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Addressing critical environmental challenges such as greenhouse gas emissions, global warming, and eutrophication demands urgent and innovative solutions. In recent years, microalgae have emerged as a promising avenue for addressing these pressing issues. In this study, the combination of dairy and municipal wastewater is proposed as a culture medium for cultivating microalgae strains capable of sequestering atmospheric CO2. Specifically, the growth of Chlorella vulgaris was investigated using Bold's basal medium, along with varying concentrations of municipal and dairy wastewater, both with and without CO2 supplementation, to assess their CO2 capture potential. Concurrently, the efficiency of chemical oxygen demand (COD), total nitrogen, potassium, and phosphate removal from the wastewater was evaluated. Additionally, the combination of wastewater media with CO2 supplementation yielded the highest CO2 uptake rates, indicating the feasibility of simultaneous CO2 capture during microalgae cultivation. Media composition with 25% municipal wastewater: 75% dairy wastewater supplemented with CO2 demonstrated superior COD elimination with a higher percentage of nutrient removal from wastewater compared to other wastewater proportions. The nutrient removal capacity of aforementioned media also comes in line with high CO2 sequestration rate (13.57 mg L−1 h−1). These findings underscore the potential of utilizing wastewater from diverse sources as a viable culture medium for microalgae cultivation, facilitating concurrent CO2 capture and wastewater treatment. [ABSTRACT FROM AUTHOR]

Biosynthesis of gold nanoparticles (GNPs) using fungal extracellular filtrate as the source of reducing and capping agent is reported here. The study includes the fabrication of GNPs using a soil fungus CO1 in a very effective way for material synthesis. Morphological, molecular, and phylogenetic studies of the fungus CO1 show that it is similar to the Aspergillus austwickii. Aspergillus austwickii CO1 is reported for the first time for GNPs synthesis in this paper. The characteristic surface plasmon resonance (SPR) peak for colloidal GNPs was observed at 532 nm. The GNPs remained stable for about 90 days at room temperature. The optimum temperature, pH, and substrate concentration were 100 °C, pH 9, and 1 mM AuCl4− concentration, respectively, to obtain maximum possible stability and monodispersity of synthesized GNPs. The GNPs were characterized using instrumental analysis. Transmission electron microscopy analysis confirmed the formation of spherical particles of size 14.7 ± 6.9 nm. The kinetics of the GNPs synthesis reaction was investigated by measuring particle size and zeta potential as a function of time. The stability of biosynthesized GNPs was better than chemically synthesized citrate-GNPs (Cit-GNPs) when exposed to high ionic concentration by the addition of sodium chloride in the GNP solution. The biosynthesized GNPs were able to resist aggregation even with the addition of 0.2 mM of NaCl, while Cit-GNPs aggregated at much lower concentration of 0.05 mM NaCl. Selective reactivity of the GNPs was observed toward Mg2+ ions, with a minimum detection limit of 40 ppm. Detection could be visualized by naked eye also. Thus, the non-toxic biosynthesized GNPs could further assist in the Mg2+ optical sensing application of water. [ABSTRACT FROM AUTHOR]

The ongoing exploration of economical, sustainable, and environment-friendly methods for synthesizing monodisperse colloidal metal nanoparticles is growing day by day due to their potential application in various fields. The use of plant derivatives in nanoparticle synthesis and their suitability as sustainable catalysts have emerged as significant areas of research. In this study, silver nanoparticles were synthesized using an aqueous extract obtained from the commonly found weed Commelina erecta, L. Extensive study is conducted to optimize various synthesis parameters such as pH, reducing agent concentration, silver nitrate concentration, and temperature. The plant extract utilized in the synthesis process contained variety of antioxidants, including malic acid, phenol, benzoic acid, and catechol, which played a crucial role in both reduction and capping during the synthesis process, thereby making them suitable for biomedical applications. The optimized synthesis process yielded silver nanoparticles with a particle size of 16.2 ± 3.1 nm. These nanoparticles exhibited excellent stability and demonstrated remarkable antibacterial activity compared to the standard antibacterial agent, streptomycin. In addition, the silver nanoparticles displayed promising antioxidant activity attributed to the presence of antioxidant functional groups on their surface. This study reports, for the first time, the synthesis of silver nanoparticles using antioxidant compounds present in C. erecta, L. plant extract. The antioxidant compounds identified through GC–MS belong to phenols, phenolic acids, and carboxylic acid groups. Furthermore, the exceptional antimicrobial and antioxidant properties exhibited by the synthesized silver nanoparticles offer new possibilities for their potential applications. [ABSTRACT FROM AUTHOR]

