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The efficiency of a novel microalgal culture system (an airlift loop bioreactor [ALB] engaged with a fluidic oscillator to produce microbubbles) is compared with both a conventional ALB (producing fine bubbles without the fluidic oscillator) and non-aerated flask culture. The impact of CO 2 mass transfer on Dunaliella salina growth is assessed, thr...
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... further study the impact of using innovative ALB on microalgal cultivation, twelve 3L-ALBs were made for screening purposes, based on a similar design. Figure 1 shows the configuration of a 3L-ALB. Gener- ally, the bioreactor is made of acrylic material, with the dimension of 285 mm in height and 124 mm in diameter. ...
Context 2
... maximum μ of 0.13 d −1 and 0.17 d −1 was achieved at flow rate of 0.9 L·min −1 (without FO) and at 1.1 L·min −1 (with FO), respectively. This overall trend was found similar to gas-liquid mass transfer study [10] (see Figures S1(a) and (b) in Supplementary in- formation). Considering both algal specific growth rate Copyright © 2013 SciRes. ...
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Citations
... Numerous studies have been conducted on microbubble dosing in different types of PBRs and open systems that reported higher biomass productivity and reduced mixing time as compared to normal bubble dosing (Table 4). Therefore, microbubble dosing is a preferable way over normal bubble dosing with higher CO 2 dissolution (Ying et al., 2013b). On the other hand, microbubble mixing has some drawbacks such as the gathering of cells on the gas-liquid interface, low light transmission, clogging of spargers micropores, and gathering of biomass onto the top that causes the death of microalgae due to insufficient water supply (Huang et al., 2017). ...
The chapter discusses the introduction to photosynthetic algae, classification, and
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deliberated. Moreover, the applications of microalgae and its biomass in bioenergy,
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... Several studies reported that algal growth, biomass and products are a function of physical and chemical parameters, including temperature, light intensity, nutrients, carbon concentration and pH [21]. Moreover, bubble size and mixing that is characterized by rotations per minute (rpm) are important factors, as they affect the mass transfer inside the medium [4,22,23] of D. salina. In intensive industrial cultivation, the algae must endure completely different stress conditions than in nature. ...
The green algae Dunaliella salina offers great potential for the food industry due to its high β-carotene content. To guarantee the economic profitability of cultivation, growth conditions must be improved. Therefore, the effects of pH and salinity on the cultivation of the green alga D. salina were investigated and optimized. The simplex method was applied to find the optimum of these two parameters to maximize the biomass and the cell number of D. salina. The optimum pH was found at 7 and 8 at a salt content of 50 g/L, with a biomass content of 1.09 and 1.11 g/L, respectively. The highest biomass was found at a salinity of 50 g/L, with a final biomass of 1.11 g/L. However, by using the simplex method, an optimum product yield was found at a salinity of 64 g/L and an initial pH value of 7.2. Thus, a biomass of 1.23 mg/mL was achieved. In the single observation of both parameters, 14 experiments were conducted to obtain a satisfactory result, whereas eight runs only were required with the simplex method. This leads to the conclusion that using the simplex method is a useful way to drastically reduce the number of required experiments.
... The CO 2 mass transfer rate is mainly determined by the volumetric mass transfer coefficient (K L a) and K L a manifests cubic increase by reducing the bubble size (Erickson, 1990). Studies have shown that the CO 2 mass transfer can be significantly elevated by using microbubble technology (Ying et al., 2013b).Cultured in microbubble induced airlift loop bioreactor, the dry biomass of Dunaliella salina was increased from 0.0067 g/L to 0.24 g/L (about 35 folds) after 17 days' culture (Zimmerman et al., 2011). Based on the feature of high mass transfer, it is possible to improve the H. pluvialis growth by replacing the conventional CO 2 feeding technologies (with bubble size around 3-6 mm) with microbubbles. ...
