Search

A salt-tolerant yeast Debaryomyces hansenii IFO 10939, which is able to grow at pH 10.0, was isolated and characterized. IFO 10939 had the ability of maintaining intracellular pH. The in vivo activation of plasma membrane ATPase was observed in cells grown at pH 6.2 during conditioning in buffer at pH 9.0. Alkalification of growth medium exhibited a significant increase in acetate and propionate production. The results suggested that the regulation of intracellular pH was involved in plasma membrane ATPase pumping protons out of the cells and weak acid formation for the source of the protons in cells growing at high pH.

We examined water conditions on a latex surface by using differential scanning calorimetry (DSC). The DSC results indicated that three kinds of water, (free water, freezable bound water, non-freezing water) exist on the latex surface. From the DSC results for several polystyrene latices, it was known that behaviors of freezable bound water, and non-freezing water were affected by initiator, surfactant, and also by co-polymerization of hydrophilic monomer. Further, according to the DSC results of carboxylated latex, it was known that water conditions were related to latex properties, (pH, solid content, latex viscosity). Furthermore, we found that latex viscosity was determined by the amount of free water. These results indicated that water conditions on a latex surface were influenced by condition and localization of hydrophilic substances.

The influence of non-Saccharomyces yeast, Kluyveromyces lactis, on metabolite formation and the ethanol tolerance of Saccharomyces cerevisiae in mixed cultures was examined on synthetic minimal medium containing 20% glucose. In the late stage of fermentation after the complete death of K. lactis, S. cerevisiae in mixed cultures was more ethanol-tolerant than that in pure culture. The chronological life span of S. cerevisiae was shorter in pure culture than mixed cultures. The yeast cells of the late stationary phase both in pure and mixed cultures had a low buoyant density with no significant difference in the non-quiescence state between both cultures. In mixed cultures, the glycerol contents increased and the alanine contents decreased when compared with the pure culture of S. cerevisiae. The distinctive intracellular amino acid pool concerning its amino acid concentrations and its amino acid composition was observed in yeast cells with different ethanol tolerance in the death phase. Co-cultivation of K. lactis seems to prompt S. cerevisiae to be ethanol tolerant by forming opportune metabolites such as glycerol and alanine and/or changing the intracellular amino acid pool.

Dynamic oscillation rheometry in combination with repeating freeze–thaw (FT) cycles (DOR-FT) was applied to evaluate the rheological change of starch gel caused by long-term retrogradation. The gels prepared from corn, wheat, rice, potato, and sweet potato starch pastes (6%, w/w) were formed on a dynamic rheometer plate and the rheological changes induced by the FT cycles were measured while their gels remained on the rheometer plate. Comparing with the storage modulus (G′) at 25°C of each starch gels without FT, G′ of corn, wheat, rice, potato, and sweet potato starch gels after three FT cycles increased by 341, 474, 167, 1368, and 631%, respectively. The DOR-FT method enabled the evaluation of the rheological changes caused by the long-term retrogradation within 1 h, which is much shorter than with the conventional puncture test. Moreover, G′ versus FT cycles could be expressed as an exponential function model, indicating that the function model would show the FT cycle dependence for the rheological change of starch gels.

Mutants of the yeast Sacchavomyces cerevisiae that are partially deficient in aldehyde dehydrogenases (ALDHs) were isolated. A mutant, AK-9, was shown to be especially defective in the NADP+-linked ALDH. The K+-activated ALDH of a mutant AK-25 was found in the cytosol, but not in the mitochondria. The strain AK-25 continuously accumulated acetate even in the phase of ethanol consumption in batch aerobic cultures. A mutant, AK-26, was defective in two isozymes of ALDH, particularly in the K+-activated ALDH. The aldh mutants of AK-9 and AK-25 were more sensitive to the growth inhibitory effects of ethanol and NaCl, but the mutant AK-26 was only sensitive to ethanol. All aldh mutants stimulated more acetaldehyde production than the wild-type strain during conditioning in media containing ethanol. The mutants except for AK-26 almost never produced acetaldehyde during conditioning in media containing 2–6% NaCl. The mutant AK-26 produced glycerol almost the same as the wild-type strain during conditioning in Na...

This study is concerned with the problem of measuring average distances between two points in two different coplanar regions. The objectives are: (1) to derive the approximated average distances associated with circular regions and to check their accuracy; and (2) to apply these approximated distances to location problems. Results show that the simple approximate formulas are accurate and useful. The approximated average distances can be applied to the analyses of varied kinds of movement phenomena in cities.

