Production of a bioflocculant from methanol wastewater and its application in arsenite removal

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.

Sustainable production of bacterial flocculants by nylon-6,6 microplastics hydrolysate utilizing Brucella intermedia ZL-06

Nylon-6,6 microplastics (NMPs) in aquatic systems have emerged as potential contaminants to the global environment and have garnered immense consideration over the years. Unfortunately, there is currently no efficient method available to eliminate NMPs from sewage. This study aims to address this issue by isolating Brucella intermedia ZL-06, a bacterium capable of producing a bacterial polysaccharide-based flocculant (PBF). The PBF generated from this bacterium shows promising efficacy in effectively flocculating NMPs. Subsequently, the precipitated flocs (NMPs + PBF) were utilized as sustainable feedstock for synthesizing PBF. The study yielded 6.91 g/L PBF under optimum conditions. Genome sequencing analysis was conducted to study the mechanisms of PBF synthesis and nylon-6,6 degradation. The PBF exhibited impressive flocculating capacity of 90.1 mg/g of PBF when applied to 0.01 mm NMPs, aided by the presence of Ca2+. FTIR and XPS analysis showed the presence of hydroxyl, carboxyl, and amine groups in PBF. The flocculation performance of PBF conformed to Langmuir isotherm and pseudo-first-order adsorption kinetics model. These findings present a promising approach for reducing the production costs of PBF by utilizing NMPs as sustainable nutrient sources.

Water management for Power-to-X offshore platforms: an underestimated item

Increasing carbon dioxide (CO₂) concentration in the atmosphere is considered one of the most important challenges today. Therefore, capturing CO₂ and producing alternative energy sources through Power-to-X (PtX) approaches have become relevant scientific topics in recent years. However, there is a significant research gap regarding water management in PtX processes, particularly in offshore operations. The present study evaluates relevant aspects and possible challenges with respect to water management as well as mass and energy balances in conceptual offshore methane and methanol production platforms. The results show that 1600 m³ of seawater must be desalinated to supply the electrolyzer and reach a daily 50-Megagram (Mg) hydrogen production. Around 1100 m³ of brine coming out of the desalination plant may be discharged to the sea as long as prior environmental impact assessments are conducted. Additionally, 273 Mg and 364 Mg CO₂ need to be generated daily by direct air capture to produce 99 Mg day^-1 methane and 265 Mg day^-1 methanol, respectively. The daily produced methane and methanol wastewater is estimated to be 223 and 149 m³, respectively. Based on the scant literature on methanol wastewater, this is expected to contain toxic substances. Zero liquid discharge (ZLD) is proposed as wastewater method. The corresponding energy demand for the water management facilities is projected to be negligible compared to the other PtX processes. The presented management of water streams in PtX platforms would not only help recover some of the resources (water, hydrogen and methanol), but also substantially contribute to the production cycle itself while leading toward a more sustainable approach.

The last 25 years of research on bioflocculants for kaolin flocculation with recent trends and technical challenges for the future

The generation of kaolin-containing wastewater is an inevitable consequence in a number of industries including mining, wastewater treatment, and bitumen processing. In some cases, the production of kaolin tailings waste during the production of bitumen or phosphate is as high as 3 times greater than the actual produced product. The existing inventory of nearly five billion barrels of oil sands tailings alone represents a massive storage and reclamation challenge, as well as a significant economic and environmental liability. Current reclamation options like inorganic coagulants and organic synthetic polymers may settle kaolin effectively, but may themselves pose an additional environmental hazard. Bioflocculants are an emerging alternative, given the inherent safety and biodegradability of their bio-based compositions. This review summarizes the different research attempts towards a better bioflocculant of kaolin, with a focus on the bioflocculant source, composition, and effective flocculating conditions. Bacillus bacteria were the most prevalent single species for bioflocculant production, with wastewater also hosting a large number of bioflocculant-producing microorganisms while serving as an inexpensive nutrient. Effective kaolin flocculation could be obtained over a broad range of pH values (1-12) and temperatures (5-95°C). Uronic acid and glutamic acid were predominant sugars and amino acids, respectively, in a number of effective bioflocculants, potentially due to their structural and charge similarities to effective synthetic polymers like polyacrylamide. Overall, these results demonstrate that bioflocculants can be produced from a wide range of microorganisms, can be composed of polysaccharides, protein or glycoproteins and can serve as effective treatment options for kaolin. In some cases, the next obstacle to their wide-spread application is scaling to industrially relevant volumes and their deployment strategies.

