It is used for the growth, reproduction and synthesis of bacteria
fermentationculture mediumIt is used for the growth, reproduction and synthesis of bacteria.It not only makes the seeds grow rapidly after inoculation, but also reaches a certainmyceliumThe concentration should also enable the growing bacteria to quickly synthesize the required products.Therefore, it is required that the composition of fermentation medium should be rich, complete, carbonnitrogen sourceit is to be noted thatQuick resultsMatch with delayed nutrition, use less quick nutrition and more delayed nutrition;Also consider appropriateCarbon nitrogen ratio, plusBufferStable pH value;And it also needsgrowth factorAnd the elements, precursors andacceleratorEtc.In addition to the elements and compounds necessary for the growth of bacteria, there are also specific elements, precursors and promoters required for the product.But if growth andbiosynthesisTotal required by the productcarbon sourceWhen the concentration of nitrogen source, phosphorus source, etc. is too high, or the requirements for the best conditions required in the growth and synthesis stages are different, the medium can be fed in batches.
Chinese name
Fermentation medium
Purpose
It is used for the growth, reproduction and synthesis of bacteria
Composition
Carbon source, nitrogen source, inorganic salt and trace element, growth factor
Not all microorganisms are necessary, but for some microorganisms that cannot synthesize these ingredients themselvesNutrients。
For example, sugar raw materialscarbon sourceOfglutamateAll production bacteria areBiotinDefective type, based on biotingrowth factor。Also as usedLysineProducing bacteriumAlmost all of them are glutamic acid producing bacteriaMutant, which are biotin deficient, and also some amino acids such asHomoserineIt needs biotin and some amino acids as growth factors.
Principles to be followed in preparing culture medium
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Microbialculture mediumIt usually refers to the artificial preparation suitable for microbial growth and reproduction, or accumulationMetabolitesThe nutrient matrix of.Broadly speaking, any medium or material that supports the growth and reproduction of microorganisms can be used as the culture medium of microorganisms.An appropriate medium formula has a great influence on the yield and quality of fermentation products.
Different culture media can be available for different microorganisms and different nutritional requirements.But their preparation must follow certain principles.
① Nutrients should meet the needs of microorganisms.Microbes of different nutritional types have different requirements for nutrition, so they should be prepared according to different requirements of bacteria for various nutrient elements.
②NutrientsThe concentration and ratio of shall be appropriate.The nutrient concentration is too low to meet the needs of microbial growth;If the concentration is too high, it will inhibit the growth of microorganisms.
When designing the ratio of the culture medium, the interaction between the components in the culture medium should also be avoided, such asPeptone、yeast extractWhen phosphate is contained in the mediumMagnesium ionPrecipitation occurs during heating;At high temperature, reducing sugar will also interact withproteinOr amino acid interaction to produce brown matter.
③ The physical and chemical conditions are suitable.PH: all kinds of microorganisms have their own growth and reproductionOptimum pH, bacteria 7.0~8.0,Actinomycetes7.5~8.5, yeast 3.8~6.0,mould4.0~5.8.For specificMicrobial strain, have their own specific optimal pH range, and sometimes greatly break through the above limits.During the growth and reproduction of microorganisms, they will produce metabolites that can change the pH of the culture medium. In particular, many microorganisms have strong acid production capacity. If they are not properly adjusted, they will inhibit or even kill themselves.When designing the medium, the pH adjustment ability of the medium should be considered.Generally, it should be addedBufferorCaCO3To stabilize the pH of the medium.
Others: others of culture mediumPhysical and chemical indicators, such asWater activity、osmotic pressureIt will also affect the cultivation of microorganisms.When preparing the culture medium, it is usually unnecessary to measure these indicators, because the optimization of various components and their concentrations in the culture medium has indirectly determined the water activity and osmotic pressure of the culture medium.In additionRedox potentialThere are also different requirements.
④ Culture objective: The composition of the culture medium directly affects the culture objective.When designing the culture medium, we must consider whether to cultivate the cell or accumulate the metabolites of the cell;Is it laboratory culture or large-scale fermentation.
Used for culturing bacteriaSeed culture mediumThe nutrient composition should be rich, and the nitrogen source content should be high, that is, the carbon nitrogen ratio should be low;On the contrary, the nitrogen source of the fermentation medium used to accumulate a large number of metabolites should be slightly lower than that of the seed medium;Of course, if the target product isNitrogenous compoundSometimes, the nitrogen source content of the culture medium should be increased.
When designing the culture medium, special consideration should also be given to the metabolitesPrimary metabolites, orSecondary metabolites。If it is a secondary metabolite, whether special elements (such asVitamin B12Medium Co) or specialPrecursor substances(e.g. productionPenicillin GShould be addedPhenylacetic acid）。When designing culture media, especially for large-scale fermentation production, we should also pay attention to the source and price of culture media componentsPreferenceMedium with wide source and low price.
