Continuous Sterilization, Definition, Process, Advantages and Disadvantages

Continuous sterilization, on the other hand, rapidly heats the media using steam condensate without a heat exchanger. Steam is injected into the system via a nozzle, and the media stays in a holding loop for a set time until it becomes sterile.

Continuous sterilization is more efficient than batch sterilization because it heats small portions of the media at a time, rather than the entire system, saving energy.

What is Sterilization?

• Sterilization is defined as the complete destruction of all forms of microbial life, including bacterial spores and prions, etc.
• Microbiological sterilization can be carried out through different chemical and physical methods.
• Heat is the most used method due to its great efficiency.
• Moist heat can be applied, processes of 121ºC are normally required for 15 minutes, or dry heat with treatments of 170º C, for two hours, although these parameters change depending on other variables of the product to be sterilized.
• Sterilization can also be achieved by filtration, through the use of filters with a pore size small enough not to allow microorganisms to pass through; this method is recommended when heat cannot be applied to the material to be sterilized.
• Other sterilization procedures are the use of ionizing radiation and gases, which, in addition to having high penetrating power, do not deteriorate the material, so they are used to sterilize single-use medical material.

Definition of Continuous Sterilization

• Continuous sterilization is an open operating system with continuous addition and discharge of the sterilizers in the system to remove or kill Microorganisms. 

• Continuous sterilization is a process where sterilizers are added throughout the process to remove microorganisms such as bacteria, fungus, spores, etc.

• Sterilizers use for sterilization such as Physical and Chemical.

What is continuous sterilization?

• Continuous sterilization is the rapid transfer of heat to the medium through steam condensate without the use of a heat exchanger/Coils.
• This method is only used for medium sterilization in large-scale fermentation plants. 
• The process includes sterilization operations such as heating, maintenance, and cooling the medium outside the fermenter before entering the fermentation process. 
• In Continuous sterilization, the culture medium is continuously pumped into a heating tower heated by direct steam, so that it can reach the temperature of 126 ~ 132℃ in a short time. 
• Then enter in the maintenance tank (or maintenance tube), keep it at the sterilization temperature for 5 to 7 minutes, and then enter the cooling tube to cool it to the inoculation temperature and directly enter the fermenter that has been sterilized in advance (empty tank sterilization).
• The cooling methods of the culture medium include spray cooling, vacuum cooling, and thin plate heat exchanger.
• There are two types of continuous sterilizers are used for sterilization of media – Indirect heat exchanger and Direct Heat exchanger or steam injectors.
• The function of the holding loop is to sterilize the medium. The heating coil or loop sterilizes the medium and the cooling loop or coil cools the medium to the fermentation temperature. This is the basic process of continuous sterilization.

Advantages of continuous sterilization

• The advantages are strong continuity, rapid sterilization and disinfection, and less damage to the nutrients in the medium. 
• It is suitable for continuous sterilization and disinfection of large-volume fermenter materials. 
• The heating time is short, which improves the utilization rate of heat; the operating conditions are constant, and the sterilization quality is stable. 
• It is easy to realize pipeline and automatic control operation.
• The utilization rate of fermentation equipment is high. 
• Because of the high-temperature instantaneous sterilization, it can not only kill microorganisms but also minimize the damage of nutrients, thereby improving the utilization rate of raw materials.
• Due to the uniform steam load, the utilization rate of the boiler is improved.
• It is suitable for automatic operation.
• It reduces the labor intensity of operators.
• The continuous elimination equipment has no leakage, no blockage, and no dead ends, ensuring complete sterilization of the main pipe and branch pipes during the pipeline disinfection process.

Disadvantages of Continuous Sterilization

• The disadvantage is that the equipment has high requirements, and additional heating and cooling devices are required.
• The operation is more difficult to handle.
• In continuous sterilization, there are many opportunities for contamination, and the contamination involves a wide range; it is not suitable for sterilization containing a large number of solid materials.
• The requirement for steam is high.