The bioreactor with sunlight supply system and gas exchange systems presented has proved feasible in ground tests and shows much promise for space use as a closed ecological life support system device. The chief conclusions concerning the specification of total system needed for a life support system for a man in a space station are the following: (1) Sunlight supply system - compactness and low electrical consumption; (2) Bioreactor system - high density and growth rate of chlorella; and (3) Gas exchange system - enough for O2 production and CO2 assimilation

Furune, H.

Matsumoto, K.

Mori, K.

Ohya, H.

English

NASA Technical Reports Server

SUNLIQIT SUPPLY AND GAS EXCIMGE SYSi'EPlS IN MICROALclAL BIOIEACTOR 
K. Mori*, H. Ohya**, K. Matsumto**, and H. Funme*** 
*Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223, Japan; **Yokoham 
National University, Tbkiwadai, Hodogaya-ku, Yokohama 240, Japan; ***La 
Foret Engineering and Infomation Service Co., 2-7-8 Toranonvn, Minato-ku, 
Tokyo 105, Japan 
ABSTRACT 
The bioreactor w i t h  sunl ight  supply system and gas exchange s y s t e m  presented here has proved 
feas ib le  i n  ground tests and shows much promise f o r  space use as a CELSS device. 
O u r  chief conclusions concerning the  specif icat ion of total system needed f o r  a l i f e  support 
system f o r  a man i n  a space s t a t i o n  are t h e  fo l lming .  
(1) Sunlight supply system : compactness and low electrical conswption. 
(2) Bioreactor system : high densi ty  and growth rate of chlorel la .  
(3) G a s  exchange system : enough f o r  0 2  production and COz assimilation. 
1NrmwcT10N 
The sunl ight  supply system /1-2/ presented w i l l  provide the visible solar radiat ion neces- 
s a r y  f o r  the  various a c t i v i t i e s  i n  the space s ta t ion ,  such as cul t iva t ion  e x p r h t s  on 
algae,  plants ,  f i shes ,  birds, and animals room, l ight ing f o r  nudules, a d  crew sun-bathing. 
Even na tura l  solar rays reaching the earth's surface contain u l t rav io le t  rays of &ium and 
long wavelengths (w-B and w-A) and infrared and heat rays, a l l  of which are harmful to 
l i f e .  On a space s t a t i o n ,  the mst dangerous short-wavelength u l t rav io le t  rays (UB-C), x- 
rays, and gamna-rays are added, and those c i t e d  above are present  i n  markedly higher inten- 
s i t y .  I t  w i l l  thus  only be a f t e r  elimination of these harmful rays that spacial solar rays 
w i l l  be u t i l i z a b l e  i n  the space s t a t i o n  f o r  activities related to the l i f e  sciences. With 
respect to the &generative Life  Support System i n  CELSS, t h e  main function of the microalgal 
bioreactor w i t h  gas exchange system to supply 02 and assimulate exhaust of co;! f o r  a man i n  
a space s ta t ion ,  though another would be to produce a lga l  biomass f o r  a human food and medi- 
cine: the  biomass protein,  carbohydrate, and/!-carotene would be useful. 
CCNCEFT AND BASIC DESIGN OF "WTAL SYSTEM 
Sunliqht Supply System 
The basic design of the sunlight supply system is s h  
i n  Figure 1 /l/. The solar rays are wllected and concen- 
t r a t e d  by a fac tor  of 10,000 by ~ a n s  of a solar collector 
assenbly prrposed of m y  stall Fresnel lenses. 
Limitation of the admitted spectral band to t h e  v i s i b l e  
region (380-770 MI wavelength) is made possible by the  
chromatic abberation of  the individual Fresnel lenses. 
Chromatic aberrat ion caused by the Fresnel lenses separates 
the EO& pints of d i f f e r e n t  wavelengths, so that placing 
the  end of the f i b e r  o p t i c  cable a t  t h e  focus of green 
l i g h t  admits rminly the visible spectrum (Figure 2) .  
The solar rays focused by each .mall lens are fed through 
the well-polished terminal end of a flexible light-con- 
