Immobilization of blue green microalgae on loofa sponge to biosorb cadmium in repeated shake flask batch and continuous flow fixed bed column reactor system

Removal of estrogens from primary settled sewage by repeated culture of Selenastrum capricornutum

Biotransformation and biodegradation of estrogenic compounds by bacteria and even fungi have been reported widely, but the role of microalgae in the elimination of estrogens from municipal wastewater treatment plants and their interaction with other microorganisms in wastewater are not clear. This study reported the feasibility of repeatedly removing a mixture of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), each was 100 μg L-1, from primary settled municipal sewage by Selenastrum capricornutum (SC), a ubiquitous microalga, in four exposure cycles, each lasted 7 days, and how they interacted with the microbial consortium in sewage. Mixed estrogen in sewage stimulated the growth of SC, and the indigenous microorganisms in sewage also affected the microalgal growth. The indigenous microorganisms, particularly bacteria, could easily remove E2 (with 99.5% removal), so the role of SC was insignificant. On the contrary, EE2 was difficult to remove by indigenous microorganisms but the removal was significantly enhanced by SC, with almost all spiked EE2 being removed, even at the end of the fourth cycle (with 99.0% removal). These results indicated that SC, together with the indigenous microorganisms in wastewater, could be repeatedly used for simultaneous removal of E2 and EE2 from municipal sewage.

Enhanced wastewater bioremediation by a sulfur-based copolymer as scaffold for microalgae immobilization (AlgaPol)

In recent years, there has been an increasing concern related to the contamination of aqueous ecosystems by heavy metals, highlighting the need to improve the current techniques for remediation. This work intends to address the problem of removing heavy metals from waterbodies by combining two complementary methodologies: adsorption to a copolymer synthesized by inverse vulcanization of sulfur and vegetable oils and phytoremediation by the microalga Chlorella sorokiniana to enhance the metal adsorption. After studying the tolerance and growth of Chlorella sorokiniana in the presence of the copolymer, the adsorption of highly concentrated Cd²⁺ (50 mg L^-1) by the copolymer and microalgae on their own and the combined immobilized system (AlgaPol) was compared. Additionally, adsorption studies have been performed on mixtures of the heavy metals Cd²⁺ and Cu²⁺ at a concentration of 8 mg L^-1 each. AlgaPol biofilm is able to remove these metals from the growth medium by more than 90%. The excellent metal adsorption capacity of this biofilm can be kinetically described by a pseudo-second-order model.

Batch and continuous fixed bed adsorption of heavy metals removal using activated charcoal from neem (Azadirachta indica) leaf powder

The present investigate was intended for adsorption of heavy metals i.e. Pb, Cu, Cr, Zn, Ni and Cd onto activated charcoal prepared from neem leaf powder (AC-NLP) using batch and column studies. Batch adsorption was performed using different variables like adsorbent dose, temperature and contact duration. Thermodynamic analysis of batch treatment concluded that adsorption is thermodynamically feasible and endothermic. This adsorption followed the Pseudo second-order kinetic model derived from correlation coefficient values of chemical kinetic studies. For column study, interpretation of breakthrough curves and parameters were conducted by varying flow rate, initial concentration and bed height; and reveal that optimum conditions were lower flow rate (5 mL/min) and lower initial concentration (5 mg/L) and higher bed height (20 cm). Comparisons of batch and column study through isotherm models were evaluated and column study is more preferred than batch treatment. Maximum Thomas adsorption capacity was achieved upto 205.6, 185.8, 154.5, 133.3, 120.6, 110.9 mg/g for Pb, Cu, Cd, Zn, Ni and Cr respectively. This removal pattern is elucidated by metal ionic properties. Various adsorbing agents such as acids and bases were utilized for adsorption–desorption of AC-NLP.

Non-suspended microalgae cultivation for wastewater refinery and biomass production

Non-suspended microalgae cultivation technology coupled with wastewater purification has received more scientific attention in recent decades. Since the non-suspended microalgae cultivation is quite different from the suspended ones, the following issues are compared in this study such as advantages and disadvantages, pollutant removal mechanisms and regulations, influential factors, and microalgae biomass accumulation. The analysis aims to support the further application of this technology. The median removal rates of COD, TN, TP, NH₄⁺-N and NO₃^--N were 91.6%, 78.2%, 87.5%, 93.2% and 81.7%, respectively, by non-suspended microalgae under the TN & TP load rates up to 150 mg·L^-1·d^-1. The main pathway for TN & TP removal is microalgae cell absorbance. Light intensity, pollutant composition and microalgae metabolic types are the major factors that influence pollutant removal and the lipid content of microalgae. Meanwhile the mechanism concerning how macro-outer conditions influence the micro-environment and further growth of non-suspended microalgae requires more investigation.