Enhanced biological antimony removal from water by combining elemental sulfur autotrophic reduction and disproportionation

Antimony (Sb), a toxic metalloid, has serious negative effects on human health and its pollution has become a global environmental problem. Bio-reduction of Sb(V) is an effective Sb-removal approach. This work, for the first time, demonstrates the feasibility of autotrophic Sb(V) bio-reduction and removal coupled to anaerobic oxidation of elemental sulfur (S⁰). In the S⁰-based biological system, Sb(V) was reduced to Sb(III) via autotrophic bacteria by using S⁰ as electron donor. Meanwhile, S⁰ disproportionation reaction occurred under anaerobic condition, generating sulfide and SO₄^2- in the bio-systems. Subsequently, Sb(III) reacted with sulfide and formed Sb(III)-S precipitate, achieving an effective total Sb removal. The precipitate was identified as Sb₂S₃ by SEM-EDS, XPS, XRD and Raman spectrum analyses. In addition, it was found that co-existing nitrate inhibited the Sb removal, as nitrate is the favored electron acceptor over Sb(V). In contrast, the bio-reduction of co-existing SO₄^2- enhanced sulfide generation, followed by promoting Sb(V) reduction and precipitation. Illumina high-throughput sequencing analysis revealed that Metallibacterium, Citrobacter and Thiobacillus might be responsible for Sb(V) reduction and S⁰ disproportionation. This study provides a promising approach for the remediation of Sb(V)-contaminated water.

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.

Preparation of a bacterial flocculant by using caprolactam as a sole substrate and its application in amoxicillin removal

High cost is one of the limiting factors in the industrial production of bioflocculant. Simultaneous preparation of bioflocculant from the contaminants in wastewater was considered as a potential approach to reduce the production cost. In this study, caprolactam was verified as sole feedstock for the growth of strain Alcaligenes faecalis subsp. phenolicus ZY-16 in batch experiments. Chemical analysis showed that the as-prepared MBF-16 consisted of heteropolysaccharides (88.3%) and peptides (9.4%). XPS result indicated the plentiful acylamino, hydroxyl and amino groups in MBF-16, which have an indispensable role in amoxicillin flocculation. The flocculation of amoxicillin can be well stimulated by Freundlich isotherm equation, and the Kf was up to 178.6524 for amoxicillin. The kinetic fitting results proved that the flocculation of amoxicillin by MBF-16 was chemisorbed. This contribution may develop a novel technology for the preparation of bacterial flocculants that can consume toxic substrates (caprolactam) and have potential applications in amoxicillin removal.

Enlightening the characteristics of bioflocculant of endophytic actinomycetes from marine algae and its biosorption of heavy metal removal

The removal of toxic heavy metal ions from contaminated environments is a great challenge and requires an alternative rapid, efficient, economical bioremediation approach. Henceforth, bioflocculant producing endophytic actinobacterial sp. was isolated from heavy metal contaminated marine environments for heavy metal biosorption process. After molecular characterization, the isolated actinomycete starin was Nocardiopsis sp. GRG 3 (KT235642). It was indicated that the maximum flocculating activity of 80.90% with glucose, and yield is 4.52 g L¹. The optimum flocculating activity was reached at pH 7 in the presence of CaCl₂ ions. Further, the bioflocculent produced Nocardiopsis sp. GRG 3 (KT235642) was characterized by fourier transform infrared analysis spectra (FTIR) and displayed the presence of carboxyl, hydroxyl, amino groups and characteristic of more polysaccharide and protein. The heavy metal sorption by bioflocculant Nocardiopsis sp. GRG 3 (KT235642) was effectively removed 55.90% Cd, 85.90% Cr, 74.7% Pb, and 51.90% Hg. Therefore, this study was proved that the bioflocculant derived from endophytic actinobacteria, Nocardiopsis sp. GRG 3 (KT235642) as a effective alternative method for decreasing the heavy metals towards sustainable environmental management.

