Production of polysaccharide-based bioflocculant for the synthesis of silver nanoparticles by Streptomyces sp

Green Synthesis, Characterization and Application of Silver Nanoparticles Using Bioflocculant: A Review

Nanotechnology has emerged as an effective means of removing contaminants from water. Traditional techniques for producing nanoparticles, such as physical methods (condensation and evaporation) and chemical methods (oxidation and reduction), have demonstrated high efficiency. However, these methods come with certain drawbacks, including the significant energy requirement and the use of costly and hazardous chemicals that may cause nanoparticles to adhere to surfaces. To address these limitations, researchers are actively developing alternative procedures that are cost-effective, environmentally safe, and user-friendly. One promising approach involves biological synthesis, which utilizes plants or microorganisms as reducing and capping agents. This review discusses various methods of nanoparticle synthesis, with a focus on biological synthesis using naturally occurring bioflocculants from microorganisms. Bioflocculants offer several advantages, including harmlessness, biodegradability, and minimal secondary pollution. Furthermore, the review covers the characterization of synthesized nanoparticles, their antimicrobial activity, and cytotoxicity. Additionally, it explores the utilization of these NPs in water purification and dye removal processes.

Efficacy of exopolysaccharide in dye-laden wastewater treatment: A comprehensive review

The discharge of dye-laden wastewater into the water streams causes severe water and soil pollution, which poses a global threat to aquatic ecosystems and humans. A diverse array of microorganisms such as bacteria, fungi, and algae produce exopolysaccharides (EPS) of different compositions and exhibit great bioflocculation potency to sustainably eradicate dyes from water bodies. Nanomodified chemical composites of EPS enable their recyclability during dye-laden wastewater treatment. Nevertheless, the selection of potent EPS-producing strains and physiological parameters of microbial growth and the remediation process could influence the removal efficiency of EPS. This review will intrinsically discuss the fundamental importance of EPS from diverse microbial origins and their nanomodified chemical composites, the mechanisms in EPS-mediated bioremediation of dyes, and the parametric influences on EPS-mediated dye removal through sorption/bioflocculation. This review will pave the way for designing and adopting futuristic green and sustainable EPS-based bioremediation strategies for dye-laden wastewater in situ and ex situ.

Tanning Wastewater Sterilization in the Dark and Sunlight Using Psidium guajava Leaf-Derived Copper Oxide Nanoparticles and Their Characteristics

Employing Psidium guajava (P. guajava) extract from leaves, copper oxide nanoparticles (CuO NPs), likewise referred to as cupric oxide and renowned for their sustainable and harmless biogenesis, have the possibility of being useful for the purification of pollutants as well as for medicinal purposes. The current study examined the generated CuO NPs and their physical qualities by using ultraviolet-visible (UV) spectroscopy. The distinctive peak at 265 nm of the CuO NP production was originally seen. Additionally, an X-ray diffraction (XRD) investigation was conducted to identify the crystalline arrangement of the produced CuO NPs, and a Fourier transform infrared (FTIR) spectroscopy examination was performed to validate the functional compounds of the CuO NPs. Additionally, the synthesized nanoparticles' catalytic activities (wastewater treatment) were analyzed in dark and sunlight modes. The catalytic properties of CuO NPs in total darkness resulted in 64.21% discoloration, whereas exposure to sunshine increased the nanomaterials' catalyst performance to 92.31%. By lowering Cr(VI), Ni, Pb, Co, and Cd in sewage by proportions of 91.4, 80.8, 68.26, 73.25, and 72.4% accordingly, the CuO NP demonstrated its effectiveness as a nanosorbent. Total suspended solids (TSS), total dissolved solids (TDS), chemical oxygen demand (COD), biological demand for oxygen (BOD), and conductance were all successfully reduced by nanotreatment of tanning effluents, with proportion reductions of 93.24, 88.62, 94.21, 87.5, and 98.3%, correspondingly.

