The cell membrane plays a critical role for discrimination of the cellular inner world from the outside environment.When bacterial cells are exposed to a certain environmental stress, their plasma membrane may be the first sensorespecially for its non–equilibrium change and then they resist to its harmful action by inducing specific physiologicalresponses. Here, mainly based on the results obtained by studies in our laboratory on Escherichia colicells and inpart Bacillus subtiliscells and spores exposed to heat stress, I briefly overview how the resistance of microbial cell tothe stress depends upon the membrane structure, how the microbial cell envelope is damaged by the stress, and howthey respond to the stress on the cell envelope. Furthermore, as a model of membrane stress biotechnology, a novelconcept of possible technology for the development of microorganism control, such as sterilization, pasteurization,disinfection and growth inhibition, by using membrane stress on harmful microorganisms, is proposed.

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Some forms of stress, such as heat shock, starvation and high salt, rapidly induced sterylglucoside (SG)in slimemold and human fibroblasts. In a true slime mold, Physarum polycephalum, induction of poriferasteryl glucoside wasfollowed by activation of a novel protein kinase and HSP production. In human fibroblasts, heat shock rapidlyinduced cholesteryl glucoside, then subsequent HSF(heat shock factor)activation and HSP (heat shock protein)induction occurred. As glycosylation of membrane sterol might be a very early and crucial step in the stress-inducedsignal transduction, we hypothesized that SG functions as a crucial lipid mediator in the process of stress responses. We showed that CG itself induced HSF activation and following HSP70 production when CG was added to a cultureof human fibroblasts, and we also showed that CG strongly inhibited gastric ulcer formation in rats under cold-restraint stress. This effect is likely mediated by HSP induction. Also, we compared the effect of CG(cholesteryl glu-coside)on ulcer formation and HSP70 induction with that of a popular effective anti-ulcer agent, geranylgeranylace-tone (GGA). Furthermore, we developed a highly sensitive assay method for the detection of CG formation, and char-acterized novel type of sterol glucosyltransferase (SGTase)in animal tissue and cultured human cells.

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The cell is a system in which large number of various functions are integrated into the micrometer scale.And theformation of the phase–separated micro domains plays an important role for this integration to make heterogeneousregions in a small area. Indeed, phase-separated micro domain, ‘raft’was found in plasma membrane of a cell.Important biological functions such as GPI–anchored protein and virus receptor are located in the raft. In order toinvestigate phase–separated micro domains, the authors have developed microscopic imaging instrument using envi-ronment sensitive fluorescence dye, laurdan. The instrument was applied to a model of raft, which elucidatedenzymic conversion of sphingomyelin to ceramide destroyed phase–separated micro domains.

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Nonionic surfactant Span80 was applied in the preparation of surfactant vesicle (niosome).We revealed that themembrane of Span80 vesicle was consisted of a mixture of sorbitan ester molecules with different four kinds of alkylchains (1~4 chains). Furthermore, the ester composition in the membrane of the vesicles with constant diameter wasfound to be almost constant because the vesicle membrane was constructed by the thermodynamic self–assembly ofthe ester molecules. Thecomparision of thecharacterization between Span80 vesicles and conventional natural–lipidliposomes revealed that the Span80 vesicles had higher values in either fluidity or membrane fusion capability, andlower values in phase-transition temperature as compared with liposomes. The characteristics of Span80 vesicleswere very effective in the application of Span80 vesicles to the drug delivery system (DDS). As a result, we coulddemonstrate the potential application of Span80 vesicles from the experiments in vitroand in vivoasalternatives toconventional liposomes inDDS.

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A novel method called “lipid–coated ice droplet hydration”for preparing giant vesicles encapsulating hydrophilicmolecules such as enzymes was developed and was utilized to construct a microbioreaction system which mimickedcellular environment. In this article, we first summarize basic concepts of the lipid–coated ice droplet hydrationmethod and then discuss its characteristics for preparing giant vesicles, including abilities of encapsulation ofhydrophilic molecules and control of vesicle size. Subsequently, enzymatic microreaction systems using giant vesi-cles prepared by our method is presented. Enzymatic reactions inside giant vesicles were conducted by transport ofsubstrate molecules via permeation through the lipid membranes of the vesicles. The experimental results demon-strated the possibility of construction of a selective enzymatic reaction system based on membrane permeability ofsubstrate molecules.

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A “Biomembrane”is a key interface to integrate production and separation of target materials through the creationof “new order”on its surface. A model biomembrane, liposome, can recognize (separate)the (bio)moleculesthrough (i)electrostatic, (ii)hydrophobic interaction, and (iii)stabilization effect of hydrogen bonds in the hydropho-bic lipid environment. A novel biomembrane-based catalysis (LIPOzyme: liposome + enzyme)can be designed anddeveloped by integrating the above recognition sites and a simple catalytic center on the liposome surface. A processdesign utilizing LIPOzyme chemistry and the recognition (bioseparation)functions of model-biomembrane (lipo-some)is the basic strategy to achieve a “Biomembrane Process Chemistry”as an application of “Membranomics”.

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We propose a new method to measure the fouling potential of feed water in the membrane separation processes.This method is using the plugging coefficient (K) in four kinds of pore blocking filtration models including the cakefiltration model with clear theoretical background as values for water quality evaluation alternative to SDI（SiltDensity Index) which is commonly used to assess the fouling potential in the membrane separation processes. Weexamined the validity of the plugging coefficient as a water quality index through comparison with SDI values. Thefollowing results were obtained. 1) Four kinds of plugging coefficient (Kb,Ki,ksand Kc) were proportional to the con-centration of foulant contained in the samples of different concentration of oolong tea diluted with ultrapure water, 2)Ki,ksand Kcmeasured with the membrane of small pore size (0.2μm) were larger than that of large pore size (0.45μm), and 3) Kiand kswere free from the influence of liquid temperature, while Kb, Kcand SDI were dependent onliquid temperature, 4) Kiand ks were well correlated with SDI15values of samples including the actual raw waterslike sea water, and 5) Kiis recommended as the water quality index because it does not contain the term of initial fluxas compared with ks.

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In recent years, many membrane manufactures are choosing PVDF as their membrane material mainly because ofits high chemical compatibility in general while our PVDF membrane has an extraordinary chemical compatibilityowing to our unique manufacturing technology. In this paper, the characteristics of our PVDF membrane and operating examples of our products with PVDF mem-brane are described.

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