ducting f i b e r ,  and are confined within its quartz core 
for transmission to the  required location. 
Solar col lect ion is prfoonred by Fresnel lenses assenbled 
i n  a honey& lattice as i l l u s t r a t e d  i n  Figure 1. 
front  face of each is covered by a protector  serving also 
as a f i l t e r .  
to scratching, and is suf f ic ien t ly  th ick  to withstand mst 
inpinging neteoroids, debris and deposi ts  that m y  be 
encountered. Moreover, i n  t h e  event of damage to the 
protector ,  the affected un i t  can be c u t  o f f  and sealed of f  
from the rest of  the system, which  can continue functioning 
i n g  independently. The space between protector  and array collector. 
The 
The protector  is  made of quartz, is r e s i s t a n t  
. a  
M 
Fig.1 Basic design of solar 
45 
https://ntrs.nasa.gov/search.jsp?R=19880002876 2020-03-20T08:39:25+00:00Z
Research &del 1450 OMA with an 0.5 nm wavelenqth'&xemnt 
independently. 
evaporation of the c o w n e n t  m t e r i a l s .  
Figure 3 is a graph showing the HIMAWARI l igh t  collector 's  
visible spectrum transmissivity. 
alrrost a l l  d t r a v i o l e t  radiation is excluded, while infrared 
heat radiation is cut by about forty percent. 
m e r  analysis was carried out w i t h  a Princeton Applied 
The space between protector and array is f i l l ed  
w i t h  an inert gas t o  allow terrperature control and t o  suppre F r e s n l . 1  Lr*l l? 
As can be seen in Figure 3, 
Light spectrum 
as0 100 'DO so0 'DO 700 000 
Y R V E  L E t I G I H  [nil 
A : Solar spectrum ( so l a r  cons tan t )  i n  space near the earth. 
I3 : Vie s m  spctrun a f t e r  passing through a IlinUWari Light 
Col lec tor  of GO% transmissivity.  
Fig.3 Graph d m n s t r a t i n g  the H h w a r i  Light Collector's 
vis ible  spectrum transmissivity and its blocking 
of W and I R  wavelengths in space. 
connected to an optical f iber  branched 
off from the m i n  trunk. 
Microalgal Bioreactor System 
Within the hexagonal bioreactor 
tank, the tubular fiber-optic l igh t  
radiators /3/ are arranged vertical-  
l y  i n  a uniform pattern to provide 
a high radiative surface per v o l u s ~  
of a lgal  suspension (Figures 4 and 5). 
Light entering the tank through the 
fiber-optic cables passes into 
acrylic opt ical  rods ( l igh t  guides), 
which form the centers of the l igh t  
radiators. Ihe cladding of these 
radiators has a lower refractive 
index than conventional quartz 
optical  f ibers.  
D i r e c t  k r s i o n  of the acryl ic  rods 
i n  the algal  suspension results i n  
l i t t le l iqh t  efflux a s  w e l l  a s  
Fig.2 Fresnel lens chronutic 
aberration l igh t  
f i l t r a t i o n  system. 
Fiber  Connector 
7 
clogging of the l igh t  openings with Fig.4 Photoautotrophic Fig.5 Fiber-optic l igh t  
microalgae. hcas ing  the rods in  bioreactor tank. radiator detai l .  
a i r - f i l led acryl ic  tubes solves both 
p r o b l m ,  and also helps scatter 
the light.  
is 1.5 mn, and mst cells axe i l l h n a t e d  from a l l  sides. 
the cladding and spced a t  one-centirrcter intervals allow l igh t  t o  escape evenly along the 
rod length to illuminate the algal  suspension (Figure 5). 
The ITliuLirmrm l ight  path through the suspension from luninant surface to algal  cell 
Wedge-shaped c u t s  passing through 
46 
Gas Exchange System 
Figure 6 shcws a schematic flow diagram of the system used for masuremnt of carbon 
dioxide dissolution in to  the solution from the gas phase. 
mde of micro-prous polypropylene mnbrane, which was supplied by the Mitsubishi Rayon Co., 
Ltd.. 
oxygen from the solution, which uses the same hollow f iber  mxlule. 
f iber  was  kept a t  reduced pressure so as to increase par t ia l  pressure difference of O2 over 
the micro-porous m r a n e .  
