High-Throughput In Vitro Screening of Changed Algal Community Structure Using the PhotoBiobox.

In a previous study, the sequential optimization and regulation of environmental parameters using the PhotoBiobox were demonstrated with high-throughput screening tests. In this study, we estimated changes in the biovolume-based composition of a polyculture built in vitro and composed of three algal strains: Chlorella sp., Scenedesmus sp., and Parachlorella sp. We performed this work using the PhotoBiobox under different temperatures (10-36°C) and light intensities (50-700 µmol/m-2/s-1) in air and in 5% CO2. In 5% CO2, Chlorella sp. exhibited better adaptation to high temperatures than in air conditions. Pearson's correlation analysis showed that the composition of Parachlorella sp. was highly related to temperature whereas Chlorella sp. and Scenedesmus sp. showed negative correlations in both air and 5% CO2. Furthermore, light intensity slightly affected the composition of Scenedesmus sp., whereas no significant effect was observed in other species. Based on these results, it is speculated that temperature is an important factor in influencing changes in algal polyculture community structure (PCS). These results further confirm that the PhotoBiobox is a convenient and available tool for performance of lab-scale experiments on PCS changes. The application of the PhotoBiobox in PCS studies will provide new insight into polyculture-based ecology.

Morphological characterization, growth appraisal, and probing biofuels potential of newly isolated Scenedesmus sp. from desert Cholistan.

Microalgae have an excellent potential for producing valuable natural products, including biofuels. Therefore, it is imperative to explore and document the existing microalgal flora and utilize their potentials to cope the increasing human needs. The present work aims at exploring and characterizing newly isolated microalgae from desert Cholistan, a habitat with myriad algal diversity. Light microscopy, scanning electron microscopy, and molecular phylogenetic approaches were used for species-level identification. Characterization and growth optimization of Scendesmus sp. were analyzed under three different growth modes to determine the most favorable conditions for increasing biomass, growth rate, and lipid content. The results revealed that mixotrophic (MT) mode significantly increases photosynthetic activity, growth rate, and lipid content with glycerol as supplement carbon source. The investigated Scenedesmus dimorphous produced a maximum dry weight of 1.73 g L-1 , improved fatty acid methyl esters profile and yield lipid up to 40% of DCW (68 g L-1 ) under MT mode, which is almost double to that of photoautotrophic cultivation. The glycerol availability in medium has been identified as the critical element for boosting growth and lipid content. Thus, it can reduce the cost of biofuel production.

Scenedesnus rotundus isolated from the petroleum effluent employs alternate mechanisms of tolerance to elevated levels of Cadmium and Zinc.

Scenedesmus rotundus was isolated from metal contaminated petroleum industry effluent and its tolerance to Cadmium and Zinc was tested using different concentrations of CdCl2 and ZnCl2 ranging from 0.001 mM to 1.0 mM of Cd and 0.03 mM to 1.21 mM of Zn amended in Bolds Basal medium. The changes in cell count recorded at regular intervals upto a period of 24 days revealed a concentration dependent inhibition in growth. Concentration of the metal, at which 50% of the cells are live and metabolically active referred to as EC50 was calculated as 0.04 mM for Cd and 0.2 mM for Zn. Further, the effect of EC50 of the metals on the protein content, uptake of metals at varying pH, oxidative stress markers including lipid peroxidation, protein oxidation andnd oxygen uptake, levels of enzymatic antioxidants such as catalase and superoxide dismutase and non-enzymatic antioxidants namely, GSH and PC4 were determined. Though a direct correlation could not be drawn between pH and metal uptake, the compartmentalization of the metal during the lag phase and exponential phase was evident, most of the metal was present in extracellular fractions in the former, while in the later it was internalized. Our study shows a clear correlation between toxicity of Cd and the ability of the algae to synthesize PC4 from GSH and chelate it leading to detoxification, while Zn treatment led to an increase in the activity of catalase and superoxide dismutase and replete GSH pools. Further the changes in the cell wall structure at EC50 of Cd and Zn were studied. This is the first report on effect of heavy metals on the structural modifications of the cell wall of Scenedesmus in general and Scenedesmus rotundus in particular, indicating appearance of granules on the entire cell surface in both Cd and Zn treatments, with the degree of granulation increasing in the order of pH 12 > 10 > 8 in Cd treatment. Further structures of higher order resembling minute wheels are observed in Cd treated cells are also reported.

