Immobilization Of Algae Research Articles

Role of Nanocellulose in Light Harvesting and Artificial Photosynthesis

Artificial photosynthesis has rapidly developed as an actual field of research, mimicking natural photosynthesis processes in plants or bacteria to produce energy or high-value chemicals. The nanocelluloses are a family of biorenewable materials that can be engineered into nanostructures with favorable properties to serve as a host matrix for encapsulation of photoreactive moieties or cells. In this review, the production of different nanocellulose structures such as films, hydrogels, membranes, and foams together with their specific properties to function as photosynthetic devices are described. In particular, the nanocellulose’s water affinity, high surface area and porosity, mechanical stability in aqueous environment, and barrier properties can be tuned by appropriate processing. From a more fundamental viewpoint, the optical properties (transparency and haze) and interaction of light with nanofibrous structures can be further optimized to enhance light harvesting, e.g., by functionalization or appropriate surface texturing. After reviewing the basic principles of natural photosynthesis and photon interactions, it is described how they can be transferred into nanocellulose structures serving as a platform for immobilization of photoreactive moieties. Using photoreactive centers, the isolated reactive protein complexes can be applied in artificial bio-hybrid nanocellulose systems through self-assembly, or metal nanoparticles, metal-organic frameworks, and quantum dots can be integrated in nanocellulose composites. Alternatively, the immobilization of algae or cyanobacteria in nanopaper coatings or a porous nanocellulose matrix allows to design photosynthetic cell factories and advanced artificial leaves. The remaining challenges in upscaling and improving photosynthesis efficiency are finally addressed in order to establish a breakthrough in utilization of nanocellulose for artificial photosynthesis.

A cyclic lipopeptide produced by an antagonistic bacterium relies on its tail and transient receptor potential-type Ca2+ channels to immobilize a green alga.

The antagonistic bacterium Pseudomonas protegens secretes the cyclic lipopeptide (CLiP) orfamide A, which triggers a Ca2+ signal causing rapid deflagellation of the microalga Chlamydomonas reinhardtii. We performed chemical synthesis of orfamide A derivatives and used an aequorin reporter line to measure their Ca2+ responses. Immobilization of algae was studied using a modulator and mutants of transient receptor potential (TRP)-type channels. By investigating targeted synthetic orfamide A derivatives, we found that N-terminal amino acids of the linear part and the terminal fatty acid region are important for the specificity of the Ca2+ -signal causing deflagellation. Molecular editing indicates that at least two distinct Ca2+ -signaling pathways are triggered. One is involved in deflagellation (Thr3 change, fatty acid tail shortened by 4C), whereas the other still causes an increase in cytosolic Ca2+ in the algal cells, but does not cause substantial deflagellation (Leu1 change, fatty acid hydroxylation, fatty acid changes by 2C). Using mutants, we define four TRP-type channels that are involved in orfamide A signaling; only one (ADF1) responds additionally to low pH. These results suggest that the linear part of the CLiP plays one major role in Ca2+ signaling, and that orfamide A uses a network of algal TRP-type channels for deflagellation.

Effect of extracellular proteins on Cd(II) adsorption in fungus and algae symbiotic system

Fungus-algae symbiotic systems (FASS) are typically used to assist in the immobilization of algae and strengthen the adsorption of heavy metals. However, the adsorption behavior of the symbiotic system and the molecular regulation mechanism of extracellular proteins in the adsorption of heavy metals have not been reported in detail. In this study, a stable FCSS (fungus-cyanobacterium symbiotic system) was used to study Cd(II) adsorption behavior. The fixation efficiency of fungus to cyanobacterium reached more than 95% at pH7.0, 30 °C, 150 rpm, and a medium ratio of 100%. The biomass, chlorophyll content, and total fatty acid content of the symbiotic system were much higher than those of cyanobacterium and fungus alone. The photosynthetic fluorescence parameters showed that the presence of fungus enhanced the light tolerance of cyanobacterium. The original light energy conversion efficiency and potential activity of PSII were enhanced, indicating that symbiosis could promote the photosynthetic process of cyanobacterium. The Cd(II) adsorption efficiency can achieve 90%. The system maintained excellent adsorption after six adsorption cycles. Differential proteins were mainly enriched in areas such as metabolism, ABC transport system, and pressure response. Cd(II) stress promotes an increase in efflux proteins. Moreover, cadmium can be fixed as much as possible by secreting extracellular proteins, and the toxicity of cadmium to cells can be alleviated by regulating the metabolism of glutathione, reducing oxidative phosphorylation level, and reducing oxidative stress, thus improving the resistance to Cd(II). Meanwhile, the expression of enzymes involved in glycolysis and the pentose phosphate pathway was upregulated, while the expression of those in the TCA cycle was downregulated. The expression of substances related to PSI and PSII in the photosynthetic system and rubisco, a key enzyme in the Calvin cycle, was significantly upregulated, indicating that the glucose metabolism and photosynthetic pathways of the symbiotic system were involved in resistance to Cd toxicity. This revealed the response mechanism of the fungus-algal symbiotic system in the process of Cd adsorption, and also provided reference value for industrial application in water treatment.

