Rice endosperm, cell wall preparation

Rice endosperm cell walls have been prepared by grinding the rice flour (obtained from the milled grains) to pass through a 50-mesh sieve and then treating the flour sequentially as follows (1) with cold water and then 1 1 ethanol/ether to defat the flour, (2) with a-amylase to remove starch and isolate the water-soluble polysaccharides from the supernatant fluid,... 

Figure 1. Scanning electron micrograph of the cell wall preparations obtained from the different parts of rice grain (7). Caryopsis coat (upper left), aleuron layer (upper right), germ (lower left) and starchy endosperm (lower right). Bars in the picture indicate 5 /zm.

While the hemicelluloses obtained from the germ, aleuron, and caryopsis coat cell walls all showed a similar monosaccharide composition, this was not the case for the endosperm tissue. Thus, a major difference in the structure of hemicellulosic polysaccharides exists between the preparations obtained from the endosperm cell walls and those from the cell walls of the other parts of the grain, i.e., rice bran. (Rice bran consists of the caryopsis coat, aleuron layer and germ.) Comparison of the detailed structural features of the hemicellulosic polysaccharides of endosperm and bran cell walls will be discussed in the following sections. 

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