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.

Environmental applications of microbial extracellular polymeric substance (EPS): A review

During the last decade, water demand and wastewater generation has increased due to urbanization around the globe which had led to an increase in the utilization of chemicals/synthetic polymers for treating the wastewaters. These synthetic polymers used during the coagulation/flocculation process are non-renewable, non-biodegradable, and have a potential neurotoxic and carcinogenic effect. From the literature it is clear that extracellular polymer substance (EPS) is a potential bioflocculant, moreover it is renewable, biodegradable, eco-friendly, non-toxic as well as economically valued product. The various identification techniques and extraction methods of EPS are elaborated. Further application of EPS as absorbent in removing the dye from the industrial effluent is presented. Moreover EPS as a potential adsorbent for heavy metal removal from the various effluent is discussed. In addition, EPS is also utilized for soil remediation and soil erosion control. Mainly, EPS as bioflocculant in treating raw water, wastewater treatment, leachate and sludge management are summarized in this review.

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.

Challenges of arsenic removal from municipal wastewater by coagulation with ferric chloride and alum

Discharge of treated municipal wastewater containing arsenic (As) may cause adverse effects on the environment and drinking water sources. Arsenic concentrations were measured throughout the treatment systems at two municipal wastewater plants in New Jersey, USA. The efficiency of As removal by ferric chloride and alum coagulants were evaluated. Besides, the effects of suspended solids in the mixed liquor, pH, and orthophosphate (PO₄^3-) on As removal were investigated. The total recoverable As (TAs) concentrations in the influent and effluent of Plant A were in the ranges of 2.00-3.00 and 1.50-2.30 μg/L, respectively. The results indicated that <30% of the As was removed by the conventional biological wastewater treatment processes. The influent and effluent TAs concentrations at Plant B was below 1.00 μg/L. The bench-scale coagulation results demonstrated for the first time that the coagulation treatment could not effectively remove As from the municipal wastewater to <2.00 μg/L. Very high doses of the coagulants (8 and 40 mg/L of Fe(III) or Al(III)) were required to reduce the TAs from 2.84 and 8.61 μg/L in the primary clarifier effluent and arsenate-spiked effluent samples to <2.00 μg/L, respectively, which could be attributed to the high concentrations of PO₄^3- and dissolved organic matters (DOM) in the wastewater. The protein DOM in wastewater may negatively impact removal efficiencies more than the DOM in natural water, which mainly consists of humic substances. Furthermore, an artificial neural network was constructed to determine the relative importance of different parameters for As removal. Under the experimental conditions, the importance followed the order: coagulant dose>dissolved PO₄^3- > initial As concentration > pH. The findings of this study will help develop effective treatment processes to remove As from municipal wastewater.

Production of a bioflocculant by using activated sludge and its application in Pb(II) removal from aqueous solution

In this study, the characteristics of a bioflocculant produced by using activated sludge as raw materials were investigated. The performance of this bioflocculant in the removal of Pb(II) from aqueous solution and the corresponding mechanisms were determined as well. After cultivating a bioflocculant-producing strain in an alkaline thermal pre-treatment sludge for 60 h, approximately 4.45 g of bioflocculant containing a protein backbone was harvested from 1 L of fermentation broth. This bioflocculant can remove 98.5% of Pb(II) from aqueous solutions under optimal conditions, which include a bioflocculant dosage of 6 mg/L and a CaCl2 concentration of 70 mg/L at a pH of 6.5.

