Nejvíce citovaný článek - PubMed ID 20652359
Productivity correlated to photobiochemical performance of Chlorella mass cultures grown outdoors in thin-layer cascades
The microalga Scenedesmus sp. (Chlorophyceae) was cultured in a raceway pond (RWP) placed in a greenhouse. The objective of this case study was to monitor the photosynthesis performance and selected physicochemical variables (irradiance, temperature, dissolved oxygen concentration) of microalgae cultures in situ at various depths of RWP. The data of actual photochemical yield Y(II), the electron transport rate monitored by in vivo chlorophyll fluorescence and photosynthetic oxygen production both in situ and ex situ revealed that (i) even in diluted cultures (0.6 g DW L-1), the active photic layer in the culture was only about 1 cm, indicating that most of the culture was "photosynthetically" inactive; (ii) the mechanism of non-photochemical quenching may not be fast enough to respond once the cells move from the surface to the deeper layers; and (iii) even when cells were exposed to a high dissolved oxygen concentration of about 200% sat and higher, the cultures retained a relatively high Y(II) > 0.35 when monitored in situ. The presented work can be used as exemplary data to optimize the growth regime of microalgae cultures in large-scale RWPs by understanding the interplay between photosynthetic activity, culture depth and cell concentration.
- Klíčová slova
- RWP, Scenedesmus, chlorophyll (Chl) fluorescence, electron transport, green microalgae, non-photochemical dissipation, oxygen production, photic layer, photosynthesis,
- Publikační typ
- časopisecké články MeSH
Photosynthesis, growth and biochemical composition of the biomass of the freshwater microalga Chlamydopodium fusiforme cultures outdoors in a thin-layer cascade were investigated. Gross oxygen production measured off-line in samples taken from the outdoor cultures was correlated with the electron transport rate estimated from chlorophyll a fluorescence measurements. According to photosynthesis measurements, a mean of 38.9 ± 10.3 mol of photons were required to release one mole of O2, which is 4.86 times higher than the theoretical value (8 photons per 1 O2). In contrast, according to the fluorescence measurements, a mean of 11.7 ± 0.74 mol of photons were required to release 1 mol of O2. These findings indicate that fluorescence-based photosynthesis rates may not be fully replace oxygen measurements to evaluate the performance of an outdoor culture. Daily gross biomass productivity was 0.3 g DW L-1 day-1 consistently for 4 days. Biomass productivity was strongly affected by the suboptimal concentration at which the culture was operated and by the respiration rate, as the substantial volume of culture was kept in the dark (about 45% of the total volume). As the cells were exposed to excessive light, the photosynthetic activity was mainly directed to the synthesis of carbohydrates in the biomass. In the morning, carbohydrate content decreased because of the dark respiration. Per contra, protein content in the biomass was lower at the end of the day and higher in the morning due to carbohydrate consumption by respiration. The data gathered in these trials are important for the future exploitation of Chlamydopodium fusiforme as a potential novel species in the field of microalgae for the production of bio-based compounds.
