Vertical Tubular Photobioreactor Research Articles

Removal of Nitrogen and Phosphorous from Synthetic Wastewater by Oscillatoria sp. Cultivated in Vertical Tubular Photobioreactor under Natural Environmental Conditions

A newly isolated cyanobacterium Oscillatoria sp. from the Sub-Himalayan region of India was assessed for nutrient removal efficiencies. It was cultivated in synthetic wastewater under uncontrolled natural environmental conditions. The filaments of cyanobacterium formed entangled mats which easily floated on the surface of the medium. This characteristic feature was exploited for easy harvesting of the biomass that is hitherto a bottleneck for the industrial scale oil production from microalgae. The cultures of Oscillatoria sp. grown in synthetic wastewater removed 93.02% of 76 mg/L nitrate and 94.11% of 51 mg/L phosphate. The fatty acid profiling of 10-day-old cultures showed the dominance of saturated and monounsaturated fatty acids. The percentages of predominant fatty acids found in Oscillatoria sp. were 25.25% myristoleic acid (14:1w5c), 23.3% myristic acid (14:0), 16.81% palmitoleic acid (16:1w7c), 14.88% palmitic acid (16:0) and 4.765% hexadecanoic acid (16:1 w5c). The biomass productivities of 0.065 g/L/day and 0.05 g/L/day were attained by the cultures grown in synthetic wastewater and control BG-11 growth media respectively. This mesocosm study was conducted under the influence of natural sunlight, uncontrolled temperatures and the presence of biological contaminants namely, bacteria and small ciliates. The main objective of the study was to mimic the outdoor conditions, which is the way forward for achieving economic and environmental sustainability in microalgae biomass production.

The synergistic effects of gamma-aminobutyric acid and salinity during the enhancement of microalgal lipid production in photobioreactors

In the present work, combined application of gamma-aminobutyric acid (GABA) and salinity was used to stimulate biolipid production in the microalga Ankistrodesmus sp. EHY in a vertical tubular photobioreactor. Under 2.5 g L−1 NaCl combined with 50 μM GABA, the strain showed 1.36- and 1.27-fold increases in lipid content (59.42%) and lipid productivity (235.13 mg L−1 d−1), respectively, compared with the control. Wide-ranging analyses of the energy yield, biodiesel quality, cellular ultrastructure, signalling molecules, and lipogenesis genes were conducted to elucidate the role of GABA plus salinity on algal lipid accumulation. By using GABA and salinity treatments, the triacylglycerol (TAG) content and energy yield were increased, whereas the carbohydrate yield was decreased. The biodiesel quality of the algal biomass-derived lipids met the approved standards. The combinational strategy also increased the levels of endogenous reactive oxidative species (ROS), Ca2+, an autophagy-related protein (ATG8), glutathione (GSH) and proline, which might be associated with the increase in lipid synthesis and salt stress tolerance. Moreover, transcriptomic and metabolomic data indicated that the expression levels of TAG assembly, antioxidative system and autophagy-related genes, and the metabolite levels of the TCA cycle, GABA shunt and several stress hormones were consistent with the enhancements in lipid accumulation and stress tolerance. In the presence of GABA and salinity, exogenous proline (50 μM) and salicylic acid (SA; 12.5 mg L−1) further increased the lipid productivity to 280.48 mg L−1 d−1 and 263.58 mg L−1 d−1, respectively. Overall, the results demonstrate the significance, mechanism and applicability of using exogenous GABA combined with salinity to effectively stimulate bioenergy production by microalgae.

