Innovative Photobioreactor Research Articles

Eco-Friendly Innovation: Hydra-Enhanced Miniature Photobioreactor for Air Pollution Reduction

According to the WHO data in 2019, nearly all of the global population resides in areas that do not meet the WHO guidelines for air quality. This study is to address the issue of indoor air pollution through the use of Photobioreactor technology and Hydrilla Verticillata plants. The experimental findings demonstrate that the rate of photosynthesis and production of oxygen bubbles by the Hydrilla plants are significantly influenced by adequate light intensity and exposure to CO2. By employing this innovative Photobioreactor technology, it is anticipated that indoor air quality can be enhanced, thereby contributing to the resolution of air pollution problems. This research adopts a combination of descriptive and experimental methods, utilizing a prototype scale for conducting experiments. Secondary data, in the form of published scientific articles from both international and national journals, serve as the source of data. The collected data is then qualitatively analyzed through descriptive means. Based on the results of data analysis, it can be concluded that this research offers valuable insights into the use of Hydrilla plants in innovative technologies for the improvement of air quality and human health, particularly by implementing photosynthesis processes within Photobioreactor technology.

Photosynthesis driven continuous hydrogen production by diazotrophic cyanobacteria in high cell density capillary photobiofilm reactors

Hydrogen (H2) is a promising fuel in the context of climate neutral energy carriers and photosynthesis-driven H2-production is an interesting option relying mainly on sunlight and water as resources. However, this approach depends on suitable biocatalysts and innovative photobioreactor designs to maximize cell performance and H2 titers. Cyanobacteria were used as biocatalysts in capillary biofilm photobioreactors (CBRs). We show that biofilm formation/stability depend on light and CO2 availabilityH2 production rates correlate with these parameters but differ between Anabaena and Nostoc. We demonstrate that high light and corresponding O2 levels influence biofilm stability in CBR. By adjusting these parameters, biofilm formation/stability could be enhanced, and H2 formation was stable for weeks. Final biocatalyst titers reached up to 100 g l−1 for N. punctiforme atcc 29133 NHM5 and Anabaena sp. pcc 7120 AMC 414. H2 production rates were up to 300 µmol H2 l-1h−1 and 3 µmol H2 gcdw-1h−1 in biofilms.

Towards biomass production and wastewater treatment by enhancing the microalgae-based nutrients recovery from liquid digestate in an innovative photobioreactor integrated with dialysis bag

Microalgae-based nutrients recovery from liquid anaerobic digestate of swine manure has been a hotspot in recent decades. Nevertheless, in consideration of the high NH4+-N content and poor light penetrability exhibited by the original liquid digestate, uneconomical pretreatment on liquid digestate including centrifugation and dilution are indispensable before microalgae cells inoculation. Herein, aiming at eliminating the energy-intensive and freshwater-consuming pretreatment on liquid digestate and enhancing microalgae growth, the dialysis bag which permits nutrients transferring across its wall surface whereas retains almost all matters characterized by impeding light transmission within the raw liquid digestate was integrated into a column photobioreactor (DB-PBR). Consequently, light availability of microalgae cells in DB-PBR was elevated remarkably and thus contributed to a 357.58% improvement on microalgae biomass concentration in DB-PBR than the conventional PBR under 80 μmol m−2 s−1. Likewise, superior nutrients removal efficiencies from liquid digestate were obtained in DB-PBR (NH4+-N: 74.84%, TP: 63.75%) over the conventional PBR (NH4+-N: 30.27%, TP: 16.86%). Furthermore, higher microalgae biomass concentration (1.87 g L−1) and nutrients removal efficiencies (NH4+-N: 95.12%, TP: 76.87%) were achieved in the DB-PBR by increasing the light intensity to 140 μmol m−2 s−1. More importantly, the DB-PBR may provide a simple and greener solution to purify other kinds of wastewater.

