Lactose metabolism processed products

Acid production by yogurt cultures is a complex biochemical process. For the purpose of this problem, assume that acid production follows first-order kinetics with respect to the consumption of lactose in the yogurt to produce lactic acid. At the start of acid production the lactose concentration is about . 5%, the bacteria concentration is 10 cells/dm. and the acid concentration at which all metabolic activity ceases is 1.4% lactic acid. 

Tryfona T, Bustard MT (2005) Fermentative production of lysine by Corynebacterium glutamicum transmembrane transport and metabolic flux analysis. Proc Biochem 40(2) 499-508 Trzecieski 1 (1983) Lactose-reduced ice cream and process for the production thereof. US Patent... 

A third, more complex possibility arises from the anaerobic conversion of lactose to lactic acid in a first process step using lactobacilli capable of producing lactic acid with high yields (more than 0.9 g of lactic acid per gram of carbon source). In a subsequent aerobic cultivation, lactic acid is metabolized to acetyl-CoA and further to PHAs by numerous strains, e.g. most common PHA producers such as C. necator, A. latus and A. vinelandii. Alternatively, lactic can be converted to PLA, if wanted. Hence, for PHA production from whey, the decision whether to apply whey lactose, hydrolysed whey lactose or a first-step fermentation towards lactic acid mainly depends on the production strain (Fig. 6). 

Separation of these two carbohydrates is of great importance both for the dairy industry and for clinical analysis. In milk products, for example, a failure in the pasteurization process can force lactose to isomerize to lactulose due to heating. Because lactulose is not metabolized and ingestion of large amounts of lactulose can produce diarrhea [227], the lactulose content in milk products is a quality feature for a perfect pasteurization. The fact that lactulose cannot be metabolized makes it valuable in clinical applications. If lactulose is administered to a patient, kidney permeability can be examined via the urinary excretion rate. 

The galactose produced in this process is subsequently converted by the liver into additional glucose, which is then further metabolized to produce energy. Many people do not produce a sufficient amount of lactase and are incapable of hydrolyzing large quantities of lactose. Instead, lactose accumulates and is ultimately broken down into CO2 and H2 by bacteria present in the intestines. Bacterial degradation of lactose produces several by-products, including lactic acid. 

Carbohydrates are generally considered to be the main ultimate products of carbon dioxide transformation in the plant by the photosynthetic process. The monosaccharides, which are produced in a series of stepwise reactions, appear to serve two major functions they are partially consumed in respiration with the production of energy, which is utilized for the numerous metabolic reactions of the plant they also serve as building units in being combined by various enzymes, or enzymatic systems, to form complex saccharides, such as sucrose, maltose, lactose, glycogen, starch, and cellulose. 

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