It  uses a hollow fiber rrodule 
Figure 7 shows the schematic flow diagram of the system used to recover dissolved 
The bore of the hollow 
l . ib l lar  F h r  Ebdule 2.purp 3.Pressure Gauge 
4.cD2 Dcsitareter 5.~41 Controller 6.Trap 
7,Bioreactor 8.NaUl Solutim 
Fig.6 Apparatus for masuremnt of carbon 
dioxide dissolution using hollow 
f iber  rrodule. 
Theoretical mthcds. Carbon dioxide dissolution. The 
bioreactor contained one liter of pure water, which was cir- 
culated through the mxlule a t  a fixed flow rate (Figure 6 ) .  
The mixture of air and CO2 was fed into the bore of the hol- 
low f iber  and dissolved into the water flowing outside of 
the fiber.  
masured by CO2 destcmter and recorded. 
mss transfer coefficient,  KL, constant, C& a t  any t h  m y  
be expressed by the following equation: 
The concentration of CO2 i n  the water, Cm, was 
Assuming overall 
1. lb l lcu  Fiber m u l e  2.Pmp 3.vcssel 
4 .Ccnsmt Tarp. kth 5.vaccun P w p  
Fig.7 Oxygen recovery system. 
c -cAL 
= exp (-% * a - t) A 
'A - '0 
where CA = H - (2) 
PA, H, and a are  partial pressure of cO2 i n  the gas mixture, 
€ienry's constant, and specific mnbrane area, respectively. 
Oxygen recovery. 
(instead of oxygen) was fed into the mxlule, where it flmed 
outside of the hollow fiber. 
surface of the micro-porous mnbrane and disappeared gradu- 
a l ly;  they were sucked through the m r a n e  because the 
pressure of the bore was kept a t  about 180 mn Hg. 
not p e m a t e  through the mnbrane. 
Chharacteristic. 
of CO2 on KL a t  two levels of water flow rate. Figure 9 
shows the effects  of water flow rate on KL. The values of 
KL s h  i n  figure were analyzed by Wilson's mthod to ob- 
t a in  l iquid phase mss transfer coefficients,  KL, and %. 
The overall mss transfer coefficient,  KL, i n  this case m y  
be expressed as follows: 
Water dispersed with t iny bubbles of air  
The bubbles attached t o  the 
Water did 
Figure 8 shows the effects  of concentration 
;=h+ E I + 1 (3)  
( 4 )  
1 - -  K  1.28 . IO-' . v O - ~  
L 
where D/I  = 0.248 [m/S1 
Fig.8 Over-all mss transfer 
Coefficient KL heavily 
depends on the wncen- 
t ra t ion of car txm diox- 
ide in the gas mixture. 
Fig.9 Over-all mss transfer 
Where I and D are nmbrane thickness and diffusivity,  respec- coefficient I<L 
t ively,  of CO2 i n  the gas mixture. increases w i t h  flow 
in  terns of m3/s.  rate of liquid. 
v is f l m  ra te  of water 
47 
EXPERIMENTAL TEST 
The bioreactor system consists of the l igh t  col- 
lection and transmission apparatus, the photo- 
autotrophic bioreactor, and the &rane device 
for  gas exchange (Figure 10). P%xLsxement and 
control devices were employed fo r  e x p r h n t a t i o n .  
11 ature of  chlorella solution upon the growth 
rate of chlorella. Although such tenperatures -10- 
are comronly much higher, the op tbun  grad91 f 
temperature fo r  chlorella occurred a t  24-26OC 
fo r  this bioreactor a t  the gas mixture given 
earlier, perhaps because of  the unique nature 
of  visible spectrum light.  
that the rate of chlorella density change in- 
creases w i t h  density but levels off  due to at- 
tenuation of the incoming light. Eventually, 
'- 
C 8 -  
; ,- 
! 6 -  Figure 12 shows 
0 
8 5 -  
0 4 -  
Bioreactor Testing without G a s  Exchange System 
.&Iar uat Collector -- p = 3.4-3.5 O 
[ P  = 4.1-4.2 
-- p =  4.1-4.2 A 
CU2= 27.6 yh 
O2 = 22.P Lh 
N2 -214.0 yh 
xenon- 
( 10.4 I)  
0 ( 8.5 I1 
( 81.1 %) 
0 0  O 
0 .  e *  
O 
0 
0 0 
. 
. A  
. A  
Apparatus and methods. The l i gh t  collector, 
called the "HIMAWAFS" /4/, is produced m r -  
c ia l ly  by a Tokyo-based engineering firm, La 
Foret Engineering and I n f o m t i o n  Service Co., 
Ltd.. 
factured to be transparent to  the vis ible  spec- 
trum (transmissivity of 96% per ten meters), 
