Microbial fermentation of carbon and nitrogen sources.

microbial nutrition requirements, all microorganisms need carbon sources, nitrogen sources, inorganic elements, water and growth materialsIf it is an aerobic microorganism, oxygen is also neededIt is very simple to prepare a medium containing pure compounds at a laboratory scale, but it is not appropriate for mass productionthe first section of the industrial fermentation mediumthe role of the fermentation medium:- meet the growth of bacteria- promote the formation of products, industrial commonly used carbon source (carbon source)1The most widely used are grain starch (corn, potato, cassava starch), starch hydrolysated to obtain glucoseConditions of use: Microorganisms must be able to secrete hydrolysis starch, pastes enzymesdisadvantages:adifficult to use, fermentation liquid is thick, generally 2.0% when added a certain alpha-amylasebThe composition is more complex, with straight chain starch and branch-chain starchadvantages:from a wide range of sources, low price, can lift the glucose effect2Glucose- All microorganisms can use glucose, but it causes a glucose effect-industrial starch hydrolysis, but the sugar solution must meet certain quality targets3Molitewaste molasses or crystalline mother liquidin the sugar industry include: sugar cane molasses (cane molasses) - high sugar, less nitrogenbeet molassesboth ingredients see P226the use of molasses attention points: in addition to the molten content, contains more impurities, adverse effects on fermentation, need to be pre-treatmentII, industrially commonly used nitrogen source (nitrogen source)1inorganic nitrogen (rapidly used nitrogen source)type: ammonia, ammonium salt or nitrate, urea characteristics: rapid absorption, but will cause changes in pH choose the appropriate inorganic nitrogen source has two layers of significance: -satisfying bacteria Growth - Stabilize and regulate the effects of pH inorganic nitrogen sources during fermentation: ammonium sulfate and ammonium nitrate Sodium nitrate 2 Organic nitrogen: Source: Some cheap raw materials such as corn syrup, soy cake powder, peanut cake powder, fishmeal, yeast leaching paste, etc Among them, corn pulp (a by-product after corn extracts starch) and bean cake powder can be both nitrogen and carbon sources complex composition: in addition to providing a nitrogen source, it also provides a large number of inorganic salts and growth factors microbes easy to use inorganic nitrogen in the early stage, the metabolism enzyme system of medium-term bacteria has been formed - organic nitrogen source The source of organic nitrogen is unstable and the composition is complex, so the effect of raw material fluctuation on fermentation should be taken into account when using organic nitrogen source , inorganic salts sulfates, phosphates, chlorides and some trace elements The inorganic salt content has a great influence on the growth of bacteria and the production of products four, growth factor micro-organisms are indispensable for microbial growth Such as amino acids, radon, radon, vitamins growth factor is not required for all microorganisms Only for some of the micro-organisms that can not synthesize these ingredients themselves is the can be less nutrients For example, glutamate production bacteria, which are carbon-derived from sugar-based raw materials, are biotin-defective (biotin auxotroph) and are derived from biotin as growth factors 1 Biotin effect: (1) mainly affects cell membrane permeability P263 (2) affects the metabolic pathways of bacteria biotin concentration sewells on bacterial growth and glutamate accumulation The concentration of biotin required for a large amount of synthetic glutamate is lower than the amount of biotin needed for the growth of bacteria, i.e the "sub-moderate amount" required for the growth of the bacteria Cause: P263, P260 (OD value) biotin overdose: bacteria multiply, do not produce or produce less glutamate biotin deficiency: bacteria growth is not good, glutamate production is also low -glutamate-producing bacteria are biotin defectal strains - to achieve the "sub-appropriate amount" required for the growth of bacteria biotin is present in animal and plant tissues and is present in a binding state with proteins Acid hydrolysis can be used separately So what raw materials can be used as biotin sources in production? 