Sterile Technical Interpretation

Sterile Technical Interpretation

Micro-giant BioEngineering  2009.06.19

  To create and maintain sterile environment during the basic preprocess of microorganism (purebred) culture fermentation is the most important. To avoid bacteria interfere and affect the harvest rate, furthermore cause failure or variation (especially the secondary products of metabolism). To make a provision of sterile technical interpretation for equipment concern as follows:

Ⅰ. No Blind Angle Design:

Arc-shaped design no angle of all the wetted part inside the fermentor (fermenter,bioreacter,bioreactor), all the ports from the nearest stop valve or blind cover (neck) must be <2d (inner diameter). All the pipes with secondary SIP are required concept of sterilization buffer room, ex. sampling valve(tube), feeding tube, transfer tube, seal…etc. All wetted parts adopt diaphragm valve or least food or pharmaceutical sanitary valve (Note: still need to take care of the sterilization method.)。

Ⅱ. Complete Sterilization:

Sterilization basically using SIP. It’s using enthalpy inside the superheated steam to achieve the sterilization. If that’s CIP; must take care of sterilize concepts.Weather sterilze throughtly or not related to these four elements below:

  1. Tempture:
    SIP basically using 121℃(but if it’s for Thermophile spores, then it takes higher temp. with three times sterilization ), even higher temperature is easier to sterilize the bacteria, but still need to consider it might destroy medium nutrients.
  2. Pressure:
    The sterilize pressure generally set between 1.2 ~ 1.5kg/cm2, but still need to deliberate where actual pressure sensor placed(there are slightly differences between the top of the tank and exhaust). The “pressure” here emphasis on heating process, the temperature and the pressure rising symmetric synchronously. It might be cold air remain causes the sterilize effect if there’s variation.
  3. Time:
    Here means during sterilization after reach sterilize temperature, generally between 20~40 min(liquid fermentation). 
    Note:If it drops below sterilize temperature during sterilization then it should be re-calculated and review the reason to avoid it.
  4. Flow:
    It would be a futile effort without flow even with temperature, pressure, time. The steam for sterilization needs to pull in from the top and make vent valve at the lowest spot (exclude cooling water), to make sure the sterilize effect of steam. Therefore all the pipes need sterilization need to install small vent valve(even sanitary drainer), T-type valve would be the best.

Ⅲ. Maintain Positive Pressure

  To ensure that the sterilization can be maintained, it is the key to keep positive pressure for the system from sterilization to harvest. Generally use filtered 0.2μm  sterile air to maintain. Therefore in case the power outage, thesterile equipmentsystem can still keep positive pressure for 12 hours or more, so all the auto valves (N.C. type)need to consider if the power outage happens.

  First enter cooling section during sterilization, relief pressure too fast will easily cause sudden boiling and thus should adopt segmented relief cooling.

  And cooling too quickly, there will be negative pressure doubt in parts, especially the exhaust spot. It can install exhaust filter to prevent the pollution of the adverse pressure. But it should be noted that the exhaust filter get wet easily then clogged. It shall retrofit the electric heating piece in the filter housing to avoid it.

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