The role of bacterial exopolysaccharides (EPS) in the synthesis of antimicrobial silver nanomaterials: A state-of-the-art review

The emergence of multi-drug resistant (MDR) pathogens poses a significant global health concern due to the failure of conventional medical treatment. As a result, the development of several metallic (Ag, Au, Zn, Ti, etc.) nanoparticles, has gained prominence as an alternative to conventional antimicrobial therapies. Among these, green-synthesized silver nanoparticles (AgNPs) have gained significant attention due to their notable efficiency and broad spectrum of antimicrobial activity. Bacterial exopolysaccharides (EPS) have recently emerged as a promising biological substrate for the green synthesis of AgNPs. EPS possess polyanionic functional groups (hydroxyl, carboxylic, sulfate, and phosphate) that effectively reduce and stabilize AgNPs. EPS-mediated AgNPs exhibit a wide range of antimicrobial activity against various pathogenic microbes, including Gram-positive and Gram-negative bacteria, as well as fungi. The extraction and purification of bacterial EPS play a vital role in obtaining high-quality and -quantity EPS for industrial applications. This study focuses on the comprehensive methodology of EPS extraction and purification, encompassing screening, fermentation optimization, pretreatment, protein elimination, precipitation, and purification. The review specifically highlights the utilization of bacterial EPS-mediated AgNPs, covering EPS extraction, the synthesis mechanism of green EPS-mediated AgNPs, their characterization, and their potential applications as antimicrobial agents against pathogens. These EPS-mediated AgNPs offer numerous advantages, including biocompatibility, biodegradability, non-toxicity, and eco-friendliness, making them a promising alternative to traditional antimicrobials and opening new avenues in nanotechnology-based approaches to combat microbial infections.

Structural Characterization, Antioxidant and Antibacterial Activities of a Novel Polysaccharide From Zingiber officinale and Its Application in Synthesis of Silver Nanoparticles

A novel polysaccharide (ZOP) was extracted from Zingiber officinale with ultrasonic assisted extraction method. ZOP monosaccharide composition and mole ratio is GlcA: GalA: Glc: Gal: Ara = 1.97:1.15:94.33:1.48:1.07. Then, the particle size of ZOP-NPs prepared by nano-precipitation method was 230.5 nm, and the polydispersity index (PDI) was 0.260. Using ZOP and ZOP-NPs as reductants and stabilizers, ZOP-AgNPs and ZOP-NPs-AgNPs were prepared. They were characterized by ultraviolet-visible spectrophotometer (UV-Vis), fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The silver chelation rate of polysaccharide silver nanoparticles (AgNPs) ranged from 68.70 to 82.12%. ZOP-AgNPs (0.5%, w/v; 1%, w/v) and ZOP-NPs-AgNPs (0.5%, w/v; 1%, w/v) exhibited a narrow particle size distribution of 31.1, 34.6, 25.1 and 27.6 nm, respectively. And the zeta potential values of them were−19.4,−21.6,−19.7,−23.8mV, respectively. The antioxidant and antibacterial activities of ZOP-NPs-AgNPs were superior to those of ZOP, ZOP-NPs and ZOP-AgNPs.

A novel polysaccharides-based bioflocculant produced by Bacillus subtilis ZHX3 and its application in the treatment of multiple pollutants

A high bioflocculant-producing bacterial strain was identified and named Bacillus subtilis ZHX3. Single-factor experiments suggested that 10 g/L starch and 5 g/L yeast extract were optimal for strain ZHX3 to produce bioflocculant MBF-ZHX3. The maximum flocculating rate reached 95.5%, and 3.14 g/L product was extracted after 3 days of cultivation. MBF-ZHX3 was mainly composed of polysaccharides (77.2%) and protein (14.8%). The polysaccharides contained 28.9% uronic acid and 3.7% amino sugar. Rhamnose, arabinose, galactose, glucose, mannose, and galacturonic acid in a molar ratio of 0.35:1.83:3.09:12.66:0.46:3.81 were detected. MBF-ZHX3 had a molecular weight of 10,028 Da and contained abundant groups (-OH, CO, >PO, C-O-C) contributing to flocculation. Adsorption and bridging was considered as the main flocculation mechanism. MBF-ZHX3 was more effective in decolorizing dyes, removing heavy metals and flotation reagents compared to polyacrylamide. The results implied that MBF-ZHX3 has the potential to substitute polyacrylamide in wastewater treatment because of its excellent biological and environmental benefits.

