This document discusses different types of filtration mechanisms and filters used for sterilizing fermentation media. It describes four key filtration mechanisms: inertial impaction, diffusion, electrostatic attraction, and interception. It then explains the differences between absolute and depth filters. Absolute filters have pore sizes smaller than particles to be removed and are 100% efficient, while depth filters have larger pores and remove particles within the filter depth. The document concludes by describing a four-filter sterilization system used for animal cell culture media, utilizing different pore size polypropylene and nylon filters to remove contaminants while minimizing protein adsorption.

1. FILTER STERILIZATION
NIPUN BARIYA

2. FILTRATION MECHANISMS
Inertial Impaction
Diffusion
Electrostatic Attraction
Interception
Inertial Impaction
1.Suspended particle in fluid stream have momentum
2.The fluid in which the particle are suspended will flow
through the filter by the rout of least resistance.
3.The particles, because of their momentum, tend to travels In
straight lines and they impacted upon the fiber were they
may remain.
4.Inertial impaction is more significant in the filtration of gases
rather than liquid.
Diffusion
1.Extremely small particle suspended in a fluid are subjected
to Brownian motion(random movement due to collision
with fluid molecules )
2.Such small particles tend to deviate from the fluid flow
pattern and may becomes impacted upon the filter fiber.
3.Diffusion more significant in the filtration of gas than
liquid.
Electrostatic attraction
1.Charged particle may be attracted by opposite charges on
the surface of the filtration fiber.
Interception
1.Particle which are larger than pore are removed by direct
interception
2.Somehow significant number of small particles which are
smaller than the pore size may also removed by interception
.
3.More than on particles arrived at a same time from same
pore.(irregular)
TYPE OF FILTERS
1.Absolute filter
2. Depth filter
Pore size Is to be smaller than the
particles to be removed
Pores size is larger than the
particles to be remove
Absolute filter
Pore size is smaller than the particles is to be
removed.100% efficient in removing Microorganisms
Filtration at surface as well as within the
filter“fixed pore filter “ constructed so as not
distorted during operation
Pore size controlled during manufacturing :
guaranteed.
Interception is the major mechanisms “ smaller
particles also removed due to depth by inertial
impaction , diffusion and attraction.
Fixed pore filter are superior for most purposes In
that they have absolute ratings, are less susceptible
to change in pressure and are likely to released
trapped particles.Dis-absolute filter was the resistance to flow they present
and hence, the large pressure drop across the filter
which represent a major operating cost.

3. Depth filter
Pore are larger than the particles are to be removed.
1.Composed of felts, woven, asbestos pads and loosely packed
fiberglass.
2.“non fixed pore filters”
3.Removal of particle by inertial impaction, diffusion and
electrostatic attraction.
4.More affected by the depth of filter and increase pressure on
filter cause large channels and displacement of previous
trapped particle.

4. FILTER STERILIZATION FOR FERMENTATION MEDIA
1.Media for animal cell culture cannot be sterilized by steam – contains
heat-labile proteins
SELECTION OF PROPER FILTER
• Ideal filtration system for the sterilization of animal cell cultur
media must be full fill with :-
* free of fungal , bacterial and mycoplasma
contamination
*minimal adsorption of protein to the filter surface
*free of viruses
*free of endotoxins

5. • Pall process filtration ltd.
• 1 filter – positively charged
polypropylene pre- filter(5μ)- removal
of coarse precipitate, clot like material
and other cross contamination
• 2filter – positively charged
polypropylene filter (0.5μ)- bulk
microbial removal ,deformable gels ,
lipid based materials and endotoxin
reduction
• 3 filter- (single layered) nylon/ polyester
positively charged filter (0.1μ) – further
microbial and endotoxin removal
• 4 final filter –( double layered) similar to
3 one(0.04μ)- removal of highly small
particles like viruses , mycoplasma and
some other particles .

6. REFERENCES
• PRINCIPLESOF FERMENTATIONTECHNOLOGY(2ND EDITION ) BY – P.F. STANBURY , A.WHITAKER , S.J. HALL
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