A facile, one-pot, rapid and cost-effective green synthesis approach is adopted for synthesis of spherical magnetite nanoparticles (Fe3O4) using Averrhoa carambola leaf extract for removal of Cr(VI). The polar biomolecules of leaf extract act as non-toxic surfactants and as reducing as well as stabilizing agents. The morphological, structural and optical properties of bio-based magnetite nanoparticles were characterized by FESEM, XRD, FT-IR, UV–VIS DRS and Raman analysis. The batch biosorption of Cr(VI) was investigated at different experimental limits such as contact time, temperature, pH, adsorbent dose and metal concentration. The experimental data was well fitted to Langmuir adsorption isotherm and found to follow linear pseudo-second-order kinetics. The maximum biosorption efficiency of bio-based magnetite nanoparticles was recorded 99.34% and can be reused proficiently upto 7 cycles. The mechanism for role of biomolecules in synthesis of nanoparticles along with the mechanism for biosorption of Cr(VI) over bio-based magnetite nanoparticles were discussed. The bio-based magnetite nanoparticles can be effectively used for removal of Cr(VI) from groundwater in contaminated areas. [ABSTRACT FROM AUTHOR]

Due to the resistance and non-biodegradable nature, dye contamination contributes to several significant environmental problems as well as a severe public health hazard. Therefore, protecting the ecosystem from these toxic compounds and the harm they cause is essential. Consequently, it is vital to protect the ecosystem against such toxins and the injury they cause. Congo red is one of the predominantly used dyes in industries. In the present work, we have devised a hetero catalyst consisted of dried biomass of microalga Scenedesmus attached with silver nanoparticles on the surface. Under the ambient condition, the biomass-silver nanocomposite was utilized as a heterogeneous catalyst for the degradation of the dye (Congo red). A number of tests were performed to determine the impact of NaBH4 concentration, pH, and composite load on the catalytic effectiveness of the composite. It was discovered that the calcined composite material made an excellent Congo red reduction catalyst. As little as 0.5 mg mL−1 of the composite was capable of reducing Congo red (200 mg L−1) by more than 90% at a rate of 0.37 mg mL−1 min−1 within 4 min of reaction time. [ABSTRACT FROM AUTHOR]

The use of functionalized gold nanoparticles (GNPs) as a colorimetric sensor for heavy metal ions has been extensively studied due to their unique optical properties and ease of functionalization. Amino acid-functionalized GNPs have emerged as a promising platform for colorimetric sensing of various pollutants, including metal ions. However, the differential metal ion selectivity of the GNPs functionalized with different amino acids remains poorly understood. This study describes the synthesis and functionalization of Tween-20-stabilized citrated gold nanoparticles (Cit-T20-GNPs) using various amino acids and their interaction with metal ions. Tween-20 was found to be essential to provide stability to the nanoparticles for functionalization. The morphology, hydrodynamic diameter, and zeta potential of the GNPs were characterized using transmission electron microscopy and dynamic electrophoretic light scattering analysis. The GNPs were then functionalized with L-threonine, L-glutamine, L-alanine, L-tryptophan, L-cysteine, L-methionine, L-arginine, L-lysine, L-proline, and glycine. The metal-induced aggregation of the functionalized GNPs was studied using twelve different metal ions. At the experimental pH (5–6), the colloidal integrity of most amino acid-functionalized Cit-T20-GNPs remained intact upon treatment with the metal ions, except for Cit-T20-Arg-GNPs and Cit-T20-Lys-GNPs. These two GNPs showed interaction with most metal ions, which led to their aggregation. The study provides insights into the specific interaction and affinity of metal ions toward different amino acid ligands and highlights the potential of designing ion-specific colorimetric sensors. The possible mechanism behind these interactions has also been speculated. [ABSTRACT FROM AUTHOR]

