0.01 M cysteine had a longer relaxation time and was more rigid than the gel without cysteine. Although adding sodium alginate to the gluten suspension containing cysteine improved the water-holding ability and homogeneity of the gel network, the film from this gel was more brittle than the gluten film with cysteine alone. Microstructural observations of the gels and films with scanning electron microscopy suggested that water evaporation was more heterogeneous from the gel containing sodium alginate than from the gel with cysteine alone. Fourier transform-infrared (FT-IR) analysis during film formation suggested that the presence of cysteine encourages interaction between gluten molecules and results in intermolecular beta-sheet formation in earlier stages than in the no additive condition. FT-IR results also suggested that the combined effect of sodium alginate and cysteine on the protein secondary structure was remarkably different from that of cysteine alone. Our results suggest that addition of a suitable amount of cysteine (0.01 M) and heat treatment to 80 degrees C during gluten gel and film formation induces a homogenous network in the gel and film by regulating disulfide-sulfide interactions.

In this study, we found that transparent gels of β-lactoglobulin (β-LG) were formed by adding different concentrations of sodium caprate to protein solutions at ambient temperature. We investigated changes in the dynamic viscoelasticity of the mixture with time at 25°C and found that more than 12% β-LG induced the formation of a viscoelastic gel with a suitable amount of sodium caprate (for example, 12% β-LG and 3.6% sodium caprate). Furthermore, we analyzed the changes in the secondary structure of proteins during the gelation step by FTIR spectroscopy. Dissociation of the β-LG dimer was first observed just after mixing with sodium caprate. Furthermore, in the β-LG protein in which the original contents were predominantly β-sheets, intermolecular β-sheets attributable to aggregation increased with a decrease in the content of intramolecular β-sheets. Sodium caprate-induced gel was heated at 80°C for 30 min after the gel was formed, and a large increase in the intermolecular β-sheet bands was observed by heat treatment. These results suggest that the formation of sodium caprateinduced gels of β-LG was accompanied by less marked changes in the protein conformation than those in heat-induced gels.We previously reported the formation of transparent and high water-holding gels from several food proteins [sesame, rice globulins, and ovalbumin (OVA) (1-3)] by heat treatment in the presence of FA salts (FAS). Particularly for OVA, desirable gels with different gel hardnesses, water-holding abilities, and transparencies were formed by changing the concentration of protein or FAS (3). Furthermore, we reported that OVA is able to form a transparent gel by the addition of a FAS such as sodium caprate or sodium oleate at room temperature (4). In that paper, we stated that 10% OVA formed a soft, transparent gel by the addition of 2% sodium caprate at ambient temperature, that the molar ratio of FAS to OVA was an important factor in forming an elastic, transparent gel, and that a molar ratio of about 45 was suitable.FAS-induced OVA gels without heat treatment have a unique gel texture that differs from those of heat-induced gels containing FAS, since heating treatment clearly affects the gel texture. This method is simple and safe; therefore, the gels will be useful materials in food processing. It is also interesting from this point of view to investigate the effects of FAS on other kinds of food proteins in addition to OVA protein.β-Lactoglobulin (β-LG) is as important a food protein as OVA; although it is a globular protein like OVA, it contains numerous β-sheets in its structure. Many reports are available on the functional properties of β-LG (5-7). Mulvihill and Kinsella (5) reported that although heating a β-LG solution at pH 8 caused an increase in viscosity, self-supporting gels were not formed unless salts such as sodium chloride or calcium chloride were added, indicating that the rheological and textural properties of the gels were markedly affected by salt concentration. On the other hand, β-LG has a FA binding site...

Gelation of ovalbumin (OVA) was induced by the addition of fatty acid salts (FAS), such as sodium caprate (NaC10:0), to the protein solution at ambient temperature. The rheological and structural properties of the fatty acid salt-induced gels (FAS-IG) were studied using two kinds of FAS. Ten percent OVA in the presence of 2% NaC10:0 formed a transparent and soft gel above 15 °C. At 3% sodium oleate (NaC18:1), a transparent and softer gel was also formed above 25 °C. When the FAS-IG was heated, the storage modulus G‘ increased to 3 times as high as that of the gel before heat treatment. Electron microscopy showed that the FAS-IG has a more homogeneous network with larger pore size than do the heat-induced FAS gel and the heated FAS-IG. Analyses by circular dichroism spectroscopy indicated that native OVA changed into molten globule state by the addition of FAS. Keywords: Ovalbumin; dynamic rheological properties; electron microscopy; CD spectroscopy; gelation; molten globule state

The hardness and water-holding ability of rice globulin gels were intermediate between those of gels of soybean and sesame globulins. Scanning electron micrographs showed that rice globulin gel had a rough network structure composed of small globular particles of protein aggregates. Effects of various reagents on solubilization of proteins from the three gel types were compared. Disulfide bonds and hydrophobic interactions contributed mainly to the stability of rice globulin gels. The contributions of disulfide bonds to both the formation and stability of rice globulin gels were greater than for sesame globulin gels.