title: Productivity correlated to photobiochemical performance of Chlorella mass cultures grown outdoors in thin-layer cascades.
abstract: This work aims to: (1) correlate photochemical activity and productivity, (2) characterize the flow pattern of culture layers and (3) determine a range of biomass densities for high productivity of the freshwater microalga Chlorella spp., grown outdoors in thin-layer cascade units. Biomass density, irradiance inside culture, pigment content and productivity were measured in the microalgae cultures. Chlorophyll-fluorescence quenching was monitored in situ (using saturation-pulse method) to estimate photochemical activities. Photobiochemical activities and growth parameters were studied in cultures of biomass density between 1 and 47 g L(-1). Fluorescence measurements showed that diluted cultures (1-2 g DW L(-1)) experienced significant photostress due to inhibition of electron transport in the PSII complex. The highest photochemical activities were achieved in cultures of 6.5-12.5 g DW L(-1), which gave a maximum daylight productivity of up to 55 g dry biomass m(-2) day(-1). A midday depression of maximum PSII photochemical yield (F (v)/F (m)) of 20-30% compared with morning values in these cultures proved to be compatible with well-performing cultures. Lower or higher depression of F (v)/F (m) indicated low-light acclimated or photo-inhibited cultures, respectively. A hydrodynamic model of the culture demonstrated highly turbulent flow allowing rapid light/dark cycles (with frequency of 0.5 s(-1)) which possibly match the turnover of the photosynthetic apparatus. These results are important from a biotechnological point of view for optimisation of growth of outdoor microalgae mass cultures under various climatic conditions.
authors.affiliation: Academy of Sciences, Institute of Microbiology, Opatovický mlýn, Třeboň, Czech Republic. masojidek@alga.cz
authors.forename: Jiří
authors.initials: J
authors.lastname: Masojídek
authors.forename: Jiří
authors.initials: J
authors.lastname: Kopecký
authors.forename: Luca
authors.initials: L
authors.lastname: Giannelli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Torzillo
mesh_terms: D018533:Biomass; D001709:Biotechnology / Q000295:instrumentation / Q000379:methods; D002708:Chlorella / Q000737:chemistry / Q000254:growth & development*; D002734:Chlorophyll / Q000502:physiology; D057446:Hydrodynamics; D008027:Light; D008962:Models, Theoretical; D017440:Photoperiod; D010788:Photosynthesis / Q000502:physiology*; D013696:Temperature
chemical_list: D002734:Chlorophyll