Simultaneous nitriles degradation and bioflocculant production by immobilized K. oxytoca strain in a continuous flow reactor

High cost is one of the limiting factors in the industrial production of bioflocculant. Simultaneous preparation of bioflocculant from the contaminants in wastewater was considered as a potential approach to reduce the production cost. In this study, butyronitrile and succinonitrile were verified as sole nitrogen sources for the growth of strain K. oxytoca GS-4-08 in batch experiments. Moreover, more than 90 % of the mixed nitriles could be degraded in a continuous flow reactor, and the bioflocculant could be prepared simultaneously in the effluent. All the as-prepared bioflocculants exhibited high flocculation efficiencies of over 90 % toward Kaolin solution. FTIR and XPS results further unveiled that, the bioflocculant samples with abundance of carboxyl, amine and hydroxyl groups may play an important role on adsorption of Pd²⁺. The adsorption process could be well simulated by Freundlich model, and the K_f values were as high as 452.8 mg^1-1/n l^1/n g^-1. The results obtained in this study not only confirm the technical feasibility for preparation of bioflocculant from various single nitrile and/or mixed nitriles, but also promise its economic feasibility.

Multiple organic substrates support Mn(II) removal with enrichment of Mn(II)-oxidizing bacteria

Three different organic substrates, K-medium, sterilized activated sludge (SAS), and methanol, were examined for utility as substrates for enriching manganese-oxidizing bacteria (MnOB) in an open bioreactor. The differences in Mn(II) oxidation performance between the substrates were investigated using three down-flow hanging sponge (DHS) reactors continuously treating artificial Mn(II)-containing water over 131 days. The results revealed that all three substrates were useful for enriching MnOB. Surprisingly, we observed only slight differences in Mn(II) removal between the substrates. The highest Mn(II) removal rate for the SAS-supplied reactor was 0.41 kg Mn⋅m^-3⋅d^-1, which was greater than that of K-medium, although the SAS performance was unstable. In contrast, the methanol-supplied reactor had more stable performance and the highest Mn(II) removal rate. We conclude that multiple genera of Comamonas, Pseudomonas, Mycobacterium, Nocardia and Hyphomicrobium play a role in Mn(II) oxidation and that their relative predominance was dependent on the substrate. Moreover, the initial inclusion of abiotic-MnO₂ in the reactors promoted early MnOB enrichment.

Intelligent-activated carbon prepared from pistachio shells precursor for effective adsorption of heavy metals from industrial waste of copper mine

A novel and efficient bio-adsorbent based on magnetic activated carbon nanocomposites (MAC NCs)-modified by sulfamic acid (H₃NSO₃) has been developed from pistachio shell precursor as agricultural by-products and then was applied for heavy metal removal. Design an experimental model (Central Composite Design (CCD)) for adopting surface response could efficiently be used for adsorption process, and it is an economical way of obtaining the optimal adsorption conditions based on the limited number of experiments. The variants of adsorbent dosage, metal ion concentration, and contact time were optimized for Cu(II) metal by CCD. In addition, adsorption capacity and isoelectric point (pHzpc) of adsorbent were studied at different pH values. Kinetic and isotherm of adsorption were investigated via the Langmuir and the pseudo-second-order model. The maximum adsorption capacity using the Langmuir model was 277.77 mg g^-1 for Cu(II) ions on H₂NSO₃-MAC NCs. Then adsorption process was investigated for ions of Fe(II), Zn(II), and Ni(II) under optimized condition. Also, the competitive adsorption of Fe(II), Zn(II), and Ni(II) ions mixed solution onto H₂NSO₃-MAC NCs was conducted. Adsorption-desorption results exhibited that the H₂NSO₃-MAC NCs can be used up to seven cycles while they have excellent performance. Finally, to evaluate the efficiency of this bio-adsorbent, the removal of heavy metals from wastewater of the Sarcheshmeh copper mine as a real sample was studied. Graphical abstract.

