Fixed-bed biosorption of cadmium using immobilized Scenedesmus obliquus CNW-N cells on loofa (Luffa cylindrica) sponge

Cadmium-Induced Physiological Responses, Biosorption and Bioaccumulation in Scenedesmus obliquus

Cadmium ion (Cd2+) is a highly toxic metal in water, even at low concentrations. Microalgae are a promising material for heavy metal remediation. The present study investigated the effects of Cd2+ on growth, photosynthesis, antioxidant enzyme activities, cell morphology, and Cd2+ adsorption and accumulation capacity of the freshwater green alga Scenedesmus obliquus. Experiments were conducted by exposing S. obliquus to varying concentrations of Cd2+ for 96 h, assessing its tolerance and removal capacity towards Cd2+. The results showed that higher concentrations of Cd2+ (>0.5 mg L-1) reduced pigment content, inhibited algal growth and electron transfer in photosynthesis, and led to morphological changes such as mitochondrial disappearance and chloroplast deformation. In this process, S. obliquus counteracted Cd2+ toxicity by enhancing antioxidant enzyme activities, accumulating starch and high-density granules, and secreting extracellular polymeric substances. When the initial Cd2+ concentration was less than or equal to 0.5 mg L-1, S. obliquus was able to efficiently remove over 95% of Cd2+ from the environment through biosorption and bioaccumulation. However, when the initial Cd2+ concentration exceeded 0.5 mg L-1, the removal efficiency decreased slightly to about 70%, with biosorption accounting for more than 60% of this process, emerging as the predominant mechanism for Cd2+ removal. Fourier transform infrared correlation spectroscopy analysis indicated that the carboxyl and amino groups of the cell wall were the key factors in removing Cd2+. In conclusion, S. obliquus has considerable potential for the remediation of aquatic environments with Cd2+, providing algal resources for developing new microalgae-based bioremediation techniques for heavy metals.

Microalgal-based macro-hollow loofah fiber bio-composite for methylene blue removal: A promising step for a green adsorbent

This study looked into how well the macro-hollow loofah fiber with and without the bio-attaching with green microalga (Chlamydomonas reinhardtii OR242521) was applied methylene blue elimination from water. Based on the results, the biosorption capacity of loofah sponge for methylene blue significantly increased with the increase of contact time, weight of microalgal biofilm, and methylene blue concentration. The maximum biosorption capacity was achieved after 120 min, after 0.042 mgg-1 biofilm weight, and MB concentration of 140 mgL-1. Furthermore, methylene blue's biosorption capacity was strongly affected by pH, reaching its maximum at pH 7. The biosorption capacity of the bio-attached loofah sponge was much higher than that of the loofah sponge, revealing that the microalgae bio-attachment enhanced the biosorption capacity of the loofah sponge. At the end of the MB biosorption process, the used bio-attached loofah sponge can still be utilized once more for the same purpose after the desorption of MB but with a lower biosorption capacity. Furthermore, the loofah sponge could also be applied as a bio-sorbent after domestic use. According to this study, the loofah sponge with or without algal biofilm attachment could be applied as a low-cost efficient bio-sorbent for methylene blue removal from water. However, the loofah sponge's ability for biosorption was dramatically increased by the bio-attachment of microalgae, making it a more potent bio-sorbent. Likewise, this study offers insights into the variables influencing the biosorption capacity of loofah sponges and bio-attached loofah sponges, which could be beneficial for enhancing the biosorption processes.