Recent advances and perspectives in efforts to reduce the production and application cost of microbial flocculants

Microbial flocculants are macromolecular substances produced by microorganisms. Due to its non-toxic, harmless, and biodegradable advantages, microbial flocculants have been widely used in various industrial fields, such as wastewater treatment, microalgae harvest, activated sludge dewatering, heavy metal ion adsorption, and nanoparticle synthesis, especially in the post-treatment process of fermentation with high safety requirement. However, compared with the traditional inorganic flocculants and organic polymeric flocculants, the high production cost is the main bottleneck that restricts the large-scale production and application of microbial flocculants. To reduce the production cost of microbial flocculant, a series of efforts have been carried out and some exciting research progresses have been achieved. This paper summarized the research advances in the last decade, including the screening of high-yield strains and the construction of genetically engineered strains, search of cheap alternative medium, the extraction and preservation methods, microbial flocculants production as an incidental product of other biological processes, combined use of traditional flocculant and microbial flocculant, and the production of microbial flocculant promoted by inducer. Moreover, this paper prospects the future research directions to further reduce the production cost of microbial flocculants, thereby promoting the industrial production and large-scale application of microbial flocculants.

Application of Aloe vera mucilage as bioflocculant for the treatment of textile wastewater: process optimization

Aloe vera is an important commodity plant which has been traditionally used for the treatment of various diseases. This study investigated the use of extracted bioflocculant from Aloe vera for the treatment of textile wastewater. The bioflocculant was extracted, purified and characterized using GC-MS, FTIR, SEM, AFM, EDX and XRD analysis. It was mainly composed of carbohydrate (19.5%) and protein (6.0%). Box-Behnken design (BBD), using 3 level-3 variables, was employed to enhance the decolorization process by optimizing the effect of various factors. A significant enhancement from 62.50 ± 0.1 to 82.01 ± 0.8% in decolorization of wastewater was observed under optimized conditions viz. bioflocculant dosage (60 mg/L), pH (5.0) and contact time (180 min). A quadratic polynomial model was adequate beside the actual statistics at an R² value of 0.99 for the response decolorization % and was in good agreement with the predicted value (82.01 ± 0.1%) obtained by the RSM model. The results of the present investigation demonstrated that Aloe vera mucilage can serve as a promising bioflocculant with high removal efficiency for solids, colour and dye from wastewater. To the best of our information, this is the first report on the use of Aloe vera mucilage as a natural bioflocculant for the treatment of dye-bearing wastewater.

Production of a bioflocculant from ramie biodegumming wastewater using a biomass-degrading strain and its application in the treatment of pulping wastewater

The major bottleneck for industrial applications of microbial flocculants is the high production cost. Here, a novel bacterium, Diaphorobacter nitroreducens R9, was isolated that can secret ligninase and cellulase and simultaneously produce bioflocculants (MBF-9) through conversion of ramie biomass. The production of MBF-9 was closely related to the ligninase and cellulase activities of D. nitroreducens. Both ligninase and cellulase showed peak activity at pH 8.5 and 6.0 and retained approximately 80% of cellulase activity and 95% of ligninase activity at pH 8.0. The optimal production conditions with the highest bioflocculant yield (3.86 g/L degumming wastewater) were determined at a fermentation time of 48 h, fermentation temperature of 30 °C, inoculum size of 4.0%, COD_Cr of ramie degumming wastewater of 1500 mg/L and initial pH of 8.0. In addition, MBF-9 removed 96.2% turbidity, 79.5% chemical oxygen demand (COD), 59.2% lignin, and 63.1% sugar from the pulping wastewater at an MBF-9 dosage of 831.57 mg/L.