Fatty Acid Profile of Microalgal Oils as a Criterion for Selection of the Best Feedstock for Biodiesel Production

Microalgae are considered to be potentially attractive feedstocks for biodiesel production, mainly due to their fast growth rate and high oil content accumulated in their cells. In this study, the suitability for biofuel production was tested for Chlorella vulgaris, Chlorella fusca, Oocystis submarina, and Monoraphidium strain. The effect of nutrient limitation on microalgae biomass growth, lipid accumulation, ash content, fatty acid profile, and selected physico-chemical parameters of algal biodiesel were analysed. The study was carried out in vertical tubular photobioreactors of 100 L capacity. The highest biomass content at 100% medium dose was found for Monoraphidium 525 ± 29 mg·L−1. A 50% reduction of nutrients in the culture medium decreased the biomass content by 23% for O. submarina, 19% for Monoraphidium, 13% for C. vulgaris and 9% for C. fusca strain. Nutrient limitation increased lipid production and reduced ash content in microalgal cells. The highest values were observed for Oocystis submarina, with a 90% increase in lipids and a 45% decrease in ash content in the biomass under stress conditions. The fatty acid profile of particular microalgae strains was dominated by palmitic, oleic, linoleic, and linoleic acids. Nutrient stress increased the amount of saturated and unsaturated fatty acids affecting the quality of biodiesel, but this was determined by the type of strain.

Biocircular platform for third generation biodiesel production: Batch/fed batch mixotrophic cultivations of microalgae using glycerol waste as a carbon source

The green microalga, Scenedesmus incrassulatus PPAY1 was cultivated in vertical tubular photobioreactor under batch/fed-batch modes. Biodiesel derived glycerol waste (BDGW) was applied as a cheap main nutrient source. For batch cultivation (BC), maximum biomass concentration was reached at 2.83 gL-1when 20 gL-1 BGW was used. In contrast, in the case of fed-batch cultivation (FBC), the maximum algae and lipid contents were achieved at 5.65 gL-1 and 58.27%, respectively when 30 and 20 gL-1 BDGW were applied. The highest lipid yield of 2.94 gL-1was found at 30 gL-1 BDGW. The analysis of the fatty acid content revealed that palmitic acid-, oleic acid- and linoleic acid- were mainly found in both BC and FBC conditions. As expected, FBC was in a better culture strategy than BC. BDGW could be used directly without any pretreatment in both algal biomass growth and microalgal oil accumulation which simplifies cultivation and reduces operating costs during biodiesel production.

Biogoriva treće generacije - procesi uzgajanja i dobijanja goriva iz mikroalgi

Energy production from biomass is gaining a lot of attention. Algal oil (microand macroalgae) can be used for biofuel production. Biofuels from this type of feedstock are called third generation biofuels or advanced biofuels. Focus of this paper is on the microalgal biofuels and on the available process technologies. Very important advantage of microalgal biofuels is that microalgae can be cultivated on any type of land, with the possibility of using wastewater streams. Microalgae can be cultivated in open systems, so called "raceway ponds" or in closed systems - photobioreactors: flat panel photobioreactors, horizontal tubular, vertical tubular photobioreactors with or without airlift. Also, basic information on cultivation conditions (photoautotrophic, heterotrophic, mixotrophic and photoheterotrophic) are presented. Available technologies for microalgal biofuels production are: transesterification, fermentation, pyrolysis, hydrothermal liquefaction, anaerobic digestion and biomass to liquids (BtL). Additionally, basic information on life cycle assessment of microalgae cultivation and CO2 sequestration potential is given in the final chapter of this work.

Pengaruh Jarak Penyekat dalam Fotobioreaktor Tubular terhadap Pertumbuhan Kultur Mikroalga Ankistrodesmus convulutus

A series of partition was constructed inside a vertical tubular photobioreactor to control the culture distribution in obtaining intermittent exposure to light area in the surface of the tubular column. A microalga, Ankistrodesmus convulutus, was grown in a batch mode in the reactor with PHM medium, light sources of fluorescent lamp 3 x 40 watt (I = 5.500 lux on the surface of the tubular) and room temperature of 27 – 310C. The experiment was carried out to study the influence of partition density which was constructed at varied distance, which were 1, 2 and 3 inch on the growth and biochemical composition of the alga. A vertical tubular photobioreactor without partition was applied as the control. The partition density did not significantly affect the optical density achievement of the culture, but it significantly affected the biomass and chlorophyll concentration, as well as the protein/carbohydrate ratio of the culture. It is believed that the intermittent exposure of algal cell to the light area leads to sincronization of the light and dark reaction of the photosynthesis, as well as to vapor the catalitic proccesses to develop the functional cell structure.