In this study, we have demonstrated an integrated approach for utilization of microalga Scenedesmus sp. for fabrication of catalytic and antimicrobial silver nanoparticle composite. The algal biomass was harvested from an open raceway pond of 30,000 L scale used for CO2 sequestration. The dried biomass served as a green, nontoxic, reducing and immobilizing agent for synthesis of silver nanoparticles, producing biomass-silver nanoparticle composite. ICP-OES was used to monitor the uptake of silver ions by biomass and subsequent formation of nanoparticles. The composite was calcined at 400 °C to fix the nanoparticles and prevent fouling. The calcined biomass-silver nanoparticle (CB-AgNP) composite was characterized using FESEM-EDAX, XRD and TGA. The CB-AgNP composite was used for the first time, as a heterogenous catalyst for reduction of a prominent industrial pollutant, p-nitrophenol. The reduction was carried out in the presence of NaBH4 in aqueous medium under ambient conditions. Batch experiments were conducted to evaluate the effect of calcination temperature, load of material and its reusability, on the catalytic efficiency of material. It was found that as low as 5 mg mL−1 CB-AgNP material reduced more than 80% and 95% of p-nitrophenol within 1 min and 15 min of exposure, respectively. Rate of PNP reduction was 0.60 mg L−1 min−1. The composite was easily recovered and reused for continuous batches of p-nitrophenol reduction. The efficiency of catalysis decreased with ten cycles of reuse; however, with an intermittent overnight water wash, the material regained its catalytic activity. Furthermore, the CB-AgNP composite also possessed excellent antimicrobial activity against pathogenic microbes. Two strains each of gram + ve and gram − ve bacteria and three strains of pathogenic fungi were used in the antimicrobial studies using well diffusion method and it was found to be active against all the microbes. The CB-AgNP composite is a potential candidate for a reusable heterogenous catalyst for designing continuous flow system for remediation of industrial effluents rich in p-nitrophenol. Its efficacy against common pathogenic bacteria and fungi can be harnessed for simultaneous antimicrobial treatment of the water. Moreover, this antimicrobial property will further inhibit the biofouling and eventual clogging of the material used in a packed column when used for water treatment. [ABSTRACT FROM AUTHOR]

The ungenerous release of metals from different industrial, agricultural, and anthropogenic sources has resulted in heavy metal pollution. Metals with a density larger than 5 g cm−3 have been termed as heavy metals and have been stated to be potentially toxic to human and animals. Algae are known to be pioneer organisms with the potential to grow under extreme conditions including heavy metal-polluted sites. They have evolved efficient defense strategies to combat the toxic effects exerted by heavy metal ions. Most of the algal strains are reported to accumulate elevated metal ion concentration in cellular organelles. With respect to that, this review focuses on understanding the various strategies used by algal system for heavy metal resistance. Additionally, the application of this metal resistance in biosynthesis of metal nanoparticles and metal oxide nanoparticles has been investigated in details. We thereby conclude that algae serve as an excellent system for understanding metal uptake and accumulation. This thereby assists in the design and development of low-cost approaches for large-scale synthesis of nanoparticles and bioremediation approach, providing ample opportunities for future work. [ABSTRACT FROM AUTHOR]