Wastewater Treatment by a Polymeric Bioflocculant and Iron Nanoparticles Synthesized from a Bioflocculant

Wastewater remains a global challenge. Various methods have been used in wastewater treatment, including flocculation. The aim of this study was to synthesize iron nanoparticles (FeNPs) using a polymeric bioflocculant and to evaluate its efficacy in the removal of pollutants in wastewater. A comparison between the efficiencies of the bioflocculant and iron nanoparticles was investigated. A scanning electron microscope (SEM) equipped with an energy-dispersive X-ray analyzer (EDX) and Fourier transform-infrared (FT-IR) spectroscopy were used to characterize the material. SEM-EDX analysis revealed the presence of elements such as O and C that were abundant in both samples, while FT-IR studies showed the presence of functional groups such as hydroxyl (–OH) and amine (–NH₂). Fe nanoparticles showed the best flocculation activity (FA) at 0.4 mg/mL dosage as opposed to that of the bioflocculant, which displayed the highest flocculation activity at 0.8 mg/mL, and both samples were found to be cation-dependent. When evaluated for heat stability and pH stability, FeNPs were found thermostable with 86% FA at 100 °C, while an alkaline pH of 11 favored FA with 93%. The bioflocculant flocculated poorly at high temperature and was found effective mostly at a pH of 7 with over 90% FA. FeNPs effectively removed BOD (biochemical oxygen demand) and COD (chemical oxygen demand) in all two wastewater samples from coal mine water and Mzingazi River water. Cytotoxicity results showed both FeNPs and the bioflocculant as nontoxic at concentrations up to 50 µL.

Insight on Extraction and Characterisation of Biopolymers as the Green Coagulants for Microalgae Harvesting

This review presents the extractions, characterisations, applications and economic analyses of natural coagulant in separating pollutants and microalgae from water medium, known as microalgae harvesting. The promising future of microalgae as a next-generation energy source is reviewed and the significant drawbacks of conventional microalgae harvesting using alum are evaluated. The performances of natural coagulant in microalgae harvesting are studied and proven to exceed the alum. In addition, the details of each processing stage in the extraction of natural coagulant (plant, microbial and animal) are comprehensively discussed with justifications. This information could contribute to future exploration of novel natural coagulants by providing description of optimised extraction steps for a number of natural coagulants. Besides, the characterisations of natural coagulants have garnered a great deal of attention, and the strategies to enhance the flocculating activity based on their characteristics are discussed. Several important characterisations have been tabulated in this review such as physical aspects, including surface morphology and surface charges; chemical aspects, including molecular weight, functional group and elemental properties; and thermal stability parameters including thermogravimetry analysis and differential scanning calorimetry. Furthermore, various applications of natural coagulant in the industries other than microalgae harvesting are revealed. The cost analysis of natural coagulant application in mass harvesting of microalgae is allowed to evaluate its feasibility towards commercialisation in the industrial. Last, the potentially new natural coagulants, which are yet to be exploited and applied, are listed as the additional information for future study.

Preparation, Performances, and Mechanisms of Microbial Flocculants for Wastewater Treatment

In recent years, close attention has been paid to microbial flocculants because of their advantages, including safety to humans, environmental friendliness, and acceptable removal performances. In this review, the preparation methods of microbial flocculants were first reviewed. Then, the performances of bioflocculants in the removal of suspended solids, heavy metals, and other organic pollutants from various types of wastewater were described and commented, and the removal mechanisms, including adsorption bridging, charge neutralization, chemical reactions, and charge neutrality, were also discussed. The future research needs on microbial flocculants were also proposed. This review would lead to a better understanding of current status, challenges, and corresponding strategies on microbial flocculants and bioflocculation in wastewater treatment.

Removal of Pollutants in Mine Wastewater by a Non-Cytotoxic Polymeric Bioflocculant from Alcaligenes faecalis HCB2

Bioflocculation is a physicochemical technique often employed to efficiently remove colloidal water pollutants. Consequently, in this study, a bioflocculant was produced, characterised and applied to remove pollutants in mine wastewater. The maximum flocculation activity of 92% was recorded at 30 °C, pH 9.0 when maltose and urea were used as energy sources and 72 h of fermentation at the inoculum size of 1% (v/v). K⁺ proved to be a favourable cation. The bioflocculant yield of 4 g/L was obtained. Scanning electron microscopy illustrated a hexagonal-like structure of the bioflocculant. It is composed of carbohydrates and proteins in mass proportion of 88.6 and 9.5%, respectively. The Fourier transform infrared spectrum revealed the presence of hydroxyl, amide and amino functional groups. More than 73% of the bioflocculant was obtained after exposure to 600 °C using the thermogravimetric analyser. Human embryonic kidney 293 (HEK 293) cells exhibited 95% viability after being treated with 200 µg/µL of the bioflocculant. The flocculation mechanisms were proposed to be as a result of a double layer compression by K⁺, chemical reactions and bridging mechanism. The removal efficiencies of 59, 72, and 75% on biological oxygen demand, chemical oxygen demand and sulphur, were obtained respectively. Thus, the bioflocculant have potential use in wastewater treatment.