since those used i n  the ummmications industry 
are transparent t o  the infrared region. 
Chlorella was cultivated within the bioreactor 
i n  two d u m  mixtures, one of pH 4.0-4.5 con- 
s i s t i ng  of (mg/L): N ,  63.572; P, 227.608; K ,  
287.308; N a ,  4.689; Mg, 394.458; Fe, 0.500; B, 
0.500; Mn, 0.500; CU, 0.200; b, 9.784, and 
one consisting of Mayers-4NA5. 
cultivated fo r  two or three.weeks i n  aerated 
and illuminated (5% CO2 a i r  a t  30 L/h and 
10,000 lx)  glass bottles before being sus- 
pended i n  the bioreactor medium. 
The opt ical  fibers are specially manu- 
Innocula were 
u 0.2-  
u 
i 
system (xenon Lmp) 
I I I 
ed by increasing the density and an optimum is 
reached. To control the density constantly is 
thus found to be an h p r t a n t  operation fo r  
minimum energy loss. Figure 13 shows tha t  the 
rate of  chlorella density change changes line- 
a r ly  w i t h  respect to the visible l i g h t  trans- 
mission energy. By approximating this linear 
relationship, higher value data p i n t s  w e r e  
plotted. 
=214.0 Lh 
( 81.1 % I  
5264.0 yh 
Tenp.- 26.0 .C 
3 e 0.4 
0 5 10 15 
Density of (;hlorella m ~ L C  Snlution : P lg/LI 
Fig. 12  Relationship between rate of chlo- 
rella density change and density 
of chlorella i n  basic solution. 
Total Gas F l w  
=264.0 Lh 
(100.0 % I  
20 25 30 
Tenperatwe of Chlorella Suspensiar I'Cl 
Fig. 11 Effect of tenperature of chlorella 
growth rate. 
Experhntal  mta 
50 100 
V i s ~ l e  Fay Trwmssum mergy p l ~  titer ( 1 W l  
Fig.13 Relationship between rate of chlo- 
rella density change and vis ible  
ray transmission energy per liter. 
48 
Dioreactor Testing with Gas Exchange System 
hterial 
Inner Dianeter Imnl 
Wemal Dianeter[mnl 
Wall mickmss Imnl 
rmn2] 
Apparatus and mthcds. In this tes t ing d r a n e  for gas 
exchange, the silicone-rubber hollcw f iber  d u l e  w a s  used 
because this one did not s h w  loadings and a change w i t h  
passage of operation t h .  
(8.4*10-6 [m/s])  is higher than polypropylene one. 
h r a n e  uni t  case is made of glass and can be a u t o c l a d .  
This d r a b e  device was  designed by L a  Foret Engineering, 
and mufac tured  by Fuji-Systens Co.. 
are sbwn i n  Figure 14. 
The operation conditions of gas exchange system are s h  
i n  Table 1. 
5W, and 3W i n  repeated cycles. The incident l igh t  inten- 
s i t y  i n  a lw earth orbit typically consists of alter- 
nating periods of th i r ty  minutes of darkness and sixty 
minutes of light. 
controllable source of i l lmina t ion  because of the simi- 
l a r i t y  of their vis ible  spectrum to that of the sun. 
Xenon lanps coupled w i t h  parabolic mirrors to produce a 
parallel flux can use the s a  chromatic aberration f i l -  
ter ing and fiber-optic ducting as  that of sunlight. Be- 
cause the lanps are separated from the bioreactor by the 
fiber-optic cables, w a s t e  heat is not a concern. 
The chlorella solution recycled throqh the bioreactor and 
rmbrane device for  gas exchange. 
Dco2 were controlled through the pressure and flow rates of 
the 032 and N2 supplies. 
production could not be analyzed directly.  
level  of 02 production and chlorella production were cal- 
culated by the r a t e  of Dco;! change. 
'fie value of si l icone KL 
The 
Its specifications 
Input p e r  levels of the Xenon larrp were 9W, 
Xenon lanps are used as an a r t i f i c i a l ,  
The levels of D3 and 
In  this test, the level of 02 
Therefore, the 
.EbkA Conparision between Si l imne  and Polypropylene. 
Silicane Fubber 
0.60 
0.90 
0.15 
0.082 
a d o r e l l a  Solution 
t 
C .s 0.5-  
Y 
o--o.3- 
pI 0.2-  
0.1 
1 0 . 4 -  
a 
yl 
1 
1' 
m o r e l l a  Solution 
- 
1) mrane thickness 25p conversion, 25OC, an3/m2.atm.24h 
During the l igh t  periods Do concentration increased while tha t  of D(1102 decreased. 