Harvesting of Scenedesmus acuminatus using ultrafiltration membranes operated in alternative feed directions.

Ultrafiltration membrane harvesting of Scenedesmus acuminatus was tested using alternative feed (AF) directions, i.e., bottom feed-top feed cycle and traditional bottom feed (BF). Both operations were investigated to compare the membrane performance and membrane fouling in microalgal harvesting process by scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and Fourier transform infrared (FTIR). The results showed that when the AF was used with and without backwashing, average flux increased by 27.9% and 17.9%, respectively, comparing with BF (68 L m-2 h-1) and the final dry weight reached 197 g L-1 and 175.8 g L-1, respectively. Microalgal cell deposition on AF membrane was reduced from 1.44 × 105 cell cm-2 on BF membrane to 7.12 × 104 cell cm-2 on AF membrane, according to SEM observation. The protein and polysaccharides on the AF membrane surface were also reduced according to CLSM and FTIR analysis. Fouling analysis along the fiber length revealed that fouling was most severe at the top section for BF as a result of a lower shear rate at the outlet. AF operation generated dynamic filtration by frequently switching flow directions, increasing the shear rate at both the top and bottom of the fibers, and therefore filtration and clean process simultaneously provided good performance.

Microalgae community shifts during the biogas upgrading in an alkaline open photobioreactor.

AIMS: To achieve the functional specialization of a microalgae community through operational tuning of an open photobioreactor used for biogas upgrading under alkaline conditions. METHODS AND RESULTS: An open photobioreactor was inoculated with an indigenous microalgae sample from the Texcoco Soda Lake. A microalgae community was adapted to fix CO2 from synthetic biogas through different culture conditions reaching a maximum of 220 mg CO2  l-1 per day. Picochlorum sp. and Scenedesmus sp. were identified as the prominent microalgae genera by molecular fingerprinting (partial sequencing of 16S rRNA and 18S rRNA genes) but only the first was detected by microscopy screening. Changes in the microalgae community profile were monitored by a range-weighted richness index, reaching the lowest value when biogas was upgraded. CONCLUSIONS: A robust microalgae community in the open photobioreactor was obtained after different culture conditions. The specialization of microalgae community for CO2 fixation under H2 S presence was driven by biogas upgrading conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The alkaline conditions enhance the CO2 absorption from biogas and could optimize specialized microalgae communities in the open photobioreactor. Denaturing gradient gel electrophoresis fingerprinting and richness index comparison are useful methods for the evaluation of microalgae community shifts and photosynthetic activity performance, particularly in systems intended for CO2 removal from biogas where the CO2 assimilation potential can be related to the microbial richness.

Microalgae harvesting by pH adjusted coagulation-flocculation, recycling of the coagulant and the growth media.

Coagulation-flocculation can be considered as one of the least energy intensive microalgae biomass harvesting processes. However, cost of the coagulant and biomass contamination are two critical issues that need to be considered. In this study, ferric chloride (72-96mg/L) was used to effectively harvest Scenedesmus sp. (530mg/L) - grown in BG-11 media and wastewater. Reducing the culture pH below 6.5, greatly improved the harvesting efficiency. Acidic solution (pH 1.0) was very effective to recover (almost 90%) the associated iron from the harvested biomass. Scenedesmus sp. was able to grow in the supernatant and utilize the residual iron in it. Iron extracted solution, with a supplementation of 9.8mg/L ferric chloride, was able to achieve similar harvesting efficiency. The potential recovery of iron from the harvested biomass and its reuse in the harvesting can improve the biomass quality for subsequent downstream processing while reducing the cost.