Evaluation of Fresh Water Actinomycete Bioflocculant and Its Biotechnological Applications in Wastewaters Treatment and Removal of Heavy Metals

This study evaluated the potential of a biopolymeric flocculant produced by Terrabacter sp. isolated from Sterkfontein Dam, South Africa. Microbial flocculants aid the aggregation of suspended solutes in solutions, thus, suggesting its alternative application to inorganic and synthetic organic flocculants, which are associated with health-related problems. The 16S rDNA analysis revealed the bacteria to have 98% similarity to Terrabacter sp. MUSC78T and the sequence was deposited in the Genbank as Terrabacter sp. with accession number KF682157.1. A series of experimental parameters such as bioflocculant dosage, cations concentrations, pH, and application of the purified bioflocculant in wastewaters treatment were investigated. In the presence of glucose as a sole carbon source, Ca²⁺ as cation at pH 8, the optimal flocculating activity attained was 85%. Optimum bioflocculant dosage of 0.5 mg/mL was able to remove chemical oxygen demand (COD), biological oxygen demand (BOD), suspended solids (SS), nitrate, and turbidity in dairy wastewater. In addition, the tested bioflocculant exhibited higher flocculating efficiency as compared to polyaluminum chloride, polyethylenime, and alum. Inductible coupled plasma optical emission spectroscopy (ICP-OES) analyses confirmed significant removal of 77.7% Fe, 74.8% Al, 61.9% Mn, and 57.6% Zn as representatives of heavy metals from treated dairy wastewater. Fourier transform infrared spectroscopy (FTIR) indicated the presence of carboxyl, hydroxyl, and amino groups in the purified bioflocculant which could be responsible for flocculation. Findings from this study showed the prospect of the studied bioflocculant as an alternative candidate in wastewater treatment and remediating of heavy metals.

Characterization of the antioxidant and anti-inflammatory properties of a polysaccharide-based bioflocculant from Bacillus subtilis F9

Microbial flocculants are versatile class of novel biomacromolecules with numerous potential industrial applications. This study sought to investigate the antimicrobial, antioxidant, and anti-inflammatory potential of a polysaccharide-based bioflocculant (PBB) extracted from Bacillus subtilis F9. To achieve this, the antioxidant activity of different PBB concentrations(100 μg/mL ̶ 1000 μg/mL) was first examined in vitro using 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radicals, and superoxide radical scavenging assays. Further, the anti-inflammatory activity of PBB against lipopolysaccharide (LPS; 1 μg/mL)-induced inflammatory mediators released from headkidney (HK)-derived macrophages of Labeo rohita was investigated. Our results revealed that the capacities of 800 μg/mL of PBB to scavenge DPPH, hydroxyl radicals, and superoxide radicals were 81.46 ± 1.37%, 66.34 ± 2.63%, and 78.03 ± 2.46%, respectively, which were slightly higher that observed following treatment with 400 μg/mL of the positive control (ascorbic acid). Further, the radical scavenging capacity of PBB was found to steadily increase with increasing concentrations of PBB. Pre-treatment with PBB also inhibited nitric oxide production in a dose-dependent manner. We next examined the effect of PBB on proinflammatory cytokines (TNF-α, and IL-1β) and anti-inflammatory cytokines (IL-10, TGF-β) via qRT-PCR and ELISA. We found that PBB markedly inhibited the LPS-induced mRNA and protein expression levels of TNF-α and IL-1β, while it significantly increased those of IL-10 and TGF-β. Further, PBB exhibited an antibacterial activity against multiple food-borne pathogens with minimal inhibitory concentration values in the range of 3 ̶ 11 mg/mL. Importantly, PBB exhibited negligible cytotoxic effects against HK macrophages. Taken together these results suggest that PBB may serve as a natural antioxidant for application in functional therapies and may also be exploited for its anti-inflammatory potential.

