Repeated-batch production of galactooligosaccharides from lactose at high concentration by using alginate-immobilized cells of Sporobolomyces singularis YIT 10047.

We investigated the production of galactooligosaccharides (GOS) from lactose by alginate-immobilized cells of Sporobolomyces singularis YIT 10047 (IM-SS). beta-Galactosidase activity was stable at 30 to 50 degrees C but decreased dramatically between 50 and 60 degrees C and disappeared at 70 degrees C in acetate buffer. The enzyme activity remaining was no more than 20% of that of unheated samples after incubation in distilled water at 55 degrees C, whereas its value was about 60% at the same temperature under buffered condition. However, activity was maintained more than 80% with 10% to 50% (w/w) lactose after incubation at 55 degrees C without buffer. In a single-batch reaction, GOS yield was 41.0% with free cells and 40.4% with IM-SS. We attempted a repeated-batch reaction using IM-SS with 600 g L(-1)lactose. IM-SS produced GOS stably for 20 batches (22 h/batch, 440 h in total) at 55 degrees C and pH 5.0 or 6.0. IM-SS produced GOS at 242 g L(-1), at a rate of 8.72 g L(-1) h(-1). Both GOS yield and production rate were higher than those in published experiments on GOS production using immobilized biocatalysts. The repeated-batch reaction with IM-SS would be an ideal system for GOS production because of its stability and high productivity.

Hypocholesterolemic mechanism of Chlorella: Chlorella and its indigestible fraction enhance hepatic cholesterol catabolism through up-regulation of cholesterol 7alpha-hydroxylase in rats.

Chlorella powder (CP) has a hypocholesterolemic effect and high bile acid-binding capacity; however, its effects on hepatic cholesterol metabolism are still unclear. In the present study, male Wistar rats were divided into four groups and fed a high sucrose + 10% lard diet (H), an H + 10% CP diet (H+CP), an H + 0.5% cholesterol + 0.25% sodium cholate diet (C), or a C + 10% CP diet (C+CP) for 2 weeks. CP decreased serum and liver cholesterol levels significantly in rats fed C-based diets, but did not affect these parameters in rats fed H-based diets. CP increased the hepatic mRNA level and activity of cholesterol 7alpha-hydroxylase (CYP7A1). CP increased hepatic HMG-CoA reductase (HMGR) activity in the rats fed H-based diets, but not in rats fed C-based diets. CP did not affect hepatic mRNA levels of sterol 27-hydroxylase, HMGR, low-density lipoprotein (LDL) receptor, scavenger receptor class B1, ATP-binding cassette (ABC) A1, ABCG5, or ABCB11. Furthermore, the effect of a 3.08% Chlorella indigestible fraction (CIF, corresponding to 10% CP) on hepatic cholesterol metabolism was determined using the same animal models. CIF also decreased serum and liver cholesterol levels significantly in rats fed C-based diets. CIF increased hepatic CYP7A1 mRNA levels. These results suggest that the hypocholesterolemic effect of CP involves enhancement of cholesterol catabolism through up-regulation of hepatic CYP7A1 expression and that CIF contributes to the hypocholesterolemic effect.

Roles of nuclear receptors in the up-regulation of hepatic cholesterol 7alpha-hydroxylase by cholestyramine in rats.

Nuclear receptors are involved in regulating the expression of cholesterol 7alpha-hydroxylase (CYP7A1), however, their roles in the up-regulation of CYP7A1 by cholestyramine (CSR) are still unclear. In the present study, male Wistar rats were divided into four groups and fed [high sucrose + 10% lard diet] (H), [H + 3% CSR diet] (H + CSR), [H + 0.5% cholesterol + 0.25% sodium cholate diet] (C), or [C + 3% CSR diet] (C + CSR) for 2 weeks. Cholestyramine decreased serum and liver cholesterol levels significantly in rats fed C-based diets, but had no effect on these parameters in rats fed H-based diets. Cholestyramine raised hepatic levels of CYP7A1 mRNA and activity in both groups. The gene expression of hepatic ATP-binding cassettes A1 and G5, regulated by liver X receptor (LXR), were unchanged and down-regulated by cholestyramine, respectively. The mRNA levels of the hepatic ATP-binding cassette B11 and short heterodimer partner (SHP), regulated by farnesoid X receptor (FXR), were not changed by cholestyramine. C-based diets, which contained cholesterol and cholic acid, increased SHP mRNA levels compared to H-based diets. Consequently, in rats fed the C+CSR diet, hepatic FXR was activated by dietary bile acids, but the hepatic CYP7A1 mRNA level was increased 16-fold compared to that in rats fed an H diet. These results suggest that cholestyramine up-regulates the expression of CYP7A1 independently via LXR- or FXR-mediated pathways in rats.

Improved separation method for highly purified lutein from Chlorella powder using jet mill and flash column chromatography on silica gel.

We investigated an improved method for the separation of high-purified lutein from a commercially available spray-dried Chlorella powder (CP) using fine grinding by jet mill and flash column chromatography on a silica gel. Saponification and extraction of lutein were enhanced 2.3-2.9-fold in jet mill-treated CP (mean particle size, 20 microm) as compared to untreated CP (mean particle size, 67 microm). The carotenoid extract was dissolved in ether-hexane (1:1 v/v) and subjected to flash column chromatography on silica gel. A mixture of alpha- and beta-carotene was eluted with hexane, followed by elution with hexane-acetone-chloroform (7:2:1 v/v). Lutein (dark-orange band) was collected after the elution of an unknown colorless compound (detected based on UV absorbance). The purity of lutein in this fraction was over 99%, and the yield was 60%. The present study provides key information for obtaining highly purified lutein using flash column chromatography on a silica gel.

Antioxidant and anti-cataract effects of Chlorella on rats with streptozotocin-induced diabetes.

The antioxidant activities of Chlorella in vitro and in vivo were investigated. Chlorella showed a strong antioxidant effect compared to various vegetables in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. To evaluate the antioxidant and anti-cataract effects in vivo, a 7.3% Chlorella powder was fed to rats with streptozotocin-induced diabetes for 11 wk. At the end of the experiment, Chlorella had decreased the blood glycated hemoglobin (hemoglobin A1c) and serum cholesterol levels significantly, however, it had not affected the serum glucose concentration. The serum lipid peroxide value (TBARS value) in the rats fed Chlorella was lower than that of the control rats. In the liver and kidney, Chlorella also reduced chemiluminescent intensities. In addition, it delayed the development of lens opacities. The lens lipid peroxide content of the rats fed Chlorella was lower than that of the control rats, however the differences were not significant. These results indicate that Chlorella has antioxidant activity and may be beneficial for the prevention of diabetic complications such as cataracts.