The principle of microbial fermentation preparation medium

1, choose the right nutrientsin general, all microorganisms need to contain carbon sources, nitrogen sources, inorganic salts, growth factors, water and energy, but because of the complex types of microbial nutrition, different microbial needs for nutrients are not the same, so first of all according to the nutritional needs of different microorganisms to prepare a targeted mediumSelf-supporting microorganisms can synthesize complex organic matter such as sugar, lipids, proteins, nucleic acids, vitamins, etcfrom simple inorganics, so the medium of self-supporting microorganisms can (or should) consist of simple inorganicsFor example, the cultureable self-supporting sulfur isobacteria, in the preparation process of the medium is not specifically added to other carbon source substances, but rely on air and water-soluble CO2 to provide carbon sources for sulfur iloby bacteriaculture other self-supporting microorganisms are similar to the above-mentioned medium composition, but the energy material has changedFor light-energy self-supporting microorganisms, in addition to the need for various types of nutrients, but also need light to provide energyThe culture of hetero-culture microorganisms needs to add organic matter to the medium, and the nutritional requirements of different types of heterotrophic microorganisms vary greatly, so their media composition is also very differentFor example, the culture of Ecoli is relatively simple, and some hetero-culture microorganisms have very complex components, such as enterocosis cyllon spout sphiny, if the preparation of culture of its synthetic medium, the need to add up to 33 growth factors in the medium, so it is usually used natural organic matter to provide it with the growth factors needed for growthin terms of the main types of microorganisms, there are bacteria, linebacteria, yeast, mold, protozoa, algae and viruses, the need to grow them different mediaIn the laboratory commonly used beef paste protein medium (or ordinary broth medium) culture bacteria, with Gao's No1 synthetic medium culture culture line bacteria, culturey yeast generally with malt juice medium, it is the malt powder mixed with 4 times water, in 58 to 65 degrees C conditions insulation 3 to 4 hours to complete lysic, adjust the concentration of sugar liquid to 10 Bahrain, after boiling with a boiling yarn, Malt powder is complex in composition and can provide enough nutrients for yeast, while cultured mold is generally used in Chas synthetic mediaprotozoa can also be cultured with medium, some protozoa need more nutrients, such as the pear-type tetramembrane pyriformis medium contains 10 amino acids, 7 vitamins, ostrich, urine and some inorganic salts, and some amoeba can grow in the simpler protein brothMost algae can use light energy, only CO2, water and some inorganic salts can grow, while some species of algae, such as Euglena, can grow with organic matter in dark conditionsSome algae need to be added to the medium with soil immersion and can be used directly when cultivating marine algae, but if marine algae need to be cultured with synthetic media in special circumstances, it is necessary to add various salts contained in the sea water to the medium2, nutrient concentration and matching appropriate the concentration of nutrients in the medium is appropriate when the micro-organisms can grow well, nutrient concentration is too low can not meet the normal growth of microorganisms need, when the concentration is too high may inhibit microbial growth, such as high concentrations of sugar, inorganic salts, heavy metal ions, not only can not maintain and promote the growth of microorganisms, but play a role in inhibiting or sterilizing In addition, the concentration ratio between the nutrients in the medium also directly affects the growth and reproduction of microorganisms and/or the formation and accumulation of metabolites, in which the carbon-nitrogen ratio (C/N) has a greater impact Strictly speaking, the carbon-nitrogen ratio refers to the molar ratio between carbon and nitrogen in a medium and sometimes to the ratio of reduced sugar to crude protein in the medium For example, in the process of producing glutamate using microbial fermentation, when the ratio of medium carbon nitrogen is 4/1, the bacteria multiply in large numbers and accumulate less glutamate, and when the medium carbon-nitrogen ratio is 3/1, the germion reproduction is inhibited and the production of glutamate increases significantly For example, in the production process of antibiotic fermentation, the growth of bacteria and the synthesis of antibiotics can be controlled by controlling the ratio between the quick-acting nitrogen (or carbon) source in the medium and the source of the late-acting nitrogen (or carbon) 3, control pH conditions the pH of the medium must be controlled within a certain range to meet the growth and reproduction of different types of microorganisms or produce metabolites The most appropriate pH conditions for the growth and reproduction of various microorganisms or the production of metabolites vary, in general, bacteria and linebacteria are suitable for growth in the pH7 to 7.5 range, yeast and mold usually grow in the pH4.5 to 6 range It is worth noting that in the process of microbial growth and reproduction, due to the decomposition and utilization of nutrients and the formation and accumulation of metabolites, will lead to changes in the medium pH, if the culture pH conditions are not controlled, often lead to microbial growth rate or/and metabolite yield reduction Therefore, in order to maintain the relative constant ity of the medium pH, the pH buffer is usually added to the medium, and the commonly used buffer is a mixture of one-hydrogen and dihydrophosphates (e.g K2HPO4 and KH2PO4) K2HPO4 solution is alkaline, KH2PO4 solution is acidic, the two substances of the ig molecular mixture solution pH of 6.8 When the accumulation of acid in the medium leads to an increase in H concentration, H and weak alkaline salts combine to form a weak acidic compound, the medium pH will not be excessively reduced, if the OH-concentration in the medium increases, OH-combined with weak acidic salts to form a weak alkaline compound, the medium pH will not be excessively elevated the K2HPO4/KH2PO4 buffer system can only be regulated within a certain pH range (pH6.4 to 7.2) Some microorganisms, such as lactic acid bacteria can produce a large number of acids, the buffer system is difficult to act as a buffer, at this time can be added to the medium insoluble carbonate (such as CaCO3) to adjust, CaCO3 is insoluble in water, will not make the medium pH excessive rise, but it can constantly neutralize the acid produced by microorganisms, while releasing CO2, the medium pH control within a certain range there are some natural buffering systems in the medium, such as amino acids, peptides, proteins are both sex estots, but also play the role of buffer