Contrasting effects of a novel biochar-microalgae complex on arsenic and mercury removal

Biochar and algae were commonly used as environmental-friendly adsorbents to treat wastewater contaminated with heavy metals. In the study, we used a biochar-microalgae complex of Coconut shell activated carbon (Csac) and Chlorella to evaluate and compare the adsorption ability of arsenic and mercury. The adsorption kinetic study showed that the adsorption efficiency of the biochar-microalgae complex for mercury was better remarkably than arsenic (about 74.84% higher in initial 1 min and 71.62% higher at adsorption equilibrium), which could be interpreted as the complex had excellent adsorption capacity for mercury. The new biochar-microalgae complex adsorbed up to 46.8 μg·g^-1 of mercury at 100 μg·L^-1 concentration. FTIR and XPS indicated that the surface of biochar-microalgae complex adsorbent had abundant oxygen-containing functional groups that could provide active sites during the adsorption process, i.e., -COOH, -OH and C-O-C et al. Compared with arsenic, the adsorption peaks of mercury moved or changed significantly, suggesting that the complex strongly adsorbed mercury and the main adsorption mechanisms were the ion exchange and complexation between functional groups and mercury ion. What must be emphasized was arsenic mainly existed as negative ions (AsO₂^-, AsO₂^3-) in water, which was the reason for the weak adsorption capacity of the biochar-microalgae complex for arsenic. In short, the adsorption efficiency and performance of the biochar-microalgae complex was significantly higher than that of arsenic (p < 0.01), and the adsorption of mercury by biochar-microalgae was chemisorption based on the single molecular layer theory.

Cadmium-resistant phosphate-solubilizing bacteria immobilized on phosphoric acid-ball milling modified biochar enhances soil cadmium passivation and phosphorus bioavailability

Cadmium (Cd) can accumulate in agriculture soil from the regular application of phosphorus (P) fertilizer. Microbiological method is considered as a potentially effective strategy that can not only remediate the Cd-contaminated soil but also provide the phosphorus needed for crop growth. However, the toxicity of Cd may affect the activity of microorganisms. To solve this problem, Klebsiella variicola with excellent phosphate solubilization ability (155.30 mg L^-1 at 48 h) and Cd adsorption rate (90.84 % with 10 mg L^-1 Cd initial concentration) was firstly isolated and identified in this study. Then, a phosphoric acid and ball milling co-modified biochar (PBC) was selected as the carrier to promote the activities of K. variicola under Cd pollution. Surface characterization revealed that the promotion of K. variicola by PBC was mainly attributed to the large specific surface area and diverse functional groups. Compared to contaminated soil, microbial PBC (MPBC) significantly increased the pakchoi biomass and phosphorus (P) content, while the Cd content in leave and root of pakchoi (Brassica chinensis L.) decreased by 25.90-43.46 % (P < 0.05). The combined application also favored the transformation of the resistant P fractions to bioavailable P, and facilitated the immobilization of 20.12 % exchangeable Cd to reducible, oxidizable, and residual Cd in the treated soil. High-throughput sequencing revealed that the response of the soil microbial community to the MPBC was more beneficial than K. variicola or PBC alone. Therefore, the application of MPBC has the potential to act as an efficient, stable, and environmentally friendly sustainable product for Cd remediation and enhanced P bioavailability in agricultural production.

Innovative method for encapsulating highly pigmented biomass from Aspergillus nidulans mutant for copper ions removal and recovery

Biosorption has been considered a promising technology for the treatment of industrial effluents containing heavy metals. However, the development of a cost-effective technique for biomass immobilization is essential for successful application of biosorption in industrial processes. In this study, a new method of reversible encapsulation of the highly pigmented biomass from Aspergillus nidulans mutant using semipermeable cellulose membrane was developed and the efficiency of the encapsulated biosorbent in the removal and recovery of copper ions was evaluated. Data analysis showed that the pseudo-second-order model better described copper adsorption by encapsulated biosorbent and a good correlation (r2 > 0.96) to the Langmuir isotherm was obtained. The maximum biosorption capacities for the encapsulated biosorbents were higher (333.5 and 116.1 mg g-1 for EB10 and EB30, respectively) than that for free biomass (92.0 mg g-1). SEM-EDXS and FT-IR analysis revealed that several functional groups on fungal biomass were involved in copper adsorption through ion-exchange mechanism. Sorption/desorption experiments showed that the metal recovery efficiency by encapsulated biosorbent remained constant at approximately 70% during five biosorption/desorption cycles. Therefore, this study demonstrated that the new encapsulation method of the fungal biomass using a semipermeable cellulose membrane is efficient for heavy metal ion removal and recovery from aqueous solutions in multiple adsorption-desorption cycles. In addition, this reversible encapsulation method has great potential for application in the treatment of heavy metal contaminated industrial effluents due to its low cost, the possibility of recovering adsorbed ions and the reuse of biosorbent in consecutive biosorption/desorption cycles with high efficiency of metal removal and recovery.

