Effects of carbon dioxide feeding rate and light intensity on the fed-batch pulse-feeding cultivation of Spirulina platensis in helical photobioreactor

摘要

The behavior of S.platensis was investigated in this study through fed-batch pulse-feeding cultures performed at different carbon dioxide feeding rates (F=0.44-1.03 g L~(-1) d~(-1)) and photosynthetic photon flux density (PPFD = 80-250 mu mol photons m~(-2) s~(-1)) in a bench-scale helical photobioreactor.To achieve this purpose,an inorganic medium lacking the carbon source was enriched by gaseous carbon dioxide from a cylinder.The maximum cell concentration achieved was 12.8gL~(-1) at PPFD = 166 mu mol photons m~(-2) s~(-1) and F=0.44 g L~(-1) d~(-1) of CO2.At PPFD = 80 and 125 mu mol photons m~(-2) s~(-1) the carbon utilization efficiency (CUE) reached maximum values of 50 and 69%,respectively,after about 20 days,and then it decreased,thus highlighting a photolimitation effect.At PPFD =166 mu mol photons m~(-2) s~(-1),CUE was >90% between 20 and 50 days.The photosynthetic efficiency reached its maximum value (9.4%) at PPFD = 125 mu mol photons m~(-2) s~(-1).The photoinhibition threshold appeared to strongly depend on the feeding rate:at high PPFD,an increase in the amount of fed CO2 delayed the inhibitory effect on biomass growth,whereas at low PPFD,excess CO2 addition caused the microalga to stop growing.