Combination of Light Emitting Diodes (LEDs) for photostimulation of carotenoids and chlorophylls synthesis in Tetradesmus sp.

In this work, Tetradesmus sp. was investigated regarding biomass and pigment production. The cultivation of Tetradesmus sp. was carried out in a BG-11 medium in addition to a vertical tubular photobioreactor (PBR) irradiated with different spectral combinations and intensities, within a 24:00 h photoperiod. The LEDs emitting light with white; red; yellow; green and blue spectrum were used alone and/or combined, with intensities varying from 13 to 190 μmol m−2 s−1. ANOVA suggested significant effects of the light combination, intensity and interaction between the factors on biomass, carotenoid and chlorophyll responses. The blue light accelerated the growth of Tetradesmus sp. in all three experiments. The combinations white:green (95 μmol m−2 s−1), red:blue (50 μmol m−2 s−1) and blue (25 μmol m−2 s−1) favored biomass growth; while white:green (190 μmol m−2 s−1), red:green (50 μmol m−2 s−1) and red (25 μmol m−2 s−1) favored the synthesis of carotenoids and chlorophylls. Culture reproduction under the spectral regions favoring pigment synthesis indicated that Tetradesmus sp. was photostimulated to synthesize both pigments, especially with red:green (50,50%) at 50 μmol m−2 s−1, where the highest production of carotenoids (6.09 ± 0.29 mg (g biomass)−1) and chlorophyll a (10.08 ± 0.75 mg (g biomass)−1) was obtained.

Carbon Dioxide Biofixation and Production of Spirulina sp. LEB 18 Biomass with Different Concentrations of NaNO3 and NaCl

ABSTRACT Microalgae are efficient at using solar energy to turn CO2 and nutrients into biomass containing lipids, proteins, carbohydrates and other compounds that may be used to produce bioproducts for human and animal consumption and pharmaceutical use. The aim of this study was to assess the effect of the NaNO3 and NaCl concentration on the growth kinetics, the biomass composition and the ability to biofix CO2 using the microalga Spirulina sp. LEB 18. The assays were carried out according to a 22 central composite design (CCD) with different concentrations of NaNO3 (1.25, 1.88 and 2.50 g L-1) and NaCl (1.00, 15.0 and 30.0 g L-1). The assays were carried out in 2 L vertical tubular photobioreactors at 30°C, 12 h light/dark and an injection of 12.0% v/v of CO2 at 0.3 vvm. The best growing results (Xmax = 1.60 g L-1, Pmax = 0.109 g L-1 d-1, μmax = 0.208 d-1) and CO2 biofixation rate (197.4 mg L-1 d-1) were observed in the assay with 1.25 g L-1 NaNO3 and 1.00 g L-1 NaCl. Increasing the NaCl concentration produced biomass with a higher carbohydrate content, while increasing the NaNO3 concentration reduced the protein concentration. According to the results, in addition to using Spirulina as a source of protein, it can also be used as a source of carbohydrates and to biologically remove CO2 from the atmosphere.

Optimization of CO2 Biofixation by Chlorella vulgaris Using a Tubular Photobioreactor

AbstractThe effects of various CO2 concentrations in CO2 bioconversion by cultivation of microalga Chlorella vulgaris were investigated using a vertical tubular photobioreactor. The response surface technique with central composite design was applied to model the CO2 biofixation rate, the specific growth rate (SGR), and the biomass productivity of C. vulgaris as function of CO2 concentration and cultivation time. The developed nonlinear model was employed to determine the optimum CO2 concentration in an air‐CO2 mixture and the cultivation time for maximum CO2 biofixation, SGR, and microalgae biomass productivity. In addition, a multiple responses optimization method was also applied to determine the maximum CO2 uptake rate, the SGR, and the biomass productivity, simultaneously. The predicted optimum values agreed well with the experimental data.