Microalgae removal with Moringa oleifera.

Moringa oleifera seed extract was tested for algae (Chlorella, Microcystis, Oocystis and Scenedesmus) removal by Jar-test technique. This coagulant can be used in drinking water treatment. Jar-test has been carried out in order to evaluate the efficiency of this natural coagulant agent inside real surface water matrix. The influence of variables has been studied in this process, including operating parameters such as coagulant dosage, initial algae concentration, pH, agitation time and water matrix. Removal capacity is verified for water with high contamination of algae while the process is not affected by the pH and water matrix. Coagulation process may be modelling through Langmuir and Freundlich adsorption hypothesis, so acceptable r2 coefficients are obtained.

Recovering Magnetic Fe3O4-ZnO Nanocomposites from Algal Biomass Based on Hydrophobicity Shift under UV Irradiation.

Magnetic separation, one of the promising bioseparation technologies, faces the challenges in recovery and reuse of magnetic agents during algal harvesting for biofuel extraction. This study synthesized a steric acid (SA)-coated Fe3O4-ZnO nanocomposite that could shift hydrophobicity under UV365 irradiation. Our results showed that with the transition of surface hydrophobicity under UV365 irradiation, magnetic nanocomposites detached from the concentrated algal biomass. The detachment was partially induced by the oxidation of SA coating layers due to the generation of radicals (e.g., •OH) by ZnO under UV365 illumination. Consequently, the nanocomposite surface shifted from hydrophobic to hydrophilic, which significantly reduced the adhesion between magnetic particles and algae as predicted by the extended Derjaguin and Landau, Verwey, and Overbeek (EDLVO) theory. Such unique hydrophobicity shift may also find many other potential applications that require recovery, recycle, and reuse of valuable nanomaterials to increase sustainability and economically viability.

Heteroaggregation between PEI-coated magnetic nanoparticles and algae: effect of particle size on algal harvesting efficiency.

Colloidal interactions between magnetic nanoparticles (NPs) and algal cells are of paramount significance to magnetophoretic separation of algal biomass from water. This study evaluated the size effect of magnetic NPs (MNPs) coated with polyethylenimine (PEI) on the separation efficiency of Scenedesmus dimorphus as well as on the recovery efficiency of MNPs from algal biomass. Results showed that algal harvesting efficiency (HE) increased from ca. 60% to 85% as the diameter of PEI-coated MNPs increased from 9 to 53 nm. Likewise, algal recovery capacity (algae/MNPs, w/w) also showed the same size dependence. But a large size (247 nm) led to a decline of algal HE, which was correctly interpreted by a settling model that predicts large sizes of MNPs could eventually reduce the settling velocity under magnetophoresis. The extended Derjaguin-Landau-Verwey-Overbeek theory revealed that the particle size and PEI coating both influenced the interaction energies (e.g., energy barrier) between MNPs and algae. Particularly, PEI coating significantly reduced the energy barrier between MNPs and algae and thereby increased their heteroaggregation and algal HE. Moreover, PEI-coated MNPs were recovered from the harvested algae biomass through a chemical-free ultrasonic method, and the recovery efficiency appeared to be higher for larger MNPs. Overall, the synthesized sizes of applied MNPs will not only affect algal HE but also have economic implications on magnetophoretic algal separation technologies.

Examining concentrations and molecular weights of thiols in microorganism cultures and in Churchill River (Manitoba) using a fluorescent-labeling method coupled to asymmetrical flow field-flow fractionation.

