1, controlling the permeability of cell membrane by physiological means.
Biotin suboptimal amount
Mechanism: Biotin is the coenzyme of acetyl-CoA carboxylase, which is the key enzyme in fatty acid synthesis. Proper amount of biotin directly inhibits membrane synthesis or causes membrane defects.
2. Control the permeability of cell membrane through mutation of cell membrane defect.
Oleic acid deficiency and glycerol deficiency
Oleic acid is an unsaturated fatty acid with double bonds (C 18) and an important fatty acid in cell membrane phospholipids. Oleic acid deficiency can not synthesize oleic acid, which leads to cell membrane defect and increased cell membrane permeability.
The phospholipid content in cell membrane of glycerol-deficient strain is lower than that of wild-type strain, which is easy to cause a large amount of glutamic acid leakage. Even in the case of excessive biotin or oleic acid, a large amount of glutamic acid can be obtained.
Inhibition of catabolic metabolites;
The repression of catabolic products (intermediate repression) refers to the inhibition of the synthesis of many enzymes (degrading enzymes, synthetic enzymes) through substrates or their decomposition products that are quickly utilized by bacteria. According to the different decomposition products, it can be divided into carbon decomposition product repression and nitrogen decomposition product repression, such as "glucose effect" and "ammonium repression"
From the molecular level, it is the decomposition products that inhibit the activity of adenylate cyclase and reduce the concentration level of cyclic 3', 5'- adenosine (cAMP).
When the concentration of cAMP in cells is high, it binds to activated protein (CAP), and activated protein urges RNA polymerase to bind to promoter gene and start transcription. Conversely, when the intracellular cAMP level is low, it affects the binding and cannot be transcribed.
Mechanism of 1 glucose inhibiting β -galactosidase biosynthesis;
A large amount of glucose reduces the intracellular cAMP concentration. As a result, there is no combination of cAMP-CRP complex on the promoter, which makes RNA polymerase unable to combine with the promoter site and structural genes unable to be transcribed and expressed.
2 ammonium repression
The regulation of nitrogen decomposition products means that the nitrogen source (especially ammonium) quickly utilized by bacteria can inhibit the synthesis of some enzymes involved in the metabolism of nitrogen-containing compounds.
For example, in primary metabolism, it can inhibit the protease synthesis of many Bacillus.
Enzymes that are usually inhibited by NH4+ include nitrite reductase, nitrate reductase, nitrogenase, acetamidase, urease, xanthine dehydrogenase, histidine and asparaginase.
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Research progress of fermentation engineering
1. Development trend and direction of fermentation engineering technology
Fermentation engineering generally refers to the process of making or producing some products by microorganisms. Including anaerobic fermentation (such as alcohol, lactic acid, acetone butanol, etc.) and aerobic fermentation (such as amino acids, citric acid, antibiotics, etc.).
Fermentation technology is one of the earliest production technologies mastered by human beings through practice, and there are many products. Traditional foods include sauce, soy sauce, vinegar, white wine and yellow wine in the east, and beer, wine and cheese in the west. These fermented foods are skillfully made by microorganisms for thousands of years with the wisdom and experience of human beings without seeing them with their own eyes.
1.2 Application field of fermentation engineering
(1) light industry
Light industry is the earliest and most widely used field of fermentation engineering technology. This field is characterized by a large number of agricultural and sideline products (mainly starch products) for deep processing, and the types of products produced are:
① Alcohol and solvents: such as beer, liquor, fruit wine, alcohol, acetone, butanol, etc.
② Organic acids: such as citric acid, lactic acid, malic acid and itaconic acid;
③ Amino acids: such as glutamic acid, lysine, methionine, phenylalanine, etc.
④ Enzymes: such as those used in food industry, textile industry and feed industry.
⑤ Functional protein, functional lipids and functional sugars.
(2) Biomedical industry
Through fermentation engineering technology, a variety of antibiotics, vaccines and some genetic engineering drugs (such as interferon and interleukin series) can be produced.
(3) Agriculture and animal husbandry
Through fermentation engineering technology, biological pesticides, biological fertilizers, plant growth regulators, feed proteins, enzymes for feed industry and so on can be produced.
(4) Environmental protection
Fermentation engineering technology can be used for sewage treatment, toxic substance degradation, solid waste treatment and soil pollution remediation.
(5) Energy development
Through fermentation engineering technology, renewable raw materials can be used to produce fuel alcohol, biogas and microbial metallurgy.
1.3 prospect of modern fermentation engineering technology
Because compared with other industries, the fermentation industry has many advantages, such as mild reaction conditions, wide sources of raw materials, low price, less investment, quick effect and remarkable economic and social benefits. In addition, fermentation engineering technology produces a wide variety of products and is widely used. Therefore, fermentation engineering has broad development and application prospects.
In recent years, the rapid development of biotechnology has strongly promoted the development of fermentation engineering technology. The application of fermentation engineering technology is an important means to directly transform biotechnology into productivity, produce various products needed by human beings and serve the society. Therefore, the final realization of genetic engineering, cell engineering and enzyme engineering technology mainly depends on fermentation engineering technology. Therefore, modern fermentation engineering is one of the important contents of biotechnology, the only way to realize the industrialization of biotechnology, and an important industrial group full of vitality and vitality in the future economic and social development.
At present, the research of fermentation engineering technology mainly focuses on the following aspects:
(1) The combination of genetic engineering, cell engineering and conventional microbial breeding methods, supplemented by physical mutagenesis methods such as laser, ion beam and γ-ray, is devoted to breeding all kinds of excellent production strains needed by fermentation industry.
(2) Developing new fermented products with high added value and social demand.
(3) Using fermentation engineering technology to replace the production of some traditional chemical products, reducing the consumption of raw materials and energy, and reducing pollutant emissions.
(4) Research and develop new technologies, new processes and new equipment for fermentation and extraction to improve product yield and save energy and reduce consumption.
(5) Large-scale industrial fermentation production technology.
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"Screening and Identification of Bacillus subtilis Strain with High Elastase Production" I have a paper here, so I can have a look.