2 Agricultural and by-product raw materials for growth factors (1) corn pulp: (corn steep liquor, CSL) the most representative Although mainly used as a source of nitrogen, but contains lactic acid, a small amount of reduced sugar and polysaccharides, rich in amino acids, nucleic acids, vitamins, inorganic salts and so on Often used as a substance that provides growth factors Therefore, in a sense, the use of corn slurry for the preparation of fermentation medium is a major discovery in the fermentation industry (2) bran hydrolysis: can replace corn syrup, but protein, amino acids and other nutrients than corn pulp (3) Molite: Two types of molasses (cane molasses, beet molasses) can replace corn syrup However, the content of organic nitrogen such as amino acids is low (4) yeast: can be used with yeast paste, yeast leaching or directly with yeast powder the preparation of the second section of starch hydrolysis in industrial production, the process of starch hydrolysis for glucose (glucose) is called starch glycation, the resulting solution is called starch hydrolysis Its main sugar is glucose Depending on the hydrolysis conditions, there are still a small amount of maltose and some other dissugar, oligosaccharides and other compound sugars , the significance of starch hydrolysis sugar 1 Most microorganisms can not directly use starch (all amino acid production bacteria can not be directly used) 2 Some microorganisms can directly use starch as raw material, but must be produced by microorganisms amylase can be carried out, the process is slow, fermentation cycle is extended 3 If starch is used directly as raw material, the high temperature of the sterilization process will lead to starch clumps and a sharp increase in the viscosity of the fermentation solution , the preparation method and principle of starch hydrolysis (i) acid solution (i) acid solution (i) acid hydrolysis method acid as a catalyst, at high temperature and high pressure to make starch hydrolysis to produce glucose 1 Hydrolysis Process: Total Reaction: (C6H10O5) n-nH2O s NC6H12O6 Process: (C6H10O5) n (C6H10O5)) x - C12H22O11 - C6H12O6 starch dextrin maltose glucose H plus no selectivity to the action point, A-1, 4-glycoside bonds and A-1, 6-glycoside bonds are cut off 2 Glucose compound reaction and decomposition reaction in the hydrolysis process, due to the action of acid and heat, a part of glucose will be compound and decomposition reaction The of the starch hydrochloric acid compound reaction glucose decomposition reaction ↙↗ ↘ compound dissaccharides 5"-hydroxymethylacet , compound polysaccharides organic acid, non-ferrous substances loss of glucose 7% and 1% adverse effects: (1) reduced glucose yield (2) make it difficult to extract products and refine saccharific fluids compound reactions: glucose molecules by 1,6 glycoside bonds combined with Jackie Urco (with bitter taste), isomal maltose and other polysaccharides (composite polysaccharides) Most of the compound sugars produced cannot be used by microorganisms, making the residual sugar high at the end of fermentation decomposition reaction: the resulting 5"-hydroxymethylacet is the root cause of pigment ations, increasing the difficulty of semenizing semen How to control the occurrence of decomposition reaction and composite reaction? (1) starch milk concentration (2) acid concentration can not be too high reason P229-230 (3) temperature 3 Evaluation advantages: simple process, hydrolysis time, high production efficiency, fast equipment turnover disadvantages: (1) by-products, affecting the purity of the sugar solution, the general DE value (glucose value) is only about 90% (2) strict requirements for starch raw materials, can not use coarse starch, can only use a higher purity of refined starch DE value: dextrose (glucose equivalent) indicates the sugar content of starch sugar reduced sugar content (%) DE value , ---------- 100% dry matter content (%) the reason for the decline in the highest point of the P231 (middle) chart? (ii) enzyme hydrolysis method) the process of hydrolysis of starch as glucose with a single-minded amylase and glycosase in two steps: (1) liquefaction: converting starch into dextrin and glutamate (2) glycation with A-amylase: converting dextrin and polysaccharides into glucose with glycosase (also known as glucose amylase) so the liquefaction and glycolysis of starch are carried out under the action of enzymes, also known as double enzyme (double enzyme hydrolysis method) liquefaction (liquification) alpha-1,4 glycoside bonds inside the alpha-amylase hydrolysis substrate, can not hydrolysis alpha-1,6 glycoside bonds, generally using high temperature-resistant amylase, so that the speed of liquefaction is accelerated 85-90 degrees C starch paste and aging: because the crystalline structure of starch particles is very resistant to enzymeaction, it is necessary to heat the starch milk first, so that starch particles absorb water expansion, paste, damage the crystalline structure paste: after the starch is heated, the starch particles expand, the crystal structure disappears, contact with each other into a paste-like liquid, even if the mixing stops, the starch will not precipitate aging: the process of rearranging the pasteized starch that has broken the hydrogen bond between molecules to form a new hydrogen bond, that is, the process of recrystallization amylase is very difficult to enter the crystallization region of aging starch, we must take appropriate measures to control the aging of paste starch The degree of fluidization control (the cause of glycation after liquefaction): If the liquefaction continues, although the final product is also glucose and maltose, but: a glycosatous de-low devalue (alpha-amylase can not hydrolyse alpha-1, 6 glycoside bonds) b liquefaction at higher temperatures, liquefaction time is longer, a part of the liquefactiond starch will be.