Review on carbon dioxide fixation coupled with nutrients removal from wastewater by microalgae

The application of microalgae in carbon dioxide (CO2) fixation coupled with wastewater treatment has been regarded as a promising and cutting-edge technology in recent years, but it still faces some problems. The CO2 fixation capacity and nutrients removal capacity of microalgae should be considered simultaneously under various environmental conditions. Moreover, breeding microalgae using a photobioreactor is required and critical for CO2 fixation and wastewater treatment. In addition, the related influenced factors, mechanisms and kinetics of CO2 fixation and nutrients removal by microalgae remains complex and unclear. Thus, this work provides an updated review of the literature regarding the application of microalgae in the remediation of wastewaters from different sources coupled with CO2 fixation, discusses the main interactions between biological or environmental factors and how they can influence nutrient removal and CO2 fixation efficiencies, and further focuses on their mechanisms and kinetics. It is found that blue-green algae are most suitable to fix CO2 integrating treated wastewater, but more microalgal strains with excellent anti-fouling performance, tolerance to high concentrations of CO2 and NH3–N performance need to be screened. Additionally, wastewater and gas conditions during the cultivation process should be optimized in research and applications, and development of innovative photobioreactors with low cost is also required. Furthermore, modelling mainly focuses on estimating biomass yield, nutrient removal rates and CO2 fixation rates, while laboratory modelling results deviated from the natural modelling results. Finally, this paper also provides insight into what should be done in future work to support the development of CO2 fixation coupled with wastewater treatment by microalgae.

Assessing the potential of microalgae for nutrients removal from a landfill leachate using an innovative tubular photobioreactor

Leachates treatment relies on the adoption of a multi-barrier strategy, involving primary, secondary, and tertiary processes. Due to their ability to grow in a wide variety of environmental conditions, and their nutritional requirements, especially in terms of nitrogen and phosphorus, microalgae appear as a promising alternative for the tertiary treatment of landfill leachates. Despite these advantages, only a few studies have promoted landfill leachates treatment using microalgae, most of them emphasizing the need for effluent dilution in water to minimize the toxicity and high color/turbidity of these effluents. An option to avoid the use of freshwater for effluent dilution would be the development of novel photobioreactors (PBRs), able to improve light absorption and, hence, light utilization efficiency by microalgae. This study evaluated the potential of Chlorella vulgaris and Tetradesmus obliquus on nitrogen (in the forms of nitrate and nitrite) removal from a pre-treated landfill leachate. Preliminary experiments using different concentrations of the pre-treated leachate were carried out in 1-L flasks. These results have shown that microalgal growth and nitrogen removal were higher in more diluted conditions. After selection of the adequate effluent concentration, a tubular PBR coupled to an optical reflector was used for biomass production. This innovative PBR is known to improve light distribution along the tube perimeter, enhancing microalgal photosynthetic activity. In fact, a significant improvement in C. vulgaris biomass productivities and nitrogen species removal efficiencies was observed in this PBR, confirming its potential as an effective platform for microalgal biomass production and tertiary treatment of landfill leachates.

Recovery of proteins from biomass grown in pig manure microalgae-based treatment plants by alkaline hydrolysis and acidic precipitation

The influence of three variables on key parameters of the protein extraction process (an alkaline hydrolysis followed by an acidic precipitation) for biomass from innovative photo-bioreactors for pig manure treatment was evaluated. Alkaline hydrolysis provided high solubilisation values (up to 66.5% of the biomass), augmenting with increasing values of the three studied variables (NaOH concentration, temperature and time). Nevertheless, moderate total (13.2%) and protein extraction yields (16.9%) were obtained, which was attributable to protein denaturation or to the low effectivity of the precipitation method. Extracts rich in proteins (53.5%–77.9%) with suitable amino acid profiles were obtained, but significant amounts of the initial lipids (up to 44.6%) were co-extracted probably due to fatty acids saponification. These results establish the first step for future studies in enhancing cell wall disruption and protein recovery by coupling alkaline hydrolysis with other mechanical pre-treatments, while considering alternative separation and purification methods.

Coupling a simple irradiance description to a mechanistic growth model to predict algal production in industrial-scale solar-powered photobioreactors.