- Klíčová slova
- Biomass composition, Chlamydopodium fusiforme, Chlorophyll fluorescence, Microalgae, Photosynthesis,
- MeSH
- biomasa MeSH
- chlorofyl a MeSH
- Chlorophyta * metabolismus MeSH
- fotosyntéza MeSH
- kyslík metabolismus MeSH
- mikrořasy * metabolismus MeSH
- sacharidy MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chlorofyl a MeSH
- kyslík MeSH
- sacharidy MeSH
The microalga Chlamydopodium fusiforme MACC-430 was cultured in two types of outdoor pilot cultivation units-a thin-layer cascade (TLC) and a raceway pond (RWP) placed in a greenhouse. This case study aimed to test their potential suitability for cultivation scale-up to produce biomass for agriculture purposes (e.g., as biofertilizer or biostimulant). The culture response to the alteration of environmental conditions was evaluated in "exemplary" situations of good and bad weather conditions using several photosynthesis measuring techniques, namely oxygen production, and chlorophyll (Chl) fluorescence. Validation of their suitability for online monitoring in large-scale plants has been one of the objectives of the trials. Both techniques were found fast and robust reliable to monitor microalgae activity in large-scale cultivation units. In both bioreactors, Chlamydopodium cultures grew well in the semi-continuous regime using daily dilution (0.20-0.25 day-1). The biomass productivity calculated per volume was significantly (about 5 times) higher in the RWPs compared to the TLCs. The measured photosynthesis variables showed that the build-up of dissolved oxygen concentration in the TLC was higher, up to 125-150% of saturation (%sat) as compared to the RWP (102-104%sat). As only ambient CO2 was available, its shortage was indicated by a pH increase due to photosynthetic activity in the thin-layer bioreactor at higher irradiance intensities. In this setup, the RWP was considered more suitable for scale-up due to higher areal productivity, lower construction and maintenance costs, the smaller land area required to maintain large culture volumes, as well as lower carbon depletion and dissolved oxygen build-up. KEY POINTS: • Chlamydopodium was grown in both raceways and thin-layer cascades in pilot-scale. • Various photosynthesis techniques were validated for growth monitoring. • In general, raceway ponds were evaluated as more suitable for cultivation scale-up.
- Klíčová slova
- Chlamydopodium, Chlorophyll fluorescence, Microalga, Oxygen production, Photosynthesis, Pilot-scale bioreactors,
- MeSH
- biomasa MeSH
- bioreaktory MeSH
- Chlorophyceae * MeSH
- Chlorophyta * MeSH
- fotosyntéza fyziologie MeSH
- kyslík MeSH
- mikrořasy * MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- kyslík MeSH
Microalgae cultures were used for a WW treatment to remediate nutrients while producing biomass and recycling water. In these trials, raceway ponds (RWPs; 1 and 0.5 ha) were located next to a municipal (WW) treatment plant in Mérida, Spain. The ponds were used for continuous, all-year-round microalgae production using WW as a source of nutrients. Neither CO2 nor air was supplied to cultures. The objective was to validate photosynthesis monitoring techniques in large-scale bioreactors. Various in-situ/ex-situ methods based on chlorophyll fluorescence and oxygen evolution measurements were used to follow culture performance. Photosynthesis variables gathered with these techniques were compared to the physiological behavior and growth of cultures. Good photosynthetic activity was indicated by the build-up of dissolved oxygen concentration up to 380% saturation, high photochemical yield (Fv/Fm = 0.62-0.71), and relative electron transport rate rETR between 200 and 450 μmol e- m-2 s-1 at midday, which resulted in biomass productivity of about 15-25 g DW m-2 day-1. The variables represent reliable markers reflecting the physiological status of microalgae cultures. Using waste nutrients, the biomass production cost can be significantly decreased for abundant biomass production in large-scale bioreactors, which can be exploited for agricultural purposes.
- Klíčová slova
- Micractinium, biomass, biostimulanting activity, chlorophyll fluorescence, large-scale bioreactor, microalga, oxygen production, photosynthesis, raceway pond, wastewater,
- Publikační typ
- časopisecké články MeSH
The present work characterizes a submerged aerated hollow fiber polyvinylidene fluorid (PVDF) membrane (0.03 μm) device (Harvester) designed for the ultrafiltration (UF) of microalgae suspensions. Commercial baker's yeast served as model suspension to investigate the influence of the aeration rate of the hollow fibers on the critical flux (CF, J c) for different cell concentrations. An optimal aeration rate of 1.25 vvm was determined. Moreover, the CF was evaluated using two different Chlorella cultures (axenic and non-axenic) of various biomass densities (0.8-17.5 g DW/L). Comparably high CFs of 15.57 and 10.08 L/m/2/h were measured for microalgae concentrations of 4.8 and 10.0 g DW/L, respectively, applying very strict CF criteria. Furthermore, the J c-values correlated (negative) linearly with the biomass concentration (0.8-10.0 g DW/L). Concentration factors between 2.8 and 12.4 and volumetric reduction factors varying from 3.5 to 11.5 could be achieved in short-term filtration, whereat a stable filtration handling biomass concentrations up to 40.0 g DW/L was feasible. Measures for fouling control (aeration of membrane fibers, periodic backflushing) have thus been proven to be successful. Estimations on energy consumption revealed very low energy demand of 17.97 kJ/m3 treated microalgae feed suspension (4.99 × 10-3 kWh/m3) and 37.83 kJ/kg treated biomass (1.05 × 10-2 kWh/kg), respectively, for an up-concentration from 2 to 40 g DW/L of a microalgae suspension.