Effects of red and blue light emitting diodes on biomass and astaxanthin of Haematococcus pluvialis in pilot scaleangled twin-layer porous substrate photobioreactors

The production of natural astaxanthin is usually accomplished by suspended cultivation of the microalgae Haematococcus pluvialis. In this study, for the purpose of cost reduction, H. pluvialis is grown in pilot scale angled twin-layer porous substrate photobioreactors with light energy from red/blue LEDs that can produce red light, blue light, or a combination of blue-red light. The total dry biomass of the microalgae reached a maximum of 40.74 g.m-2under blue-red LEDs. The early initiation of blue-red LED illumination (on day 2) after algae immobilization in the biofilm resulted in the highest accumulation of astaxanthin in the dry biomass, which reached a maximum of 1.3% (w/w) after 10 d of culture.

Mechanism and challenges behind algae as a wastewater treatment choice for bioenergy production and beyond

Conventional wastewater (WW) treatment uses activated sludge process, which is accepted worldwide. However, the sustainability of such a process is questioned in terms of emissions, energy savings, and economic benefits. Microalgae based WW treatment has been proposed as a viable alternative to conventional WW treatment. In microalgae treatment, WW including organics and nutrients gets converted to algae, while reclaimed water is discharged back to the environment. Microalgae could be used as a precursor for biochemicals, biofuels or other bio-based products. There are different technologies within microalgae-based WW treatment including adsorption, accumulation, and immobilization of algae. This review attempts to understand the mechanisms of these technologies on how nutrients and organics are removed from WW. Though it is a viable alternative, there are several challenges and limitation that exist in this technology which needs to be addressed to have a commercial perspective. Algae based WW treatment is analysed for its limitation and has been reported here. Beyond WW treatment, this method should also be looked as an emission reduction strategy through CO2 fixation.

Biosorption of uranium(VI) by bi-functionalized low cost biocomposite adsorbent

This paper presents biosorption properties of U(VI) by bi-functionalized biocomposite adsorbent consists of macro marine algae ( Jania rubens) and yeast ( Saccharomyces cerevisiae) immobilized on silica gel. Removal of U(VI) from aqueous solution by biosorption on biocomposite in a single component system with pH, initial concentration of U(VI), various contact time and temperature was investigated. Experimental equilibrium biosorption data was analyzed by five two-parameter equations, namely; Langmuir, Freundlich, Dubinin–Radushkevich (D–R), Temkin and Flory–Huggins isotherms. Among these isotherm models, the Temkin model fits better with the experimental data compared to others. Thermodynamic parameters, such as the enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) were calculated from the slope and intercept of logK d vs. 1/T plot. Results suggested that the bi-functionalized low cost biocomposite adsorbent is a suitable biosorbent material to remove uranium ions from diluted aqueous solutions. On the other hand, immobilization of algae and yeast on silica gel was found to improve their interaction properties with uranium ions in biosorption process.

Empleo de microalga <i>Scenedesmus obliquas</i> en la eliminación de cromo presente en aguas residuales galvánicas

Dumping wastewaters from plating industry with a high content in chromium is a potential hazard for people and environment. It is known that some metals, including the heavy metals, at low concentrations participate in different metabolic routes, but at high concentration are toxic for many living organisms. Some microorganism taking the heavy metals from the environment are capable of concentrating and accumulating large quantities of them in different citoplasmatic structures with no-toxic effects. Microalgae have affinity by the polyvalent metals making possible their use as depollutant agent in waters that contains dissolved metallic ions as alternative methods when others methods of recycle are unusable. In this report a chromium removal study from a plating wastewater, using scenedesmus obliquus culture was made. The removal efficiency of Cr (VI) was 12 % and Cr (III) was 27 % and for condition of algae's immobilization removal of Cr (III) was 95 %.