Implications for industrial application of bioflocculant demand alternatives to conventional media: waste as a substitute

The biodegradability and safety of the bioflocculants make them a potential alternative to non-biodegradable chemical flocculants for wastewater treatment. However, low yield and production cost has been reported to be the limiting factor for large scale bioflocculant production. Although the utilization of cheap nutrient sources is generally appealing for large scale bioproduct production, exploration to meet the demand for them is still low. Although much progress has been achieved at laboratory scale, Industrial production and application of bioflocculant is yet to be viable due to cost of the production medium and low yield. Thus, the prospects of bioflocculant application as an alternative to chemical flocculants is linked to evaluation and utilization of cheap alternative and renewable nutrient sources. This review evaluates the latest literature on the utilization of waste/wastewater as an alternative substitute for conventional expensive nutrient sources. It focuses on the mechanisms and metabolic pathways involved in microbial flocculant synthesis, culture conditions and nutrient requirements for bioflocculant production, pre-treatment, and also optimization of waste substrate for bioflocculant synthesis and bioflocculant production from waste and their efficiencies. Utilization of wastes as a microbial nutrient source drastically reduces the cost of bioflocculant production and increases the appeal of bioflocculant as a cost-effective alternative to chemical flocculants.

Bioconversion of kitchen wastes into bioflocculant and its pilot-scale application in treating iron mineral processing wastewater

In this study, the feasibility of converting kitchen waste into bioflocculant using Bacillus agaradhaerens C9 was analyzed. The result showed that strain C9 could secrete various degrading enzymes, including amylase, protease, lipase, cellulase, xylanase and pectinase, promoting the hydrolysis of kitchen waste. Strong alkaline fermentation condition was able to induce the bioflocculant production, and inhibit the growth of contaminated bacteria, which avoids the sterilization process of kitchen waste. The optimum fermentation condition for enzymatic hydrolysis and bioflocculant production was 40 g/L kitchen waste, 37 °C, pH 9.5, and the highest bioflocculant yield of 6.92 g/L was achieved. Furthermore, bioflocculant was applied to treat pilot-scale (30 L) of mineral processing wastewater for the first time, and the removal rate of 92.35% was observed when 9 mg/L bioflocculant was added into wastewater. Therefore, this study could promote the resource utilization of kitchen waste and recycling of mineral processing wastewater.

Production of a bioflocculant from Klebsiella sp. OS-1 using brewery wastewater as a source

This study evaluated the potential of bioflocculant production from a Klebsiella strain using brewery wastewater as nutrients. The bioflocculant named OS-1B produced by Klebsiella sp. OS-1 exhibited a good flocculating activity to kaolin clay suspension (around 95%), when the diluted brewery wastewater with 7.2 mg/L total nitrogen and 1013 mg/L COD_Cr was used as a nitrogen source. Glucose (15 g/L) is the most favorable carbon source for Klebsiella sp. OS-1 in bioflocculant production from brewery wastewater. The yielded bioflocculant is pH tolerant and thermally stable, suggesting its good industrial potential. OS-1B mainly comprises polysaccharide (69.4%) and protein (24.5%). Fourier-transform infrared spectra indicate the presence of hydroxyl, carboxyl, esters and amino groups in the bioflocculant molecules. Combined with the results of zeta potential measurements, bridging is suggested as the main flocculation mechanism for OS-1B flocculation with kaolin. Overall, brewery wastewater can be used as a substrate to produce bioflocculants.

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.

Characterization and coagulation-flocculation performance of a composite flocculant in high-turbidity drinking water treatment

Klebsiella variicola B16, a microbial bioflocculant (MBF-B16)-producing bacteria, was isolated and identified by its 16S rRNA sequence, biochemical properties, and physiological characteristics. The effects of culture conditions on MBF-B16 production, including carbon source, nitrogen source, C/N ratio, initial pH, and culture temperature, were investigated in this study. Results showed that 6.96 g of MBF-B16 could be extracted from a 1-L culture broth under optimized conditions. Chemical analysis showed that polysaccharide and protein were the main components. The neutral sugar consisted of galactose only, which was proposed in Klebsiella genus for the first time. In addition, a composite flocculant (CF) that contains polyaluminum ferric chloride (PAFC) and MBF-B16 for the removal of turbidity and SS in drinking water was optimized by response surface methodology. CF could reduce PAFC dosage by about 56.2-72%. Charge neutralization and adsorption bridging effect were the primary flocculation mechanisms.