In this study, molecular weights of thiols from four laboratory cultures (Scenedesmus obliquus, Chlorella vulgaris, Euglena gracilis, and Attheya septentrionalis) and the Churchill River (Manitoba) were assessed using a fluorescent-labeling method such as monobromotrimethylammoniobimane (qBBr) and asymmetrical flow field-flow fractionation (AF4) coupled to a fluorescence detector. Concentrations of thiols in extracellular fractions ranged from 6.39 ± 3.39 to 39.2 ± 7.43 µmol g(-1), and intracellular concentrations ranged from 11.5 ± 4.52 to 41.0 ± 4.1 µmol g(-1). In addition, molecular weights (MW) of intracellular thiol ranged from 493 ± 24 to 946 ± 12 Da whereas extracellular thiol MWs varied from 443 ± 36 to 810 ± 174 Da. The novel method of combining AF4 to an on-line fluorometer and the incorporation of the thiol tag provided information regarding thiol concentration and composition of controlled and natural systems. Furthermore, the proposed methods allow for the simultaneous measurement of thiol and DOM MWs produced by microorganisms. By assessing characteristics of naturally produced thiols and lab-grown thiols, information regarding heavy metal complexation can be determined.

A cost analysis of microalgal biomass and biodiesel production in open raceways treating municipal wastewater and under optimum light wavelength.

Open raceway ponds are cost-efficient for mass cultivation of microalgae compared with photobioreactors. Although low-cost options like wastewater as nutrient source is studied to overcome the commercialization threshold for biodiesel production from microalgae, a cost analysis on the use of wastewater and other incremental increases in productivity has not been elucidated. We determined the effect of using wastewater and wavelength filters on microalgal productivity. Experimental results were then fitted into a model, and cost analysis was performed in comparison with control raceways. Three different microalgal strains, Chlorella vulgaris AG10032, Chlorella sp. JK2, and Scenedesmus sp. JK10, were tested for nutrient removal under different light wavelengths (blue, green, red, and white) using filters in batch cultivation. Blue wavelength showed an average of 27% higher nutrient removal and at least 42% higher chemical oxygen demand removal compared with white light. Naturally, the specific growth rate of microalgae cultivated under blue wavelength was on average 10.8% higher than white wavelength. Similarly, lipid productivity was highest in blue wavelength, at least 46.8% higher than white wavelength, whereas FAME composition revealed a mild increase in oleic and palmitic acid levels. Cost analysis reveals that raceways treating wastewater and using monochromatic wavelength would decrease costs from 2.71 to 0.73 $/kg biomass. We prove that increasing both biomass and lipid productivity is possible through cost-effective approaches, thereby accelerating the commercialization of low-value products from microalgae, like biodiesel.

Influences of surface coating, UV irradiation and magnetic field on the algae removal using magnetite nanoparticles.

Magnetophoretic separation is a promising and sustainable technology for rapid algal separation or removal from water. This work demonstrated the application of magnetic magnetite nanoparticles (MNPs) coated with a cationic polymer, polyethylenimine (PEI), toward the separation of Scenedesmus dimorphus from the medium broth. The influences of surface coating, UV irradiation, and magnetic field on the magnetophoretic separation were systematically examined. After PEI coating, zeta potential of MNPs shifted from −7.9 ± 2.0 to +39.0 ± 3.1 mV at a pH of 7.0, which improved MNPs-algae interaction and helped reduce the dose demand of MNPs (e.g., from 0.2 to 0.1 g·g(­1) while the harvesting efficiency (HE) of over 80% remained unchanged). The extended Derjaguin­Landau­Verwey­Overbeek theory predicted a strong attractive force between PEI-coated MNPs and algae, which supported the improved algal harvesting. Moreover, the HE was greater under the UV365 irradiation than that under the UV254, and increased with the irradiation intensity. Continuous application of the external magnetic field at high strength remarkably improved the algal harvesting. Finally, the reuse of MNPs for multiple cycles of algal harvesting was studied, which aimed at increasing the sustainability and lowering the cost.

Growth and lipid accumulation characteristics of Scenedesmus obliquus in semi-continuous cultivation outdoors for biodiesel feedstock production.

