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Screening and breeding of microbial enzymes production

Data: 2020-11-05


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Screening and breeding of microbial enzymes production

Strains are important conditions for industrial fermentation to produce enzyme preparations. The purpose of strain breeding is to improve the characteristics of known strains or production strains to meet the requirements of industrial production. Natural breeding based on the natural variation of bacterial species, and according to the basic theories and techniques of microbial genetics, artificial methods are used to cause bacterial species to mutate or form new hybrids, and then screen to obtain mutants or hybrids according to the requirements of industrial microbiology. This is the basic content of current strain breeding.

The position of strain breeding in enzyme production is becoming more and more important. Excellent strains are not only related to increasing the yield of enzyme preparations and the utilization efficiency of fermentation raw materials, but are also closely related to increasing enzyme varieties, shortening the production cycle, and improving fermentation and extraction process conditions. 

The continuous improvement in the yield and quality of enzyme preparations is the result of continuous progress in strain breeding, fermentation and extraction, but the role of strain breeding is the first and fundamental. The improvement of fermentation medium composition and fermentation conditions can give full play to the production potential of the strain and increase the fermentation unit, but the improvement of these factors cannot leave the inherent genetic characteristics of the strain itself. 

The improvement of the extraction method can increase the recovery rate of the enzyme, but the ideal maximum recovery rate can only reach the limit of the potential yield of the strain. Therefore, the yield and quality of enzymes are mainly determined by the characteristics of the bacteria.

The screening of enzyme-producing strains is the same as the screening of other fermentation products, generally including strain collection, enrichment, strain separation and purification, and production performance identification.

1. Bacteria sample collection

Before sampling, it is necessary to investigate where the microbial enzymes production  to be screened may be distributed more, and purposefully seek for good bacteria from nature. 

For example, to isolate protein-producing bacteria, you can go to the soil or the soil where meat and fish are often stacked. Look for it in the feces of carnivores; microorganisms that secrete cellulase and hemicellulose are commonly found in fallen leaves and compost of forests; microorganisms that produce pectinase are found in spoiled fruits and vegetables; in grain and oil chemical plants Lipase strains are often easily separated from the surrounding soil, because these soils have been polluted by oil for a long time, and the microorganisms that decompose fat multiply. 

Thermophiles can secrete enzymes with high heat stability, and the enzymes secreted by alkaliphiles have the optimum pH The former is mainly distributed in hot spring water, spontaneous heat-generating compost, desert soil or similar breeding grounds, and the latter mainly exists in lime-rich places.

2. Enrichment

The so-called enrichment is to provide favorable conditions for the growth of microorganisms with ideal properties and increase their relative number in the culture. 

When the general bacterial sample contains a small amount of microorganisms to be separated, enrichment culture is beneficial to the screening of certain enzyme-producing bacteria. 

The enrichment can be achieved by controlling the culture temperature, pH or nutrient components. For example, if starch is used as the sole or main carbon source in culture, those microorganisms that are most suitable for starch metabolism under the conditions used will eventually prevail, and strains that produce amylase can be isolated on starch agar plates.

3. Strain purification and separation

Through enrichment culture, pure microorganisms cannot be obtained because the sample itself contains a wide variety of microorganisms. There are often two methods for purebred separation, namely dilution separation method and streaking method. 

In order to improve the efficiency of separation, some rapid screening techniques can be used, such as the choice of suitable medium and enzyme activity determination methods. 

When insoluble substrates (such as chitin or cell walls purified from other microorganisms) are used as the sole carbon source or supplemental carbon sources are incorporated into the culture medium, a transparent circle may appear around the enzyme-producing colony after incubation. 

However, when using a soluble substrate, the polymer needs to be precipitated or dyed to show the transparent circle; another method is to couple the substrate with a dye. The commonly used dye is blue dye such as bright blue (rema zol) And azure (a xu re).

4. The new performance test

Obtaining new isolates is only the first step in the screening of strains. The number of new isolates is often dozens or hundreds of strains, and it is necessary to further determine the performance of the new isolates. First, perform the preliminary screening work, that is, first activate the newly isolated strains, perform a shake flask test or other technical methods, eliminate most of the poorly performing isolates, and then select several strains with good performance for production performance Testing is often called re-screening work. After dozens of re-screening, 1-2 strains of practical value were determined.

The Paragon bio-engineering company provides high-quality fermentation equipment and corresponding auxiliary equipment to help customers produce high-quality lipase and other enzyme preparations.