Reducing sugar determination

Hydrolysis of xylan produces principally D-xylose.71 By hydrolysis of straw xylan in 3% nitric acid, Heuser and Jayme72 obtained crystalline D-xylose in 85% yield. Using a similar procedure, Hampton, Haworth and Hirst70 obtained a yield of 93% crystalline D-xylose from esparto xylan. A practically identical yield was indicated by reducing sugar determination made on the hydrolysis products of corn seedling xylan.68... 

Fig. 2. Reducing sugars ( ) determined by DNS method and OD (A) vs time for aerobic batch cultivation of T. reesei Rut-C30. The initial growth medium was a Mandels medium with 10 g/L of glucose as the carbon source. At t = 67 h, Solka Floe was added to a concentration of 10 g/L. (There were no measurements of OD after the addition of cellulose.)...

Tests currently available to identify and quantify microbial damage are reviewed by Allen et al. [484]. These tests include GUAM fluidity tests, pH determinations, reducing sugar determinations, microscopic techniques, and staining methods. 

With crude enzymes from Aspergillm niger imder optimal conditions (for this enzyme, pH 4.5 at 47 C.), Walseth 60) was able to degrade a particularly reactive cellulose (preswollen with phosphoric acid) to the extent of 96 % and to account for the loss of weight as D-glucose (by reducing-sugar determinations). 

Emmerich Method. This method is for determination of trace amounts of reducing sugars in pure sucrose and white and refined sugars with reducing sugar content up to 0.15%. The test is carried out in a nitrogen atmosphere and is based on the reduction of 3,6-dinitrophthahc acid. 

Knight and Allen. This is a copper reduction method for reducing sugars in white sugar up to 0.02%. It utilizes EDTA to determine excess unreacted copper. Tests undertaken in 1994 to extend the range of this method were unsuccesshil. In spite of poor performance in ring tests, it remains an official ICUMSA method. 

Luff Schoorl. This method is for the determination of total reducing sugars in molasses and refined symps after hydrolysis. It is a copper-reducing method that forms the basis of some molasses purchasing contracts. 

Colorimetric Methods. Numerous colorimetric methods exist for the quantitative determination of carbohydrates as a group (8). Among the most popular of these is the phenol—sulfuric acid method of Dubois (9), which rehes on the color formed when a carbohydrate reacts with phenol in the presence of hot sulfuric acid. The test is sensitive for virtually all classes of carbohydrates. Colorimetric methods are usually employed when a very small concentration of carbohydrate is present, and are often used in clinical situations. The Somogyi method, of which there are many variations, rehes on the reduction of cupric sulfate to cuprous oxide and is appHcable to reducing sugars. 

In the sugar industry, where the goal is to determine the exact amount of sucrose present, the analysis of other components is essential to determine purity. The most important of these, besides reducing sugars discussed, are moisture, ash, and color. Also relevant are methods used to determine particle-size distribution and insoluble matter. 

Oxidation of the aldehyde group of an aldose to form a carboxyUc acid or carboxyUc acid anion is often used analytically to determine the amount of reducing sugar. The Benedict and Fehling methods measure the amount of reducing sugar present in a fluid. In these reactions, the oxidant, Cu ", is reduced to Cu". Cu" precipitates as CU2O, which can be measured in a variety of ways. In the ToUens test, Ag" is reduced to Ag. ... 

Mode of action and kinetics. Routine polygalacturonase assays were performed in a reaction mixture containing 50 mM Na-acetate pH 4.2 and 0.25 % w/v pga at 30 °C. The release of reducing sugars was determined according to Stephens et al. [9]. For determination of pH optima the 50 mM Na-acetate buffer was replaced by Mcllvain buffers. 

The strains were cultured on Mandels medium + 1% citrus pectin for 5 days and the enzymatic activities of culture filtrates were determined on three substrates citrus pectin, polygalacturonic acid and filter paper, (a) extracellular proteins are in p.g/ml. (b) p>ectinolytic activities on pectin (PC) and on polygalacturonic acid (TO) and Pectin esterase (PE) are in units/ml. (c) total cellulolytic activity (filter paper, fp) are in mg of liberated reducing sugars/ml. 

Gritzapis, P. and Timotheou-Potamia, M. (1989). Determination of reducing sugars with a 2,4-dinitrophenolate-selective membrane electrode. Anal. Chim. Acta 218, 37-46. 

Peris-Tortajada, M., Puchades, R., and Maquieira, A. (1992). Determination of reducing sugars by the neocuproine method using flow injection analysis. Food Chem. 43,65-69. 

A number of reducing agents have been determined directly using tetrazolium salts. Thus, the analyses of reducing sugars,423,424 hydraz-ides, 425 sulfides and thiols,426 ascorbic acid,427,428 formaldehyde,429 L-... 

Gramnegative bacteria. The polysaccharide is determined as reducing substances after acid hydrolysis. Some polysaccharides yielded only one reducing sugar others yielded two or more sugars. 

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