Efficiency of light utilization of Chlamydomonas reinhardtii under medium-duration light/dark cycles.
The light regime inside a photobioreactor is characterized by a light gradient with full (sun)light at the light-exposed surface and darkness in the interior of the bioreactor. Consequently, depending on the mixing characteristics, algae will be exposed to certain light/dark cycles. In this study the green alga Chlamydomonas reinhardtii was cultivated under five different light regimes: (1) continuous illumination; (2) a square-wave light/dark cycle with a light fraction (epsilon) of 0.5 and a duration (t(c)) of 6.1 s; (3) epsilon=0.5, t(c)=14.5 s; (4) epsilon=0.5, t(c)=24.3 s and (5) epsilon=0.8, t(c)=15.2 s. The biomass yield on light energy, protein per photons, decreased under light/dark cycles (epsilon=0. 5) in comparison to continuous light (CL), from 0.207 (CL) to 0.117-0.153 g mol(-1) (epsilon=0.5). Concomitantly, the maximal specific photosynthetic activity, oxygen production per protein, decreased from 0.94 (CL) to 0.64-0.66 g g(-1) h(-1) (epsilon=0.5). Also the quantum yield of photochemistry, yield of the conversion of light energy into chemical energy, decreased from 0.47 (CL) to 0. 23 (epsilon=0.5, t(c)=24.3 s). Apparently, C. reinhardtii is not able to maintain a high photosynthetic capacity under medium-duration light/dark cycles and since specific light absorption did not change, light utilization efficiency decreased in comparison to continuous illumination.
Janssen
M
M
Food and Bioprocess Engineering Group, Department of Food Technology, Wageningen University, 6700 EV, Wageningen, The Netherlands. marcel.janssen@algemeen.pk.wau.nl
de Winter
M
M
Tramper
J
J
Mur
L R
LR
Snel
J
J
Wijffels
R H
RH
D000818:Animals; D019149:Bioreactors; D016825:Chlamydomonas reinhardtii / Q000254:growth & development*; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism; D005453:Fluorescence; D008027:Light; D010100:Oxygen / Q000378:metabolism; D010777:Photochemistry; D017440:Photoperiod; D010788:Photosynthesis
D002734:Chlorophyll; D010100:Oxygen