High density cell culture ofrhodotorula glutinis using oxygen enriched air

R e c e i v e d A u g u s t 12 HIGH DENSITY CELL CULTURE OF RHODOTORULA GLUTINIS USING OXYGEN-ENRICHED AIR Department of Biological Science and Engineering Korea Advanced Institute of Sc

R e c e i v e d A u g u s t 12

HIGH DENSITY CELL CULTURE OF RHODOTORULA GLUTINIS

USING OXYGEN-ENRICHED AIR

Department of Biological Science and Engineering

Korea Advanced Institute of Science and Technology

POB 150, Chongyang, Seoul, KOREA

SUMMARY

concentration of biomass was I00-II0 g/L, whereas with oxygen-enriched

under oxygen limitation and low oxygen requirement under lipid- accumulating condition were found to be advantageous for the high density culture of this microbe

INTRODUCTION Recently, interests for the microbial lipid production have been renewed because of the advent of biotechnology and of the unstable

Rhodotorula glutinis is an extensively studied SCO (Single Cell Oil) microbe (Yoon & Rhee, 1983) Oleagenicity of this yeast is relatively

continuous culture as well as batch culture was known to be suitable for accumulation of the intracellular lipid (Gill, et ai.,1977; Yoon & Rhee, 1983)

However, SCO process is far from industrial realization because of economics, although SCO processes using industrial wastes such as whey

1979) were reported recently In the study described in this communi-

biomass concentration using oxygen-enriched a i r Improvement of volu- metric productivity by using high density culture along with several advantages of the high density culture (Matsumura, 1983) would make a positive step to realizing the SCO process in foreseeable future

MATERIALS AND METHODS

Northern Regional Research Center, USDA, Peoria, IL U.S.A

minerals in gram p e r L 5N-HCI: FeSO4"7H20, 40; CaCI2"2H20 , 40;

MgS04 7H20 and 20.0 g Yeast Extract in 1 L of 60% glucose solution

in a custom-made 5 L fermenter with 2 L initial working volume

and was maintained at 30-60% of air saturation by controlling manually

- 2 v/v/m) For the aeration with oxygen-enriched air, premixed oxygen

feeding was controlled manually according to residual concentration measured intermittently during the culture (1-5%) For the calculation

and agitation at each sampling time

nitrogen was analyzed by micro-Kjeldahl method (A.O.A.C., 1980) Lipid

1982) followed by Folch's washing (Folch et al., 1957)

RESULTS

even under oxygen-limiting condition to reach ii0 g/L concentration

$1utinis did not produce any fermentative by-products even under oxygen-limiting condition

Another fed-batch culture was carried out to produce intracellular lipid by limiting the nitrogen source for the cells previously grown

constant after the exhaustion of nitrogen source and content of the

hr after the start of lipid accumulating condition

centrifugation Classical two phases were observed in the high density culture that yielded 40% lipid content

1 0 0

O~

ul

t O

E

c~

9 ~ L

Time, hr

.5

0

ul c"

> -

0

0

_D.O

El

20

0 20" 40 60 80 100 120

TIRE, hr

F i g i Fed batch culture of R glutinis with air

a) O_-limited growth: Dissolved oxygen fell to zero at the

Z indicated point

b) 02-limited growth was shifted to nitrogen limitation (N.L.)

O ~

150

,_1

r

cq

,-n

50

0 6 - 9

c).o,.-o ,,.~.)

%

"l"q-n i

4 0

T I M E h r

80

O

o

- 4 0

I - 2:

IJu

- 3 0 P

Z

1 - - U

(3

20 E

oj o

Fig 2 Fed-batch culture of R glutinis with oxygen-enriched

maintained at 40% (• 20%) of air saturation

DISCUSSION

seems to be close to maximum cell concentration in the continuously

corresponded to 75% of broth volume after centrifugation The viscosity

concentration 200 g/L (Mori, et al., 1979)

compared to those of batch and continuous culture (60%) The reason for the low lipid content in high density culture is not clear at present

It may be, however, caused by high concentration of salts added during the course of culture, because in high density culture it was difficult

to maintain the concentration of salts in the range physiologically

be concentrated because of increasing concentration of biomass

Oxygen requirement in lipid-accumulating phase was low as shown in Fig lb It was consistent with the result analyzed theoretically using

should be the positive aspects of SCO process over the other processes because usual limitation of bioreactor productivity comes from mass or

the fermentative byproducts that was found to be the main constraints

in a high density culture of E coli B (Pan et al., 1986)

REFERENCES

Mikrobiol., 15, 522

pp 858

24, 1165

Brisbane

226, 497

Microbiol., 33, 231

Pan, J G., and Rhee, J S (1985b) Korean J Chem Eng., 2, 81

Submitted

Rattray, J B M (1984) JAOCS, 61, 1701