Civil Engineering Reference
In-Depth Information
and oxygen to the growing cells nearly ideal, and creating a product that has twice the
water holding capacity of a typical BC pellicle from static cultures. Moreover, this rotat-
ing disk bioreactor is more ei cient than common surface cultures (BC production
86.78% higher than in traditional static conditions) and reduces the time of a run to
about 3.5 days instead of the usual 12-20 days.
h e aerosol bioreactor (Figure 2.5) is another novel system that involves the genera-
tion of an aerosol spray of glucose and its even distribution to bacterial cells on the
culture medium-air interface. h is process results in homogeneous pellicles of BC with
superior mechanical properties than those produced under traditional static condi-
tions. BC can also be generated, not as one thick membrane but, as several 3-4 cm
thick slices, by interruption of glucose supply. Furthermore, this new bioreactor elimi-
nates the problems inherent to traditional static cultivation of BC: the hindering of BC
growth by the wall ef ect, the rate of mass transfer limitation of the glucose supply and
the culture medium enrichment with by-products; and of ers the theoretical prospect
of an unlimited, continuous production rate [44].
An alternative approach to BC production is through agitated cultivation, which
generates small pellets, i bers, irregular masses or spherical particles instead of mem-
branes ( Figure 2.6 ) [45-47] .
BC produced in agitated cultures shows a microscopic structure similar to that
obtained under static conditions (Figure 2.7). However, its nanoi bers are curved and
entangled with one another, in contrast with the highly extended ones attained under
static conditions, resulting in a denser structure. In addition, agitated BC has a lower
degree of polymerization and crystallinity index, and higher water holding capacity
than the one obtained under static conditions [38].
pH probe
feed in
air ain
caustic in
disks
Motor
Figure 2.4
Schematic diagram of a rotary disk reactor (reproduced with permission from [43]) and
photographs of the apparatus. Reproduced with permission from [7].
Nutrient broth aerosol
Spread of aerosol
Air
Aerosol
Nutrient broth
BC culture
Generation of aerosol
Figure 2.5
Mechanism of BC production using an aerosol bioreactor and the formation of BC slices by
interrupting the glucose supply. Reproduced with permission from [44].
