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Fermentation Engineering
This is a mind map about fermentation engineering, with a detailed introduction and comprehensive description. I hope it can help interested friends learn.
Edited at 2023-11-24 01:30:57
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Fermentation Engineering
- bacteria
This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
- Plant asexual reproduction
This is a mind map about plant asexual reproduction, and its main contents include: concept, spore reproduction, vegetative reproduction, tissue culture, and buds. The summary is comprehensive and meticulous, suitable as review materials.
- Reproductive development of animals
This is a mind map about the reproductive development of animals, and its main contents include: insects, frogs, birds, sexual reproduction, and asexual reproduction. The summary is comprehensive and meticulous, suitable as review materials.
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- Outline
Fermentation Engineering
concept
A biotechnology system that utilizes the growth, reproduction and metabolic activities of microorganisms and uses modern chemical technology to mass-produce useful substances.
Also known as: Microbial Engineering
Classification
solid fermentation
Microorganism → wet solid medium → fermentation process of growth, reproduction and metabolism.
Features
advantage
The culture medium is simple and comes from a wide range of sources
The fermentation process does not require strict aseptic operation
Ventilation for oxygen supply and temperature control
Fermentation residue disposal is simple
Conidia can be stored for long periods of time and can be reused.
The culture medium, bacterial growth, absorption of nutrients, and secretion of metabolites are uneven everywhere.
shortcoming
Detection and control of fermentation parameters are difficult
Difficult to continuously and automatically
High labor intensity, large floor area, easy to contaminate with miscellaneous bacteria
liquid submerged fermentation
Development history
natural fermentation period
First generation microbial fermentation technology ——Establishment of pure fermentation
Turning point 1: pure fermentation
Leeuwenhoek: Microscope → Microorganism
Pasteur: alcoholic fermentation ← yeast
Koch: Pure culture technique of bacteria
Second generation microbial fermentation technology ——In-depth cultivation technology
Turning point 2: Aeration and mixing technology
penicillin
Turning point 3: Metabolically controlled fermentation technology
artificial mutagenesis
Turning point 4: Change of fermentation raw materials
The earliest fermentation production of food substitutes using non-carbohydrate as raw materials: SCP (single cell protein)
Third generation microbial fermentation technology ——Construction of genetically engineered bacteria
Turning point 5: Construction of genetically engineered bacteria
Genetic engineering technology & cell fusion technology
fermentation medium
Type of culture medium (according to usage)
slant medium
seed culture medium
fermentation medium
Preparation of culture medium
Use of carbon sources
molasses
Crystallization mother liquor during sugar production
By-products of the sugar industry
More impurities → need pretreatment
Glutamic acid fermentation → pretreatment to remove biotin
glucose
All microorganisms can use
cause glucose effect
starch
Can relieve glucose effect
Use of nitrogen source
Inorganic nitrogen source
type
Ammonium salt
Nitrate
ammonia
Features
Microorganisms absorb quickly → available nitrogen
Physiological acid/alkaline substances
Inorganic nitrogen source (nitrogen source) → bacterial utilization → microbial physiological function (metabolism) → formation
Choosing a suitable inorganic nitrogen source has two meanings
Satisfy bacterial growth
Stabilize & adjust pH of fermentation process
organic nitrogen source
source
Complex ingredients
Provide nitrogen source
Provide a large amount of inorganic salts & growth factors
precursor
Added to the fermentation medium → biosynthetic process: directly bound to the product molecules → substances that greatly increase the yield of the product.
Serine: Glycine; Penicillin Fermentation medium: Phenylacetic acid
product accelerator
An additive that is not a necessary nutrient for cell growth & is not a precursor, but can increase production when added.
Mode of action
growth factors
Delayed bacterial autolysis
Change metabolic pathways
Decrease respiration
Improve ventilation effect
Reduce product concentration
Optimization of culture medium
experiment method
single factor test
multifactorial test
Uniform design
orthogonal experimental design
response surface analysis
Example
Preliminary identification of possible culture medium components
Select the appropriate carbon source & concentration through single factor experiment
Determine nitrogen source, inorganic salts & concentration through single factor experiment
Fermentation results of improved culture medium
Sterilization of media
Thermal death kinetics of microorganisms
Logarithmic residue law
Culture medium: Moist heat sterilization → The rate at which microorganisms in the culture medium die due to heat (denaturation of proteins in the microorganisms) is directly proportional to the number of remaining microorganisms.
K value (specific thermal death rate constant)
Influencing factors
Types and existence of microorganisms
Sterilization temperature
The larger the K value↑, the easier it is for microorganisms to die
Degree of sterilization
Microbial residue: N=10^-3/can
After sterilization 10^3 times, the chance of surviving a viable spore is 1 time.
