Cell disruption - comparison of ultrasound and ultra-high pressure

Breaking cells and extracting high-purity, highly active proteins or peptides is the common aspiration of every researcher and biotech worker.

Ultrasonic crushing is most popular in cell disruption. Its principle is to use the dispersion effect of ultrasonic waves in the liquid to cause cavitation of the liquid, thereby breaking the solid particles or cell tissue in the liquid. Ultrasonic crushing is easy to operate, but the cost of crushing is high and it is easy to cause a sharp rise in temperature. During medium-to-large-scale operation, chemical free radicals are generated to inactivate certain sensitive active substances. For the fermentation broth of different strains, the effect of ultrasonication is quite different. In general, bacilli are more easily broken than cocci, and Gram-negative bacterial cells are more easily broken than Gram-positive bacterial cells, and the yeast is less broken. With the deepening of scientific research and the development of production, the demand for proteins or peptides with high activity is increasing. Ultrasonic crushing has not been able to meet people's needs.
(Simulation of ultrasonic cavitation phenomenon)

The principle of high-pressure cell disruption is different from the principle of ultrasonic fracture. Under the action of high pressure, the sample is ejected from the high-pressure chamber at a high speed, and the speed can reach several hundred meters per second. This high-speed jet of slurry is directed onto the stationary impact ring and forced to change direction to flow out of the outlet tube. Cells undergo high-speed shear, collision, and cavitation effects during this series of processes, causing cell disruption.

It is generally believed that a pressure exceeding 100 MPa is an ultra high pressure. Under ultra-high pressure conditions, the non-covalent binding in the stereostructure of the biopolymer changes, the cell membrane is broken, the components in the bacteria are leaked, the life activities are stopped, and the microbial cells are destroyed and die. Therefore, the ultra-high pressure homogenizer has been paid attention to and widely used in cell disruption.

Microbial ultra-high pressure treatment

The advent of the low-temperature ultra-high pressure continuous flow cell disruptor has filled the gap in the market. Especially in terms of maintaining protein or polypeptide activity, the effect of a low temperature ultra-high pressure continuous flow cell disrupter is significant. This is because the whole process of injection, crushing and sampling is carried out in a 4~6 °C low temperature circulating water bath, and the heat generated when the cells are crushed by high pressure is absorbed by the cooling circulating water. In the aspect of internal core structure design, the low-temperature ultra-high pressure continuous flow cell disruptor , after repeated design, calculation and experiment, found the best ratio of shear, collision and cavity. This unique design not only ensures cell breakage, but also maximizes the activity of the protein or peptide.

We used a brand of ultrasonic cell disruptor and a low-temperature ultra-high pressure continuous flow cell disrupter to break the same amount of E. coli for comparative experiments. The experimental results show that the activity of the polypeptide obtained by ultrasonication using a certain brand is 110 U/mg, and the data obtained by using a low-temperature ultra-high pressure continuous flow cell disrupter is 155 U/mg. The activity of the polypeptide after disruption by the low-temperature ultra-high pressure continuous flow cell disrupter was 40% higher than that of the ultrasonic disruption.

1 Reference: Expression and purification and identification of recombinant glucagon-like peptide-1 derived polypeptide, Chinese Journal of Biotechnology, 2009, 29(6): 1~6.

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