- Klíčová slova
- energy, filtration, harvesting, membrane, microalgae,
- Publikační typ
- časopisecké články MeSH
We have worked out a rapid 1-day test based on photosynthesis measurements to estimate suitable growth temperature of microalgae cultures. To verify the proposed procedure, several microalgae-Chlorella, Nostoc, Synechocystis, Scenedesmus, and Cylindrospermum-were cultured under controlled laboratory conditions (irradiance, temperature, mixing, CO2, and nutrient supply) to find the optima of photosynthetic activity using the range between 15 and 35 °C. These activities were recorded at each temperature step after 2 h of acclimation which should be sufficient as oxygen production and the PQ cycle are regulated by fast processes. Photosynthetic activity was measured using three techniques-oxygen production/respiration, saturating pulse analysis of fluorescence quenching, and fast fluorescence induction kinetics-to estimate the temperature optima which should correspond to high growth rate. We measured all variables that might have been directly related to growth-photosynthetic oxygen evolution, maximum photochemical yield of PSII, Fv/Fm, relative electron transport rate rETRmax, and the transients Vj and Vi determined by fast fluorescence induction curves. When the temperature optima for photosynthetic activity were verified in growth tests, we found good correlation. For most of tested microalgae strains, temperature around 30 °C was found to be the most suitable at this setting. We concluded that the developed test can be used as a rapid 1-day pre-screening to estimate a suitable growth temperature of microalgae strains before they are cultured in a pilot scale.
- Klíčová slova
- Chlorophyll fluorescence, Electron transport rate, Microalgae, Photosynthesis measurements, Rapid test, Temperature optimisation,
- MeSH
- Chlorella růst a vývoj metabolismus účinky záření MeSH
- fotosyntéza MeSH
- kinetika MeSH
- kultivační techniky metody MeSH
- kyslík metabolismus MeSH
- mikrořasy růst a vývoj metabolismus účinky záření MeSH
- Scenedesmus růst a vývoj metabolismus účinky záření MeSH
- sinice růst a vývoj metabolismus účinky záření MeSH
- světlo MeSH
- teplota MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- Názvy látek
- kyslík MeSH
In this work, the key moments of the development of the so-called thin-layer cascades (TLC) for microalgae production are described. Development started at the end of the 1950s when the first generation of TLCs was set-up in former Czechoslovakia. Since, similar units for microalgae culturing, which are relatively simple, low-cost and highly productive, have been installed in a number of other countries worldwide. The TLCs are characterized by microalgae growth at a low depth (< 50 mm) and fast flow (0.4-0.5 m/s) of culture compared to mixed ponds or raceways. It guarantees a high ratio of exposed surface to total culture volume (> 100 1/m) and rapid light/dark cycling frequencies of cells which result in high biomass productivity (> 30 g/m2/day) and operating at high biomass density, > 10 g/L of dry mass (DW). In TLCs, microalgae culture is grown in the system of inclined platforms that combine the advantages of open systems-direct sun irradiance, easy heat derivation, simple cleaning and maintenance, and efficient degassing-with positive features of closed systems-operation at high biomass densities achieving high volumetric productivity. Among significant advantages of thin layer cascades compared to raceway ponds are the operation at much higher cell densities, very high daylight productivities, and the possibility to store the culture in retention tanks at night, or in unfavourable weather conditions. Concerning the limitations of TLCs, one has to consider contaminations by other microalgae that limit cultivation to robust, fast-growing strains, or those cultured in selective environments.