Various innovative photobioreactor designs have been proposed to increase production of algae-derived biomass. Computer models are often employed to test these designs prior to construction. In the drive to optimise conversion of light energy to biomass, efforts to model the profile of irradiance levels within a microalgal culture can lead to highly complex descriptions which are computationally demanding. However, there is a risk that this effort is wasted if such optic models are coupled to overly simplified descriptions of algal physiology. Here we demonstrate that a suitable description of microalgal physiology is of primary significance for modelling algal production in photobioreactors. For the first time, we combine a new and computationally inexpensive model of irradiance to a mechanistic description of algal growth and test its applicability to modelling biofuel production in an advanced photobioreactor system. We confirm the adequacy of our approach by comparing the predictions of the model against published experimental data collected over a 2 ½-year period and demonstrate the effectiveness of the mechanistic model in predicting long-term production rates of bulk biomass and biofuel feedstock components at a commercially relevant scale. Our results suggest that much of the detail captured in more complicated irradiance models is indeed wasted as the critical limiting procedure is the physiological description of the conversion of light energy to biomass.Electronic supplementary materialThe online version of this article (doi:10.1007/s10811-016-0892-6) contains supplementary material, which is available to authorized users.

A method to determine photosynthetic activity from oxygen microsensor data in biofilms subjected to evaporation

Phototrophic biofilms are widely distributed in nature and their ecological importance is well recognized. More recently, there has been a growing interest in using artificial phototrophic biofilms in innovative photobioreactors for production of microalgal biomass in biotechnological applications. To study physiological processes within these biofilms, microsensors have been applied in several studies. Here, the ‘light–dark shift method’ relies on measurement of photosynthetic activity in terms of light-induced oxygen production. However, when applied to non-submerged biofilms that can be found in numerous locations in nature, as well as in some types of photobioreactors, limitations of this approach are obvious due to rapid removal of gaseous species at the biofilm surface. Here, we introduce a mathematical correction to recover the distribution of the actual photosynthetic activity along the depth gradient in the biofilm, based on a numerical solution of the inversed diffusion equation of oxygen. This method considers changes in mass transport during the measurement period as can found on biofilms possessing a thin flow/mass transfer boundary layer (e. g., non-submerged biofilms). Using both simulated and real microsensor data, the proposed method was shown to be much more accurate than the classical method, which leads to underestimations of rates near the biofilm surface. All test profiles could be recovered with a high fit. According to our simulated microsensor measurements, a depth resolution of ≤20μm is recommended near the surface. We conclude that our method strongly improves the quality of data acquired from light–dark measurements of photosynthetic activity in biofilms.

Evaluation of wastewater treatment in a novel anoxic–aerobic algal–bacterial photobioreactor with biomass recycling through carbon and nitrogen mass balances

Algal–bacterial symbiosis, implemented in an innovative anoxic–aerobic photobioreactor configuration with biomass recycling, supported an efficient removal of total organic carbon (86–90%), inorganic carbon (57–98%) and total nitrogen (68–79%) during synthetic wastewater treatment at a hydraulic and sludge retention times of 2days and 20days, respectively. The availability of inorganic carbon in the photobioreactor, determined by its supply in the wastewater and microalgae activity, governed the extent of nitrogen removal by assimilation or nitrification–denitrification. Unexpectedly, nitrate production was negligible despite the high dissolved oxygen concentrations, denitrification being only based on nitrite reduction. Biomass recycling resulted in the enrichment of rapidly settling algal flocs, which supported effluent total suspended solid concentrations below the European Union maximum discharge limits. Finally, the maximum nitrous oxide emissions recorded were far below the emission factors reported for wastewater treatment plants, confirming the environmental sustainability of this innovative photobioreactor in terms of global warming impact.

Improving protein production of indigenous microalga Chlorella vulgaris FSP-E by photobioreactor design and cultivation strategies.

Fish meal is currently the major protein source for commercial aquaculture feed. Due to its unstable supply and increasing price, fish meal is becoming more expensive and its availability is expected to face significant challenges in the near future. Therefore, feasible alternatives to fish meal are urgently required. Microalgae have been recognized as the most promising candidates to replace fish meal because the protein composition of microalgae is similar to fish meal and the supply of microalgae-based proteins is sustainable. In this study, an indigenous microalga (Chlorella vulgaris FSP-E) with high protein content was selected, and its feasibility as an aquaculture protein source was explored. An innovative photobioreactor (PBR) utilizing cold cathode fluorescent lamps as an internal light source was designed to cultivate the FSP-E strain for protein production. This PBR could achieve a maximum biomass and protein productivity of 699 and 365 mg/L/day, respectively, under an optimum urea and iron concentration of 12.4 mM and 90 μM, respectively. In addition, amino acid analysis of the microalgal protein showed that up to 70% of the proteins in this microalgal strain consist of indispensable amino acids. Thus, C. vulgaris FSP-E appears to be a viable alternative protein source for the aquaculture industry.

