The purpose of separation of pretreatment and solid solution
1. Separation of cells, bacteria and other suspended particles (the sediment of cell debris, nucleic acids and proteins);
2. Remove some soluble substances;
3. Change the properties of filtrate (reduce viscosity, etc.) to facilitate the subsequent operation.
1. Extracellular products: should be transferred to the liquid phase as far as possible, normally adjust Ph to acidic or alkaline ;
2. Intracellular products: first collecting cells, breaking wall, releasing biochemical substances into liquid phase, and then separating cell debris;
3. The follow-on operation is usually based on the liquid phase of biochemical substances.
First,Pretreatment of fermentation
(a),The removal of high - priced inorganic ions
1. Remove the calcium ion: Add oxalic acid. Oxalic acid solubility is small, when dosage is large, can use its salt, such as sodium oxalate;
2. Remove magnesium ions: Add sodium tripolyphosphate, which forms a soluble complex with magnesium ions：Na5P3O10+Mg++⇌MgNa3P3O10+2Na+
3. Remove iron ions： Add potassium ferrocyanide to form Prussian blue precipitate
(b),removal of hybrid proteins
isoionic point, heating denaturalization, Protein is removed by adsorption
(c),Coagulation and flocculation technology
Second,Fermentation liquid filtration
The fermentation liquid contains a large number of bacteria, cell fragments and residual solid medium components. The filtration is the separation process of solids and liquids suspended in the fermentation liquid. In filtration, it is required to filter quickly, clarify the filtrate, and have high yield, but the fermentation liquid is often difficult to filter and is still a weak link in production.
(a),The filtration characteristics of fermentation liquid and the Weight ratio resistance of filter cake.
(b),Factors that affect the filtration rate
Bacterial species, fermentation conditions (composition of medium, uncompleted culture medium, fermentation cycle) filtration conditions: pressure, etc
(c),Improved filtering performance
1.Add the filter aid
2. Add reactant
3. The glutinous substance was decomposed by enzyme preparation
4. The treatment of bacterial fermentation
(d),Solid liquid separation equipment selection
The fermentation liquid of different characters should choose different solid-liquid separation devices. Common separation equipment: plate and frame filter press, drum vacuum filter and settlement separator.
The advantages of plate and frame filter press are: the filter area is large, the filter force (pressure difference) can be adjusted substantially, and can withstand higher pressure difference. Therefore, the adaptability of the fermentation fluid of different filtration characteristics is strong, and it has the advantages of simple structure, low price and low power consumption. Defect is cannot continuous operation, heavy equipment, high labor intensity, poor sanitation condition, the auxiliary time of non-production is long (including open plate and frame, discharge cake, wash filter cake, wash filter cloth, repress the plate and frame, etc.), hinder the improvement of the filtration efficiency.
Automatic plate and frame filter is a kind of new type of pressure filter equipment, such as the disassembly of the plare and frame, the removal of the filter residue, the cleaning of the filter cloth. It greatly reduces the auxiliary time of non-production and reduces labor intensity.
Dazhang- Automatic membrane filter press
Common technical measures: for the small thallusl, viscous fermentation liquid, filter aid can be added or adopt pretreatment by flocculation then filtration; For the difficult filtration of bacillus subtilis fermentation, a thin filter frame can be used to reduce filter cake resistance. In addition, can use membrane filter press. At the end of the filtration, compressed air will be pumped into the filter plate and the membrane to squeeze the filter cake secondly.