In an effort to identify suitable microalgal species for biodiesel production, seven species were isolated from various habitats and their growth characteristics were compared. The results demonstrated that a green alga Scenedesmus obliquus could grow more rapidly and synthesize more lipids than other six microalgal strains. S. obliquus grew well both indoors and outdoors, and reached higher µmax indoors than that outdoors. However, the cells achieved higher dry weight (4.36 g L(-1)), lipid content (49.6%) and productivity (183 mg L(-1) day(-1)) outdoors than in indoor cultures. During the 61 days semi-continuous cultivation outdoors, high biomass productivities (450-550 mg L(-1) day(-1)) and µmax (1.05-1.44 day(-1)) were obtained. The cells could also achieve high lipid productivities (151-193 mg L(-1) day(-1)). These results indicated that S. obliquus was promising for lipids production in semi-continuous cultivation outdoors.

Algae harvesting for biofuel production: influences of UV irradiation and polyethylenimine (PEI) coating on bacterial biocoagulation.

There is a pressing need to develop efficient and sustainable separation technologies to harvest algae for biofuel production. In this work, two bacterial species (Escherichia coli and Rhodococus sp.) were used as biocoagulants to harvest Chlorella zofingiensis and Scenedesmus dimorphus. The influences of UV irradiation and polyethylenimine (PEI)-coating on the algal harvesting efficiency were investigated. Results showed that the UV irradiation could slightly enhance bacteria-algae biocoagulation and algal harvesting efficiency. In contrast, the PEI-coated E. coli cells noticeably increased the harvesting efficiencies from 23% to 83% for S. dimorphus when compared to uncoated E. coli cells. Based on the soft-particle Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, an energy barrier existed between uncoated E. coli cells and algal cells, whereas the PEI coating on E. coli cells eliminated the energy barrier, thereby the biocoagulation was significantly improved. Overall, this work presented groundwork toward the potential use of bacterial biomass for algal harvesting from water.

Utilization of agricultural residues of pineapple peels and sugarcane bagasse as cost-saving raw materials in Scenedesmus acutus for lipid accumulation and biodiesel production.

The aim of this study is to optimize the lipid accumulation in microalgae by using two agricultural residues of pineapple peels and sugarcane bagasse as low-cost organic carbon sources. Green microalgae Scenedesmus acutus was isolated and selected for cultivation. Effects of three initial sugar concentrations and the stage for adding sugar during cultivation on biomass and lipid production were investigated. The results clearly showed that two-stage cultivation is more suitable than one-stage. The maximum biomass concentration and productivity were obtained at 3.85 g/L and 160.42 mg/L/day when sugarcane bagasse was used. The highest lipid content and lipid yield was reached at 28.05 % and 0.93 g/L when pineapple peels were used, while in the case of sugarcane bagasse, 40.89 % and 1.24 g/L lipid content and yield were obtained. Lipid content was found in normal condition (autotrophic) at 17.71 % which was approximately 2.13-fold lower than when sugarcane bagasse was used (40.89 %). Biodiesel production via in situ transesterification was also investigated; the main fatty acids of palmitic acid and oleic acid were found. This work indicates that using agricultural residues as organic carbon sources could be able to increase lipid content and reduce the cost of biofuel production.

Nutrient removal and lipid accumulation properties of newly isolated microalgal strains.

In this work, four microalgae including Chlorella sp. SDEC-10, Chlorella ellipsoidea SDEC-11, Scenedesmus bijuga SDEC-12 and Scenedesmus quadricauda SEDC-13 isolated from a local lake have been investigated for the properties of growth, nutrient removal and lipid accumulation in synthetic sewage. Their biomass ranged between 0.4 and 0.5g/L. The total phosphorus removal efficiency of four strains was nearly 100%, but in the case of total nitrogen and ammonium the removal efficiency was relatively low. Their lipid content, ranging from 25.92% to 27.76% and corresponding to the lipid productivity 7.88-18.08mg/L/d, was higher than that obtained in BG-11. Palmitic acid and oleic acid were the predominant compositions found through fatty acids analysis. S. quadricauda SDEC-13 performed best both in nutrient removal and in lipid production among the four strains.

A novel suspended-solid phase photobioreactor to improve biomass production and separation of microalgae.