Biological sequestration of cadmium (Cd) and retention of adsorbed cadmium as cadmium sulphide (CdS) nanoparticles inside the cell by a lipid-producing green algae Scenedesmus-24 is reported. The microalga was able to grow in the growth media containing 30 mg L of cadmium without any growth inhibition. Adsorption of Cd(II) was dependent on the pH of the medium, initial concentration of cadmium, density of algal biomass (biosorbent dose), and contact time. The adsorption follows Langmuir isotherm pattern with an estimated maximum cadmium adsorption capacity at 50 mg g. The kinetics of adsorption followed Lagergren's pseudo-second-order model. FTIR analysis revealed the presence of different functional groups on the algal biomass which may be responsible for adsorption of Cd(II). After adsorption, the bound metal ions were retained in the microalgal biomass as CdS nanoparticles. Presence of CdS nanoparticle was confirmed by XRD and TEM analysis. The results of the present study conclusively demonstrate that the microalga Scenedesmus-24 may be a promising candidate for sequestration of cadmium from cadmium polluted water and also its recovery as precious CdS nanoparticles. [ABSTRACT FROM AUTHOR]

Copper slag was subjected to in-depth mineralogical characterization by integrated instrumental techniques and evaluated for the efficacy of physical beneficiation and mixed meso-acidophilic bioleaching tests towards recovery of copper. Point-to-point mineral chemistry of the copper slag is discussed in detail to give better insight into the association of copper in slag. Characterization studies of the representative sample revealed the presence of fayalite and magnetite along with metallic copper disseminated within the iron and silicate phases. Physical beneficiation of the feed slag (~0.6% Cu) in a 2 L working volume flotation cell using sodium isopropyl xanthate resulted in Cu beneficiation up to 2-4% and final recovery within 42-46%. On the other hand, a mixed meso-acidophilic bacterial consortium comprised of a group of iron and/or sulfur oxidizing bacteria resulted in enhanced recovery of Cu (~92-96%) from the slag sample. SEM characterization of the bioleached slag residue also showed massive coagulated texture with severe weathered structures. FE-SEM elemental mapping with EDS analysis indicated that the bioleached residues were devoid of copper. [ABSTRACT FROM AUTHOR]

Advances in applied and industrial microbial biotechnology have opened up many new avenues for application of several microorganisms. A group of certain metal reducers such as the dissimilatory iron reducing microorganisms possess an inherent potential to reduce oxidized metals under strict anaerobic/facultative anaerobic condition, thereby opening possibilities to combat environmental pollution. This unique property has invited researchers towards understanding the metabolic regulatory pathways that enables the microbes to thrive under extreme environmental conditions. Currently, dissimilatory iron reducing bacteria (DIRB) is in the focus of researchers to elucidate the specific mechanisms responsible for microbial metal reduction. The recent advances towards understanding the metabolism of iron reduction in Shewanella and Geobacter, the model DIRB has been covered in this review. It is believed that the metabolic insights into the Fe (III) reduction systems of the model DIRB; Shewanella and Geobacter (as discussed in the review) can be a basis for metabolic engineering to provide improved practical applications. With the advancement of our existing knowledge on the metabolic processes of the model iron reducers, applications ranging from laboratory to field scale practices can be carried out. DIRB has gained immense interest for its application in the field of bioremediation, electrobiosynthesis, and bioelectronics in this decade. It can therefore be anticipated that the forthcoming years will see more applications of microbial iron reducers based on the existing as well as advanced metabolic informations available in open source literature. [ABSTRACT FROM AUTHOR]

Two different microbial biosurfactants S9BS and CHBS were isolated from Lysinibacillus fusiformis S9 and Bacillus tequilensis CH. Cytotoxicity effect of these biosurfactants on human embryonic kidney cancerous cell (HEK-293) were studied with the help of 3-(4,5-dimethylthiazol-2yl-)-2, 5-diphenyl tetrazolium bromide (MTT) assay and morphological changes were observed under inverted microscope. The biosurfactants exhibited positive cytotoxic effect on HEK-293 cell line. It was found that LC of S9BS and CHBS were 75 and 100 μg ml, respectively. Further cell cycle and apoptosis analysis of biosurfactant-treated HEK-293 cell line were done by FACS. In this study, cytotoxic effect of glycolipid biosurfactant against HEK-293 cell lines is reported for the first time. Mechanism towards increased membrane permeability of biosurfactant-treated cancer cell may be the incorporation of its lipid moiety into the plasma membrane leading to formation of pores and membrane disruption. Hence, these microbial biosurfactants can prove to be significant biomolecule for cancer treatment. [ABSTRACT FROM AUTHOR]