Sterilization temperature & sterilization time
The relationship between K value and temperature
K changes with temperature
Nutrients are destroyed by heat
Thermal sterilization of culture medium → miscellaneous bacteria die & culture medium: unstable components are destroyed by heat
Can be regarded as: first-order reaction
The relationship between Kd value & heating temperature
The decomposition rate constant Kd value varies with substance type & temperature
Eg. Vitamins are most easily destroyed and have the highest Kd value.
Comparison of thermal killing of bacteria & thermal destruction of nutrients
Effect of activation energy on reaction rate and sensitivity to temperature changes
For reactions with large activation energy, the reaction rate changes greatly with temperature.
The activation energy is very small, and the reaction rate changes very little with temperature.
Important conclusions on sterilization kinetics ——High temperature short-term sterilization
In a reaction with a large activation energy, the reaction rate changes greatly with temperature; in a reaction with a small activation energy, the reaction rate changes slightly with temperature;
The ΔE of the thermal destruction reaction of bacterial spores is very high, while the ΔE of the thermal destruction reaction of most nutrients is very low;
Therefore, increasing the sterilization temperature will accelerate the death rate of bacterial spores, thus shortening the sterilization time;
Since the ΔE of thermal destruction of nutrients is very low, increasing the temperature can only slightly increase the thermal destruction reaction rate. However, due to the significant shortening of sterilization time, the amount of destroyed nutrients is greatly reduced;
Both: rapid sterilization
It can also: effectively preserve the nutrients in the culture medium.
Operation method
Batch sterilization
process
heating up
Insulation
cool down
All in: Fermentation tanks
Sterilization: mainly achieved during the heat preservation process
Continuous sterilization
step
heating
Heating facilities
Insulation
Insulation facilities
cool down
Cooling facilities
Sterilization: Prepare the culture medium → transport it to culture medium devices such as fermentation tanks at the same time
Compare
Fermentation strains and their expanded culture
strain
Require
The cost of training is not high
Culture conditions are easy to control
Fast growth
Bacteria are not prone to mutation & degradation
Safe and highly resistant
Breeding, conservation and rejuvenation
natural selection
mutation breeding
cross breeding
protoplast fusion
genetic engineering technology
See Microbiology, Genetic Engineering, Cell Engineering section
Expanded culture of bacterial strains
concept
The purpose of seed expansion
Inoculum size requirements;
Domestication of bacterial strains;
Shorten fermentation time and ensure production level.
Types and methods of seed expansion
Static culture & aeration culture
Solid culture & liquid culture
Shallow culture & deep culture
liquid submerged fermentation Seed expansion and cultivation process
laboratory stage
No need for seed jar×
Production workshop stage
Seed culture is carried out in seed tanks√
Microbial fermentation equipment
type
Aerobic fermentation equipment
liquid
Mechanical stirring type
air lift
Self-aspirated
solid
Ventilated koji making pit
pile of music
Anaerobic fermentation equipment
liquid
Fermentation tank, fermentation tank
solid
Wine cellar, fermentation tank
Mechanically stirred and ventilated fermentation tank
tank
Carbon steel/stainless steel
mixer
Break bubbles, accelerate and increase dissolved oxygen; accelerate nutrient and heat transfer.
Baffle
Prevent the formation of vortex in the center of the liquid surface and enhance its turbulence and dissolved oxygen mass transfer.
Change the flow direction of fermentation liquid and promote the combination of gas and liquid
Defoaming device
Fermentation liquid: Contains protein and other foaming substances → Fermentation: Easy to produce foam → Severe foaming → Fermentation liquid overflows with exhaust gas & increases the chance of bacterial contamination.
Aerobic fermentation production Two defoaming methods
① Chemical defoamer
②Mechanical defoaming
Shaft seal
The gap between the tank top/tank bottom & shaft → seal to prevent leakage & contamination of bacteria
Coupling
Upper and lower mixing shaft → strong rigid connection
air distribution device
Blow in sterile air and distribute the air evenly
heat exchange device (heat exchanger)
Heating, disinfection, sterilization, cooling of fermentation medium & can adjust the temperature during fermentation process
Air lift fermenter (ALR)
Internal circulation type
External circulation type
Self-spray fermentation tank
Mechanically stirred self-spray fermentation tank
Jet self-priming fermentation tank
Wenshi tube fermentation tank
Overflow self-priming fermentation tank
Alcohol fermentation tank
cylinder
Fermenter
cooling device
washing device
New beer fermentation equipment
Conical jar
Asahi can
union tank
Fermentation process control
Intermediate control of temperature
Factors causing changes in fermentation temperature ——Fermentation heat
heat of fermentation
The net heat released during fermentation.
thermogenic factors
biothermal
concept
The production bacteria themselves generate a large amount of heat during the growth and reproduction process.