... The pH value was recorded every 30 s, measured by a pH meter (FiveEasy Plus 28). The total carbon concentration (C T ) was calculated based on the pH value by using Equation S8 reported in Ying et al. (Ying et al., 2013a(Ying et al., , 2013b, ½C T = À 1 + 10 pHÀ6:381 + 10 2pHÀ16:758 Á À 10 ÀpH À 10 pHÀ14 + Na + Á 10 À2pH 10 À6:381ÀpH + 2 3 10 À16:758 Equation S7 ...
Haematococcus pluvialis, the richest bioresource for natural astaxanthin, encounters a challenge of achieving high growth rate when it comes to mass biomass production. Base on substrate consumption model and Redfield ratio, rapid algae growth benefits from a proper carbon supply. However, the conventional cultivation schemes with limited carbon dioxide (CO2) supply and inefficient carbon mass transfer could have constrained the carbon capture and growing ability of H. pluvialis. We hypothesize that optimal H. pluvialis growth improvement may be achieved by efficient CO2 supply. Here, in this study, we first identified the carbon consumption of H. pluvialis during exponential growth. Then, a novel microbubble-driven photobioreactor (MDPBR) was designed to satisfy the carbon demand. The novel microbubble photobioreactor improve the CO2 supply by reducing bubble size, significantly elevating the CO2 mass transfer. With only 0.05 L min⁻¹ of gas flow rate, higher cell growth rate (0.49 d⁻¹) has been achieved in MDPBR.
... It has been regarded as a new horizon for pollution control in cleaner production and water renewability improvement, which is environmental friendly, economically viable, and high efficient . These ultrafine-sized bubbles can be generated from changes in pressure and temperature, photochemical reactions, and fluid dynamics (Wang et al., 2018a) or added by gas sparging directly (Ying et al., 2013;McClure et al., 2020). Unlike ordinary millibubbles, MNBs can remain in liquid solution for a long time due to their small buoyancy (Lyu et al., 2019), show high mass transfer efficiency and free radical generation ability (Temesgen et al., 2017). ...
As an environmental friendly cleantech, micro/nano bubbles (MNBs) have been increasingly used for pollution control in cleaner production and water renewability improvement, and many works used optical density (OD) as proxy for the concentration of chemical/biological substances in liquid samples. This study reported that MNBs induced considerable light scattering and impacted the measured OD of liquid samples. The experimental results showed that bubble aeration increased the OD at wavelengths of 300-600 nm by 0.14-0.50 in commonly used bio-cultural medium and deionized water. The scattered light that fell outside the effective forward range increased the OD, and this increase was dependent on the bubble size and light wavelength. The Mie calculations showed that the scattering of smaller bubble is stronger and results in more OD increase. By defining the OD deviation < 0.01, the critical thresholds of bubble size were calculated using the Kepler conjecture and Beer-Lambert’s law. For the commonly used wavelength 600 nm, the OD increase can be neglected only for bubbles with diameter > 263 μm in water. The finite-difference time-domain simulation illustrated the highly nonuniform electric field near the bubble, and verified the higher scattering efficiencies at shorter wavelength. De-bubbling samples from MNB systems via short-term sonication eliminated light scattering. Findings from this work delineated the optical properties of MNBs, highlighted resulting impact on optical measurement and proposed a de-bubbling method in water treatment.
... However, there is a high potential in more cost-effective use of them (Joo et al., 2001). Ying et al. (2013) studied the effect of using airborne photo-bioreactor on the D. salina microalgae growth compared to aeration-free flux system. In their study, the microalgae culture was initially investigated at 25 • C, 50 μmol/m 2 .s ...
... The aeration was carried out using an enriched gas with 95% N 2 and 5% CO 2 for 30 min/day and 18-day cultivation period. Findings revealed that the use of airborne photo-bioreactor increases the chlorophyll content of the microalgae by 6-8 times and raises its specific growth rate by 20-40% as compared to the aeration-free flask culture system (Ying et al., 2013). Guedes et al. (2011) found that semi-continuous cultivation of D. salina at 25 • C yielded 80 g/m 3 .day ...