Bioleaching studies for chalcopyrite contained ball mill spillages are very scarce in the literature. We developed a process flow sheet for the recovery of copper metal from surface activated (600 °C, 15 min) ball mill spillage through bio-hydrometallurgical processing route. Bioleaching of the activated sample using a mixed meso-acidophilic bacterial consortium predominantly A. ferrooxidans strains was found to be effective at a lixiviant flow rate of 1.5 L/h, enabling a maximum 72.36% copper recovery in 20 days. Mineralogical as well as morphological changes over the sample surface were seen to trigger the bioleaching efficiency of meso-acidophiles, thereby contributing towards an enhanced copper recovery from the ball mill spillage. The bio-leach liquor containing 1.84 g/L Cu was purified through solvent extraction using LIX 84I in kerosene prior to the recovery of copper metal by electrowinning. Purity of the copper produced through this process was 99.99%. [ABSTRACT FROM AUTHOR]

A biosurfactant producing microbe isolated from a river bank was identified as Lysinibacillus fusiformis S9. It was identified with help of biochemical tests and 16S rRNA gene phylogenetic analysis. The biosurfactant S9BS produced was purified and characterized as glycolipid. The biosurfactant showed remarkable inhibition of biofilm formation by pathogenic bacteria like Escherichia coli and Streptococcus mutans. It was interesting to note that at concentration of 40 μg ml the biosurfactant did not show any bactericidal activity but restricted the biofilm formation completely. L. fusiformis is reported for the first time to produce a glycolipid type of biosurfactant capable of inhibiting biofilm formation by pathogenic bacteria. The biosurfactant inhibited bacterial attachment and biofilm formation equally well on hydrophilic as well as hydrophobic surfaces like glass and catheter tubing. This property is significant in many biomedical applications where the molecule should help in preventing biofouling of surfaces without being toxic to biotic system. [ABSTRACT FROM AUTHOR]

Biosurfactants are amphiphilic molecules having hydrophobic and hydrophilic moieties produced by various microorganisms. These molecules trigger the reduction of surface tension or interfacial tension in liquids. A biosurfactant-producing halophile was isolated from Lake Chilika, a brackish water lake of Odisha, India (19°41′39″N, 85°18′24″E). The halophile was identified as Bacillus tequilensis CH by biochemical tests and 16S rRNA gene sequencing and assigned accession no. KC851857 by GenBank. The biosurfactant produced by B. tequilensis CH was partially characterized as a lipopeptide using thin-layer chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance techniques. The minimum effective concentration of a biosurfactant for inhibition of pathogenic biofilm ( Escherichia coli and Streptococcus mutans) on hydrophilic and hydrophobic surfaces was found to be 50 μg ml. This finding has potential for a variety of applications. [ABSTRACT FROM AUTHOR]

Bioleaching of a low grade chalcopyrite (ball mill spillage material) was tested for copper recovery in shake flasks. The original samples (as received) were thermally activated (600°C, 30 min) to notice the change in physico-chemical and mineralogical characteristics of the host rock and subsequently its effect on copper recovery. A mixed culture of acidophilic chemolithotrophic bacterial consortium predominantly entailing Acidithiobacillus ferrooxidans strain was used for bioleaching studies and optimization of process parameters of both original and thermally activated samples. Mineralogical characterization studies indicated the presence of chalcopyrite, pyrite in the silicate matrix of the granitic rock. Field emission scanning electron microscopy coupled with Energy dispersive spectroscopy (FESEM-EDS) and X-ray Fluorescence (XRF) analysis indicated mostly SiO. With pH 2, pulp density 10% w/v, inoculum 10% v/v, temperature 30°C, 150 r·min, 49% copper could be recovered in 30 days from the finest particle size (−1 + 0.75 mm) of the original spillage sample. Under similar conditions 95% copper could be recovered from the thermally activated sample with the same size fraction in 10 days. The study revealed that thermal activation leads to volume expansion in the rock with the development of cracks, micro and macro pores on its surface, thereby enabling bacterial solution to penetrate more easily into the body, facilitating enhanced copper dissolution. [ABSTRACT FROM AUTHOR]