Synthesis and characterization of size- and shape-controlled silver nanoparticles

Silver nanoparticles (AgNPs) have application potential in diverse areas ranging from wound healing to catalysis and sensing. The possibility for optimizing the physical, chemical and optical properties for an application by tailoring the shape and size of silver nanoparticles has motived much research on methods for synthesis of size- and shape-controlled AgNPs. The shape and size of AgNPs are reported to vary depending on choice of the Ag precursor salt, reducing agent, stabilizing agent and on the synthesis technique used. This chapter provides a detailed review on various synthesis approaches that may be used for synthesis of AgNPs of desired size and shape. Silver nanoparticles may be synthesized using diverse routes, including, physical, chemical, photochemical, biological and microwave -based techniques. Synthesis of AgNPs of diverse shapes, such as, nanospheres, nanorods, nanobars, nanoprisms, decahedral nanoparticles and triangular bipyramids is also discussed for chemical-, photochemical- and microwave-based synthesis routes. The choice of chemicals used for reduction and stabilization of nanoparticles is found to influence their shape and size significantly. A discussion on the mechanism of synthesis of AgNPs through nucleation and growth processes is discussed for AgNPs of varying shape and sizes so as to provide an insight on the various synthesis routes. Techniques, such as, electron microscopy, spectroscopy, and crystallography that can be used for characterizing the AgNPs formed in terms of their shape, sizes, crystal structure and chemical composition are also discussed in this chapter.

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Microbial Flocculants as an Alternative to Synthetic Polymers for Wastewater Treatment: A Review

Microorganisms such as bacteria, fungi, and microalgae have been used to produce bioflocculants with various structures. These polymers are active substances that are biodegradable, environmentally harmless, and have flocculation characteristics. Most of the developed microbial bioflocculants displayed significant flocculating activity (FA > 70–90%) depending on the strain used and on the operating parameters. These biopolymers have been investigated and successfully used for wastewater depollution in the laboratory. In various cases, selected efficient microbial flocculants could reduce significantly suspended solids (SS), turbidity, chemical oxygen demand (COD), total nitrogen (Nt), dye, and heavy metals, with removal percentages exceeding 90% depending on the bioflocculating materials and on the wastewater characteristics. Moreover, bioflocculants showed acceptable results for sludge conditioning (accepted levels of dry solids, specific resistance to filtration, moisture, etc.) compared to chemicals. This paper explores various bioflocculants produced by numerous microbial strains. Their production procedures and flocculating performance will be included. Furthermore, their efficiency in the depollution of wastewater will be discussed.

Production and flocculating properties of a compound biopolymer flocculant from corn ethanol wastewater

A compound biopolymer flocculant (CBF) produced using corn ethanol wastewater as substrate was investigated. After optimization of culture conditions, 3.08 g/L of purified CBF was extracted from the culture broth following 48 h of cultivation. The CBF macromolecule is mainly composed of protein (15.9%) and polysaccharide (81.8%). The polysaccharide component includes neutral sugars (28.92%), amino sugars (4.04%) and uronic acid (11.69%), with the neutral sugars being glucose, mannose, and lactose at a molar ratio of 4.1:1.5:1.9. CBF is pH tolerant from 3.0 to 12.0 and thermal tolerant from 20 to 100 °C, allowing for its application over a wide range of conditions. Furthermore, the Langmuir model better describes CBF adsorption on kaolin clay, as compared to the Freundlich model. Charge neutralization and bridging mechanisms are the primary flocculation mechanisms. In addition, CBF shows a high methylene blue removal efficiency. These results indicate that this compound biopolymer flocculant has great potential in dye wastewater treatment.

Exploiting Microbial Polysaccharides for Biosorption of Trace Elements in Aqueous Environments-Scope for Expansion via Nanomaterial Intervention

With pollution sounding high alarms all around us, there is an immediate necessity for remediation. In most cases, the remediation measures require further remediation-the anti-pollutants themselves cause pollution. In this correspondence, the search deepens towards natural biogenic components that can be used for bioremediation. Polysaccharide and biosorption have been themes in discussion for quite some time, where a slow decline in the enthusiasm in this area has been observed. This review revisits the importance of using polysaccharide based materials for biosorption. The need for polysaccharide-based nanocomposites, which hold better promise for greater deliverables, is emphasized as a means of rejuvenating the future perspectives in this area of application.

