142
O. Pulz and K. Scheibenbogen
system, as well as the fibre system transferring the light into the reactor chamber.
The latter consists of vertically fixed side-emitting acryl fibres (diameter 3 mm)
covered by transparent protective rods, thus forming tubular radiation bodies
with a diameter of 1 cm (calculated average radiation density approximately
75 liE m- 2 s - 1 at the surface of the radiation bodies during afternoon sun). With
91 densely packed tubes Mori established an O/V-ratio of 755.4 m -1 against
2.4 1 algal suspension, although nearly 60% of the reaction space was occupied
by the lillumination body. With this arrangement, at an initial concentration of
5 gd.wt.1-1 Chlorella pyrenoidosa, Mori has achieved a productivity of
9.6 g d.wt. 1-i d-1, recalculated by calibrating pH decrease with growth rate,
which represents not quite an undisputed peak value. With a xenon high
pressure lamp, used for sunlight simulation, the growth rate was reduced to
5.3 g d.wt. 1-1 d-1 despite the increased (by 23%) light input.
The idea to utilize sunlight by collective devices for biological carbon
dioxide fixation was investigated by Hirata et al. [131], although growth rates
obtained with Chlorella sp. have proven to be distinctly lower. Nevertheless,
Fresnel lens systems are an interesting subject of controlled and defined intake
of natural light in closed vessels. They are used by Eriksen et al. [132] for
constant daylight illumination of algal cells in their tubular "lumostats".
The biophotoreactor developed by Matsunaga et al. [133] for the preparation of glutamate by immobilized cells of the cyanobacteria Synechococcus sp. is
operated only with artificial light. The reactor consists of a column (length
90 cm, diameter 7 cm) which contains 661 parallel fixed light diffusing optical
fibres (LDOF). A LDOF (diameter 1 mm) consists of a PMMA core and
a fluorescein sheath. Internal tensions are produced by additional hot/cold
treatment and cause the diffusion effect. The light of a 400-W metal-vapour
lamp produces at the surface of the fibres an emitting density of 20 ~tE m-2s-1;
for 1.81 algal suspension an O/V-ratio of 692 m -1 is established, the fibres
taking 13.5% of the reaction space. Takano et al. [134] have used this photoreactor for the determination of the growth of cyanobacteria adapted to low
light intensity as liquid culture. They determined a maximum growth of
2 g d.wt. 1-1 d- 1 and a final concentration of 11.2 g d.wt. 1-1 in batch cultivation
with continuous filtration. Main interest was laid on the conversion of CO2 to
biomass. The maximum conversion rate amounted to 4.44 g CO21-1 d- 1 and
by far exceeded the value 0.1-2.6 g d.wt.1- ~ d- 1 of traditional reactors [135],
which despite the low radiation density confirms the excellent efficiency of this
concept. This type of photobioreactor was further used successfully for the
cultivation of Isoehrysis, the production of docosahexanoic acid respectively
[136].
Pulz et al. [115] reported on the development of heat sterilizable LDOFs
which emit light evenly along their length. The simultaneous demand for
sterilization and scale-up suggested basing the whole lighting system on conventional fermentation vessels. A unit of 1600 fibres of 1 mm diameter was constructed for 10-1 fermenters representing a surface/volume ratio of 150 m-1. External
light supply was established by a special reflector with a small, pulsed light
O. Pulz and K. Scheibenbogen
system, as well as the fibre system transferring the light into the reactor chamber.
The latter consists of vertically fixed side-emitting acryl fibres (diameter 3 mm)
covered by transparent protective rods, thus forming tubular radiation bodies
with a diameter of 1 cm (calculated average radiation density approximately
75 liE m- 2 s - 1 at the surface of the radiation bodies during afternoon sun). With
91 densely packed tubes Mori established an O/V-ratio of 755.4 m -1 against
2.4 1 algal suspension, although nearly 60% of the reaction space was occupied
by the lillumination body. With this arrangement, at an initial concentration of
5 gd.wt.1-1 Chlorella pyrenoidosa, Mori has achieved a productivity of
9.6 g d.wt. 1-i d-1, recalculated by calibrating pH decrease with growth rate,
which represents not quite an undisputed peak value. With a xenon high
pressure lamp, used for sunlight simulation, the growth rate was reduced to
5.3 g d.wt. 1-1 d-1 despite the increased (by 23%) light input.
The idea to utilize sunlight by collective devices for biological carbon
dioxide fixation was investigated by Hirata et al. [131], although growth rates
obtained with Chlorella sp. have proven to be distinctly lower. Nevertheless,
Fresnel lens systems are an interesting subject of controlled and defined intake
of natural light in closed vessels. They are used by Eriksen et al. [132] for
constant daylight illumination of algal cells in their tubular "lumostats".
The biophotoreactor developed by Matsunaga et al. [133] for the preparation of glutamate by immobilized cells of the cyanobacteria Synechococcus sp. is
operated only with artificial light. The reactor consists of a column (length
90 cm, diameter 7 cm) which contains 661 parallel fixed light diffusing optical
fibres (LDOF). A LDOF (diameter 1 mm) consists of a PMMA core and
a fluorescein sheath. Internal tensions are produced by additional hot/cold
treatment and cause the diffusion effect. The light of a 400-W metal-vapour
lamp produces at the surface of the fibres an emitting density of 20 ~tE m-2s-1;
for 1.81 algal suspension an O/V-ratio of 692 m -1 is established, the fibres
taking 13.5% of the reaction space. Takano et al. [134] have used this photoreactor for the determination of the growth of cyanobacteria adapted to low
light intensity as liquid culture. They determined a maximum growth of
2 g d.wt. 1-1 d- 1 and a final concentration of 11.2 g d.wt. 1-1 in batch cultivation
with continuous filtration. Main interest was laid on the conversion of CO2 to
biomass. The maximum conversion rate amounted to 4.44 g CO21-1 d- 1 and
by far exceeded the value 0.1-2.6 g d.wt.1- ~ d- 1 of traditional reactors [135],
which despite the low radiation density confirms the excellent efficiency of this
concept. This type of photobioreactor was further used successfully for the
cultivation of Isoehrysis, the production of docosahexanoic acid respectively
[136].
Pulz et al. [115] reported on the development of heat sterilizable LDOFs
which emit light evenly along their length. The simultaneous demand for
sterilization and scale-up suggested basing the whole lighting system on conventional fermentation vessels. A unit of 1600 fibres of 1 mm diameter was constructed for 10-1 fermenters representing a surface/volume ratio of 150 m-1. External
light supply was established by a special reflector with a small, pulsed light