The Hemicelluloses. I. The Hemicellulose of Wheat Flour

Abstract

SOME years ago, Schulze described the preparation of nitrogen-free residues from leguminous seeds, which yielded on hydrolysis with dilute acids reducing sugars. The precursors of these sugars which were not actually isolated were called by Schulze "hemicellulosesl."During the course of some researches on the constituents of the cell-wall substances of plants by Clayson, Norris and Schryver [1921], it was found that, by means of N sodium hydroxide solution, substances could be extracted from all the materials investigated, which were soluble in the more concentrated alkaline solutions, but not in very weak alkali; they could be precipitated from the alkaline solutions on addition of acids, and as they yielded reducing sugars on hydrolysis with acids, they were assumed to belong to the class of products termed by Schulze the "bemicelluloses." Most of the products isolated gave on hydrolysis relatively large amounts of pentoses, and all of them gave a blue coloration with iodine.It was decided to continue investigations with the object of isolating in bulk these so-called "hemicelluloses" and of determining their distribution and later on their function in plant-tissues. The distribution appears to be a very wide one. In some lignified tissues they exist in relatively large quantities ("wood-gums"), and the product isolated many years ago from barley by O'Sullivan and called by him "amylan" also apparently belongs to this class.The first investigations were carried out on leguminous seeds from which a " hemicellulose " and also " cytopectic acid " [see Clayson, Norris and Schryver, 1921] were isolated and in extending the work to cereals wheat flour was chosen as the chief material for research. By means of the process described in detail below, a product giving a blue coloration with iodine like starch, but differing in many essential properties from this substance, was isolated. It is shown in the second communication [Schryver and Thomas, 1923] that the same product can also be isolated from the commercial starches.

Hemicellulose as a Storage Carbohydrate in Woody Plants, With Special Reference to the Apple

“…Another interesting observation made by SCHELLENBERG (22) is that in various organs of Molinia coerulea, when cell wall thickenings appear after leaf fall (Oct.-Nov.), starch disappears, and when they are redissolved in the spring starch is present once more, thus suggesting a possible connection between starch and hemicellulose. In all instances hemicellulose of this nature could be removed by hydrolysis with hydrochloric and sulphuric acids (3)(4)(5) than that of starch, and that it is laid down primarily in the fall and disappears when growth is resumed. And HARVEY (8) has shown that of the total polysaccharides in apple shoots, by far the largest fraction is made up of pentoses, thus indicating that hemicelluloses are primarily pentosans, as was suggested by SPOEHR (27).…”

“…Thus it is at least suggestive that these three interesting compounds of the plant cell wall may be generically connected. Furthermore, recent studies by SCHRYvER and coworkers (4,25) and by LING and NANJI (14) Latety quite convincing proof has been secured that substances of the type of galacturonic and glycuronic acids and their polymeric anhydrides, the poly-galacturonic and -glycuronic acids appear to be the main building stones from which plant cell membranes (hemicelluloses), and pectins as well, are constructed (6,18). This particular group of polysaccharides has the characteristics of both carbohydrates and acids.…”