Adsorption characteristics of Cr(VI) on microalgae immobilized by different carriers

To solve the problem of harvesting microalgae during heavy metal adsorption, six different carriers were selected in this study to compare the adsorption behavior of microalgae after immobilization. The results of the scanning electron microscope (SEM) and adsorption showed chitosan as a carrier showed the best immobilization effect and adsorption advantages after immobilizing microalgae. The optimal immobilized carrier-chitosan was obtained under the following conditions of chitosan: acetic acid (2:40), microalgae concentration (10⁸ cells mL^-1), and immobilization time (18 h). The optimal adsorption conditions were as follows: temperature: 30 °C, pH: 7.0, adsorption dose: 1.5 g L^-1, initial ion concentration: 40 mg L^-1. The adsorption capacity of metal ions can reach 37.1 mg g^-1 Cr(VI), 25.98 mg g^-1 Cu(II), 25.06 mg g^-1 Pb(II), and 24.62 mg g^-1 Cd(II), respectively. The desorption efficiency in 0.5 mol L^-1 NaOH desorption solution reached 90.01%. After five adsorption-desorption cycles, excluding chitosan (∼70%), the adsorption efficiency of other adsorbents decreased with an increase in the recycling times. Chitosan was a suitable carrier for the immobilization of Synechocystis sp. PCC6803. Fourier transform infrared spectroscopy and Raman spectra analysis showed that groups belonging to the microalgae were detected after the microalgae in different carriers, indicating that the microalgae were immobilized with the carriers. At the same time, the energy spectrum changed before and after adsorption indicated the specific functional groups of microalgae played an important role in the adsorption process. The kinetic and isothermal model data showed that the adsorption process was mainly chemical adsorption and homogeneous monolayer adsorption. Moreover, X-ray diffraction showed the interlayer peak strength decreased significantly, indicating that the interlayer structure was stretched after Cr(VI) ion exchange. X-ray photoelectron spectroscopy analysis showed that the Cr adsorption process involves the reduction of Cr(VI) to Cr(III).

Feasibility and comparative analysis of cadmium biosorption by living scenedesmus obliquus FACHB-12 biofilms

Microalgal biofilm has been recognized as a cost-effective biorsorbent for heavy metal and a promising method for microalgae-water separation. In this study, living suspended Scenedesmus obliquus FACHB-12 (isolated from southern China) and its biofilm with different carriers were investigated to remove cadmium from aqueous solution. S. obliquus FACHB-12 biofilm with luffa sponge carrier showed highest cadmium removal efficiency at 92.7% compared to biofilm with K3 carrier (75.3%) and significantly higher than suspended S. obliquus FACHB-12 (61.8%) in 2 h experiment with initial Cd²⁺ concentration at 3.0 mg/L at pH = 6.0 with 0.8 g/L of biomass under room temperature. S. obliquus FACHB-12 biofilm with K3 and luffa sponge carrier also demonstrated higher tolerance towards increased Cd²⁺ concentration with highest biosorption efficiency at 85.1% and 90.35% respectively under 20 mg/L of Cd²⁺, while suspended S. obliquus FACHB-12 biosorption efficiency achieved 81.4% under 10 mg/L of Cd²⁺ and started to decline over increased cadmium concentration. The adsorption kinetics for all experimental groups followed the pseudo-second-order adsorption model, with biosorption equilibrium favored in Langmuir isotherm. The maximum biosorption capacity estimated by Langmuir isotherm reached 133.14 mg/g biomass in S. obliquus FACHB-12 biofilm with luffa sponge carrier, followed by 78.76 mg/g with K3 carrier, and 60.03 mg/g with suspended S. obliquus FACHB-12. Results suggest an efficient, inexpensive microalgal biofilm with biological carrier system could enhance high cadmium removal for advanced wastewater treatment and provide a cost-effective method for microalgae harvesting process.

