Hiroshi Yanagishita

Surface active properties and antimicrobial activities of mannosylerythritol lipids as biosurfactants produced by Candida antarctica

Abstract The interfacial and antimicrobial properties of two kinds of mannosylerythritol lipids (MEL-A and B), which were produced as biosurfactants from soybean oil by a yeast strain of Candida antarctica T-34, were investigated. MEL showed excellent surface and interfacial tension lowering actions and critical micelle concentrations (CMC). At CMCs, they reduced the surface tension and the interfacial tension against n-tetradecane to about 28 and 2 mN m−1, respectively. These interfacial properties are equivalent to those of other biosurfactants reported and ordinary glycolipid-type synthetic surfactants. MEL also exhibited antimicrobial activity particularly against Gram-positive bacteria, and their minimum inhibitory concentrations were significantly smaller than those of sucrose and sorbitan monoesters of fatty acids.

Separation of acetic acid-water mixtures by pervaporation through silicalite membrane

Polycrystalline silicalite membranes were prepared on two kinds of porous supports by hydrothermal synthesis. The pervaporation performance of the silicalite membrane obtained was investigated using an acetic acid-water mixture as a feed. The silicalite membrane on the sintered stainless steel support selectively permeates acetic acid in the concentration of the feed acetic acid in the region of 5 to 40 vol%. However, the membrane on the porous alumina support showed no separation for the aqueous acetic acid solution. From the fact that the top layer of the membrane on the alumina support was not composed of pure silicalite but ZSM-5 zeolite crystals, which contained Bronsted acidic sites (Si(OH)Al) in the framework, it was suggested that the acidic sites associated with the framework aluminums play an important role in the separation of the acetic acid-water mixture. A long-term test of the pervaporation was also carried out to clarify the stability of the membrane.

Microbial conversion of n-alkanes into glycolipid biosurfactants, mannosylerythritol lipids, by Pseudozyma (Candida antarctica)

Abstractn-Alkanes ranging from C12 to C18 were converted into glycolipid biosurfactants, mannosylerythritol lipids (MEL), by resting cells of Pseudozyma (Candida) antarctica T-34. The highest yield (0.87 g g−1 substrate) was obtained from 6% (v/v) of n-octadecane after 7 days reaction. The amount of MEL reached 140 g l−1 by intermittent feeding of the substrate.

Improvement of ethanol selectivity of silicalite membrane in pervaporation by silicone rubber coating

In order to improve the pervaporation performance of silicalite membrane, two types of silicone rubber, KE45 and KE108, were coated on the membrane surface. The initial molecular weight of KE108 is high and vulcanizing starts when it comes into contact with moisture in air, whereas the initial molecular weight of KE45 is low and vulcanizing starts when it is mixed with a catalyst. KE108 was found to be more effective than KE45 in enhancing the ethanol selectivity of silicalite membranes. A membrane coated using a 3 wt.% KE108 hexane solution showed separation factor of α=125 with a total flux of 0.14 kg/m2 h.

Separation of methanolrmmethyl-tert-butyl ether mixture by pervaporation using silicalite membrane

The polycrystalline silicalite membrane was prepared on a porous sintered stainless steel support and its pervaporation performance was investigated using a MeOH/MTBE mixture as a feed. It was found that the MeOH selectivity of pervaporation is considerably higher than that of distillation. This indicates that the silicalite membrane permeates methanol preferentially. From the results of the competitive adsorption experiments and the temperature dependence of permeation rates of MeOH and MTBE, it was suggested that the selective sorption of MeOH into the membrane takes place and that the transportation of MTBE within the membrane is strongly suppressed as compared with that of MeOH.