Influencing factors
strains
The greater the nutrient utilization rate, the greater the heat production.
Medium ingredients
The richer the ingredients, the more heat is produced
fermentation period
High heat production during logarithmic growth phase
Fermentation type
Aerobic fermentation produces more heat than anaerobic fermentation.
The heat carried away by the air.
Heat lost from the tank wall.
Stir hot
Heat is generated due to stirring in the mixer.
Heat dissipation factors
heat of evaporation
The heat removed by evaporation of a liquid.
During aeration, the water in the fermentation liquid is evaporated, and the heat required for water evaporation is
Sensible heat
Sensible heat is very small and can generally be ignored.
radiant heat
The amount of radiant heat depends on the temperature difference between the tank temperature and the environment.
It is larger in winter and smaller in summer, generally not exceeding 5% of the fermentation heat.
How to calculate heat during fermentation
(1) Measure the cooling water flow rate and inlet and outlet temperature for a certain period of time
(2) Calculation based on the temperature increase of the fermentation broth
(3) Calculated based on the combustion value of the compound
Effect of temperature on microbial fermentation
Effect of temperature on microbial growth
The growth of different microorganisms has different temperature requirements.
Temperature ↑ → Growth and reproduction of microorganisms ↑ → But the speed of enzyme inactivation ↑ → Advance bacterial aging → Shortened fermentation cycle → Extremely detrimental to fermentation production.
Microorganisms are more harmed by high temperatures than by low temperatures.
Above the maximum temperature, microorganisms die quickly;
Below the minimum temperature, microbial metabolism is greatly inhibited and does not die immediately.
Effect of temperature on product formation
product formation reaction rate
The temperature suitable for microbial growth is not necessarily the temperature suitable for product formation.
Product synthesis direction
Temperature affects the physical properties of fermentation broth
Oxygen solubility
The rate of decomposition and absorption of some substrates by bacteria
Selection and control of optimal fermentation temperature
Optimum fermentation temperature
The temperature that is most suitable for the growth/product synthesis of a certain type of production bacteria.
control
Choose according to different strains of bacteria
Different types of microorganisms contain different enzyme systems and properties.
Choose according to growth stage
Early stage of fermentation: slightly higher temperature
Mid-term: The temperature is slightly lower
Later stage: increase the temperature
Changes due to different ventilation conditions
Poor aeration conditions: the optimal fermentation temperature may be lower than that under good aeration conditions
According to bacterial growth status
Fast growth: maintain high temperature for a shorter time
Slow growth: maintain high temperature for a longer time
Consider the composition and concentration of the culture medium
The culture medium is thin: the ingredients are easier to use: the temperature can be lower
Intermediate control of dissolved oxygen
Cellular demand for oxygen
oxygen
One of the components that make up the cell itself & its metabolites
Directly participate in some biochemical reactions
different microbial species Different oxygen consumption and sensitivity
Specific oxygen consumption rate (respiratory intensity)
The amount of oxygen consumed by stem cells per unit mass in unit time molO2/(kg stem cells·s)
critical dissolved oxygen concentration
When there are no other limiting substrates in the culture medium, the lowest dissolved oxygen concentration does not affect the growth and reproduction (respiration) of aerobic microorganisms.
Medium composition & concentration Affects cells' oxygen consumption rate
Carbon source type
When the carbon source of the hydrocarbon type is used as a culture medium, the oxygen consumed is ≈ three times that of carbohydrates.
matrix concentration
Cell oxygen uptake and Culture time & cell concentration related
oxygen uptake rate
Refers to the amount of oxygen consumed per unit volume of culture medium per unit time, in molO2/m3·s
Accumulation of harmful metabolites → inhibiting cellular respiration
The effect of dissolved oxygen concentration on cell growth & product formation may be different
Main factors affecting oxygen transfer rate
oxygen partial pressure in air
The oxygen saturation concentration C* can be increased by adding pure oxygen or enriched oxygen into the ventilation, or increasing the tank pressure.
improve
ventilation flow
Ventilation volume ↑ → Linear velocity of air ↑ → ↑Oxygen transfer coefficient KL.
Excessive air linear speed → the stirring impeller blades cannot disperse the air → large bubbles formed by the air flow overflow around the shaft → the stirring efficiency & dissolved oxygen content are greatly reduced.
Stirring rate
is an effective method to improve the dissolved oxygen coefficient.
Why?
① Stirring can break large air bubbles into small bubbles, which increases the contact area between oxygen and liquid. Moreover, the rising speed of small bubbles is slower, and the contact time between oxygen and liquid increases accordingly.
② Stirring causes the liquid to move in a vortex, causing the bubbles to rise not in a straight line but in a spiral motion, which prolongs the movement route of the bubbles and increases the gas-liquid contact time.