Magnetic fields as triggers of microalga growth: evaluation of its effect on Spirulina sp.

This study aimed at evaluating the influence of magnetic field on the growth and biomass composition of Spirulina sp., cultivated in vertical tubular photobioreactors. Magnetic fields of 5, 30 and 60mT generated by electric current and ferrite magnets were applied at different lengths of time. The magnetic field of 30 and 60mT for 1hd−1 stimulated the growth, thus leading to higher biomass concentration by comparison with the control culture. Increase in productivity, protein and carbohydrate contents were 105.1% (60mT for 1hd−1), 16.6% (60mT for 24hd−1) and 133.2% (30mT for 24hd−1), respectively. These values were higher than the ones of the control. Results showed that magnetic field may influence the growth of Spirulina sp., since it triggers a stimulating effect and can leads to twofold biomass concentration in equal cultivation time periods.

Biological CO2 fixation using Chlorella vulgaris and its thermal characteristics through thermogravimetric analysis.

The present research is focused on cultivation of microalgae strain Chlorella vulgaris for bio-fixation of CO2 coupled with biomass production. In this regard, a single semi-batch vertical tubular photobioreactor and four similar photobioreactors in series have been employed. The concentration of CO2 in the feed stream was varied from 2 to 12% (v/v) by adjusting CO2 to air ratio. The amount of CO2 capture and algae growth were monitored by measuring decrease of CO2 concentration in the gas phase, microalgal cell density, and algal biomass production rate. The results show that 4% CO2 gives maximum amount of biomass (0.9gL(-1)) and productivity (0.118gL(-1)day(-1)) of C. vulgaris in a single reactor. In series reactors, average productivity per reactor found to be 0.078gL(-1)day(-1). The maximum CO2 uptake for single reactor also found with 4% CO2, and it is around 0.2gL(-1)day(-1). In series reactors, average CO2 uptake is 0.13gL(-1)day(-1) per reactor. TOC analysis shows that the carbon content of the produced biomass is around 40.67% of total weight. The thermochemical characteristics of the cultivated C. vulgaris samples were analyzed in the presence of air. All samples burn above 200°C and the combustion rate become faster at around 600°C. Almost 98wt% of the produced biomass is combustible in this range.

Static magnetic fields in culture of Chlorella fusca: Bioeffects on growth and biomass composition

Static magnetic fields (SMF) are being studied in microorganism cultures and there are reports that it could accelerate growth or cause changes in metabolism. Thus, this study aims to evaluating the influence of SMF on growth and biomass composition obtained in culture of Chlorella fusca LEB 111 in vertical tubular photobioreactor (VTP). SMF of 30 and 60mT was generated by ferrite magnets and applied for 24hd−1 and 1hd−1 for 15 days. The growth of C. fusca was evaluated by kinetic parameters and the biomass obtained was evaluated by protein, carbohydrate, and lipid content. SMF of 60mT for 24hd−1 increased the biomass concentration and the carbohydrate content, it was 20.5% and 24.8% higher than control culture, respectively. Magnetic treatment is a new method to culture microalgae that can accelerate growth and increase compounds of interest, which can be used as food or biofuel.

Microalgae biomass production using wastewater: Treatment and costs: Scale-up considerations

This work is part of a LIFE project to treat urban wastewater from Águas da Figueira (AdF, Figueira da Foz, PT) using a vertical tubular photobioreactor (PBR) prototype (150L), to be scaled up and integrated in a waste water treatment plant (WWTP). The PBR was inoculated with three different microalgae: Chlorella vulgaris (Cv), Scenedesmus obliquus (Sc) and Consortium C (ConsC), isolated from the effluent. The study intends to find the best microalga in terms of wastewater remediation, biomass productivity and quality, for further uses, such as biofuel, biofertilizer and bioplastic production.The experiments achieved volumetric productivities of 0.1g/L·d (Cv), 0.4g/L·d (Sc) and 0.9g/L·d (ConsC). The maximum removals attained by Cv, Sc and ConsC were: 84, 95 and 98% for total nitrogen; 95, 92 and 100% for phosphorus; and 36, 63 and 64% for COD, respectively. The treated water had values that are in accordance with environmental legislation (Directive 98/15/CE).Electrocoagulation was tested and resulted in an energy saving of 89%, compared with centrifugation alone. For drying the biomass, a solar dryer was used. Costs of overall processes versus conventional technologies are discussed and compared with other facilities and target values.