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.

Removal of arsenite by a microbial bioflocculant produced from swine wastewater

This paper focused on the production and characteristics of a bioflocculant by using swine wastewater and its application in removing arsenite from aqueous solution. A series of experimental parameters including bioflocculant dose, calcium ions concentration, and solution pH value on arsenite uptake were evaluated. Results have demonstrated that a bioflocculant of 3.11 g L^-1 was achieved as the maximum yield after 60 h fermentation, with a main backbone of polysaccharides. Maximum arsenite removal efficiency of 99.2% can be reached by adding bioflocculant in two stages: 3 × 10^-3% (w/w) in the 1.0 min's rapid mixing (180 rpm) and 2 × 10^-3% (w/w) after 2.0 min's slow mixing (80 rpm) with pH value fixed at 7. Negative Gibbs free energy change (ΔG^o) indicated the spontaneous nature of arsenite removal. Arsenite was removed by the bioflocculant through bridging mechanisms.

Valorization of untreated rice bran towards bioflocculant using a lignocellulose-degrading strain and its use in microalgal biomass harvest

BACKGROUND

Microalgae are currently considered as a promising feedstock for the production of biofuels and high-value products. However, the efficient harvest of microalgal biomasses from their culture broth is a major challenge. The harvesting of algal biomass by flocculation combined with gravity sedimentation is more convenient and cost-effective than traditional methods such as centrifugation and filtration. Compared to inorganic and chemically synthetic flocculants, bioflocculants are a suitable choice for microalgal harvest due to their biodegradable and nontoxic properties. Nonetheless, the high production costs associated with expensive substrates hinder the commercial applications of bioflocculants. Previous studies have shown that the hydrolysates of lignocellulosic biomasses from dilute acid hydrolysis can be utilized as an inexpensive carbon source for the production of bioflocculants. However, the toxic by-products generated in the dilute acid hydrolysis step limit the efficiency of subsequent fermentation. The strains that produce bioflocculants by using untreated lignocellulosic materials can circumvent the pretreatment process, as well as promote the application of bioflocculants in microalgal harvest.

RESULTS

Under alkaline fermentation conditions, the alkaliphilic strain Bacillus agaradhaerens C9 secreted 1.69 IU/mL of alkali-tolerant xylanase and 0.06 IU/mL of cellulase, indicating that this particular strain can efficiently convert untreated rice bran into bioflocculant (RBBF-C9), thereby circumventing rice bran pretreatment for downstream fermentation. The optimal fermentation conditions that result in the highest bioflocculant yield (12.94 g/L) were as follows: 20 g/L of untreated rice bran, 3 g/L of yeast extract, and 20 g/L of Na2CO3 at 37 °C for 24 h. RBBF-C9 contained 74.12% polysaccharides and 4.51% proteins, and was estimated to be 137 kDa. Furthermore, the bioflocculant RBBF-C9 exhibited good flocculating efficiency (91.05%) of oil alga Chlorella minutissima UTEX2341 when 60 mg/L of RBBF-C9 was added into the algal culture broth.

CONCLUSIONS

This study demonstrated that untreated rice bran is a suitable inexpensive substrate for the production of bioflocculants, and thus provides a novel approach in utilizing rice bran. The extracted bioflocculants may be potentially used in biomass harvesting of the oil algae C. minutissima UTEX2341 from the culture broth.