Inoculation of Cd-contaminated paddy soil with biochar-supported microbial cell composite: A novel approach to reducing cadmium accumulation in rice grains

Bioremediation of heavy metal-contaminated soil using metal-resistant microbes is a promising remediation technology. However, as exogenous bacteria sometimes struggle to survive and grow when introduced to new soils, it is important to develop appropriate carriers for microbial populations. In this study, we report a novel approach to remediating Cd-contaminated rice paddy soil using biochar-supported microbial cell composites (BMCs) produced from agricultural waste (cornstalks). Pot experiments showed that amendment with BMC was more efficient at reducing root and grain Cd content than pure bacteria, while improving soil Cd fractionation toward more stabilized and less labile forms. Bacteria in the BMC medium grew more readily with more abundant metabolites than those raised in free cells, probably because biochar provides shelter via porous structures (as confirmed by scanning electron microscopy) as well as additional nutrients. Overall, the improved long-term production of microbial biomass caused by BMC inoculation results in a higher remediation efficiency. Our results demonstrate the feasibility of using biochar as an appropriate carrier for metal-tolerant bacteria to remediate Cd-contaminated paddy fields.

Adsorption of cadmium from aqueous solutions by novel Fe3O4- newly isolated Actinomucor sp. bio-nanoadsorbent: functional group study

A novel bio-nanocomposite was prepared by the combination of fungal biomass and Fe₃O₄ magnetic nanoparticles. The result of XRD and EDAX analysis indicated that Fe₃O₄ Actinomucor sp. bio-nanoadsorbent was prepared. Our experiments showed that the adsorption kinetics and isotherm of this material comply with the pseudo-second-order and the Langmuir models, respectively. The maximum adsorption capacity (q_max) of this novel bio-nanoadsorbent was obtained as 29.49 mg/g. The thermodynamic analysis revealed that the adsorption of Cd²⁺ is spontaneous and exothermic. The optimum temperature, initial concentration, contact time and pH for adsorption system of cadmium were about 45 °C, 400 mg/L, 120 min and 7, respectively. Pretreatment of adsorbent by NaOH and SDS significantly increased cadmium adsorption capacity. SEM images showed that Fe₃O₄ nanoparticles were immobilized successfully on the fungus cell surface. Contribution of the carboxyl, hydroxyl, amine and Fe-O functional groups of the bio-nanoadsorbent in the binding to cadmium ions was revealed by FTIR analysis. Results from regeneration studies indicated reusability of the adsorbent up to 91%. According to experimental results, it could be claimed that bio-nanocomposite of Fe₃O₄-Actinomucor sp. is a novel efficient adsorbent for removal of metal ions from aqueous solutions, and hence it has potential to be used in the environmental pollution cleanup programs.

Utilization of Non-Living Microalgae Biomass from Two Different Strains for the Adsorptive Removal of Diclofenac from Water

In the present work, the adsorptive removal of diclofenac from water by biosorption onto non-living microalgae biomass was assessed. Kinetic and equilibrium experiments were carried out using biomass of two different microalgae strains, namely Synechocystis sp. and Scenedesmus sp. Also, for comparison purposes, a commercial activated carbon was used under identical experimental conditions. The kinetics of the diclofenac adsorption fitted the pseudo-second order equation, and the corresponding kinetic constants indicating that adsorption was faster onto microalgae biomass than onto the activated carbon. Regarding the equilibrium results, which mostly fitted the Langmuir isotherm model, these pointed to significant differences between the adsorbent materials. The Langmuir maximum capacity (Qmax) of the activated carbon (232 mg∙g−1) was higher than that of Scenedesmus sp. (28 mg∙g−1) and of Synechocystis sp. (20 mg∙g−1). In any case, the Qmax values determined here were within the values published in the recent scientific literature on the utilization of different adsorbents for the removal of diclofenac from water. Still, Synechocystis sp. showed the largest KL fitted values, which points to the affinity of this strain for diclofenac at relative low equilibrium concentrations in solution. Overall, the results obtained point to the possible utilization of microalgae biomass waste in the treatment of water, namely for the adsorption of pharmaceuticals.