A novel suspended-solid phase photobioreactor (ssPBR) was proposed in this paper to solve the problem of microalgal expensive and complex harvest system for biomass/biofuel production. In this ssPBR, solid carriers were added and kept suspended by aeration. Part of microalgae could attach and grow on the carriers. By catching carriers, microalgae could easily be separated from liquid phase. Three kinds of Carriers A, B, C made of cotton, mohair and linen, respectively, were used in this study. Compared with the reactor without carriers, the biomass production in each ssPBR was increased by adding these three kinds of carriers at a dosage of 2g/L, and the maximum increments of biomass were 2.2×10(5) (10.3%), 7.8×10(4) (3.9%) and 4.4×10(5) (20.5%)cells/mL, respectively. By increasing the dosage of Carriers-C to 4g/L, the maximum increment of microalgal biomass could reach up to about 30% in the ssPBR compared with control group.

Agrobacterium-mediated transformation of three freshwater microalgal strains.

Microalgal transformation has gained interest in recent years. Agrobacterium-mediated transformation remains as the most efficient method for the development of transgenic plants and microalgae due to its wide host range, inexpensive procedure and transfer of large segments of DNA. In the present study, three different microalgal species were isolated from freshwater environment and identified based on the morphological characteristics and ITS-2 region amplification. Agrobacterium-mediated transformation was successful for the isolates Chlorella sp., Ankistrodesmus sp and Scenedesmus bajacalifornicus. Gene integration and expression was confirmed by PCR amplification of hptII and GUS histochemical assay. A. tumifaciens contamination was checked by amplification of npt II gene (kanamycin resistant) which lies outside the T-border. Based on GUS assay, transformation efficiencies were found to be 12.25% for Chlorella sp. 2.96% for Scenedesmus bajacalifornicus and 3.5% for Ankistrodesmus sp.

Enhancing lutein productivity of an indigenous microalga Scenedesmus obliquus FSP-3 using light-related strategies.

Lutein, one of the main photosynthetic pigments, is a promising natural product with both nutritional and pharmaceutical applications. In this study, light-related strategies were applied to enhance the cell growth and lutein production of a lutein-rich microalga Scenedesmus obliquus FSP-3. The results demonstrate that using white LED resulted in better lutein production efficiency when compared to the other three monochromatic LEDs (red, blue, and green). The lutein productivity of S. obliquus FSP-3 was further improved by adjusting the type of light source and light intensity. The optimal lutein productivity of 4.08 mg/L/d was obtained when using a TL5 fluorescent lamp at a light intensity of 300 µmol/m(2)/s, and this performance is better than that reported in most related studies. Moreover, the time-course profile of lutein accumulation in the microalga shows that the maximal lutein content and productivity were obtained at the onset of nitrogen depletion.

Isolation and heterotrophic cultivation of mixotrophic microalgae strains for domestic wastewater treatment and lipid production under dark condition.

Cultivating microalgae heterotrophically could overcome the light dependency, and thus increase the yield of microalgal lipid per unit area. In this study, three newly isolated strains of microalgae (Scenedesmus sp. ZTY2, Scenedesmus sp. ZTY3 and Chlorella sp. ZTY4) from a domestic wastewater treatment plant were heterotrophically cultivated in domestic wastewater with no illumination. During the cultivation, the algal densities of Scenedesmus species and Chlorella species were increased by 203.0% and 60.5% comparing with the initial densities, respectively. After 11-day cultivation, the lipid contents of Scenedesmus sp. ZTY2, Scenedesmus sp. ZTY3 and Chlorella sp. ZTY4 reached 69.1%, 55.3% and 79.2%, respectively. The DOC removal efficiencies of these three strains were 63.4%, 52.9% and 64.4%, and the biomass yield were 1.65, 1.98 and 2.31mg biomass/mg DOC, respectively. This is the first report about the heterotrophic cultivation of microalgae strains for domestic wastewater treatment and lipid production under dark condition.