Organic nitrogen source and regulation of amino acid fermentation process
April 22, 2020
Amino acids are the basic substances that constitute an organism, and they play an extremely important role in life activities. The main functions of amino acids are to constitute proteins, convert to sugar or fat, nitrogen balance, provide one-carbon units necessary for the synthesis of nucleotides, and participate in the synthesis of important active substances such as hormones and vitamins.
Amino acids can be widely used in the fields of food, medicine, feed, cosmetics, polymeric materials and agriculture. They have always been used as bulk fermented biological products and have typical representative significance.
How the organic nitrogen source plays a regulatory role in the metabolic flow of amino acid fermentation and how it is regulated have always been a key topic in the amino acid fermentation industry as well as important practical significance for guiding fermentation production.
Most L-amino acids are made by biological fermentation, of which L-glutamic acid, L-lysine, and L-threonine are 3 types of amino acids with the largest production. During the fermentation of these 3 amino acids, the substrate conversion rate, acid production level, and extraction yield are all at high level, and the technology is relatively mature. The remaining small varieties of amino acids currently has deficiencies in the acid production level or conversion rate, which has a lot of space for development.
Here, we list the specific problems existing in the fermentation production of small varieties of amino acids:
1. Low acid production capacity and poor stability of strains;
2. The fermentation control technology and extraction process are relatively backward and the cost is relatively high;
3. Large consumption of resources and energy and heavy environmental pollution;
4. Fewer innovative varieties and weak product development capabilities.
The regulation of fermentation process is very important to improve acid production. For most amino acids, the regulation of nitrogen source is an important method to improve acid production.
Nitrogen sources refer to nutrients that constitute a source of nitrogen in microbial cells and metabolites, and are mainly divided into inorganic nitrogen sources and organic nitrogen sources.
Commonly used organic nitrogen sources are soybean meal and its hydrolysate, peanut cake powder and its hydrolysate, corn steep liquor and dry powder, animal origin peptone, soy peptone, yeast powder, yeast peptone, yeast extract, etc. However, downstream products such as soybean meal and peanut cake powder have poor processing control and the cost of raw materials of them keep increasing. Animal-derived deep-processed products are impacted by several factors such as product fluctuations and animal sources. There is an urgent need to expand the range of raw materials and develop cost-effective raw materials.
Yeast extract, from primary grown baker's yeast, has good performance and stable quality. It is rich in free amino acids, vitamins and nucleotides, which is conducive to the absorption and utilization of microorganisms.
The main role of nitrogen source in the process of amino acid fermentation includes:
1. Participate in the synthesis of nitrogenous substances such as bacterial proteins and nucleic acids;
2. The amino source of synthetic amino acids;
3. Adjust the pH value to form amino acid ammonium salt.
The inorganic nitrogen source has stable quality, single composition, and can be quickly used, but lacks nutrients. Organic nitrogen source is rich in nutrients and complex in composition, rich in protein, peptides, free amino acids, sugar, fat and growth factors, which can promote the rapid growth of microorganisms, shorten the fermentation period, and lengthen the acid production period.
The organic nitrogen source can regulate the growth rate and acid production rate of the bacteria. For example, the free amino acids in yeast extract and corn steep liquor are directly used by bacteria, which is conducive to the growth of the bacteria. However, nitrogen in peptone mainly exists in the form of large-molecule protein, which needs to be further degraded into small-molecule peptides and amino acids before being used. Its utilization rate is slow, but it is conducive to the formation of metabolites.
By controlling the ratio of the fast-released nitrogen source and the slow-released nitrogen source, the coordination of the growth period and metabolic product formation period can be controlled to achieve the target of increasing yield. From the perspective of stability and being easily used by microorganisms, yeast, especially baker's yeast, is the best organic nitrogen source. Because it belongs to microorganisms as well, the nutritional structure is closer to microorganisms, and there is no transgenic and Diseases, allergens and other issues, so it is a kind of safe, stable, efficient and clean organic nitrogen source for fermentation and culture media.
Senior manager of Angel Yeast APAC Division
About Angel Microbial Nutrition：
Angel YE, rich in protein, amino acids, peptides, nucleotides, B vitamins and trace elements. With the advantages of having no allergic source and being non-transgenic, high efficiency and stable quality, Angel YE are widely applied in the biological laboratories and industrial-scale fermentation, promoting the product safety and technical progress in the global fermentation industry.
Angel Yeast Company is a high-tech listed company specializing in yeast and biotech. Product business covers Yeast and Baking, Yeast Extract-Savoury, Nutrition & Health and Biotechnology fields. It is one of the world's leading companies in the yeast industry. Angel has 12 holding subsidiaries and provides products and services for more than 150 countries and regions.
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