Biotechnology - Yu.O. Sazykin 2006

General Biotechnology
Main Stages of the Biotechnological Process
Sealing and Sterilization of Equipment

Aseptic production conditions require the sterilization of all equipment internals and material streams prior to THE START OF the process. However, this alone is not sufficient. Sterility must be maintained throughout the entire operating cycle. In other words, the technological process must be protected from contamination by ensuring the leaktight integrity of all equipment connections.

The piping and instrumentation diagram of any fermenter includes dozens of various sealing elements. The most common of these—flange connections and shut-off Valves—are vulnerable to leakage when assembled with the fermenter piping.

Systems operating under aseptic conditions must provide the capability to sterilize all internal points of apparatus and communication lines. To achieve this, saturated steam under pressure is passed through the fermenters prior to loading. However, certain challenges arise here. This applies, for example, to open pipe ends—pipe sections connected at one end to the fermenter cavity and exposed to the atmosphere at the other. These include the exhaust air line (for air that has passed through the fermenter) and sampling assemblies.

It is impossible to build up elevated pressure in an open pipe end; consequently, the Temperature there will not exceed 100 °С, necessitating longer Treatment times. Typically, a tap-in is made in the pipe, and steam is continuously fed into the open pipe end during operation. In the case of so-called "dead legs," it is difficult to ensure air displacement and steam Circulation. Usually, two valves are installed in the pipeline, with steam supply and condensate drainage located between them.

Large-scale industrial fermenters are sterilized for one hour at 125–130 °С.