Green Microalgae Scenedesmus Obliquus Utilization for the Adsorptive Removal of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) from Water Samples

In view of the valorisation of the green microalga Scenedesmus obliquus biomass, it was used for the biosorption of two nonsteroidal anti-inflammatory drugs, namely salicylic acid and ibuprofen, from water. Microalgae biomass was characterized, namely by the determination of the point of zero charge (pH_PZC), by Fourier transform infrared (FT-IR) analysis, simultaneous thermal analysis (STA) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Kinetic and equilibrium batch experiments were carried out and results were found to fit the pseudo-second order equation and the Langmuir isotherm model, respectively. The Langmuir maximum capacity determined for salicylic acid (63 mg g⁻¹) was larger than for ibuprofen (12 mg g⁻¹), which was also verified for a commercial activated carbon used as reference (with capacities of 250 and 147 mg g⁻¹, respectively). For both pharmaceuticals, the determination of thermodynamic parameters allowed us to infer that adsorption onto microalgae biomass was spontaneous, favourable and exothermic. Furthermore, based on the biomass characterization after adsorption and energy associated with the process, it was deduced that the removal of salicylic acid and ibuprofen by Scenedesmus obliquus biomass occurred by physical interaction.

Cultivating Chlorella sorokiniana AK-1 with swine wastewater for simultaneous wastewater treatment and algal biomass production

Swine wastewater is rich in nitrogen and organic carbon which are essential macronutrients for microalgal growth. Three indigenous microalgal strains (Chlorella sorokiniana AK-1, Chlorella sorokiniana MS-C1, and Chlorella sorokiniana TJ5) were examined for their growth capability in untreated swine wastewater. C. sorokiniana AK-1 showed the best tolerance towards swine wastewater, and obtained the highest biomass concentration (5.45 g/L) and protein productivity (0.27 g/L/d) when grown in 50% strength swine wastewater. Cell immobilization using sponge as the solid carrier further enhanced maximal biomass concentration and protein productivity to 8.08 g/L and 0.272 g/L/d, respectively. Reuse of microalgae loaded sponge resulted in an average biomass production and protein productivity of 6.51 g/L and 0.15 g/L/d, respectively. The COD, TN and TP removal efficiency for the swine wastewater was 90.1, 97.0 and 92.8%, respectively. This innovative swine wastewater treatment method has demonstrated excellent performance on simultaneous swine wastewater treatment and protein-rich microalgal biomass production.

The improved methods of heavy metals removal by biosorbents: A review

For decades, a vast array of innovative biosorbents have been found out and used in the removal of heavy metals, including bacteria, algae and fungi, etc. Although extensive biological species have been tried as a biosorbent for heavy metals removal, for removal efficiency or economy efficiency limited, it has failed to make a substantial breakthrough in practical application. Thus, many improved methods based on biosorbents emerged. In this review, based on the literature and our research results, we highlight three types of novel methods for biosorbents removal of heavy metals: chemical modification of biosorbents; biomass and chemical materials combination; multiple biomass complex systems. We mainly focus on their configuration, biosorption performance, their creation method, regeneration/reuse, their application and development in the future. Through the comparative analysis of various methods, we think that intracellular autogenous nanomaterials may open up another window in biosorption of heavy metals area. At the same time, the combination of various treatment methods will be the development tendency of heavy metal pollution treatment in the future.

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.

Microfluidic chip for automated screening of carbon dioxide conditions for microalgal cell growth

This paper reports on a microfluidic device capable of screening carbon dioxide (CO₂) conditions for microalgal cell growth. The device mainly consists of a microfluidic cell culture (MCC) unit, a gas concentration gradient generator (CGG), and an in-line cell growth optical measurement unit. The MCC unit is structured with multiple aqueous-filled cell culture channels at the top layer, multiple CO₂ flow channels at the bottom layer, and a commercial hydrophobic gas semipermeable membrane sandwiched between the two channel layers. The CGG unit provides different CO₂ concentrations to support photosynthesis of microalgae in the culture channels. The integration of the commercial gas semipermeable membrane into the cell culture device allows rapid mass transport and uniform distribution of CO₂ inside the culture medium without using conventional agitation-assisted convection methods, because the diffusion of CO₂ from the gas flow channels to the culture channels is fast over a small length scale. In addition, automated in-line monitoring of microalgal cell growth is realized via the optical measurement unit that is able to detect changes in the light intensity transmitted through the cell culture in the culture channels. The microfluidic device also allows a simple grayscale analysis method to quantify the cell growth. The utility of the system is validated by growing Chlamydomonas reinhardtii cells under different low or very-low CO₂ levels below the nominal ambient CO₂ concentration.