Enhancing the production of eicosapentaenoic acid (EPA) from Nannochloropsis oceanica CY2 using innovative photobioreactors with optimal light source arrangements

Binary combinations of LEDs with four different colors were used as light sources to identify the effects of multiple wavelengths on the production of eicosapentaenoic acid (EPA) by an isolated microalga Nannochloropsis oceanica CY2. Combining LED-Blue and LED-Red could give the highest EPA productivity of 13.24mgL−1d−1, which was further enhanced to 14.4mgL−1d−1 when using semi-batch operations at a 40% medium replacement ratio. A novel photobioreactor with additional immersed light sources improved light penetration efficiency and led to an 38% (0.170–0.235gL−1d−1) increase in the microalgae biomass productivity and a 9% decrease in electricity consumption yield of EPA (10.15–9.33kW-h(g EPA)−1) when compared with the control (i.e., without immersed light sources). Operating the immersed LEDs at a flashing-frequency of 9Hz further lowered the energy consumption yield to 8.87kW-h(g EPA)−1.

Design, construction and evaluation of solarized airlift tubular photobioreactor

An innovative photobioreactor is developed for growing algae in simulated conditions. The proposed design comprises of a continuous tubular irradiance loop and air induced liquid circulation with gas separation through air lift device. The unique features of air lift system are to ensure the shear free circulation of sensitive algal culture and induce light/dark cycles to the photosynthetic micro-organisms. The design strategy employs to model and construct a 20-liter laboratory scale unit using Boro-silicate glass tubing. The material is selected to ensure maximum photon transmission. All components of the device are designed to have flexibility to be replaced with an alternative design, providing fair chance of modification for future investigators. The principles of fluid mechanics are applied to describe geometrical attributes of the air lift system. Combination of LEDs and Florescent tube lights (Warm white) were used to illuminate the photosynthesis reaction area providing a possibility to control both illumination duration and light intensity. 200 Watt Solar PV system is designed to power up the device which included air pump (100 Watt) and illumination system (100 Watt). Algal strain Chlorella sp was inoculated in photobioreactor which was sparged with air and carbon dioxide. The growth was sustained in the batch mode with daily monitoring of temperature, pH and biomass concentration. The novel photobioreactor recorded a maximum experimental average yield of 0.65 g/l.day (11.3 g/m2.day) as compared to theoretical modeled yield of 0.82 g/l.day (14.26 g/m2.day), suggesting the device can be efficiently and cost-effectively employed in the production of algal biomass for biofuels, concomitantly mitigating CO2.

Single cell protein production of Euglena gracilis and carbon dioxide fixation in an innovative photo-bioreactor

The biological fixation using microalgae has been known as an effective and economical carbon dioxide reduction technology. Carbon dioxide (CO 2) fixation by microalgae has been shown to be effective and economical. Among various algae, a species Euglena gracilis was selected as it has advantages such as high protein content and high digestibility for animal feed. A kinetic model was studied in order to determine the relationship between specific growth rate and light intensity. The half-saturation constant for light intensity in the Monod model was 178.7 μmol photons/m 2/s. The most favorable initial pH, temperature, and CO 2 concentration were found to be 3.5, 27 °C, and 5–10% (vol/vol), respectively. Light intensity and hydraulic retention time were tested for effects on cell yield in a laboratory-scale photo-bioreactor of 100 l working volume followed by semi-continuous and continuous culture. Subsequently, an innovative pilot-scale photo-bioreactor that used sunlight and flue gas was developed to increase production of this bioresource. The proposed pilot-scale reactor showed improved cell yield compared with the laboratory-scale reactor.