Crude protein microbial

The used BSG hydrolyzate conqjosition is shown in Table 2. It has approximately 26 g F of monosaccharides and a low level of microbial inhibitors, specially aliphatic acids, and furan derivatives compared to similar hemicellulosic hydrolyzates used for SCP production, e.g., eucalyptus wood [28] and sugar cane bagasse [7,8]. Also, it has a low content of phenolic compounds. Crude protein has a concentration of about 1.2 g F. Much of this nitrogen (about half) is in ammonia form, the rest as amino acids (data not shown). 

The chemical nature of crude protein in feedstuffs is the primary factor determining how rapidly it is degraded to ammonia or escapes microbial degradation. To compare feedstuffs, feed nitrogen can be divided into NPN, true protein, and unavailable fractions, which Pichard and van Soest (1977) labeled as the A, B, and C fractions, respectively (Fig. 18.3). The A fraction is rapidly attacked by rumen bacteria and converted to ammonia. Approximately 20% of the crude protein in SBM is in the A fraction and is degraded in the rumen at a rate of 300%/h (NRC, 1996). In contrast, a more undegradable protein source like distillers grains has 6% of the crude protein in the A fraction. 

The nitrogen value of feed materials represents the quantity of amino acids from dietary and microbial origin absorbed in the digestive tract It is expressed in digestible crude protein for the horse, called MADC (INRA, 1984 INRA, 1990 Tisserand and Martin-Rosset, 1996). 

Microbial protein contributes towards satisfying this demand. The yield of microbial crude protein is related to the energy available to the rumen microorganisms in terms of fermentable metabolisable energy ... 

MEferm is assumed to be 0.1 ME for silages and 0.05 ME for brewery and distillery by-products, and MEfat is 35 MJ/kg. The assumption made here for silage must be suspect. The major fermentation product in well-made silages is lactate, and there is evidence that several rumen bacteria, notably Megasphaera elsdenii (see Table 8.3 in Chapter 8), are able to utilise lactate with the production of propionate. The microbial crude protein yield (g) is calculated as follows ... 

The proportion of the microbial crude protein present as true protein is assumed to be 0.75 and the true digestibility to be 0.85, and the contribution of microbial protein (DMP) to the truly absorbed amino acids is ... 

Finally, to convert microbial DM to microbial protein, it is assumed that rumen microbes contain 100 gN/kg DM and that microbial crude protein consists of 160 g N/kg DM, providing a microbial crude protein content of 625 g/kg microbial DM. Microbial crude protein is converted to digestible microbial true protein by multiplying by 0.6375, as described earlier. 

Traditional fermenters with microorganisms are used to obtain products in most of these applications. A typical industrial fermenter is constructed from stainless steel. Mixing of the microbial culture in fermenters is achieved by mechanical stirring, often with baffles. Airlift bioreactors have also been applied in the manufecturing of food products such as crude proteins synthesized by microorganisms. Mixing and liquid circulation in these bioreactors are induced by movement of an injected gas (such as air). 

McNeill DM, Komolong M, Gobius N, Barber D (2000) Influence of dietary condensed tannin on microbial crude protein supply in sheep. In Brooker JD (ed) Tannins in livestock and human nutrition, ACIAR Proceedings number 92. Australian Centre for International Agricultural Research, Canberra... 

The source of a protein is generally tissue or microbial cells. The first step in any protein purification procedure is to break open these cells, releasing their proteins into a solution called a crude extract. If necessary, differential centrifugation can be used to pre-... 

Conventionally, the first attribute known about an enzyme used to be its function, usually in a crude extract. This property was screened for in microbial cultures or in tissue samples. The crude extract was then purified to homogeneity and the protein subjected to biochemical studies to learn of its pH and T profiles, its pi and subunit composition, catalytically important residues, and other properties. Proteolytic digestion of the protein with subsequent Edman degradation led to the primary sequence, but no information on the secondary structures such as a-heli-ces and [5-sheets or the folding in three dimensions of the polypeptide chain. The primary sequence could have been used to deduct the gene sequence but, with the degeneration of the code, several possibilities for certain amino acids occur, which makes prediction of the gene sequence a risk. 

Four major objectives in the chemical modification of food proteins are (a) the blocking of deteriorative reactions (b) improvement of physical properties (c) improvement of properties related to acceptability, such as flavor and color and (d) improvement of nutritional properties. Modifications also may aid the physical separation from crude animal, plant, or microbial material and may inactivate or remove relatively small amounts of undesirable substances. There is considerable interest among food technologists in chemical modification as a means of changing the physical characteristics of proteins to give, e.g., better solu-... 

Phospholipid contents are very similar (about 1 to 2% dry matter) in microbial, plant, and animal tissues. If the content of neutral lipids is low, phospholipids may account for 20 to 40% of lipid extracts (e.g., in marine invertebrates). In egg yolk, 23% of the total lipids are phospholipids and other polar lipids (Kuksis, 1985). On the contfary, in adipose tissue or in oilseeds, the content of phospholipids is between 1 and 3% of total lipids. In oilseeds rich in oil (such as in rapeseed), it is lower than in oilseed with lower oil content (such as soybeans) when the results are expressed in % oil content, but much the same if the content is expressed in terms of total dry matter of the oilseed. Phospholipids are mainly extracted by nonpolar solvents, together with other lipids, and are obtained in the crude oil. However, in the original material, phospholipids are primarily bound to proteins (e.g., in membranes) or may be bound to other tissue components for example, phospholipids interact with chlorophyll pigments, where they may form complexes between the magnesium ion of the chlorophyll molecule and the phospho group of the phospholipids. 

---