Rice bran hemicelluloses

Rice bran hemicelluloses reduce thymus atrophy in rats (Takenaka, 1992). Hikino et al. (1988) isolated and purified four glycan fractions from rice bran hemicelluloses and named them as Oryzabrans A, B, C, and D. All these glycans were shown to improve the peripheral utilization of insulin, resulting in significant hypoglycemic activity (Hikino et al., 1988 Hikino and Hayashi, 1989). Several investigations into rice bran polysaccharides and hemicelluloses (Masayoshi et al., 1987) have indicated a strong improvement in the immune... 

TAKENAKA s, ITOYAMA Y (1993) Rice bran hemicellulose increases the peripheral blood lymphocytes in rats. Life Sciences, 52(1) 9-12. 

The carbohydrates in rice bran are made up of the cell wall components such as polysaccharides, oligosaccharides, hemicelluloses, starch and some sugars. The health benefits of rice bran polysaccharides and hemicelluloses are discussed under phytochemicals of rice bran below. It is lactose-free and gluten-free. The water-soluble non-starchy polysaccharides, oligosaccharides and hemicelluloses are concentrated in the water-soluble fraction of rice... 

TAKENAKA s (1992) Hemicellulose in rice bran fiber reduces thymus atrophy in rats treated wih bis-tri-n-butyn oxide. Chemosphere, 25(3) 327-34. 

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. 

Figure 3. Structure of hemicellulosic polysaccharides obtained from rice bran, (a) Deduced from the results of methylation analysis described in ref. 13.

Potential resources of xylans are by-products produced in forestry and the pulp and paper industries (forest chips, wood meal and shavings), where GX and AGX comprise 25-35% of the biomass as well as annual crops (straw, stalks, husk, hulls, bran, etc.), which consist of 25-50% AX, AGX, GAX, and CHX [4]. New results were reported for xylans isolated from flax fiber [16,68], abaca fiber [69], wheat straw [70,71], sugar beet pulp [21,72], sugarcane bagasse [73], rice straw [74], wheat bran [35,75], and jute bast fiber [18]. Recently, about 39% hemicelluloses were extracted from vetiver grasses [76]. 

R. oryzae strains have several advantageous characteristics, including the ability to directly utilize non-pretreated cellulose and hemicellulose, tolerance to the inhibitors present in acid hydrolysates of lignocellulosic biomass, and the ability to produce fumaric acid, a four-carbon unsaturated dicarboxylic acid [57]. Recently, the white rot fungus Trametes hirsute was shown to be capable of directly fermenting starch, wheat bran, and rice straw to ethanol without prior acid or enzymatic hydrolysis [58]. 

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