Dunaliella Salina is a carotene-producing microalgae well-known for its superb ability to accumulate valuable beta-carotene. The factors affecting the bio-beta-carotene production from Dunaliella salina microalgae have been investigated in this study. First, the different usages of Dunaliella salina, especially for the production of beta-carotene, are described. Then, the factors affecting the process of obtaining beta-carotene from Dunaliella salina in the culture system, culture conditions, and downstream processes are investigated. Investigations show that application of airborne photo-bioreactor culture system improves the mechanism of production. It was found that among the culture conditions, the parameters such as ambient salinity, temperature, and intensity of illumination are the most effective ones. The optimal values for these parameters, the highest cellular density of Dunaliella salina and the highest beta-carotene production are determined. The extraction step is known as the most critical step in the downstream processes of beta-carotene production.
... In general, the model green alga D. salina has proved to be an excellent organism to explore the effects of FO generated microbubbles on growth of microalgae. Ying, Gilmour, Shi, and Zimmerman (2013) showed a 20%-40% increase in the growth rate of D. salina when microbubbles were used in an airlift bioreactor. This comparison was between fine bubbles (around 600 μm) and microbubbles (around 300 μm) in an otherwise identical bioreactor. ...
Microbubbles have been involved in industrial processing since the 1970s with the introduction of dissolved air flotation into common practice. The turn of the century saw microbubbles become regularly used in medical imaging. But in bioprocessing, only this decade has seen rapid advances in R&D, with some bioprocesses, particularly in wastewater treatment, adopted at full industrial scale, and others at pilot scale, such as anaerobic digestion and fermentation, which is full industrial scale for many biomanufacturing and pharmaceutical processes. This article reviews the methods of microbubble generation only briefly, as it turns out only one generation method, fluidic oscillation through microporous diffusers, has the requisite features for introduction into full scale fermentation processes. Subsequently, six fundamental physicochemical hydrodynamics mechanisms that have been exploited by microbubble innovations in bioprocessing are presented and analyzed, particularly for the roles they play in bioprocessing applications. Some examples are drawn with applications to microalgal and yeast processing, as well as usage in wastewater treatment processes. Because the smallest microbubbles can increase rates in some of these six fundamental processes by several orders of magnitude over conventional processing methods, with the optimal contacting patterns, the promise for wider exploitation in bioprocessing is substantial.
... In keeping with this previous research on wavelength shifting materials, the work presented here considers the influence of two different wavelength shifting materials on the growth of Dunaliella salina CCAP 19/30 in an ALB. Dunaliella was chosen as the algae species because of its high CO 2 uptake properties (Ying et al. 2013). In addition, D. salina CCAP19/30 strain was chosen because it does not produce high amounts of β-carotene in contrast to other strains of D. salina such as CCAP19/18 (Olmos et al. 2009). ...
The availability of light is one of the key driving factors for photosynthesis. Chlorophyll and accessory pigments absorb light at some of the wavelengths present in the solar spectrum. If all other requirements are available in abundance, introducing more light to the system at wavelengths that can be absorbed will increase the growth rate of microalgae and the final biomass achieved up to the level of photosaturation. Therefore, the effect of shifting the spectrum of light available such that the photons unutilized in photosynthesis are converted to those that can be utilised was investigated. Spectral shifts converting UV light to blue light and green light to red light were carried out using films produced with Coumarin and Solvent Orange respectively. Dunaliella salina (CCAP 19-30) was grown in an airlift photobioreactor (ALB) which was coated with the wavelength shifting films. Dunaliella final biomass in the ALB, as determined by the optical density, were shown to increase by 36.9% for UV to blue light conversion and by 18.8% for green to red light conversion when using a coated ALB compared with an uncoated one.
... The alga used in this study exhibited normal growth up to 30 th day and showed an ample amount of total carotenoids production at the higher pH (pH 8.0). The obtained results are contradicting to the report of Ying et al 48 . The investigators observed that once after 9 days of inoculation, the pH barely increased and growth was inhibited. ...
