Ethanol metabolism during development

In conlcusion, the rates of ethanol metabolism and the activity of hepatic alcohol dehydrogenase are both reduced in fetal life and in the newborn when compared with values obtained in the adult. Significant microsomal ethanol oxidizing system and catalase activities are detected early in fetal life and do not increase during further fetal development However, the contribution of these two enzymes to the m vivo metabolism of ethanol during development remains to be evaluated. 

The dynamic behavior of the cell metabolism initiated by different external effects (addition of substrates or inhibiting reagents) can be followed via this instantaneous method. These effects can be used to control the overall process and optimize the bioprocess. Meyer and Beyeler [50] developed a control system for a continuous yeast cultivation process. Here the increase up to the optimal dilution rate was controlled via fluorescence monitoring. The dilution rate was only increased when no negative effect on the metabolic state of the cells was observed. During the cultivation of Candida utilis the fluorescence signal was used for the addition of substrate ethanol. The addition was started when... 

Maturation effected the following changes In enzymes and metabolites in orange fruit ethanol and acetaldehyde accumulated to levels of 10 mM and 0.08 mM, pyruvate decreased about 30%, pyruvate decarboxylase increased over 4 fold, alcohol dehydrogenase increased about 2 fold, the NADH to NAD ratio increased 21/2 fold and the terminal oxidase developed CN-insensitivity. The fraction of the total alternative respiratory pathway in actual use increased from 0.46 to 1.08. Induction of the alternative, CN-insensitive oxidase during maturation was interpreted as indicating that membrane function was modified which affected metabolic pathways resulting in the accumulation of ethanol and acetaldehyde. 

Elevation of the ethanol content occurs during the maturation stage of fruit development when acidity declines, total solids increase, and the flavor compounds accumulate to characteristically ripe levels. Since ethanol is a normal product of anaerobic respiration in plants, its accumulation signals a change in the pathway of energy metabolism. This summary of research on the control of ethanol accumulation in citrus fruit describes an approach to identify the role of energy metabolism in the bioregulation of maturation. 

Bacteria do not transform all of the malic acid contained in the grape. From the start, during alcoholic fermentation, yeasts metabolize a maximum of 30% of the malic acid. The product, pyruvate, then enters one of many yeast metabolic pathways—notably leading to the formation of ethanol. This malo-alcoholic fermentation is catalyzed at the first stage by the malic enzyme. The bacteria must develop a sufficient population before malolactic fermentation can truly start. The production of L-lactic acid is coupled with the decrease in malic acid (Figure 6.3). 

The whole, uncrushed berry also develops an anaerobic metabolism when placed in a carbon dioxide atmosphere. During this phenomenon, various chemical and physicochemical processes occur, especially ethanol production. They are linked to the functioning of the cells in the whole berry but, in contrast to yeasts, grape berry cells are not very tolerant of ethanol. Ethanol production is therefore limited it varies from 1.21 to 1.89% volume for the Carignan variety, regardless of the must sugar concentration, when between 184... 

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