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Breeding of high-yield strains

Data: 2020-11-08

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Breeding of high-yield strains

Generally, the bacterial strains isolated from nature have a low concentration of economically valuable products and cannot be used in industrial production, so we must try to improve the production capacity of the bacterial strains. 

Although suitable medium and culture conditions can be selected, the effect achieved is not significant because the cell's own synthesis ability is limited. Because the potential production capacity of cells is controlled by genetic genes, only by changing the gene structure can the internal synthesis level of cells be improved. 


Using methods such as mutagen mutation or gene recombination to screen cells with changes in gene structure and increased synthesis levels is a commonly used selection method, and it is also a more effective and successful method.

1. Mutation breeding

Mutagens of physical and chemical factors are commonly used. These mutagens mainly cause changes or damage to the nuclear DNA and produce mutant strains, from which the enzyme-producing strains with positive mutagenic effects are obtained. 

This is a method of random screening of mutants. The selection of mutagen, what dosage and how to judge the mutagenic effect are some of the frequently encountered problems. 

Generally speaking, there are no mutagens that can specifically induce high yields. The basic basis for selecting mutagens is the microbial material itself. 


However, long-term scientific experiments have provided us with the experience of mutagenesis: 

For example, for vegetative cells in the vigorous growth period, both physical and chemical mutagens can be used; if spores or other resting cells are used as materials, they should be selected directly Mutagens that act on genetic material, such as ionizing radiation, nitrous acid, etc.; it is also believed that constantly changing mutagens is better than using a single mutagen; combined treatment of several mutagens is more effective than a common mutagen it is good. 


In addition, the fatality rate and the mutagenic effect, especially the positive mutation rate, do not have a parallel relationship, but it can be used as a corroboration of the mutagenic effect. 

If the lethality rate is very low, it should be considered whether the dosage used and the conditions after treatment are appropriate. The lethality that causes mutagenic effects is different for different mutagens. 

For example, submineral guanidine is a highly effective The mutagenic agent has a better mutagenic effect when the lethality rate is low (less than 50%), and the positive mutagenic effect of ultraviolet or ionizing radiation is higher when the lethality rate is higher (above 95%).

2. Genetic recombination breeding

Gene reconbination refers to the process of forming a new combination of genes, commonly known as gene recombination. The traits of the new combination gene are different from the original gene, that is, the cell of the recombinant gene can show genetic traits different from the parent strain, and the cell of this genetic recombination is a variant. 

In prokaryotic cells and eukaryotic cells, the genetic material that determines gene replication and gene function is deoxyribonucleic acid (DNA), while the genetic material that functions in viruses can be either DNA or ribonucleic acid (RNA). 

Gene recombination The mechanism is that the composition and structure of genetic material change, causing cell physiological and metabolic changes.

There are three types of gene recombination technology:

(1) Cell hybridization technology. Cell hybridization technology is a method of using different kinds of cells to join each other to exchange chromosomes to obtain genetic variants of gene recombination.


(2) Por top last fusion technology Many important incomplete fungi, such as Penicillium and yeast, lack their own hyphae fusion ability, so their somatic cell recombination is limited, even if they are used " The “forced heterokaryotic mycelium” method, in which the fusion of complementary auxotrophic hyphae is carried out in a basic medium, is not easy to be completely successful. 

Both intra-genus and intra-specific hybridization are very difficult, but if the cell wall is broken and the naked protoplasts fuse, it may be much easier to achieve the reorganization of genetic material, including eukaryotic and prokaryotic cells.


(3) Recombinant DNA technology Recombinant DNA uses plasmids, restriction enzymes and DNA polymerases to construct heterologous DNA technology in vitro. 

This technology is very useful for easy manipulation of genes and the construction of recombinant DNA molecules that never occur in nature. 

If the recombinant DNA is a plasmid, the artificially synthesized plasmid can be implanted into another bacterial cell (called the host) using transformation experiments, and it can replicate. 

If the gene of the synthetic plasmid can be expressed in the host cell , This is a brand new phenotype. 

In recent years, in the field of enzyme preparations, the use of recombinant DNA technology to obtain high-yielding strains has become more and more common, and new technologies such as DNA shuffling have emerged.


The Paragonbio-engineering company provides high-quality fermentation equipment and corresponding auxiliary equipment to help customers produce high-quality enzyme preparations.