Plant continued protein contents

In fresh herbage, 75-90 per cent of the total nitrogen is present as protein. After harvesting, rapid proteolysis (hydrolysis of peptide bonds) occurs and, after a few days of wilting in the field, the protein content may be reduced by as much as 50 per cent. The extent of protein degradation varies with plant species, DM content and temperature. Once the material is ensiled, proteolysis continues but the activity declines as the pH falls. The products of proteolysis are amino acids and peptides of varying chain length. 

In the continuous system, as shown in Figure 30.4C, by constantly removing contents from the fermentor, the process is now open with respect to all components. Typically, the addition of feed and the removal of broth are equal, resulting in a constant volume. Under these conditions, a steady state is achieved wherein all parameters become constant. Such a system is widely used for physiological studies. However, industrial uses are typically limited to the production of biomass (single cell protein) for food or feed, and waste treatment plants. 

There has been much speculation about using supercritical carbon dioxide because using this technology eliminates safety issues as carbon dioxide is not flammable and the oil is better quality (139), but no such plants have been constructed to process soybeans. This is due to the absence of a commercially feasible means of continuously feeding soybean flakes into a high-pressure vessel and removing the spent flakes. Recently, one company has developed a screw press in which supercritical carbon dioxide is injected into the barrel. This equipment has been successfully used to produce soybean meal with lower residual oil contents than typically produced by screw pressing and with httle heat denaturation of the protein. 

Fig. 32. Typical experimental data ( + ) for an isometric protein-RNA plant virus, southern bean mosaic virus (SBMV) in its (a) compact and (b) swollen states [555]. For a given H20 buffer content, note the shift in the position of the subsidiary mimima to lower Q which accompanies the increase in the virus radius of about 10% in the swollen state. The continuous curve at each contrast is that calculated for a four-shell model of SBMV, and has been smeared to allow for neutron beam divergence and wavelength spread.

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