In vivo safety evaluation of antibacterial silver chloride nanoparticles from Streptomyces exfoliatus ICN25 in zebrafish embryos

Silver chloride nanoparticles were synthesized from the cell-free culture supernatant of Streptomyces strain using green synthesis approach with good yield. The nanoparticles were characterized by UV-Vis, IR, SEM, AFM and XRD techniques. These nanoparticles exhibited broad spectrum of antibacterial activity towards Methicillin-resistant Staphylococcus aureus, Methicillin sensitive S. aureus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumonia at ≤ 2 μg/ml minimal inhibitory concentrations. In vivo bioassay in nanoparticles treated zebrafish embryos exhibited 16 μg/ml dose as maximal cardiac safety concentration and further increases in concentration revealed adverse effects such as pericardial bulging, mouth protrudation, hemorrhage and yolk sac elongation. The less toxicity of nanoparticles treated embryos in terms of cardiac assessment and lethality analysis was observed. The dose below 5 μg/ml is concluded as an in vitro and in vivo therapeutic dose. The properties of this biosynthesized nanoparticle suggest a path towards developing antibiotic nanoparticles that are likely to avoid development of multidrug resistance.

Production, characterization and structural modification of exopolysaccharide-based bioflocculant by Rhizobium radiobacter SZ4S7S14 and media optimization

Synthesis of the exopolysaccharide-based bioflocculant Rhizobium radiobacter SZ4S7S14 was researched and medium optimized for enhanced production of bioflocculant. D-Mannose and yeast extract were found to be best carbon and nitrogen sources for maximal yield of bioflocculant. The bioflocculant samples obtained in different media with different carbon and nitrogen sources were further analyzed by SEM-EDX and FT-IR. FT-IR spectroscopy of the bioflocculant samples, obtained in different carbon/nitrogen sources showed slight modification of the structures of biopolymers. SEM micrographs revealed that exopolysaccharide-based bioflocculant of R. radiobacter SZ4S7S14 looks like bricks, and chemical structure of it can be varied due to utilized carbon and nitrogen source.

Synthesis of silver nanoparticles using bacterial exopolysaccharide and its application for degradation of azo-dyes

In this study, the synthesis and characterization of exopolysaccharide-stabilized sliver nanoparticles (AgNPs) was carried out for the degradation of industrial textile dyes. Characterization of AgNPs was done using surface plasmon spectra using UV-Vis spectroscopy, X-ray diffraction (XRD) and Raman spectroscopy. The morphological nature of AgNPs was determined through transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), which indicated that the AgNPs were spherical in shape, with an average size of 35 nm. The thermal behaviour of AgNPs revealed that it is stable up to 437.1 °C and the required energy is 808.2J/g in TGA-DTA analysis. Ability of EPS stabilized AgNPs for degradation of azo dyes such as Methyl orange (MO) and Congo red (CR) showed that EPS stabilized AgNPs were found to be efficient in facilitating the degradation process of industrial textile dyes. The electron transfer takes place from reducing agent to dye molecule via nanoparticles, resulting in the destruction of the dye chromophore structure. This makes EPS-AgNPs a suitable, cheap and environment friendly candidate for biodegradation of harmful textile dyes.

Removal of cadmium by bioflocculant produced by Stenotrophomonas maltophilia using phenol-containing wastewater

Bioflocculants have been applied in numerous applications including heavy metals removal. A major bottleneck for commercial application of bioflocculant is its high production cost. Phenol-containing wastewater are abundantly available. However, the toxic phenol inhibited the microbial activities in the subsequent fermentation processes. Consequently, strains that can secrete phenol-degrading enzymes and simultaneously produce bioflocculants through directly degrading the phenol are of academic and practical interests. A phenol-degrading strain, Stenotrophomonas maltophilia ZZC-06, which can produce the bioflocculant MBF-06 using phenol-containing wastewater, was isolated in this study. The effects of culture conditions including initial pH, dissolved oxygen, phenol concentration, inoculum size, and temperature on MBF-06 production were analyzed. The experimental results showed that over 90% flocculating activity was achieved when the phenol was used as a carbon source and 4.99 g/L of MBF-06 was achieved under the optimized condition: 2.0% dissolved oxygen, 800 mg/L phenol concentration, 10% inoculum size, an initial pH of 6.0, and a temperature of 30 °C. The bioflocculant MBF-06 contained 71.2% polysaccharides and 27.9% proteins. The feasibility of cadmium removal using MBF-06 was evaluated. The highest flocculating efficiency for cadmium was 81.43%. This study shows for the first time that Stenotrophomonas maltophilia ZZC-06 can directly convert phenol into a bioflocculant, which can be used to effectively remove cadmium.

