Part B | 9.5
290 Part B Tools and Methods in Marine Biotechnology
Table 9.8 Summary of planar photobioreactor design parameters necessary to achieve 20 kg per day biomass production schedule
Parameter
Value and units
Initial cell density C x;I
0:1 g cell L 1
Final cell density C x;f
2:0 g cell L 1
Cultivation time in batch culture t f
22 h
Initial nutrient concentration
C N;i
8:5 mmol N L 1
Incident light intensity I o
150 mol photons m 2 s 1
Mean light intensity at C x;f I m
50 mol photons m 2 s 1
Planes of illumination ˛
2
Light path length L
15 cm
Total cultivation volume V
9648 L (five 2000 L units)
Single vessel width W
6:67 m
Single vessel height H
2:0 m
Peak CO 2 -TR
5:69 mmol CO 2 L 1 h 1
CO 2 partial pressure P A
0:0035 atm (3500 ppm)
Bicarbonate concentration at P A
for pH 8.0, [HCO
3
10:3 mmol L 1
Aeration gas flow rate at P A for
peak CO 2 -TR v a =V
0:69 min 1
Mass transfer coefficient for
peak CO 2 -TR k L a
57:3 h 1 (with 3500 ppm
CO 2 )
production rate (r p ) of 20 kg d
1 is
V D
r p t f
C x;f C x;i
D
20 kg d
22 h 1 d.24 h/
.2:0 0:1/ g l 1 1 kg.1000 g/ 1 D 9649 l :
A culture volume of 9649 L may be too large for a single planar vessel, and so it is decided to build five
2000 L photobioreactors operating in parallel for a total cultivation volume of 10 000 L. For a single planar
vessel, the light path length L or thickness of the vessel is fixed at 15 cm. Furthermore, the height of each
vessel (H) is set at 2 m for the culture, 2:4 m for the
entire vessel to accommodate the gas headspace. The
width of each vessel is, therefore, 6:67 m. The final
recommended design parameters are summarized in Table 9.8.
Based on these design parameters, chemical and energy inputs can be calculated. For example, the inlet
mass flow rate of CO 2 in the aeration gas (F A ) based
on the peak CO 2 -TR and the required culture volume is
F A D CO 2 TR V
D 5:92 mmol CO 2 l h
1 44 mg CO 2
1 mmol 1
1 kg
10 6 mg
9649 l
D 2:51 kg CO 2 h
1
;
which includes both CO 2 supplied by ambient air and
the CO 2 addition to the aeration gas. The total aeration gas flow rate at this CO 2 molar flow rate of
2:51 kg CO 2 h
1 (0:95 mol CO 2 min
1 ) at 25
ı C and
3500 ppm CO 2 partial pressure is
v a;min
D
F A RT
P A
D
0:95 mol CO 2 min
1 0:08206 l atm mol
1 K
1
.273 C 25/ K/= 0:0035 atm
D 6652
l
min
;
and the minimum aeration rate per unit volume (vvm) at
this peak CO 2 -TR is
vvm D
v a
V
D
6652 l min
1
9649 l
D 0:68 min
1
:
To achieve a k L a of 57:3 h
1 at a minimum aeration
rate of 0:68 vvm, the bubble size of the aeration system
is adjusted to achieve this value.
9.5 Future Directions for Process Scale Enclosed Photobioreactors
There are two pathways that will drive the future development of process scale photobioreactors.
First, high-value compounds from phototrophic marine organisms will drive the development of artificially
illuminated photobioreactors. New process biotechnologies for the production of high-value compounds
by phototrophic marine organisms in a GMP environment will require artificially illuminated photobioreactors located indoors within climate-controlled manufacturing facilities, similar to those used by fermentation
processes. Furthermore, photobioreactors operating in
a GMP environment must be easily sterilized and fully
290 Part B Tools and Methods in Marine Biotechnology
Table 9.8 Summary of planar photobioreactor design parameters necessary to achieve 20 kg per day biomass production schedule
Parameter
Value and units
Initial cell density C x;I
0:1 g cell L 1
Final cell density C x;f
2:0 g cell L 1
Cultivation time in batch culture t f
22 h
Initial nutrient concentration
C N;i
8:5 mmol N L 1
Incident light intensity I o
150 mol photons m 2 s 1
Mean light intensity at C x;f I m
50 mol photons m 2 s 1
Planes of illumination ˛
2
Light path length L
15 cm
Total cultivation volume V
9648 L (five 2000 L units)
Single vessel width W
6:67 m
Single vessel height H
2:0 m
Peak CO 2 -TR
5:69 mmol CO 2 L 1 h 1
CO 2 partial pressure P A
0:0035 atm (3500 ppm)
Bicarbonate concentration at P A
for pH 8.0, [HCO
3
10:3 mmol L 1
Aeration gas flow rate at P A for
peak CO 2 -TR v a =V
0:69 min 1
Mass transfer coefficient for
peak CO 2 -TR k L a
57:3 h 1 (with 3500 ppm
CO 2 )
production rate (r p ) of 20 kg d
1 is
V D
r p t f
C x;f C x;i
D
20 kg d
22 h 1 d.24 h/
.2:0 0:1/ g l 1 1 kg.1000 g/ 1 D 9649 l :
A culture volume of 9649 L may be too large for a single planar vessel, and so it is decided to build five
2000 L photobioreactors operating in parallel for a total cultivation volume of 10 000 L. For a single planar
vessel, the light path length L or thickness of the vessel is fixed at 15 cm. Furthermore, the height of each
vessel (H) is set at 2 m for the culture, 2:4 m for the
entire vessel to accommodate the gas headspace. The
width of each vessel is, therefore, 6:67 m. The final
recommended design parameters are summarized in Table 9.8.
Based on these design parameters, chemical and energy inputs can be calculated. For example, the inlet
mass flow rate of CO 2 in the aeration gas (F A ) based
on the peak CO 2 -TR and the required culture volume is
F A D CO 2 TR V
D 5:92 mmol CO 2 l h
1 44 mg CO 2
1 mmol 1
1 kg
10 6 mg
9649 l
D 2:51 kg CO 2 h
1
;
which includes both CO 2 supplied by ambient air and
the CO 2 addition to the aeration gas. The total aeration gas flow rate at this CO 2 molar flow rate of
2:51 kg CO 2 h
1 (0:95 mol CO 2 min
1 ) at 25
ı C and
3500 ppm CO 2 partial pressure is
v a;min
D
F A RT
P A
D
0:95 mol CO 2 min
1 0:08206 l atm mol
1 K
1
.273 C 25/ K/= 0:0035 atm
D 6652
l
min
;
and the minimum aeration rate per unit volume (vvm) at
this peak CO 2 -TR is
vvm D
v a
V
D
6652 l min
1
9649 l
D 0:68 min
1
:
To achieve a k L a of 57:3 h
1 at a minimum aeration
rate of 0:68 vvm, the bubble size of the aeration system
is adjusted to achieve this value.
9.5 Future Directions for Process Scale Enclosed Photobioreactors
There are two pathways that will drive the future development of process scale photobioreactors.
First, high-value compounds from phototrophic marine organisms will drive the development of artificially
illuminated photobioreactors. New process biotechnologies for the production of high-value compounds
by phototrophic marine organisms in a GMP environment will require artificially illuminated photobioreactors located indoors within climate-controlled manufacturing facilities, similar to those used by fermentation
processes. Furthermore, photobioreactors operating in
a GMP environment must be easily sterilized and fully