Oxalic acid is a prominent metabolite secreted by several fungi under specific conditions, which acts as a metal chelating agent. Amongst different fungal species, Aspergillus niger is favored as the best option for microbial production of oxalic acid. The present study deals with the oxalic acid over production by A. niger in response to manganese supplement to its growth medium, which in turn improves the recovery of nickel from pre-treated chromite overburden(COB) during fungal bioleaching. The metabolic pathway in oxalate bio-synthesis by A. niger involves one prominent cytoplasmic enzyme oxaloacetate acetylhydrolase (OAH), which catalyzes the breakdown of oxaloacetate metabolic intermediate to oxalate and acetate. Oxalic acid production was increased due to supplement of manganese to the culture medium of the A. niger. Manganese acts as cofactor for OAH enzyme; further, it enhances the catalytic activity of OAH to produce more oxalate. With oxalic acid production by A. niger, nickel recovery from pre-treated COB was improved. During the study, a maximum of nickel recovery was achieved up to 38.6% from pre-treated COB by adding 80 ppm of manganese to the culture media, whereas 24.0% of nickel was recovered without supplement of manganese (experiments were performed at 30 °C and the COB pulp density 2% w/v). [ABSTRACT FROM AUTHOR]

A process flowsheet was developed to recover copper metal from the lean sulfide ore of copper available at Malanjkhand, Hindustan Copper Limited (HCL), India. Copper pregnant leach solution (PLS) obtained from bio-heap leaching of chalcopyrite containing 0.3% copper was purified through solvent extraction (SX) and the copper recovered by electrowinning (EW). The copper-free raffinate obtained from SX stripping unit was returned back to the bioleaching circuit. The purity of the electrolytic copper produced at pilot scale was found to be 99.96%. During electrowinning, the effect of flow rate of electrolyte on current efficiency and energy consumption was also studied. [ABSTRACT FROM AUTHOR]

n eco-friendly microbial method for synthesis of silver colloid solution with antimicrobial activity is developed using a fungal strain of Penicillium purpurogenum NPMF. It is observed that increase in concentration of AgNO increases the formation of silver nanoparticle. At 5 mM concentration highly populated polydispersed nanoparticles form. Furthermore, change in pH of the reaction mixture leads to change in shape and size of silver nanoparticles. At lower pH two peaks are observed in the absorption spectra showing polydispersity of nanoparticles. However, highly monodispersed spherical nanoparticles of 8-10 nm size form with 1 mM AgNO concentration at pH 8. Antimicrobial activity of nanoparticles is demonstrated against pathogenic gram negative bacteria like Escherichia coli and Pseudomonas aeruginosa, and gram positive bacteria like Staphylococcus aureus. The antimicrobial activity of silver nanoparticles obtained at different initial pH show strong dependence on the surface area and shape of the nanoparticles. [ABSTRACT FROM AUTHOR]

Bacillus tequilensis strain CH had been previously shown to produce a biosurfactant. In this study, chemical structure of the purified biosurfactant was determined by using high performance liquid chromatography and liquid chromatography-mass spectroscopy as a 10 amino acid cyclic lipopeptide (CL). The cyclic lipopeptide was found to be active against Anopheles culicifacies larvae with a LC50 of 110 µg/ml in 2 days. 1 ppm cadmium (Cd) which had a profound mutagenic effect on the cell division of onion (Allium cepa) root tip cell resulting in abnormal metaphase, abnormal anaphase and nuclei elongation was partially reversed in the presence of 0.1 mg/ml of CL (52% cells dividing normally and 8% with abnormal division) and was comparable to control experiment where no Cd was present. Thus, the CL described in this report may have applications in eliminating larvae from water repository systems and in reversing the effects of cadmium pollution. [ABSTRACT FROM AUTHOR]