Masayoshi Takakuwa

Change of lipid composition of Zygosaccharomyces rouxii after transfer to high sodium chloride culture medium

Abstract The change of the lipid composition was investigated in Zygosaccharomyces rouxii cells transferred from NaCl-free to 2 M NaCl medium. After the transfer thesterol and phospholipid contents increased, and phospholipids with higher oleic acid contents and higher negative charge increased. These changes of membrane lipid may be required for the adaptation of Z. rouxii cells to a high NaCl environment.

Depression of synthesis of linoleyl residue in Zygosaccharomyces rouxii cells by sodium chloride

Abstract The syntheses of fatty acyl residues in a salt-tolerant yeast, Zygosaccharomyces rouxii, were compared under 4 growth conditions as follows, transfer from; (A) NaCl-free medium to the same medium, (B) NaCl-free medium to 2 M NaCl medium, (C) 2 M NaCl medium to the same medium, and (D) 2 M NaCl medium to NaCl-free medium. The synthesis of linoleyl residue 18:2) was depressed by the presence of 2 M NaCl while that of oleyl residue (18:1) was not. Under condition D, however, the synthesis of 18:2 recovered in the NaCl-free medium. These phenomena were confirmed through pulse-labeling and chase experiments. It is suggested that desaturation from 18:1 to 18:2 may be depressed by the presence of 2 M NaCl.

Physicochemical and Immunochemical Properties of a Thermo-labile Antigen (TLA b) from the Yeast Cell Surface

The physicochemical and immunochemical properties of a thermo-labile antigen (TLA b) which is located on the cell surface were studied. The sedimentation constant (S20.w), molecular weight with the sedimentation equilibrium method and intrinsic viscosity were 7.33S, 81,000 and 0.0313 dlg–1, respectively. TLA b was composed of two identical subunits on the basis of Nterminal amino acid analysis. The circular dichroic (CD) spectrum of the TLA b had a negative maximum at around 218 nm. TLA b was estimated to have at least twelve antigenic determinants by analysis of the quantitative precipitin reaction. The number of molecules of TLA b per cell was estimated to be 5.65 × 106 , this corresponded to 1.14% by weight of the fresh yeast.

DEGRADATION OF PHOSPHOLIPIDS IN CELL MEMBRANE DURING STORAGE OF PRESSED BAKER'S YEAST

ABSTRACT In this experiment, variations in lipid components of yeast washings and yeast homogenate were investigated during the storage of pressed bakers yeast at 30°C. The amount of lipids in yeast washings increased toward the softening of yeast, and that of phospholipids in yeast homogenate decreased continuously during storage. There were two stages in the degradation of phospholipids; the earlier period of storage (Stage I) and the later period of storage (Stage II). Free fatty acids, which were mainly the products of the degradation of phospholipids, accumulated not in Stage I, but in Stage II, particularly at the softening. These findings suggest that phospholipids were degraded by phospholipase toward the softening. Such an inference was supported by the experiment using L-α-phosphatidylcholine(di[1-14C] palmitoyl). KEYWORDS Softening of pressed yeast;, two stages in phospholipid degradation;, fatty acid accumulation;, order in degraded phospholipids;, contribution of phospholipase.

Studies on Dry Yeast (VI): Change of Dry Yeast in the Fermenting Activity and the MB-stainability during Storage at 0° and 30°C

When the sample was taken from the fermenting dry bakers’ yeast suspension, the ratio of yeast cells negative to methylene blue staining (MBN) was calculated easily and exactly. MBN decreased more slowly than any of three factors of fermenting power, which were shown with three quotients (Qco2 (20′~40′), ΔQco2, Qco2 (max)), during the storage of the dry yeast. ΔQco2 was the most inconstant of three quotients and the inconstancy was particularly clear in storage at 0°C, where others were almost constant.

Studies on Dry Yeast. (IV):Mechanism of Fermentation of Dry Bakers' Yeast

The volume of carbon dioxide evolved in a shaking apparatus was measured at fixed intervals, and it was confirmed that the fermentation of dry yeast generally depends on three factors and that they are represented with an initial fermenting activity, a power which recovers fermenting activity, and a maximum fermenting activity. This expression of fermenting power was compared with usual expressions and it was proved to be more reasonable, particularly, for deciding the initial fermenting activity.