Kazuhito Hayakawa

Effect of a γ-aminobutyric acid-enriched dairy product on the blood pressure of spontaneously hypertensive and normotensive Wistar–Kyoto rats

We investigated the blood-pressure-lowering effects of γ-aminobutyric acid (GABA) and a GABA-enriched fermented milk product (FMG) by low-dose oral administration to spontaneously hypertensive (SHR/Izm) and normotensive Wistar–Kyoto (WKY/Izm) rats. FMG was a non-fat fermented milk product produced by lactic acid bacteria, and the GABA contained in FMG was made from the protein of the milk during fermentation. A single oral dose of GABA or FMG (5 ml/kg; 0·5 mg GABA/kg) significantly ( P >0·05) decreased the blood pressure of SHR/Izm from 4 to 8 h after administration, but did not increase that of WKY/Izm rats. The hypotensive activity of GABA was dose-dependent from 0·05 to 5·00 mg/kg in SHR/Izm. During the chronic administration of experimental diets to SHR/Izm, a significantly slower increase in blood pressure with respect to the control group was observed at 1 or 2 weeks after the start of feeding with the GABA or FMG diet respectively ( P >0·05) and this difference was maintained throughout the period of feeding. The time profile of blood-pressure change due to administration of FMG was similar to that of GABA. FMG did not inhibit angiotensin 1-converting enzyme. Furthermore, an FMG peptide-containing fraction from reverse-phase chromatography lacked a hypotensive effect in SHR/Izm rats. The present results suggest that low-dose oral GABA has a hypotensive effect in SHR/Izm and that the hypotensive effect of FMG is due to GABA.

High density culture of Lactobacillus casei by a cross-flow culture method based on kinetic properties of the microorganism

Abstract The characteristics of Lactobacillus casei with respect to specific rates of cellular growth, glucose consumption and lactic acid production were elucidated through a study of cultivation with cross-flow filtration using a heatproof inorganic membrane module. These characteristics indicated that the feed rate of fresh medium per unit of culture volume D should be changed in proportion to the cellular growth as D = ν · X / S f = 0.032 X , in order to obtain both a high cell growth rate and a high cell mass yield against glucose consumed. At a constant feed rate of 0.30 1/h, 34 h and 214 l of fresh medium were required to obtain a cell concentration of 40 g/ l (10 11 CFU/ml). On the other hand, by changing the feed rate based on the above equation, only 14 h and 162 l of fresh medium were needed to secure the same cell concentration. The volume of fresh medium required for the cultivation by changing the feed rate was 76% of that needed at a constant feed rate.