Study of metal bioaccumulation by nuclear microprobe analysis of algae fossils and living algae cells

Microscopic ion-beam analysis of palaeo-algae fossils and living green algae cells have been performed to study the metal bioaccumulation processes. The algae fossils, both single cellular and multicellular, are from the late Neoproterozonic (570 million years ago) ocean and perfectly preserved within a phosphorite formation. The biosorption of the rare earth element ions Nd 3+ by the green algae species euglena gracilis was investigated with a comparison between the normal cells and immobilized ones. The new Leipzig Nanoprobe, LIPSION, was used to produce a proton beam with 2 μm size and 0.5 nA beam current for this study. PIXE and RBS techniques were used for analysis and imaging. The observation of small metal rich spores ( <10 μm ) surrounding both of the fossils and the living cells proved the existence of some specific receptor sites which bind metal carrier ligands at the microbic surface. The bioaccumulation efficiency of neodymium by the algae cells was 10 times higher for immobilized algae cells. It confirms the fact that the algae immobilization is an useful technique to improve its metal bioaccumulation.

Comparison of the effects of nitrogen concentration on nutrient removal, growth and physiological characteristics of immobilized and free Chlorella Vulgaris: I. growth and nutrient removal

The effects of nitrogen concentration on nutrient removal and the growth of immobilized and free Chlorella vulgaris were compared through laboratory ‐ scale batch experiment. The nitrogen concentration had much less influence on immobilized algae than free algae. During the 6 days experimental period, at nitrogen concentrations of 10, 20, 40 and 80 mg.l−1, immobilized algae achieved the growth rates of 0.168, 0.242, 0.137 and 0.093 day−1, and removed 62.0%, 78.0%, 91.2% and 97.1% total ‐ N, respectively, and 85–90% NH4 +‐N as well as more than 90% PO4 3−P. However, free algae obtained the growth rates of 0.071, 0.090, 0.059 and ‐0.021 day−1, and removed 36. 8%, 61.8%, 70.1%, and 45.9% total ‐ N, respectively. Especially at nitrogen concentration of 80 mg.l−1, its removal efficiency of NH4 +‐ N was only 22.2%, and at nitrogen concentration of 10 mg.l−1 that of PO4 3−‐P was only 38.7%. It shows that the immobilization of algae may protect cells against the inhibition of high nitrogen concentration and low N:P ratio. The nutrient removal of immobilized algae increased as nitrogen concentrations increased, but was not much correlated with the increase of cells number. This result suggests that nutrient removal of immobilized algae may be more dependent on the physiological activities of algae entrapped in Ca ‐ alginate, which makes its removal processes of nutrient different from free algae. The present study shows that immobilized Chlorella vulgaris has great potentialities for removing nutrient from wastewater with high nitrogen concentration loading or with a wide range of nitrogen/phosphorus.

Comparison of the effects of nitrogen concentration on nutrient removal, growth and physiological characteristics of immobilized and free Chlorella Vulgaris: II.chlorophyll content, fluorescence spectra and nitrate reductase activity

The effects of nitrogen concentrations on chlorophyll content, fluorescence emission spectra and nitrate reductase activity of immobilized Chlorella vulgaris were investigated using laboratory‐scale batch experiments, as compared with free alage. At the nitrogen concentrations of 10, 20, 40, and 80 mg.l−1, the chlorophyll contents of immobilized algae were respectively 1.79, 1.38, 1.28 and 1.58‐fold that of free algae, the NR activities of immobilized algae were respectively 2.71, 1.41, 2.23 and 1.33‐fold that of free algae. The chlorophyll a/b values of immobilized algae at all nitrogen concentrations maintained similarity and all increased as cultural time developed, whilst those of free algae at high nitrogen concentrations (40 and 80 mg.l−1) were slightly higher than that at low nitrogen concentrations (10 and 20 mg.l−1). It shows that the immobilization is beneficial to the synthesis of chlorophyll a and that the high nitrogen concentration injured chlorophyll b of free algae to a certain extent. In addition, the immobilization of algae can slower the decline of the PS II activity and this decline is more slight at 80 mg.l−1 nitogen than at 20 mg.l−1 nitrogen. The result supports the idea that immobilization has some stimulating and protective effects on algae cells and that immobilized algae have great advantages of treating wastewater with high concentration loading or poorly— balanced nutrients over free algae.