tion. It is therefore useful to divide the bioreactor types which have been used
in SSF into four general categories, based on the mixing and aeration provided
(Table 3 and Fig. 5) [2, 107, 131]. With respect to mixing, two strategies are
available – the substrate bed may either be left static or mixed only infrequently,
or alternatively might be mixed continuously or frequently. With respect to
aeration two strategies are also available – the air can either be circulated
around the substrate bed or blown forcefully through it.
5.2
Unmixed Beds and the Absence of Forced Aeration – Trays
A tray bioreactor consists of a chamber, which may be as small as an incubator
or as large as a room, within which a number of trays are located. The environment is usually controlled by controlling the temperature and humidity of the
air blown through the chamber. Individual trays may be constructed of plastic,
wood, bamboo, or metal. Plastic bags have also been used. The bed in a tray may
be left static or may be turned by hand once per day.
Biochemical Engineering Aspects of Solid State Bioprocessing
103
Table 3. Guide to the major considerations in the selection of an appropriate SSF bioreactor
based on the characteristics of the process organism
Fast growing organism
Slow growing organism
(process of 1–5 days)
(process of 1–4 weeks)
– Prevention of entry of
– Prevention of entry of
contaminants is less
contaminants is crucial
crucial
– Continuous systems
– Continuous systems can
probably not suitable
be considered
Organism cannot tolerate
– Bioreactor choice es– Tray fermentations may
mixing
sentially limited to
be appropriate, but even
– Bed must be static, or
packed beds
with a slow grower bed
mixed only infrequently
– The Zymotis design
thickness will be limited
– In static beds temperature
(a packed bed with closely
to the order of 5–10 cm
and gas gradients are unspaced internal heat
avoidable
transfer plates) is probably
best [131]
Organism can tolerate mixing – Available designs are
– Stirred bed bioreactors
– Agitation helps in heat
rotating drum, stirred
designed for aseptic
removal, prevents high presdrum, stirred bed, gasoperation have already
sure drops, allows even
solid fluidized bed and
been proven at scales up
replenishment of water
rocking drum [107]
to 200 kg
and provides homogeneity – The stirred bed bioreactor – Rotating or stirred drums
of INRA [2] has already
can probably be used
been proven at 25 tonne
even though aeration
scale
and heat removal may be
– Rotating drums might be
poorer than other
required if the mixing must stirred designs
be gentle
in SSF into four general categories, based on the mixing and aeration provided
(Table 3 and Fig. 5) [2, 107, 131]. With respect to mixing, two strategies are
available – the substrate bed may either be left static or mixed only infrequently,
or alternatively might be mixed continuously or frequently. With respect to
aeration two strategies are also available – the air can either be circulated
around the substrate bed or blown forcefully through it.
5.2
Unmixed Beds and the Absence of Forced Aeration – Trays
A tray bioreactor consists of a chamber, which may be as small as an incubator
or as large as a room, within which a number of trays are located. The environment is usually controlled by controlling the temperature and humidity of the
air blown through the chamber. Individual trays may be constructed of plastic,
wood, bamboo, or metal. Plastic bags have also been used. The bed in a tray may
be left static or may be turned by hand once per day.
Biochemical Engineering Aspects of Solid State Bioprocessing
103
Table 3. Guide to the major considerations in the selection of an appropriate SSF bioreactor
based on the characteristics of the process organism
Fast growing organism
Slow growing organism
(process of 1–5 days)
(process of 1–4 weeks)
– Prevention of entry of
– Prevention of entry of
contaminants is less
contaminants is crucial
crucial
– Continuous systems
– Continuous systems can
probably not suitable
be considered
Organism cannot tolerate
– Bioreactor choice es– Tray fermentations may
mixing
sentially limited to
be appropriate, but even
– Bed must be static, or
packed beds
with a slow grower bed
mixed only infrequently
– The Zymotis design
thickness will be limited
– In static beds temperature
(a packed bed with closely
to the order of 5–10 cm
and gas gradients are unspaced internal heat
avoidable
transfer plates) is probably
best [131]
Organism can tolerate mixing – Available designs are
– Stirred bed bioreactors
– Agitation helps in heat
rotating drum, stirred
designed for aseptic
removal, prevents high presdrum, stirred bed, gasoperation have already
sure drops, allows even
solid fluidized bed and
been proven at scales up
replenishment of water
rocking drum [107]
to 200 kg
and provides homogeneity – The stirred bed bioreactor – Rotating or stirred drums
of INRA [2] has already
can probably be used
been proven at 25 tonne
even though aeration
scale
and heat removal may be
– Rotating drums might be
poorer than other
required if the mixing must stirred designs
be gentle