Enhancing cadmium bioremediation by a complex of water-hyacinth derived pellets immobilized with Chlorella sp

A complex of water-hyacinth derived pellets immobilized with Chlorella sp. was applied, for the first time, in the bioremediation of Cadmium (Cd). The Cd(II) removal efficiency of the complex was optimized by investigating several parameters, including the pellet materials, algal culture age, and light intensity. Results showed that the Cd(II) removal efficiency was positively related to the algal immobilization efficiency and the algal bioaccumulation capacity. Since higher surface hydrophilicity leads to higher immobilization efficiency, the water-hyacinth leaf biochar pellet (WLBp) was selected as the optimal carrier. A maximum Cd(II) removal efficiency of 92.45% was obtained by the complex of WLBp immobilized with algal cells in stationary growth phase and illuminated with a light intensity of 119 μmol m^-2 s^-1. Recovery tests on both microalgal cells and the WLBp demonstrated that the algal cells and the biochar pellet can be economically recycled and reused.

Anionically reinforced hydrogel network entrapped fungal cells for retention of cadmium in the contaminated aquatic media

A novel biomass/polymer composite was fabricated by embedding Thamnidium elegans cells in acrylic network of p(3-Methoxyprophyl)acrylamide p(MPA) enriched with 2-Akrylamido-2-methyl-1-propane sulfonic acid (AMPS). Cd(II) retention potential of hydrogel (p(MPA-co-AMPS)) increased by 20.66% times after this enrichment. The gel matrix could be effectively entrapped the biomass and resulting sorbent applied to remove Cd(II) from water in batch and continuous modes. The main physico-chemical parameters are discussed in addition to characterization, regeneration and application studies of the suggested sorbent. Equilibrium occurred within 30 min and Langmuir model predicted the equilibrium data. Kinetics of Cd(II) removal onto immobilized biomass is modeled using the pseudo-second-order rate equation. Maximum monolayer sorption capacity was estimated to be 123.76 mg g^-1 at 25 °C. Designed composite was successfully applied for the removal of Cd(II) from industrial wastewater. EDTA and HNO₃ can be efficiently used for Cd(II) recovery and composite sorbent recycled for at least 12 cycles with nearly stable sorption performance.

Microalgal-biochar immobilized complex: A novel efficient biosorbent for cadmium removal from aqueous solution

The feasibility of the bioremediation of cadmium (Cd) using microalgal-biochar immobilized complex (MBIC) was investigated. Major operating parameters (e.g., pH, biosorbent dosage, initial Cd(II) concentration and microalgal-biochar ratio) were varied to compare the treatability of viable algae (Chlorella sp.), biochar and MBIC. The biosorption isotherms obtained by using algae or biochar were found to have satisfactory Langmuir predictions, while the best fitting adsorption isotherm model for MBIC was the Sips model. The maximum Cd(II) adsorption capacity of MBIC with a Chlorella sp.: biochar ratio of 2:3 (217.41mgg^-1) was higher than that of Chlorella sp. (169.92mgg^-1) or biochar (95.82mgg^-1) alone. The pseudo-second-order model fitted the biosorption process of MBIC well (R²>0.999). Moreover, zeta potential, SEM and FTIR studies revealed that electrostatic attraction, ion exchange and surface complexation were the main mechanisms responsible for Cd removal when using MBIC.

