Enhancement of adsorption of cyanobacteria, Microcystisa aeruginosaby bacterial-based compounds.

In the present study, algicidal bacteria cultivated in an aqueous medium were utilized as a surface modification agent to develop an efficient adsorbent for the removal of Microcystis aeruginosa. The modification considerably enhanced M. aeruginosa cell removal efficiency. Moreover, the introduction of bio-compounds ensured specificity in the removal of M. aeruginosa. Additionally, the cyanotoxin release and acute toxicity tests demonstrated that the adsorption process using the developed adsorbent is environmentally safe. Furthermore, the practical feasibility of the adsorptive removal of M. aeruginosa was confirmed through cell removal tests performed using the developed adsorbent in a scaled-up reactor (50 L and 10 tons). In these tests, the effects of the adsorbent application type, water temperature, and initial cell concentration on the M. aeruginosa removal efficiency were evaluated. The results of this study provide novel insights into the valorization strategy of biological algicides repurposed as adsorbents, and provide practical operational data for effective M. aeruginosa removal in scaled-up conditions.

Chitosan-modified cotton fiber: An efficient and reusable adsorbent in removal of harmful cyanobacteria, Microcystis aeruginosa from aqueous phases.

In the present study, to remove harmful cyanobacterial species Microcystis aeruginosa from aqueous phases, adsorption-based strategy was utilized. For this strategy, the surface of cotton fiber was modified using chitosan molecules to develop a highly efficient and ecofriendly adsorbent in removal of Microcystis aeruginosa from aqueous solution. The pristine cotton fiber could not remove M. aeruginosa, while the chitosan-modified cotton (CS-m-Cotton) showed the 95% of cell removal efficiency within 12 h. The surface characteristics of chitosan-modified cotton compared to the pristine cotton fiber was examined by various surface analysis methods. In addition, the pre-treatment of pristine cotton using sodium hydroxide solution was an important factor for enhancement of chitosan modification efficiency on the cotton fiber. The developed chitosan-modified cotton fiber could be reusable for M. aeruginosa cell removal after the simple desorption treatment using ultrasonication in alkaline solution. During the repeated adsorbent regeneration and reuse, the chitosan-modified cotton maintained its M. aeruginosa removal efficiencies (>90%). From the acute toxicity assessment using the chitosan-modified cotton and, the measurements of chemical oxygen demand and microcystin level changes in the M. aeruginosa treatment process using the adsorbent, the environmental safety of the adsorption strategy using the developed adsorbent could be confirmed. Based on our results, the chitosan-modified cotton fiber could be proposed as an efficient and ecofriendly solution for remediation of harmful cyanobacterial species occurring water resources.

Ultrasonic Treatment Enhanced Astaxanthin Production of Haematococcus pluvialis.

In this study, effects of ultrasonic treatment on Haematococcus pluvialis (H. pluvialis) were investigated. It has been confirmed that the ultrasonic stimulation acted as stress resources in the red cyst stage H. pluvialis cells containing astaxanthin, resulting in additional astaxanthin production. With the increase in production of astaxanthin, the average diameter of H. pluvialis cells increased accordingly. In addition, to determine how ultrasonic stimulation had an effect on the further biosynthesis of astaxanthin, genes related to astaxanthin synthesis and cellular ROS level were measured. As a result, it was confirmed that astaxanthin biosynthesis related genes and cellular ROS levels were increased, and thus ultrasonic stimulation acts as an oxidative stimulus. These results support the notion on the effect of the ultrasonic treatment, and we believe our novel approach based on the ultrasonic treatment would help to enhance the astaxanthin production from H. pluvialis.

Polyethylenimine linked with chitosan improves astaxanthin production in Haematococcus pluvialis.

Astaxanthin is receiving increasing interest as an antioxidant and high value-added secondary metabolite. Haematococcus pluvialis is the main source for astaxanthin production, and many studies are being conducted to increase the production of astaxanthin. In this study, we linked polyethylenimine (PEI) with chitosan to maintain astaxanthin-inducing ability while securing the recyclability of the inducer. Astaxanthin accumulation in H. pluvialis was induced to 86.4 pg cell-1 with the PEI-chitosan fiber (PCF) treatment prepared by cross-linking of 10 µM PEI and low molecular weight (MW) chitosan via epichlorohydrin. PEI concentration affected the astaxanthin accumulation, whereas the MW of chitosan did not. In addition, the PCF treatment in H. pluvialis increased the reactive oxygen species (ROS) content in cells, thereby upregulating the transcription of enzymes involved in astaxanthin biosynthesis. PCF can be reused multiple times with the maintenance of over 90% of the astaxanthin production efficiency. This study offers a reusable PCF stimulation strategy for enhancing natural astaxanthin content, and PCF treatment will easily increase the production scale or reduce production costs by using recyclability that is not available in current methods. KEY POINTS: • Polyethylenimine-chitosan fiber (PCF) was applied to Haematococcus pluvialis • PCF promotes astaxanthin accumulation by enhancing oxidative stress in H. pluvialis • PCF can be reused multiple times with maintaining over 90% production efficiency.