Dunaliella salina has been widely reported in the halophilic environment. The present study first time reveals and reports the presence of green alga D. salina identified by both morphological and molecular identification from Andaman and Nicobar Islands, a rainy tropical environment. Besides, it was adapted for the optimization of total carotenoid production by using Taguchi tool with various combinations of different parameters, like light intensity, pH, salinity, NaNO3 and NaH2PO4 in basal De Walne’s medium of which 40µEm-2s-1 light intensity showed maximum production of 249.24 µg/mL of total carotenoid followed by NaNO3, NaH2PO4, pH, and salinity. Hence, this study proves that D. salina possesses the character of adapting to the extreme habitats with total carotenoid production.
... Holes in the top of the PTFE mount allow gas to flow towards the plasma discharge before forming the bubbles in the tank above. The tank has a volume of 1.1 l and at its center there is a draft tube, which as bubbles rise induces convection currents, effectively mixing the solution and eliminating the need for mechanical mixing [22]. Although quartz crucibles and a stainless-steel membrane were used in this study, the rest of reactor is the same as that reported in [23,24]. ...
In this study we examine both the effect of changing the applied voltage waveform shape and the modulation on-time on the amount of ozone dissolved within a liquid in a dielectric barrier discharges (DBD) bubble reactor. In this device, the discharge forms at the gas–liquid interface allowing for effective transfer of the plasma effluent into the liquid. To produce different voltage waveforms, a multilevel inverter power supply capable of generating arbitrary waveforms without switching-on and switching-off transients has been used. Of the four waveforms used in the study (sinusoidal, sawtooth, square and short-pulse), the square waveform was found to be the most efficient at producing the highest ozone concentration for a fixed peak voltage and average power. To determine the effect of the modulation on-time, the number of cycles during the on-time were increased from 1 up to 1000, adjusting the off-time accordingly to maintain the same duty cycle. Shorter on-time periods were found to be more efficient. Experimental and computational results indicate that the time between subsequent discharges is critical for increased ozone
generation efficacy, as this needs to be long enough for ozone produced in one discharge event to diffuse away from the discharge region before the next discharge event occurs, thereby avoiding its partial destruction in the plasma. This insight provides a valuable criterion for the optimization of DBD reactors used in novel biomedical, agricultural and
environmental applications.
... Energy efficient fluidic oscillation-mediated microbubbles have been demonstrated to improve mass transfer rates significantly due to their high surface to volume ratio, and this technology has been applied to various processes needing efficient gas-liquid mass transfer such as waste water treatment, aqua culture and bioreactors [20,21]. In addition to improved mass transfer, microbubbles provide efficient mixing of the reactor contents, removing the need for mechanical mixing; hence reducing the energy requirement for pretreatment [22]. This plasma-microbubble reactor treatment has been demonstrated as an effective approach in pretreating lignocellulosic biomass for bioethanol production [23]. ...
... A draft tube with a height of 50 mm and a diameter of 80 mm is positioned in the tank as shown in Fig. 1. The draft tube dimensions and placement are calculated according to [22]. ...
Cellulose recalcitrance is one of the major barriers in converting renewable biomass to biofuels or useful chemicals. A pretreatment reactor that forms a dielectric barrier discharge plasma at the gas-liquid interface of the microbubbles has been developed and tested to pretreat α-cellulose. Modulation of the plasma discharge provided control over the mixture of species generated, and the reactive oxygen species (mainly ozone) were found to be more effective in breaking-up the cellulose structure compared to that of the reactive nitrogen species. The effectiveness of pretreatment under different conditions was determined by measuring both the solubility of treated samples in sodium hydroxide and conversion of cellulose to glucose via enzymatic hydrolysis. Solutions pretreated under pH 3 buffer solutions achieved the best result raising the solubility from 17% to 70% and improving the glucose conversion from 24% to 51%. Under the best conditions, plasma-microbubble treatment caused pronounced crevices on the cellulose surface enhancing access to the reactive species for further breakdown of the structure and to enzymes for saccharification.