Design of hybrid PVA-CA-Jania rubens biomatrix for removal of lead

Polyvinyl alcohol-sodium alginate (PVA-SA) matrix was fabricated and red algae Jania rubens was embedded for removal of lead from aqueous solutions. The Pb(II) uptake rate was rapid primarily at 1 h and equilibrium was achieved within 2 h. The optimum pH was 5, the data were well fitted by Langmuir and Freundlich models, and R_L values are in the range of 0.1-0.38. The sorption capacity (q_e) of PVA-calcium alginate (CA)-J. rubens matrix increased from 10.77 to 37.195 mg g^-1 with increasing Pb(II) concentration from 24.86 to 98.75 mg L^-1 at the temperature of 30°C and pH 5. The sorption capacity (q_e) and maximum biosorption (q_m) were noted as 37.179 ± 0.32 and 71.43 mg/g, respectively. The adsorption process was well described by pseudo-second-order model. The reaction is endothermic, is spontaneous, and increases in randomness. The functional groups present on matrix, i.e., -OH, -C-N, -C-O,-CO-NH, -NH₂, -SH, and -C-OH, were intensely involved in the process. Scanning electron microscopy results revealed the morphological changes due to adsorption of Pb(II) on and inside of PVA-CA-J. rubens matrix. Desorption study indicates the efficient regeneration of PVA-CA-J. rubens biomass matrix for three cycles and is a promising matrix for removal of Pb(II) and can be used in continuous systems.

Packed-bed column biosorption of chromium(VI) and nickel(II) onto Fenton modified Hydrilla verticillata dried biomass

The present study represents the first attempt to investigate the biosorption potential of Fenton modified Hydrilla verticillata dried biomass (FMB) in removing chromium(VI) and nickel(II) ions from wastewater using up-flow packed-bed column reactor. Effects of different packed-bed column parameters such as bed height, flow rate, influent metal ion concentration and particle size were examined. The outcome of the column experiments illustrated that highest bed height (25cm); lowest flow rate (10mLmin(-1)), lowest influent metal concentration (5mgL(-1)) and smallest particle size range (0.25-0.50mm) are favourable for biosorption. The maximum biosorption capacity of FMB for chromium(VI) and nickel(II) removal were estimated to be 89.32 and 87.18mgg(-1) respectively. The breakthrough curves were analyzed using Bed Depth Service Time (BDST) and Thomas models. The experimental results obtained agree to both the models. Column regeneration experiments were also carried out using 0.1M HNO3. Results revealed good reusability of FMB during ten cycles of sorption and desorption. Performance of FMB-packed column in treating secondary effluent was also tested under identical experimental conditions. Results demonstrated significant reduction in chromium(VI) and nickel(II) ions concentration after the biosorption process.

Bio-recovery of non-essential heavy metals by intra- and extracellular mechanisms in free-living microorganisms

Free-living microorganisms may become suitable models for recovery of non-essential and essential heavy metals from wastewater bodies and soils by using and enhancing their accumulating and/or leaching abilities. This review analyzes the variety of different mechanisms developed mainly in bacteria, protists and microalgae to accumulate heavy metals, being the most relevant those involving phytochelatin and metallothionein biosyntheses; phosphate/polyphosphate metabolism; compartmentalization of heavy metal-complexes into vacuoles, chloroplasts and mitochondria; and secretion of malate and other organic acids. Cyanide biosynthesis for extra-cellular heavy metal bioleaching is also examined. These metabolic/cellular processes are herein analyzed at the transcriptional, kinetic and metabolic levels to provide mechanistic basis for developing genetically engineered microorganisms with greater capacities and efficiencies for heavy metal recovery, recycling of heavy metals, biosensing of metal ions, and engineering of metalloenzymes.

Cd-Resistant Strains of B. cereus S5 with Endurance Capacity and Their Capacities for Cadmium Removal from Cadmium-Polluted Water

