Activated sludge surface with negative charge, physicochemical sludge with positive charge, is a lot of people know, so biochemical sludge selection of cationic flocculant, physicochemical mud selection of anionic flocculant. But why does activated sludge have a negative charge? This is related to the main composition of activated sludge bacteria, the charge of bacteria determines the charge of activated sludge, Panjin Hongshi Environmental Protection Technology Co., Ltd. take you to fully analyze the principle of bacteria with charge!
1. What is isoelectric point?
Isoelectric point (pI) : In a solution of a certain pH, amino acids or proteins dissociate into cations and anions with equal tendency or degree to become facultative ions, which are electrically neutral. The pH of the solution is called the isoelectric point of the amino acid or protein.
The action of an isoelectric point
In a solution of a certain pH, amino acids dissociate into cations and anions with equal tendency and degree, and the net charge is zero, which is electrically neutral. At this point, the pH of the solution is called the isoelectric point of the amino acid.
The charge of amphoteric ions varies with the pH value of the solution. When the positive and negative charges of amphoteric ions are equal, the pH value of the solution is its isoelectric point.
When the pH of the external solution is greater than the pI value of the amphoteric ion, the amphoteric ion releases the proton with negative charge.
When the pH of the external solution is less than the pI value of the amphoteric ion, the amphoteric ion protonates positively.
The solubility of amino acids in solution is minimum when the isoelectric point is reached.
2. What is ph?
PH refers to the degree of acidity and alkalinity of the solution, generally expressed by PH value.
PH < 7 is acidic, pH =7 is neutral, and pH > 7 is alkaline.
PH value, also known as hydrogen ion concentration index, pH value, is a scale of the activity of hydrogen ions in a solution, which is usually a measure of the degree of acidity and of a solution. The concept was first proposed in 1909 by Danish biochemist Søren Peter Lauritz Sørensen. P stands for German Potenz, meaning power or concentration, and H stands for hydrogen ion (H). Sometimes pH is also written in the Latin form pondus hydrogenii.
Under normal conditions (25℃, 298K), when the pH<7, the solution is acidic, when the pH>7, the solution is alkaline, when the pH=7, the solution is neutral.
Note: pH value is allowed to be less than 0, such as hydrochloric acid (10 mol/L) pH -1.
3, the difference between isoelectric point and ph
Amino acids contain both amino and carboxyl groups, which are amphoteric electrolytes and exist in the form of facultative ions or polar ions in aqueous solution. The facultative ions of amino acids accept protons to form cations in acidic solutions and release protons to form anions in basic solutions. When the net charge of amino acids is zero, the pH becomes isoelectric.
In other words, the isoelectric point of an amino acid has little to do with the ph of its environment, and only determines its form in an aqueous solution.
The isoelectric point may be acidic or alkaline, not neutral!
4. Charge properties of bacteria
Between 50 and 80% of the dry weight of bacteria is protein, which consists of 20 amino acids ed by peptide bonds in a certain sequence. And the main component of the cell wall of bacteria also has protein, so the isoelectric point of bacteria and amino acid isoelectric point close!
The isoelectric point of bacteria is known to be between Ph 2 and 5. 2 ~ 3 for Gram-positive bacteria and 4 ~ 5 for gram-negative bacteria.
In general, the bacterial culture, staining, testing and utilization process are all higher than the isoelectric point of bacteria under alkaline (7 ~ 7.5), neutral and acidic (6 ~ 7) conditions, so all the bands
