Bacteria galactose

Another fermentation process is described by Fayolle et al.14 In this work, processes producing lactic acid bacteria were studied. Samples were extracted from the reactor and assayed by conventional methods and scanned in the IR. Equations were generated, using PLS, for lactose, galactose, lactic acid, and biomass. The SEP for each of these constituents was, respectively, 3.4, 1.5, 0.9, and 0.9 g/1. 

Osmotic laxatives (e.g., lactulose, sorbitol) are poorly absorbed or nonabsorbable compounds that draw additional fluid into the GI tract. Lumen osmolality increases, and fluid movement occurs secondary to osmotic pressure. Lactulose is a synthetic disaccharide that is poorly absorbed from the GI tract, since no mammalian enzyme is capable of hydrolyzing it to its monosaccharide components. It therefore reaches the colon unchanged and is metabolized by colonic bacteria to lactic acid and to small quantities of formic and acetic acids. Since lactulose does contain galactose, it is contraindicated in patients who require a galactose-free diet. Metabolism of lactulose by intestinal bacteria may result in increased formation of intraluminal gas and abdominal distention. Lactulose is also used in the treatment of hepatic encephalopathy. 

In a paper concerned primarily with the determination of neutral sugars, Richey and coworkers examined the O-trimethylsilyl derivatives of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galactose.171 Similar methods for determining these compounds have also been used in studies on human milk,545 yeasts and bacteria,1,2 blood-group oligosaccharides,405 and urine.118 These methods were also included in a model study on the isothermal determination of sugars.256... 

Figure 10.12 Metabolism of lactose by lactic acid bacteria many Lactobacillus species/strains can not metabolize galactose (from Cogan and Hill, 1993).

Glucose is the preferred carbon source for yeast, as it is for bacteria. When glucose is present, most of the GAL genes are repressed—whether galactose is present or not. The GAL regulatory system described above is effectively overridden by a complex catabolite repression system that includes several proteins (not depicted in Fig. 28-29). 

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