Results. 
tion. 
The opposite occurred during the dark periods. 
f r o m  Figure 15. 
repeated. 
of 02 production. 
Figure 15 shws O r b i t  cycle l igh ts  alternation's e f fec t  on Dco, and Do concentra- 
The photosynthetic reaction was demnstrated 
During each i l lmina t ion  cycle, the Do and Dco2 concentration pattern was 
Figure 16 shows the relationship between vis ible  ray transmission energy and rate 
The p e r f o m c e  of the mnbrane gas exchanger was  constant through the 
long duration of the experiment. 
10 I- I 
0 90 180 270 160 
0.81 
4 
A 
8 
I I I 
0 5 10 
Visible  Ray Trananrssion mqy : Eo IW! 
fh l rni t i l  1-8 TJi;rlrw tlm-,-: Illimirrnirr timl Fig.16 Relationship between rate  of 02 
Fig. 15 O r b i t  cycle alternating l i g h t ' s  production and vis ible  ray 
transmission energy. e f fec t  on Do32 and Do concentration. 
49 
The bioreactor with sunlight supply system and gas exchange system presented here has 
proved feasible i n  ground tests and shms much promise for  space use as  a CEISS device. 
Our chief conclusions concerning the  specification of total system needed for  a l i f e  support 
System for a rn i n  a space station are the fo l lming  (Table 2 ) .  
(1) Sunlight supply system : area of solar ray receiving lens : 6.29-9.37 n?, electrical 
p e r  conslnrption : 37-56 W. 
(2) Bioreactor system : v o l m  of chlorella solution : 50 L, radiative surface per l i ter  : 
0.58 d / L ,  s ize  of bioreactor tank : 0.4 q d  x 1.0 m. 
(3) Gas exchange system : effective d r a n e  area of silicone-rubber h o l l m  d u l e  : 1.33 d .  
Chlorella photosynthetic efficiency is 7%, which is higher than tha t  one of high plant (0.1- 
1 .0%) .  
space station. 
Microalgal bioreactor system w i l l  be best system for  a l i f e  s u p p r t  system i n  a 
Table 2 -red per fomce and simulated specification of total system. , 
1. 
2. 
3. 
4. 
5. 
6. 
a) eqerinental data b) predicated data 
1) Average mss of 02 needed p r  day for a rrtvl in a space station is 686 g /5/. 
2) The rate of  
3) Definition of the fornula 
cunsrnrpticn as chlorella respitation (basal netatolism) is 108 o f  photosynthetic b i m s s .  
( 6 )  
* 
AQI : chimq in total nuss of chlorella [q] 
A : Solar mnstant valm : 1,35JlW/dl k : visrble spc tm energy fraction : 48111 
EO ' 8 6 0 l ~ d / W I  I51 , EO = A . k . SL . T 
E& : energy p~ mit b i m s s  chlorella : 5.6lkcal/ql 
4 )  The electrical  p~ mnslnption of HIPWAN pee one square mter of lens is 5 . 9 3 l W d I  / 6 / .  
5 )  The rate of Xemn lanp electrical  p e r  change for vis ible  ray transmission enerw is lOl8J. 
REFERENCES 
K. Mri, N. Tanatsugu and M. Y-hita, V i s i b l e  so la r - ray  supply system f o r  space s t a t i o n ,  A c t a  
Astronautica.  (the Journal of the I n t e r n a t i o n a l  Acadeny o f  A s t r o n a u t i c s ) ,  Vo1.13, No.2, p.71 (1985) 
K. Mri, Photoautotrophic b i o r e a c t o r  us ing  v i s i b l e  solar r a y s  condensed by Fresne l  l e n s e s  and t rans-  
mitted throgh o p t i c a l  fibers, Biotechnology and Bioengineering, No.15, p.331 (1986) 
John Wiley 6 Sons, Inc.  
K. mri ( i n v e n t o r ) ,  "Photoradiator",  Japanese P a t e n t  Appl ica t ion  No.78,809/82, 78,810/82, 97,459/82, 
99,775/82. 
K. Mri ( i n v e n t o r ) ,  "Apparatus for C o l l e c t i n g  and Transmi t t ing  Solar Energy", U.S. P a t e n t  N0.4,461,278 
R.D. Johnson, A c losed  l i fe -suppor t  system for spa= colonies ,  77-ENAs-18 (1978) ASIT publ ica t ion  
M. Oleson and R.L. Olson, Conceptual des ign  o p t i o n  study-controlled e c o l o g i c a l  l ife support system 
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50 


Sunlight supply and gas exchange systems in microalgal bioreactor

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