Glucan components

Somewhat analogous to these rice products is Oatrim, a material based on oat flour. It was developed at the Northern Laboratory of the USDA and is offered commercially by several firms. Oatrim contains 5% proteia, 5% P-glucan, 2% pentosans, and 83% maltodextrias. Unique properties are claimed based on the P-glucan component, and preparation of Oatrim is disclosed ia USDA pubHcations and patents. Briefly, oat flour is broken down by a-amylase, then the water-soluble component is dried and is the product of commerce, aimed at ground meat product usage. 

Preswelled Sephacryl S-1000 was prepared in a K26/100 column (88 X 2.6 cm). Equilibration with 0.005 M NaOH containing 0.002% NaN3 at a flow rate of 0.67 ml/min was achieved after 20 hr. Sample solutions were applied with a 5-ml injection loop. The mass and iodine-complexing potential of separated glucan components was determined off-line for each of the subsequently eluted 5-ml fractions. Based on the determined mass of carbohydrate for each of the fractions, elution profiles such as Fig. 16.1 were constructed. 

In summary, semipreparative Sephacryl S-1000 proved to be an appropriate system for the separation of glucan components of any kind of branching... 

Improvement of fibre diffraction by chemical means was exampled by the results obtained with hydrolytic and other extractions of fungal tissue, in particular with reference to the (1-3)-/ -D-glucan component in the fibrous mycelial ropes (rhizomorphs) of Armillaria mellea. The rhizomorphs in the native state produce only one, oriented but diffuse and weak spacing attributable to (1-3)--D-glucan. After the adequate chemical extractions they yielded a complete fibre... 

Some authors have fractionated whole cells to prepare individual wall components. However, in view of the numerous contaminating components from the cytoplasm (especially glycogen), it is preferable in cell wall studies to use clean well-washed cell walls. A commonly used procedure (see Scheme 1), adapted from Manners et al. (3), shows the steps involved in the separation of the main components. A crucial step is the separation of two components in the alkali-insoluble polysaccharide fraction. Investigators prior to 1968 were not aware that the alkali-insoluble glucan contained a water-soluble p-( 1 — 6)-glucan component... 

Alkali-insoluble Glucan. Since this is the structural component of the cell wall responsible for the rigidity and tensile strength of the wall, its chemical composition is of special interest. The alkali-insoluble residue, whether obtained by alkali extraction of whole cells or of cell walls, must first be extracted repeatedly with dilute (0.5M) acetic acid at 90°C to remove glycogen and a /3-(l- 6)-linked glucan component... 

The enormous interest in augmenting the world s supply of protein from microbial sources (135) has focussed much attention on this source of protein as a nutrient for animals as well as humans. However, there is some evidence that if intact yeast cells are included in a diet, the tough polysaccharide-containing cell wall may constitute at least a partial barrier in the effective utilization of the protein of the cytoplasm. One reason for this is the absence of enzymes in the digestive tract of humans and most warm-blooded animals capable of hydrolyzing the microfibrillar / -glucan component of the cell wall (135,136). Other factors may include the inability of the proteolytic enzymes of the digestive track to make effective contact with the cells protein. 

The increases in activities of both 1,3-3-glucan hydrolases and chitinase in response to infection appears to be part of a general plant resistance mechanism. The nature of the inducers of the enzymes is not clear but 3,6-3-glucan components of the cell walls of the invading fungi may be involved. This is supported by the observation that when melon seedlings were placed in a solution (0.08%) of the 3,6-3-glucan laminarin for 18h at 15 C there was a subsequent increase in the level of... 

Yeast cells produce two storage polymers, trehalose (a disaccharide) and glycogen. In addition they synthesize the mannan and glucan components of the cell wall (see Chapter 16). The synthesis of both storage polymers commences with the formation of uridine diphosphate glucose (UDPG) catalysed by UDPG-pyrophosphorylase ... 

---