The goal of this study was to identify Cd-resistant bacterial strains with endurance capacity and to evaluate their ability to remove cadmium ions from cadmium-polluted water. The Bacillus cereusS5 strain identified in this study had the closest genetic relationship with B. cereus sp. Cp1 and performed well in the removal of Cd²⁺ions from solution. The results showed that both the live and dead biomasses of the Cd²⁺-tolerant B. cereus S5 strain could absorb Cd²⁺ ions in solution but that the live biomass of the B. cereus S5 strain outperformed the dead biomass at lower Cd²⁺concentrations. An analysis of the cadmium tolerance genes of B. cereus S5 identified ATPase genes that were associated with cadmium tolerance and involved in the ATP pumping mechanism. The FTIR spectra revealed the presence of amino, carboxyl and hydroxyl groups on the pristine biomass and indicated that the cadmium ion removal ability was related to the structure of the strain. The maximum absorption capacity of the B. cereus S5 strain in viable spore biomass was 70.16 mg/g (dry weight) based on a pseudo-second-order kinetic model fit to the experimental data. The Langmuir and Langmuir-Freundlich isotherm adsorption models fit the cadmium ion adsorption data well, and the kinetic curves indicated that the adsorption rate was second-order. For Cd²⁺ concentrations (mg/L) of 1–109 mg/L, good removal efficiency (>80%) was achieved using approximately 3.48–10.3 g/L of active spore biomass of the B. cereus S5 strain. A cadmium-tolerant bacteria-activated carbon-immobilized column could be used for a longer duration and exhibited greater treatment efficacy than the control column in the treatment of cadmium-polluted water. In addition, a toxicity assessment using mice demonstrated that the biomass of the B. cereus S5 strain and its fermentation products were non-toxic. Thus, the isolated B. cereus S5 strain can be considered an alternative biological adsorbent for use in emergency responses to severe cadmium pollution and in the routine treatment of trace cadmium pollution.

Expression of type 2 diacylglycerol acyltransferse gene DGTT1 from Chlamydomonas reinhardtii enhances lipid production in Scenedesmus obliquus

Microalgal strains of Scenedesmus obliquus have the great potential for the production of biofuels, CO2 fixation, and bioremediation. However, metabolic engineering of S. obliquus to improve their useful phenotypes are still not fully developed. In this study, S. obliquus strain CPC2 was genetically engineered to promote the autotrophic growth and lipid productivity. The overexpression plasmid containing the type 2 diacylglycerol acyltransferse (DGAT) gene DGTT1 from Chlamydomonas reinhardtii was constructed and transformed into S. obliquus CPC2, and the positive transformants were obtained. The expression of DGTT1 gene was confirmed by reverse transcription PCR analysis. Enhanced lipid content of the transformant S. obliquus CPC2-G1 by nearly two-fold was observed. The biomass concentration of the recombinant strains was also 29% higher than that of the wild-type strain. Furthermore, the recombinant strain CPC2-G1 was successfully grown in 40 L tubular type photobioreactor and open pond system in an outdoor environment. The lipid content, biomass concentration, and biomass productivity obtained from 40 L tubular PBR were 127.8% 20.0%, and 232.6% higher than those obtained from the wild-type strain. The major aim of this work is to develop a tool to genetically engineer an isolated S. obliquus strain for the desired purpose. This is the first report that genetic engineering of S. obliquus has been successful employed to improve both the microalgal cell growth and the lipid production.

Synthesis of novel ion-imprinted polymers by two different RAFT polymerization strategies for the removal of Cs(i) from aqueous solutions

In this work, two novel Cs(i) ion-imprinted polymers (Cs(i)-IIP1 and Cs(i)-IIP2) have been prepared by surface imprinting technique with different RAFT polymerization strategies based on support matrix of SBA-15.

Bioremoval of heavy metals by bacterial biomass

Heavy metals are among the most common pollutants found in the environment. Health problems due to the heavy metal pollution become a major concern throughout the world, and therefore, various treatment technologies such as reverse osmosis, ion exchange, solvent extraction, chemical precipitation, and adsorption are adopted to reduce or eliminate their concentration in the environment. Biosorption is a cost-effective and environmental friendly technique, and it can be used for detoxification of heavy metals in industrial effluents as an alternative treatment technology. Biosorption characteristics of various bacterial species are reviewed here with respect to the results reported so far. The role of physical, chemical, and biological modification of bacterial cells for heavy metal removal is presented. The paper evaluates the different kinetic, equilibrium, and thermodynamic models used in bacterial sorption of heavy metals. Biomass characterization and sorption mechanisms as well as elution of metal ions and regeneration of biomass are also discussed.