Bioinspired 2D-Carbon Flakes and Fe3O4 Nanoparticles Composite for Arsenite Removal

Development of carbon-based materials has received tremendous attention owing to their multifunctional properties. Biomaterials often serve as an inspiration for the preparation of new carbon materials. Herein, we present a facile synthesis of a new bioinspired graphene oxide-like 2D-carbon flake (CF) using a natural resource, waste onion sheathing (Allium cepa). The 2D-CF was further decorated with crystalline Fe3O4 nanoparticles for applications. Superparamagnetic Fe3O4 nanoparticles (7 nm) were well-dispersed on the surface of the 2D-CF, which was characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, Raman spectrometry, and transmission electron microscopy. Batch As(III) adsorption experiments showed that aqueous arsenic ions strongly adsorbed to the Fe3O4@2D-CF composite. The adsorption capacity of the Fe3O4@2D-CF composite for As(III) was 57.47 mg g(-1). The synergetic effect of both graphene oxide-like 2D-CF and Fe3O4 nanoparticles aided in excellent As(III) adsorption. An As(III) ion adsorption kinetics study showed that adsorption was very fast at the initial stage, and equilibrium was reached within 60 min following a pseudo-second-order rate model. Owing to the excellent superparamagnetic properties (52.6 emu g(-1)), the Fe3O4@2D-CF composite exhibited superb reusability with the shortest recovery time (28 s) among reported materials. This study indicated that Fe3O4@2D-CF composites can be used for practical applications as a global economic material for future generations.

Silica sol-gel encapsulated methylotrophic yeast as filling of biofilters for the removal of methanol from industrial wastewater

This research suggests the use of new hybrid biomaterials based on methylotrophic yeast cells covered by an alkyl-modified silica shell as biocatalysts. The hybrid biomaterials are produced by sol-gel chemistry from silane precursors. The shell protects microbial cells from harmful effects of acidic environment. Potential use of the hybrid biomaterials based on methylotrophic yeast Ogataea polymorpha VKM Y-2559 encapsulated into alkyl-modified silica matrix for biofilters is represented for the first time. Organo-silica shells covering yeast cells effectively protect them from exposure to harmful factors, including extreme values of pH. The biofilter based on the organic silica matrix encapsulated in the methylotrophic yeast Ogataea polymorpha BKM Y-2559 has an oxidizing power of 3 times more than the capacity of the aeration tanks used at the chemical plants during methyl alcohol production. This may lead to the development of new and effective industrial wastewater treatment technologies.

Production of bioflocculants prepared from formaldehyde wastewater for the potential removal of arsenic

A novel bioflocculant (MBF-79) prepared using formaldehyde wastewater as carbon resource was investigated in the study. The optimal conditions for bioflocculant production were determined to be an inoculum size of 7.0%, initial pH of 6.0, and formaldehyde concentration of 350 mg/L. An MBF-79 of 8.97 g/L was achieved as the maximum yield. Three main elements, namely C, H, and O, were present in MBF-79 with relative weigh percentages of 39.17%, 6.74%, and 34.55%, respectively. The Gel permeation chromatography analysis indicated that the approximate molecular weight (MW) of MBF-79 was 230 kDa. MBF-79 primarily comprised polysaccharide (71.2%) and protein (27.9%). Additionally, conditions for the removal of arsenic by MBF-79 were found to be MBF-79 at 120 mg/L, an initial pH 7.0, and a contact time 60 min. Under the optimal conditions, the removal efficiencies of arsenate (0.5 mg/L) and arsenite (0.5 mg/L) were 98.9% and 84.6%, respectively. Overall, these findings indicate bioflocculation offers an effective alternative method of decreasing arsenic during water treatment.

Complete Genome Sequence of Turicibacter sp. Strain H121, Isolated from the Feces of a Contaminated Germ-Free Mouse

Turicibacterbacteria are commonly detected in the gastrointestinal tracts and feces of humans and animals, but their phylogeny, ecological role, and pathogenic potential remain unclear. We present here the first complete genome sequence ofTuricibactersp. strain H121, which was isolated from the feces of a mouse line contaminated following germ-free derivation.