Exopolysaccharide-Based Bioflocculant Matrix of Azotobacter chroococcum XU1 for Synthesis of AgCl Nanoparticles and Its Application as a Novel Biocidal Nanobiomaterial

A simple and green method was developed for the biosynthesis of AgCl nanoparticles, free from Ag nanoparticles, using the exopolysaccharide-based bioflocculant of nitrogen fixing Azotobacter chroococcum XU1 strain. AgCl nanoparticles were characterized by UV-Vis, X-ray diffraction (XRD), Fourier Transform-Infra Red (FT-IR) and Scanning electron microscopy-energy dispersive X-ray (SEM-EDX). The concentration-dependent and controllable method for the synthesis of AgCl nanoparticles of a certain size and morphology was developed. As-synthesized AgCl nanoparticles were characterized bya high content of AgCl and exhibited strong antimicrobial activity towards pathogenic microorganisms such as E. coli, S. aureus and C. albicans. The biofabricated AgCl nanoparticles can be exploited as a promising new biocidalbionanocomposite against pathogenic microorganisms.

Production of a Novel Fucoidanase for the Green Synthesis of Gold Nanoparticles by Streptomyces sp. and Its Cytotoxic Effect on HeLa Cells

Marine actinobacteria-produced fucoidanases have received considerable attention as one of the major research topics in recent years, particularly for the medical exploitation of fucoidans and their degradation products. The present study describes the optimization and production of a novel fucoidanase for the green synthesis of gold nanoparticles and its biological applications. The production of fucoidanase was optimized using Streptomyces sp. The medium components were selected in accordance with the Plackett-Burman design and were further optimized via response surface methodology. The fucoidanase was statistically optimized with the most significant factors, namely wheat bran 3.3441 g/L, kelp powder 0.7041 g/L, and NaCl 0.8807 g/L, respectively. The biosynthesized gold nanoparticles were determined by UV-vis spectroscopy and were further characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis, and high-resolution transmission electron microscopy. Furthermore, the biosynthesized gold nanoparticles exhibited a dose-dependent cytotoxicity against HeLa cells and the inhibitory concentration (IC50) was found to be 350 µg/mL at 24 h and 250 µg/mL at 48 h. Therefore, the production of novel fucoidanase for the green synthesis of gold nanoparticles has comparatively rapid, less expensive and wide application to anticancer therapy in modern medicine.

Marine polysaccharide-based nanomaterials as a novel source of nanobiotechnological applications

Research on marine polysaccharide-based nanomaterials is emerging in nanobiotechnological fields such as drug delivery, gene delivery, tissue engineering, cancer therapy, wound dressing, biosensors, and water treatment. Important properties of the marine polysaccharides include biocompatibility, biodegradability, nontoxicity, low cost, and abundance. Most of the marine polysaccharides are derived from natural sources such as fucoidan, alginates, carrageenan, agarose, porphyran, ulvan, mauran, chitin, chitosan, and chitooligosaccharide. Marine polysaccharides are very important biological macromolecules that widely exist in marine organisms. Marine polysaccharides exhibit a vast variety of structures and are still under-exploited and thus should be considered as a novel source of natural products for drug discovery. An enormous variety of polysaccharides can be extracted from marine organisms such as algae, crustaceans, and microorganisms. Marine polysaccharides have been shown to have a variety of biological and biomedical properties. Recently, research and development of marine polysaccharide-based nanomaterials have received considerable attention as one of the major resources for nanotechnological applications. This review highlights the recent research on marine polysaccharide-based nanomaterials for biotechnological and biomedical applications.