Application of immobilized waste brewery yeast cells for Cd2+ removal: Equilibrium and kinetics

In this investigation, the removal of Cd2+ ions by a brewery waste biomass in immobilized (Ca-alginate beads) form was studied. The removal process was conducted at room temperature under batch conditions (magnetic stirring) using different initial cadmium concentrations. The equilibrium of biosorption was reached in 150 minutes for all employed initial concentrations. The maximum biosorption capacity was calculated to be 5.96 mg Cd2+ g-1 yeast for an initial Cd2+ concentration of 169 mg L-1. Langmuir and Freundlich adsorption isotherms were used to correlate the equilibrium adsorption data. Based on the correlation coefficients, it was concluded that the Langmuir isotherm is more suitable for describing the equilibrium data of cadmium biosorption. In addition, first and pseudo-second order kinetic models were applied to describe the biosorption process. The kinetic parameters for the pseudo-second order kinetics were determined.

Immobilized microalgae for removing pollutants: review of practical aspects

This review analyzes the state-of-the-art of a specific niche in biological wastewater treatment that uses immobilized eukaryotic microalgae (and several prokaryotic photosynthetic cyanobacteria), with emphasis on removing nutrients with the support of microalgae growth-promoting bacteria. Removal of other pollutants by this technology, such as heavy metals and industrial pollutants, and technical aspects related to this specific subfield of wastewater treatment are also presented. We present a general perspective of the field with most known examples from common literature, emphasizing a practical point of view in this technologically oriented topic. The potential venues of future research in this field are outlined and a critical assessment of the failures, limitations, and future of immobilized microalgae for removal of pollutants is presented.

Statistical optimization of alpha-amylase production with immobilized cells of Streptomyces erumpens MTCC 7317 in Luffa cylindrica L. sponge discs

The purpose of this investigation was to study the effect of Streptomyces erumpens cells immobilized in various matrices, i.e., agar-agar, polyacrylamide, and luffa (Luffa cylindrica L.) sponge for production of alpha-amylase. Luffa sponge was found to be 21% and 51% more effective in enzyme yield than agar-agar and polyacrylamide, respectively. Response surface methodology was used to evaluate the effect of three main variables, i.e., incubation period, pH, and temperature on enzyme production with immobilized luffa cells. The experimental results showed that the optimum incubation period, pH, and temperature were 36h, 6.0, and 50 degrees C, respectively. The repeated batch fermentation of immobilized cells in shake flasks showed that S. erumpens cells were more or less equally physiologically active on the support even after three cycles of fermentation (3,830-3,575 units). The application of S. erumpens crude enzyme in liquefying cassava starch was studied. The maximum hydrolysis of cassava starch (85%) was obtained with the application of 4ml (15,200 units) of crude enzyme after 5 h of incubation.

Immobilization of Streptomyces clavuligerus on loofah sponge for the production of clavulanic acid

Clavulanic acid, a naturally occurring powerful inhibitor of bacterial beta-lactamases, is produced by Streptomyces clavuligerus. The high void volume, permeability, and low cost of fibrous matrices prompted the use of Luffa cylindrica as a matrix for the immobilization of S. clavuligerus for the production of clavulanic acid. Immobilization of S. clavuligerus onto loofah sponge discs was studied with respect to the optimization of the inoculum size (number of discs) and its reusability for clavulanic acid production. Best yield of 1125 microg ml(-1) clavulanic acid was reached with two discs of loofah sponge (each approximately 0.136 g dry weight) and 120 h duration in the first cycle. Data obtained during four reusable cycles showed reduction in the initiation time of clavulanic acid production, resulting in higher levels of clavulanic acid in shorter time duration. Immobilization of S. clavuligerus on to loofah sponge discs, therefore, permit repeated reuse under the specified fermentation conditions for clavulanic acid production.