Removal of Nitrogen and Phosphorus From Reject Water Using Chlorella vulgaris Algae After Partial Nitrification/Anammox Process.

Wastewater containing nutrients like ammonia, nitrite, nitrate and phosphates have been identified as the main cause of eutrophication in natural waters. Therefore, a suitable treatment is needed. In classical biological processes, nitrogen and phosphorus removal is expensive, especially due to the lack of biodegradable carbon, thus new methods are investigated. In this paper, the new possibility of nitrogen and phosphorus removal in side stream after the partial nitrification/Anammox process is proposed. Research was carried out in a lab-scale vertical tubular photobioreactor (VTR) fed with real reject water, from dewatering of digested sludge, after partial nitrification/Anammox process from lab-scale sequencing batch reactor (SBR). Nitrogen and phosphorus concentrations were measured every three days. The average nitrogen and phosphorus loads were 0.0503 ± 0.036 g N g(vss)/d and 0.0389 ± 0.013 g P g(vss)/d accordingly. Results have shown that microalgae were able to efficiently remove nitrogen and phosphorus. The average nitrogen removal was 36.46% and phosphorus removal efficiency varied between 93 and 100%.

Comparison of four outdoor pilot-scale photobioreactors.

BackgroundMicroalgae are a potential source of sustainable commodities of fuels, chemicals and food and feed additives. The current high production costs, as a result of the low areal productivities, limit the application of microalgae in industry. A first step is determining how the different production system designs relate to each other under identical climate conditions. The productivity and photosynthetic efficiency of Nannochloropsis sp. CCAP 211/78 cultivated in four different outdoor continuously operated pilot-scale photobioreactors under the same climatological conditions were compared. The optimal dilution rate was determined for each photobioreactor by operation of the different photobioreactors at different dilution rates.ResultsIn vertical photobioreactors, higher areal productivities and photosynthetic efficiencies, 19–24 g m−2 day−1 and 2.4–4.2 %, respectively, were found in comparison to the horizontal systems; 12–15 g m−2 day−1 and 1.5–1.8 %. The higher ground areal productivity in the vertical systems could be explained by light dilution in combination with a higher light capture. In the raceway pond low productivities were obtained, due to the long optical path in this system. Areal productivities in all systems increased with increasing photon flux densities up to a photon flux density of 30 mol m−2 day−1. Photosynthetic efficiencies remained constant in all systems with increasing photon flux densities. The highest photosynthetic efficiencies obtained were; 4.2 % for the vertical tubular photobioreactor, 3.8 % for the flat panel reactor, 1.8 % for the horizontal tubular reactor, and 1.5 % for the open raceway pond.ConclusionsVertical photobioreactors resulted in higher areal productivities than horizontal photobioreactors because of the lower incident photon flux densities on the reactor surface. The flat panel photobioreactor resulted, among the vertical photobioreactors studied, in the highest average photosynthetic efficiency, areal and volumetric productivities due to the short optical path. Photobioreactor light interception should be further optimized to maximize ground areal productivity and photosynthetic efficiency.

English

Microalgae use photosynthesis as their principal metabolic mechanism to obtain organic carbon from the inorganic carbon contained in CO2 using solar energy. This process releases oxygen into the atmosphere. The aim of this study was to determine the most appropriate biomass concentration for growing Spirulina sp. LEB 18 (Cyanobacteria) in a vertical tubular photobioreactor with biomass removal and recycling of the medium to maximize CO2 biofixation. The maximum CO2 biofixation was obtained when the culture was maintained at 600 mg L-1 biomass concentration. Under this condition, the highest CO2 biofixation value was 186.8 ± 73.1 mg L-1 d-1, and the maximum productivity was 85.9 ± 6.0 mg L-1 d-1.   Key words: Biofixation, carbon dioxide, microalgae, recycling, tubular photobioreactor.

