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PubMed2000

High-yield fermentation of pentoses into lactic acid.

Lactobacillus species capable of fermenting glucose are generally incapable of utilizing xylose for growth or fermentation. In this study, a novel aspect of a well-known Lactobacillus strain, L. casei subsp. rhamnous (ATCC 10863), was uncovered: it can ferment xylose as efficiently as glucose. This strain is a registered organism, extremely stable on long-term operation. Fermentation by this strain is characterized by an initial lag phase lasting 24-72 h before xylose consumption takes place. The yield (grams/gram) of lactic acid from xylose is in excess of 80% with initial volumetric productivity of 0.38 g/(L.h). Acetic acid is the primary byproduct formed at the level of about 10% of the lactic acid. In addition to xylose, it can ferment all other minor sugars in hemicellulose except arabinose. Subjected to mixed sugar fermentation, this strain consumes glucose first, then mannose, followed by almost simultaneous utilization of xylose and galactose. It shows high tolerance for lactic acid as well as extraneous toxins. It can ferment the mixed sugars present in acid-treated hydrolysate of softwood, giving yields similar to that of pure sugar but at a slower rate.

Arabinose↗
PubMed1992

Effects of insulin, glucocorticoids and thyroid hormones on the activities of key enzymes of glycolysis, glutaminolysis, the pentose-phosphate pathway and the Krebs cycle in rat macrophages.

In the present study the effects of insulin, glucocorticoids and thyroid hormones on macrophage metabolism and function were investigated. The maximum activities of hexokinase, glucose-6-phosphate dehydrogenase, glutaminase and citrate synthase were determined in macrophages obtained from hormone-treated rats and those cultured for a period of 48 h in the presence of hormones. Macrophage phagocytosis was markedly inhibited by dexamethasone and thyroid hormones, remaining unchanged when insulin was added to the culture medium, however. The changes in the enzyme activities caused by hormone treatments of the rats were very similar to those found in culture. Insulin enhanced citrate synthase and hexokinase activities and diminished those of glutaminase and glucose-6-phosphate dehydrogenase. Dexamethasone had a similar effect except on glucose-6-phosphate dehydrogenase. The addition of thyroid hormones to the culture medium raised the activities of glutaminase and hexokinase and reduced that of citrate synthase. The results presented support the suggestion that the effects of insulin, glucocorticoids and thyroid hormones on immune and inflammatory responses could well be mediated through changes in macrophage metabolism.

Animals↗
PubMed1990

The influence of lipogenic and lipolytic conditions on the pentose phosphate pathway dehydrogenases in rat-kidney-cortex.

The effects of various lipogenic and antilipogenic states on the activities of rat-kidney cortex glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase have been studied. These conditions are related to the long-term administration of different diets, such as high-carbohydrate (80%) and high-fat (23%), and also to a state of fast. Contrary to what happens in liver cells and kidney cortex during a high protein diet administration, none of these nutritional conditions produced significant changes in the kinetics of either kidney hexose monophosphate dehydrogenases.

Animals↗