Technology for producing recombinant proteins from the milk of farm animals
Fodder yeast. Yeast are grown on hydrolysates of waste wood and other cellulose-containing plant material, which in the hydrolysis form carbohydrates asily assimilable for microorganisms. In the technology of obtaining feed protein residues cellulose and wood industry, straw, cotton hulls, sunflower baskets, flax, corn cobs, sugar beet molasses, potato pulp, grape squeeze, brewer's grain, little decomposed peat, bard of alcohol production, waste of confectionery and dairy industries are commonly used as a raw material. Chopped plant material containing a large amount of cellulose, hemicellulose, pentosans, are subjected to acid hydrolysis under increased pressure and temperature, in the results of 60-65% polysaccharides are hydrolyzed to monosaccharides. The resulting hydrolyzate was separated from the lignin. The excess of acid used for hydrolysis, is neutralized with milk of lime or ammonia water. After cooling and settling minerals, vitamins and other substances necessary for microorganisms are added to hydrolyzate. Obtained in this way growing medium is served in fermenter , where the cultivation of yeast is conducted. For cultivation on hydrolysates of vegetative waste are most effective yeast genera are Candida, Torulopsis, Saccharomyces, which can use as a carbon source hexose, pentose and organic acids. In optimal conditions, from 1 ton of waste softwood it is possible to get 200 kg of fodder yeast.
For obtaining of feeding yeast the deep cultivation technology in special apparatus – fermenters is used. Fermenters ensure constant mixing of microbial cells suspension in the liquid medium and the optimum conditions of aeration. Operating cycle of cultivation yeast culture takes about 20 hours. By the end of the cycle culture fluid with suspended yeast cells in it is derived from fermenter, and it is served again with nutrient substrate and culture of yeast cells to new cultivation. Suspension of microbial cells derived from the fermenter is fed to a flotation unit, with which yeast biomass is separated from the culture fluid. In the process of flotation foaming of suspension occurs. In this case microbial cells float to the surface together with the foam, which is separated from the liquid phase by decantation. After settling yeast mass is concentrated by the separator. For better digestibility of yeast in the body of animals special treatment of microbial cells (mechanical, ultrasonic, thermal, enzymatic) is carried out, providing the destruction of their cell membranes. Then yeast mass is evaporated to the desired concentration and dried (moisture of the finished product should not exceed 8-10%). The dry yeast mass contains 40-60% crude protein, 25-30% of digestible carbohydrates, 3.5% crude fat, 6.7% fiber, and mineral elements, many vitamins (up to 50 mg%). By treating yeast with ultraviolet rays it is possible to enrich it with vitamin D2, which is formed from ergosterol contained in them. To improve the physical properties of the final product feed yeast is produced in granular form.
In Russia and other oil-producing countries have developed technology for production of fodder yeast from n-paraffin of oil. Yeast cells can use as sources of carbon straight-chain hydrocarbons with carbon numbers from ten to thirty. They are liquid fraction with boiling temperature of 200-320 ° C, which are isolated from its oil by distillation. Candida guilliermondii is the most effective strains of yeast for cultivation on n-paraffin oil. Isolation and drying of yeast mass is conducted approximately by the same technology as in the hydrolysis production. Dried yeast mass is granulated and used as a protein-vitamin concentrate (PVC) for animal feeding, containing up to 50-60% of proteins.
National Center for Biotechnology of the Republic of Kazakhstan developed the new technology for obtaining of microbiological protein feed for animals. Several versions of feed additives are obtained: feed yeast based on Saccharomyces cerevise, Candida tropicalis CK-4, as well as microbial L-lysine on the basis of lysine-producer Brevibacterium 92. Experiments were carried out on submerged cultivation Candida tropicalis CK-4 in fermenter using as a carbon substrate glucose in fed-batch regime. Conditions of cultivation of lysine producer in batch-mode are developed. Experimental batch of animal feed additive based on the yeast Saccharomyces cerevise (S.K.Barbasova et al., 2011) is obtained.
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