Amination of Non-Functional Polyvinyl Chloride Polymer Using Polyethyleneimine for Removal of Phosphorus from Aqueous Solution.

The eutrophication of freshwater environments caused by an excess inflow of phosphorus has become a serious environmental issue because it is a crucial factor for the occurrence of harmful algal blooms (HABs) in essential water resources. The adsorptive removal of phosphorus from discharged phosphorus containing effluents has been recognized as one of the most promising solutions in the prevention of eutrophication. In the present study, a polyvinyl chloride (PVC)-polyethyleneimine (PEI) composite fiber (PEI-PVC) was suggested as a stable and recoverable adsorbent for the removal of phosphorus from aqueous phases. The newly introduced amine groups of the PEI-PVC were confirmed by a comparison between the FT-IR and XPS results of the PVC and PEI-PVC. The phosphorus sorption on the PEI-PVC was pH dependent. At the optimum pH for phosphorus adsorption (pH 5), the maximum adsorption capacity of the PEI-PVC fiber was estimated to be 11.2 times higher (19.66 ± 0.82 mg/g) than that of conventional activated carbon (1.75 ± 0.4 mg/g) using the Langmuir isotherm model. The phosphorus adsorption equilibrium of the PEI-PVC was reached within 30 min at pH 5. From the phosphorus-loaded PEI-PVC, 97.4% of the adsorbed amount of phosphorus on the PEI-PVC could be recovered by employing a desorption process using 1M HCl solution without sorbent destruction. The regenerated PEI-PVC through the desorption process maintained a phosphorus sorption capacity almost equal to that of the first use. In addition, consistently with the PVC fiber, the PEI-PVC fiber did not elute any toxic chlorines into the solution during light irradiation. Based on these results, the PEI-PVC fiber can be suggested as a feasible and stable adsorbent for phosphorus removal.

Microalgal secondary metabolite productions as a component of biorefinery: A review.

The interest in developing microalgae for industrial use has been increasing because of concerns about the depletion of petroleum resources and securing sustainable energy sources. Microalgae have high biomass productivity and short culture periods. However, despite these advantages, various barriers need to be overcome for industrial applications. Microalgal cultivation has a high unit price, thus rendering industrial application difficult. It is indispensably necessary to co-produce their primary and secondary metabolites to compensate for these shortcomings. In this regard, this article reviews the following aspects, (1) co-production of primary and secondary metabolites in microalgae, (2) induction methods for the promotion of the biosynthesis of secondary metabolites, and (3) perspectives on the co-production and co-extraction of primary and secondary metabolites. This paper presents various approaches for producing useful metabolites from microalgae and suggests strategies that can be utilized for the co-production of primary and secondary metabolites.

Semi-continuous immobilized cultivation of Porphyridium cruentum for sulfated polysaccharides production.

In this study, semi-continuous immobilized cultivation of Porphyridium cruentum through calcium alginate beads was performed for sulfated polysaccharides (SPs) production. The cell biomass and daily SPs productivity in the calcium alginate bead immobilized culture were increased by up to 79 ± 3.4% and 45.6 ± 3.2%, compared to those in the control, respectively. Furthermore, simultaneous application of immobilization and blue wavelength illumination further increased the phycobiliproteins content by 260 ± 9%, compared to those in the control. Similarly, nutrient deficiencies in combination with immobilization increased daily SPs productivity by about twice that of the control. The chemical composition and biological activity of the extracellular polymeric substances produced through immobilization were similar to those of the control. This study suggests the potential application of calcium alginate beads-based immobilization for continuous and high-efficiency SPs production using P. cruentum.

Amination of cotton fiber using polyethyleneimine and its application as an adsorbent to directly remove a harmful cyanobacterial species, Microcystis aeruginosa, from an aqueous medium.