An integrated approach for biodiesel and bioethanol production from Scenedesmus bijugatus cultivated in a vertical tubular photobioreactor

Algae are considered promising renewable feedstocks for the production of alternative fuels. In this study, an indigenous strain of Scenedesmus bijugatus found commonly in the fresh water bodies was isolated and evaluated for biofuels production. The alga was successfully mass cultivated in the custom made vertical tubular photobioreactor (250L capacity) at semi-continuous mode. During the cultivation period, the volumetric biomass and lipid productivity were assessed. The alga S. bijugatus produced 0.26gL−1d−1 of dry biomass and 63mgL−1d−1 of lipids, respectively. Algal biomass was harvested by a combined harvesting process involving coagulation and flocculation using Iron (III) sulfate and an organic polymer which resulted in 98% harvesting efficiency. Lipid extraction using hexane:diethyl ether (1:2 ratio) resulted in maximum extraction of lipids. This study also examined sequential stages of esterification and transesterification to convert lipids to biodiesel. The maximum biodiesel yield of 0.21g/g of dry biomass was obtained through the acid base catalytic process. The biodiesel fuel properties were tested and observed that most of the properties complying with ASTM D6751 specifications. The lipid extracted residual biomass recorded a yield of 0.158g of bioethanol per g. This study confirmed the potential of lipid extracted biomass for the production of bioethanol to improve the economic feasibility of microalgal biorefinery.

Use of mixed culture bacteria for photofermentive hydrogen of dark fermentation effluent

Hydrogen production (HP) from dark fermentation effluent of starch wastewater via vertical tubular photo-bioreactor was investigated. The reactor was inoculated with mixed culture of bacteria and operated at light intensity of 190W/m2. Hydraulic retention time (HRT) and organic loading rate (OLR) was varied between 0.9 to 4.0h and 3.2 to 16gCOD/l.d., respectively. Increasing the HRT from 0.9 to 2.5h, significantly (P<0.05) increased HP from 1±0.04 to 3.05±0.19l/d, respectively. However, minimal increase in HP occurred when increasing the HRT up to 4.0h. The HP remained unaffected when increasing the OLR from 3.2 to 6.4gCOD/l.d. Further increase in the OLR up to 8.2 and 16gCOD/l.d., resulted in a drop in HP i.e. 0.96 and 0.19l/d, respectively. Microbial community analysis of the reactor samples showed the presence and dominance of hydrogen producing purple non-sulfur phototrophic (PNS) bacterium, Rhodopseudomonas palustris in the reactor.

Bioethanol production from Scenedesmus obliquus sugars: the influence of photobioreactors and culture conditions on biomass production

A closed-loop vertical tubular photobioreactor (PBR), specially designed to operate under conditions of scarce flat land availability and irregular solar irradiance conditions, was used to study the potential of Scenedesmus obliquus biomass/sugar production. The results obtained were compared to those from an open-raceway pond and a closed-bubble column. The influence of the type of light source and the regime (natural vs artificial and continuous vs light/dark cycles) on the growth of the microalga and the extent of the sugar accumulation was studied in both PBRs. The best type of reactor studied was a closed-loop PBR illuminated with natural light/dark cycles. In all the cases, the relationship between the nitrate depletion and the sugar accumulation was observed. The microalga Scenedesmus was cultivated for 53days in a raceway pond (4,500L) and accumulated a maximum sugar content of 29% g/g. It was pre-treated for carrying out ethanol fermentation assays, and the highest ethanol concentration obtained in the hydrolysate fermented by Kluyveromyces marxianus was 11.7g/L.

Erratum to: Media optimization of Parietochloris incisa for arachidonic acid accumulation in an outdoor vertical tubular photobioreactor

Erratum to: Media optimization of Parietochloris incisa for arachidonic acid accumulation in an outdoor vertical tubular photobioreactor