BIOTECHNOLOGY - V. H. Gerasymenko - 2006

Part II. Special Biotechnologies

Chapter 21. BIOTECHNOLOGY OF PROTEIN PRODUCTION

21.1. PRODUCTION OF SINGLE-CELL PROTEINS

The term "Single-Cell Protein" (SCP) was first coined in the 1960s to refer to microbial Proteins produced by mass cultures of Yeasts or Bacteria used for human consumption or animal feed. The advantage of biotechnological protein production is that it is independent of weather and climate conditions, requires no arable land, is highly intensive, and is easily automated.

Microorganisms acting as protein producers exhibit a very high rate of biomass accumulation, which is 500–5000 times higher than that of plants or animals. Microbial Cells are capable of accumulating substantial amounts of protein (yeasts — up to 60%, bacteria — up to 75% by dry weight). The protein content in the dry matter of microbial biomass can range from 19 to 90% (Table 21.1). Due to the high Specificity of microorganisms, microbiological production avoids multi-stage processes, and Biosynthesis itself proceeds under mild conditions at a Temperature of 30-45 ^oC, pH 3-6, and a pressure of ~ 0.1 MPa; it is less labor-intensive compared to agricultural production and organic Protein Synthesis.

Microorganisms as protein producers also have the advantage of being able to utilize A wide variety of substances as substrates, most of which are waste products from other industries. Their raw material sources include liquid petroleum paraffins, natural gas and biogas methane, methyl and ethyl alcohols, plant raw Materials, agricultural and industrial wastes and by-products (straw, sunflower seed husks, flax and hemp shives, tops, sawdust, wood shavings, Cellulose, molasses, whey, manure biomass, etc.).

Class="center">Table 21.1.

Protein content in cells of certain bacteria and Fungi, % of dry mass

(Yelinov N.P., 1995)

Yeasts, bacteria, microscopic fungi, and unicellular Algae are most commonly used as microbial producers for protein synthesis. The Diversity of Nutritional types and species composition of microorganisms makes it possible to select the most suitable raw materials for Biosynthesis and the best protein-producing strains.

Single-cell organisms are characterized by a high protein content ranging from 40 to 80% or more. Single-cell protein contains all (10) Essential Amino Acids (Table 21.2) and is rich in Lysine, which determines its biological value. Supplementing lysine-deficient plant feed with single-cell biomass helps bring its amino acid profile closer to optimal. A drawback of single-cell biomass is the deficiency in Sulfur-Containing Amino Acids, primarily Methionine. Its concentration in single cells is approximately half that found in fish meal; however, soy protein shares this same limitation.

Protein-rich single-cell biomass is assimilated by farm animals with high efficiency. For instance, 1 ton of fodder Yeast yields 0.4–0.6 tons of pork, up to 1.5 tons of poultry meat, and 25–30 thousand eggs, while saving 5–7 tons of grain. This is of great economic significance, given that nearly 80% of the world's agricultural land is dedicated to feed production.

Table 21.2.

Essential amino acid content in microbial, plant, and animal proteins, % (Khazin D.A., 1987).

Selective breeding allows for the Isolation of the most productive microorganism strains capable of efficiently utilizing novel raw material sources. Recombinant DNA technologies offer vast opportunities, enabling the improvement of existing producers or the creation of entirely new ones.

All these advantages have driven the rapid development of microbial protein technology, which constitutes the largest-tonnage sector in biotechnology. By 1980, the Soviet Union had already become the world's leading producer of single-cell proteins, with national production reaching 1.1 million tons per year.