In the present study, we applied an adsorption-based strategy for the removal of a harmful cyanobacterial species, Microcystis aeruginosa, using cotton fiber. Considering the negatively charged surface properties of M. aeruginosa cells in aqueous phases, aminated cotton fibers were prepared through polyethyleneimine (PEI) modification on the pristine cotton fibers. The aminated surface properties of PEI-modified cotton fiber (PEI-cotton) were confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and potentiometric titration analyses. The pristine cotton fiber could not remove the M. aeruginosa cells, but the PEI-cotton could efficiently remove 98.7% of M. aeruginosa cells from the aqueous medium. In addition, removed cells could be observed on the sorbent surface by field emission scanning electron microscopy (FE-SEM) analysis. PEI-cotton fabricated in 3% PEI solution could remove M. aeruginosa cells (97.9%) more efficiently compared to that fabricated in 1% (82.1%) and 2% (86.2%) of PEI solutions. From the toxicity assessment of the PEI-cotton using Daphnia magna, negligible toxicity of PEI-cotton was confirmed. Our results indicate that the application of PEI-cotton fibers for the removal of M. aeruginosa cells could be suggested as a feasible, effective, and eco-friendly method of harmful algal bloom (HAB) control in water resources.

Phosphorus adsorption behavior of industrial waste biomass-based adsorbent, esterified polyethylenimine-coated polysulfone-Escherichia coli biomass composite fibers in aqueous solution.

This study sought to develop a highly efficient adsorbent material for phosphorus (P) removal via valorization of industrial Escherichia coli biomass waste. To ensure an easy and fast recovery after the sorption process, the E. coli biomass waste was immobilized into polysulfone matrix. Additionally, to improve P sorption capacity, the sorbent surface was coated with polyethylenimine (PEI) and further chemically modified. The P uptakes of the developed sorbent (decarboxylated PEI-modified polysulfone-biomass composite fiber, DC-PEI-PEF) were significantly affected by pH. Moreover, the maximum sorption capacity (qmax) of DC-PEI-PEF was estimated as 30.46 ± 1.09 mg/g at neutral pH, as determined by a Langmuir isotherm model. Furthermore, DC-PEI-PEF could reach sorption equilibrium within 5 min and exhibited reusability potential. The partition coefficient of the newly developed material (DC-PEI-PEF) was calculated as 0.387 mg/g⋅µM at 4 mg/L of initial P concentration and decreased as initial P concentrations increased. Therefore, DC-PEI-PEF could be suggested as a promising adsorbent for application in direct phosphorus removal from natural aquatic environments.

Application of a polyethylenimine-modified polyacrylonitrile-biomass waste composite fiber sorbent for the removal of a harmful cyanobacterial species from an aqueous solution.

Cyanobacterial harmful algal blooms (Cyano-HABs) in water resources involving algal species such as Microcystis aeruginosa have become a serious environmental issue due to their severely negative effects. In the present study, an adsorption-based strategy was employed to control M. aeruginosa, with industrial waste-derived Escherichia coli biomass valorized to produce polyethylenimine-modified polyacrylonitrile-E. coli biomass composite fiber (PEI-PANBF). PEI-PANBF removed approximately 80% of M. aeruginosa cells from an aqueous solution without causing any cell damage. Interestingly, the thickness of PEI-PANBF had a strong influence on the efficiency of M. aeruginosa cell removal. In addition, PEI-PANBF simultaneously removed M. aeruginosa cells and their toxic secondary metabolite, microcystin-LR, from aqueous media. Thus, our proposed fiber represents a feasible utilization method of industrial waste biomass as a biosorbent for the control of Cyano-HABs.

Silica-deposited phospholipid nanotubules as a plausible drug targeting system.

An aqueous dispersion of self-organized phospholipid tubules has been utilized as the template for silica-deposited nanotubules (approximately 0.5 microm thick and >10 microm long) by a sol-gel method. The formation of the hybrid tubules was mechanistically investigated by controlled sol-gel reaction. The incorporation of silica increases the mechanical and thermal stability of tubule geometry. After bioconjugating Ni(2+)-nitrilotriacetic acid (Ni-NTA) to the surface of chemically modified tubules containing primary amine groups, green fluorescent protein (GFP)-6 His and A33scFv-6 His were further bioconjugated in order to investigate a potential application of these hollow silica tubules as vehicle for targeted controlled release. The resulting tubules bound and internalized to SW1222 endothelial human colon carcinoma cells that express the A33 cell-surface glycoprotein more specifically than HT29 cells that do not express this antigen.