Dietary fibers were prepared as alkali- and acid-insoluble fractions with chemical phosphorylation from Tossa jute (Corchorus olitorius), defatted soybean (Glycine max), and Shiitake (Lentinula edodes). The dietary fiber fractions treated with alkaline solution containing sodium metaphosphate had the lower protein content and higher total dietary fiber content than those of the preparations without phosphorylation. Alkaline extraction followed by phosphorylation led to a 1.5-fold increase in the water holding capacity of dietary fiber compared with no phosphorylation, whereas the binding capacity to bile acids of dietary fiber was almost the same. The alkali- and acid-insoluble extraction with phosphorylation provided an efficient preparation of water-insoluble dietary fiber with high-water holding capacity from various food sources.

A new antifungal substance, 11-hydroxy-9(Z)-undecenoic acid, was isolated from the leaves of wild rice (Oryza officinalis, W-0002) which is resistant to the rice blight fungus (Pyricularia oryzae P2), together with the known 12-hydroxy-9(Z)-dodecenoic acid and azelaic acid monomethyl ester, and its structure was established on the basis of spectroscopic data and chemical synthesis.

Mitochondrial aldehyde dehydrogenase ALD5 of Saccharomyces cerevisiae is involved in the biosynthesis of mitochondrial electron transport chain, and the ald5 mutant is incompetent for respiration. With use of the mutant, we examined the detoxication of H2O2 generation by fatty acid beta-oxidation in peroxisome. The ald5 mutant (AKD321), as well as the 746 rho0 mutant, was more resistant to H2O2 stress than the wild type. However, overexpression of the MDH3 gene that was involved in the reoxidation of NADH during fatty acid beta-oxidation caused a decrease in cell viability of AKD321 to H2O2 stress, while the 746 rho0 mutant had no such effect. Intracellular H2O2 concentration increased approximately fourfold in MDH3 overexpressing ald5 strain (MD3-AKD321), compared with AKD321. The peroxisomal catalase activity of MD3-AKD321 decreased by 83% to that of AKD321. And also, the overexpression of MDH3 had only a weak effect in MDH3 overexpressing 746 rho0 strain, decreasing by 14% to that of 746 rho0 mutant. The increased palmitoyl CoA oxidation by overexpression of MDH3 gene was the same in both strains. Under conditions of MDH3 overexpression, peroxisomal catalase (CTA1) appears to be a limiting factor to oxidative stress. These observations point to an important, as yet unidentified, role of mitochondrial aldehyde dehydrogenase (ALD5) to endogeneous oxidative stress in peroxisome.

A gene encoding β-glucosidase was cloned from a thermophilic anaerobe strain NA10 into Escherichia coli . The 4.6 kb of Hin dIII fragment was shown to direct the synthesis of β-glucosidase. A homologous DNA sequence was found to be present in strain NA10 by Southern blot analysis. The β-glucosidase was purified from the recombinant E. coli . The molecular weight of the enzyme was estimated to be 50.1 kDal using SDS-polyacrylamide gel electrophoresis. The enzyme was heat stable; the optimum pH and temperature were 5.5 and 85°C, respectively. The enzyme could hydrolyse low molecular weight β-1,3 and β-1,4 glucans. The β-glucosidase was produced in the cytosol of the recombinant E. coli (7–20% of total protein), without fusion to any E. coli promoter sequences.

The result of sensory evaluation of sake showed that acetic acid imparted desirable acidity when the proportion of acetic acid to lactic acid was about 1/3, even if the concentration of acetic acid was 0.75 g/l. Glycerol balanced the acidity and brought about a harmony between sweetness and acidity in sake. A high-acetate producing sake yeast (MHA-3) was isolated from mutants having low NADH dehydrogenase (NDE) activity. MHA-3 produced 15 times more acetate and 5 times more lactate than the parental strain Kyokai no. 901 (K-901) in a small-scale sake brewing test using 10 kg of rice. In addition, the concentrations of glycerol in sake brewed with MHA-3 were approximately 1.5-fold higher than in that brewed with K-901. The proportion of acetic acid to lactic acid was about 1/3 in sake fermented with MHA-3 and it exhibited a good balance between sweetness and acidity. The activities of glycerol-3-phosphate dehydrogenase (GPD) and aldehyde dehydrogenase (ALD) in MHA-3 were 1.4-fold and 3.1-fold, respectively, higher than those in K-901 while the activity of NDE was 40% that of K-901. MHA-3 accumulated higher amounts of acetate and glycerol than K-901 in static YNB10 medium. The concentrations of acetic acid produced, depending on the quantity of yeast cells added, increased in conjunction with increases in glycerol produced. We suggest that NDE might be linked with GPD and that the nde mutants, which can be used in sake brewing, produced higher amounts of acetate and glycerol.