Microalgae are able to metabolize inorganic selenium (Se) to organic forms (e.g. Se-proteins); nevertheless at certain Se concentration culture growth is inhibited. The aim of this work was to confirm the hypothesis that the limit of Se tolerance in Chlorella cultures is related to photosynthetic performance, i.e. depends on light intensity. We studied the relation between the dose and irradiance to find the range of Se tolerance in laboratory and outdoor cultures. At low irradiance (250 µmol photons m-2 s-1), the daily dose of Se below 8.5 mg per g of biomass (<20 µM) partially stimulated the photosynthetic activity (relative electron transport rate) and growth of Chlorella cultures (biomass density of ~1.5 g DW L-1) compared to the control (no Se added). It was accompanied by substantial Se incorporation to microalgae biomass (~0.5 mg Se g-1 DW). When the Se daily dose and level of irradiance were doubled (16 mg Se g-1 DW; 500 µmol photons m-2 s-1), the photosynthetic activity and growth were stimulated for several days and ample incorporation of Se to biomass (7.1 mg g-1 DW) was observed. Yet, the same Se daily dose under increased irradiance (750 µmol photons m-2 s-1) caused the synergistic effect manifested by significant inhibition of photosynthesis, growth and lowered Se incorporation to biomass. In the present experiments Chl fluorescence techniques were used to monitor photosynthetic activity for determination of optimal Se doses in order to achieve efficient incorporation without substantial inhibition of microalgae growth when producing Se-enriched biomass.
- Klíčová slova
- Chlorella, Chlorophyll fluorescence, Growth, Irradiance intensity, Photosynthesis, Selenium incorporation,
- Publikační typ
- časopisecké články MeSH
The aim of this work was to study the effect of Se(+VI) on viability, cell morphology, and selenomethionine accumulation of the green alga Chlorella sorokiniana grown in batch cultures. Culture exposed to sublethal Se concentrations of 40 mg · L(-1) (212 μM) decreased growth rates for about 25% compared to control. A selenate EC50 value of 45 mg · L(-1) (238.2 μM) was determined. Results showed that chlorophyll and carotenoids contents were not affected by Se exposure, while oxygen evolution decreased by half. Ultrastructural studies revealed granular stroma, fingerprint-like appearance of thylakoids which did not compromise cell activity. Unlike control cultures, SDS PAGE electrophoresis of crude extracts from selenate-exposed cell cultures revealed appearance of a protein band identified as 53 kDa Rubisco large subunit of Chlorella sorokiniana, suggesting that selenate affects expression of the corresponding chloroplast gene as this subunit is encoded in the chloroplast DNA. Results revealed that the microalga was able to accumulate up to 140 mg · kg(-1) of SeMet in 120 h of cultivation. This paper shows that Chlorella sorokiniana biomass can be enriched in the high value aminoacid SeMet in batch cultures, while keeping photochemical viability and carbon dioxide fixation activity intact, if exposed to suitable sublethal concentrations of Se.
- MeSH
- bioreaktory mikrobiologie MeSH
- Chlorella cytologie účinky léků fyziologie MeSH
- kyselina selenová aplikace a dávkování MeSH
- proliferace buněk účinky léků fyziologie MeSH
- selenomethionin izolace a purifikace metabolismus MeSH
- techniky vsádkové kultivace metody MeSH
- velikost buňky účinky léků MeSH
- viabilita buněk účinky léků fyziologie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- kyselina selenová MeSH
- selenomethionin MeSH