Improved crown ether-based chiral stationary phase

Abstract An improved crown ether-based chiral stationary phase (CSP) was prepared by dynamic coating of a reversed-phase silica gel with a new chiral crown ether which was designed to have more lipophilicity than the previously used one, while preserving the basic structure responsible for chiral recognition. The CSP showed not only excellent enantioselectivity for amino acids, but also higher stability against organic solvents in the mobile phase. No desorption of the crown ether from the support was observed in a mobile phase containing up to 40% of methanol. An increase in methanol concentration in the mobile phase gave rise to a decrease in the retention of amino acids and an increase in the “apparent” enantioselectivity, i.e., the separation coefficient and the resolution factor. A possible retention mechanism is proposed to explain these behaviours.

Potentials of silicalite membranes for the separation of alcohol/water mixtures

Polycrystalline silicalite membranes were prepared on porous sintered stainless steel and alumina supports. The liquid separation potential of the membrane was investigated using various alcohol/water mixtures by pervaporation. The silicalite membrane showed a high alcohol permselectivity. Adsorption experiments of water and alcohols suggest that the high alcohol permselectivity is attributable to the selective sorption of alcohol into the silicalite membrane.

Microbial Production of Glyceric Acid, an Organic Acid That Can Be Mass Produced from Glycerol

ABSTRACT Glyceric acid (GA), an unfamiliar biotechnological product, is currently produced as a small by-product of dihydroxyacetone production from glycerol by Gluconobacter oxydans. We developed a method for the efficient biotechnological production of GA as a target compound for new surplus glycerol applications in the biodiesel and oleochemical industries. We investigated the ability of 162 acetic acid bacterial strains to produce GA from glycerol and found that the patterns of productivity and enantiomeric GA compositions obtained from several strains differed significantly. The growth parameters of two different strain types, Gluconobacter frateurii NBRC103465 and Acetobacter tropicalis NBRC16470, were optimized using a jar fermentor. G. frateurii accumulated 136.5 g/liter of GA with a 72% d-GA enantiomeric excess (ee) in the culture broth, whereas A. tropicalis produced 101.8 g/liter of d-GA with a 99% ee. The 136.5 g/liter of glycerate in the culture broth was concentrated to 236.5 g/liter by desalting electrodialysis during the 140-min operating time, and then, from 50 ml of the concentrated solution, 9.35 g of GA calcium salt was obtained by crystallization. Gene disruption analysis using G. oxydans IFO12528 revealed that the membrane-bound alcohol dehydrogenase (mADH)-encoding gene (adhA) is required for GA production, and purified mADH from G. oxydans IFO12528 catalyzed the oxidation of glycerol. These results strongly suggest that mADH is involved in GA production by acetic acid bacteria. We propose that GA is potentially mass producible from glycerol feedstock by a biotechnological process.

Supported liquid membranes for enantioselective transport of amino acid mediated by chiral crown ether - effect of membrane solvent on transport rate and membrane stability

Abstract The effect of membrane solvent on transport efficiency and membrane stability was investigated in a crown ether-mediated enantioselective amino acid transport system. Relatively non-volatile organic liquids were evaluated as membrane solvents in a supported liquid membrane (SLM) using a microporous polymer film as solid support. For the organic liquids giving high fluxes and a high enantioselectivity, the membrane stability was assessed by operating the membranes for periods of up to 90 days. During these experiments, test-runs were repeated daily and thus the experiments were termed ‘repeated-run’ experiments. The best organic liquids were found to be o -nitrophenyl octyl ether (ONPOE) and p -nitrophenyl heptyl ether (PNPHE). SLMs with these organics were stable for more than 50 repeated-runs. The factors controlling the membrane efficiency are discussed on the basis of the physico-chemical properties of the organic liquids, and it is found that the membrane solvent must have both a high dielectric constant and low solubility in water for the SLMs to be highly stable and permeable.

Production of highly concentrated ethanol in a coupled fermentation/pervaporation process using silicalite membranes

The fermentation performance of a coupled fermentation/pervaporation process using silicalite membranes, which are ethanol permselective for an ethanol/water solution, was studied. The process exhibited about a 20% increase in an average glucose consumption rate as compared with that without the pervaporation unit. A strong correlation was observed between the membrane flux and the consumption rate. Ethanol concentrations in the permeates reached a maximum of 85% (v/v).