Simultaneous control of turbidity and dilution rate through adjustment of medium composition in semi-continuous Chlamydomonas cultures.
For production of starch in algal cultures, a growth rate limited by a nutrient is an important factor. Under phototrophic conditions, turbidity must be also paid attention, as the shading effect may affect its productivity. Semi-continuous cultivation methods, which enable control of turbidity and dilution rate (D) at the same time, have been developed for evaluation of those factors on starch production in Chlamydomonas sp. A specific feature of the methods is in a process of alternately feeding medium adjusted at two different nitrogen (N) concentrations. In the turbidostat-based method, a turbidostat culture was operated repeating three steps of determining D within a preset interval, alternating media by comparing the D with a preset value, and adjusting D in the next interval by feeding the selected medium. In the chemostat-based method, turbidity of a chemostat culture was controlled by repeating two steps of alternating media by comparing transmitted photon flux intensity (I) with a preset value and adjusting I by feeding the selected medium. D controlled by the turbidostat-based method reached quickly a preset value as low as 0.010/h, and then it was dispersed around but above the preset value. On the other hand, mean N concentrations of fed media formed a plateau. In the chemostat-based method, I was well controlled to a preset value while the mean N concentrations were a bit fluctuated. Starch concentration varied from 0.052 to 0.41 g/L with turbidity and D defined by these methods.
Faculty of Agriculture, Utsunomiya University, Utsunomiya, Japan.
Isamu
I
Maeda
Yoshiaki
Y
Seto
Shunsaku
S
Ueda
Yukoh
Y
Cheng
Junko
J
Hari
Masaya
M
Kawase
Hitoshi
H
Miyasaka
Kiyohito
K
Yagi
D000818:Animals; D001709:Biotechnology / Q000295:instrumentation / Q000379:methods; D002696:Chlamydomonas / Q000254:growth & development* / Q000302:isolation & purification; D003470:Culture Media; D007700:Kinetics; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation / Q000379:methods; D017785:Photons; D013213:Starch / Q000096:biosynthesis
D003470:Culture Media; D013213:Starch