③ Stirring makes the fermentation liquid move in turbulent flow, thereby reducing the thickness of the liquid film around the bubbles and reducing the liquid film resistance, thus increasing the dissolved oxygen mass transfer coefficient.
④ Stirring disperses the bacterial cells and avoids agglomeration, which is conducive to increasing the contact area during solid-liquid transfer and uniform driving force. It also reduces the thickness of the liquid film on the surface of the bacterial cells, which is conducive to the transfer of oxygen.
Air distribution duct type
The form of the air distribution tube, the diameter of the nozzle and the relative position of the distance between the tube nozzle and the bottom of the tank: have a great impact on the oxygen dissolution rate.
Culture fluid viscosity
The viscosity of the culture solution increases, the mass transfer resistance increases, and the oxygen transfer rate decreases.
Surfactant
Surface active substances with hydrophilic and hydrophobic ends such as fats and oils used for defoaming in the culture solution are distributed at the air-liquid interface, increasing the transmission resistance.
ionic strength
Generally, the bubbles generated in electrolyte solutions are smaller than those in water and have a larger specific surface area.
Under the same conditions, the KLα of the electrolyte solution is larger than that of water.
Bacterial liquid concentration
As microorganisms grow, the cell concentration in the fermentation broth increases and the KLα value becomes smaller.
Process means to control dissolved oxygen
change ventilation rate
In the case of low ventilation, increasing ventilation to increase dissolved oxygen concentration has a very significant effect.
When the air flow rate is already very high, increasing the ventilation rate will not have an obvious effect, but will produce certain side effects.
Change mixing speed
Generally speaking, changing the stirring speed has a better effect than changing the aeration.
When the speed is low, the effect of increasing the speed is obvious.
When the rotational speed is already very high, increasing the rotational speed will not only increase the power consumption, but also break up the mycelium due to the shearing effect of stirring, promote autolysis of the mycelium and reduce the output.
Oxygen partial pressure that changes gas composition
The method of introducing pure oxygen can change the oxygen content in the air, increase the C* value, and thus improve the oxygen supply capacity.
Change tank pressure
In fact, it changes the partial pressure of oxygen to increase C*, thereby increasing the oxygen supply capacity. But this method is not very effective.
Change the physical and chemical properties of fermentation broth
Add antifoaming agent, add sterile water, and change the composition of the culture medium.
Add oxygen transfer intermediate medium
Hemoglobin; hydrocarbons (kerosene, paraffin, toluene and water, etc.); fluorocarbons.
Effect of pH value during fermentation
Fermentation process pH changes
General law
growth stage
Early stage: pH is relatively stable
Rapid growth period: pH changes greatly
Production stage
pH tends to stabilize
autolysis stage
pH rise
reason
matrix metabolism
Glucose metabolism
Sugar is broken down into small molecules of acid and alcohol, and the pH drops.
Lack of sugar and rising pH: one of the signs of feeding.
Nitrogen metabolism
-NH2 in amino acids is utilized: pH decreases;
Urea is decomposed into NH3, the pH rises, and the pH drops after NH3 is utilized;
When the carbon source is insufficient, the nitrogen source is used as a carbon source: the pH rises.
Physiological acid/base metabolism
After being utilized, the pH drops/rises.
formation of certain products
Organic acids are produced: lowering the pH
Antibiotics such as erythromycin, chloramphenicol, and spiramycin are alkaline: causing the pH to rise.
Bacterial autolysis
In the later stages of fermentation, the pH rises. →Instructions to terminate fermentation.
Ventilation, contamination, etc.
Effect of pH changes on fermentation
Growth and reproduction of microorganisms
enzyme activity
Affects the charge on the cell membrane → changes the permeability of the cell membrane
Dissociation of certain nutrients & intermediate products in the culture medium.
Microbial form
Amount & direction of metabolite formation
Product stability
During fermentation Selection and control of optimal pH value
Selection principle
Conducive to microbial growth
Maximize yield
Optimum pH value for microbial cell growth & metabolite formation
Various types of microorganisms adapt to the pH range
Yeast: 3.8-6.0
Mold: 4.0-5.8
Bacteria: 6.5-7.5
Actinomycetes: 6.5-8.0
Optimum pH value for microbial growth stage & product synthesis stage: often different
Characteristics of strains →
Chemical properties of the product →
pH control
Adjust the C/N and pH of the base material and make it have good buffering capacity.
Substance that maintains pH: CaCO3
Reagents with buffering capacity: phosphate buffer
Adjust pH by feeding
Sugar supplement rate
Low NH2-N & low pH: add ammonia; low NH2-N & high pH: add (NH4)2SO4
Urea as nitrogen source
When there is a conflict between feeding materials and adjusting pH, add acid and alkali to adjust pH.
Adjust ventilation, change temperature, tank pressure, etc. as emergency measures