3 Preparation of Media
31
- Laminar flow cabinet
- Membrane filters
There are filters of various sizes available. Usually, a filter with a pore
size of 0.2 Jlm or smaller is used for decontamination. The materials of
which filters are made are also diverse. Filters made of cellulose acetate
or cellulose nitrate filters are common. Various types of filter holders
have also been devised. Sterilized sets of filters and filter holders are available as disposable filter sets. Glass or autoclavable plastic filter holders
are also available. The filter holders are sterilized by autoclaving after
the setting up of filters in them. Filters and filter sets are available in
various sizes (with regard to the diameter of the filter disc). Small filters
(3 mm or 13 mm in diameter) are useful for the filtration of minute
amounts of liquid.
- Culture media
- Physiological solutions
Procedure
1. In case of a bottle-type filter system, pour the liquid into the upper
compartment of the system. The liquid may drop through the filter
gradually (Fig. 1).
2. If faster filtration is required, apply a pump to either reduce the pressure of the lower compartment of the filter system by sucking the air
from an outlet of the compartment, or increase the pressure of the
upper compartment of the system by sending compressed air through
an inlet of the compartment (see chapter 1, Fig. 13). Instead of sending compressed air, nitrogen gas from a cylinder may be used.
3. If a filter gets clogged with minute particles or dust, change the filter.
To avoid clogging of the filter, stepwise prefiltration through filters
with a larger pore size is recommended. For example, filter the medium through a series of filters of the following pore size: 0.8 Jlm,
0.6 Jlm, 0.4 Jlm, and 0.2 Jlm.
4. When filtration is finished, pour the sterilized medium into a medium
bottle in a laminar flow cabinet.
5. In the case of cylinder- or top-type filters, connect the filter to a peristaltic pump. Place the receiver medium bottle in a laminar flow cabinet. Send the medium to the filter by driving the pump (Fig. 2). For
sterilization of very small amounts (for example, less than 50 ml) of
medium, inject the medium into the receiver vessel via a syringe
through a filter (Fig. 3).
Comments
Autoclavable media or physiological saline are sterilized by heating at
121°C for 15 min. Take the solutions out of the autoclave as soon as possible after the 15 min has elapsed. Be sure that the pressure gauge shows
zero when you open the autoclave.
Solutions
31
- Laminar flow cabinet
- Membrane filters
There are filters of various sizes available. Usually, a filter with a pore
size of 0.2 Jlm or smaller is used for decontamination. The materials of
which filters are made are also diverse. Filters made of cellulose acetate
or cellulose nitrate filters are common. Various types of filter holders
have also been devised. Sterilized sets of filters and filter holders are available as disposable filter sets. Glass or autoclavable plastic filter holders
are also available. The filter holders are sterilized by autoclaving after
the setting up of filters in them. Filters and filter sets are available in
various sizes (with regard to the diameter of the filter disc). Small filters
(3 mm or 13 mm in diameter) are useful for the filtration of minute
amounts of liquid.
- Culture media
- Physiological solutions
Procedure
1. In case of a bottle-type filter system, pour the liquid into the upper
compartment of the system. The liquid may drop through the filter
gradually (Fig. 1).
2. If faster filtration is required, apply a pump to either reduce the pressure of the lower compartment of the filter system by sucking the air
from an outlet of the compartment, or increase the pressure of the
upper compartment of the system by sending compressed air through
an inlet of the compartment (see chapter 1, Fig. 13). Instead of sending compressed air, nitrogen gas from a cylinder may be used.
3. If a filter gets clogged with minute particles or dust, change the filter.
To avoid clogging of the filter, stepwise prefiltration through filters
with a larger pore size is recommended. For example, filter the medium through a series of filters of the following pore size: 0.8 Jlm,
0.6 Jlm, 0.4 Jlm, and 0.2 Jlm.
4. When filtration is finished, pour the sterilized medium into a medium
bottle in a laminar flow cabinet.
5. In the case of cylinder- or top-type filters, connect the filter to a peristaltic pump. Place the receiver medium bottle in a laminar flow cabinet. Send the medium to the filter by driving the pump (Fig. 2). For
sterilization of very small amounts (for example, less than 50 ml) of
medium, inject the medium into the receiver vessel via a syringe
through a filter (Fig. 3).
Comments
Autoclavable media or physiological saline are sterilized by heating at
121°C for 15 min. Take the solutions out of the autoclave as soon as possible after the 15 min has elapsed. Be sure that the pressure gauge shows
zero when you open the autoclave.
Solutions