Removal of arsenite by a microbial bioflocculant produced from swine wastewater

Isolation and characterization of Stenotrophomonas pavanii GXUN74707 with efficient flocculation performance and application in wastewater treatment

The identification of microorganisms with excellent flocculants-producing capability and optimization of the fermentation process are necessary for the wide-scale application of bioflocculants. Therefore, we isolated and identified a highly efficient flocculation performance strain of Stenotrophomonas pavanii GXUN74707 from the sludge. The optimal fermentation and flocculation conditions of strain S. pavanii GXUN74707 was in fermentation medium with glucose and urea as the carbon and nitrogen sources, respectively, at pH 7.0 for 36 h, which treatment of kaolin suspension with 0.5 mL of the fermentation broth resulted in a flocculation rate of 99.0%. The bioflocculant synthesized by strain S. pavanii GXUN74707 was found mainly in the supernatant of the fermentation broth. Chemical analysis revealed that the pure bioflocculant consisted of 79.70% carbohydrates and 14.38% proteins. The monosaccharide components of MBF-GXUN74707 are mainly mannose (5.96 μg/mg), galactose (1.86 μg/mg), and glucose (1.73 μg/mg). Infrared spectrometric analysis showed the presence of carboxyl (COO-), hydroxyl (-OH) groups. The SEM images showed clumps of rod-shaped bacteria with adhesion of extracellular products. Furthermore, the strain decolored dye wastewater containing direct black, direct blue, and Congo red by 89.2%, 95.1%, 94.1%, respectively. The chemical oxygen demand (COD) and biological oxygen demand (BOD) removal rates after treatment of aquaculture wastewater with the fermentation broth were 68% and 23%, respectively. This study is the first to report the performance and application of strain Stenotrophomonas pavanii in wastewater flocculation. The results indicate that strain S. pavanii is a good candidate for the production novel bioflocculants and demonstrates its potential industrial practicality in biotechnology processes.

Hyperproduction of extracellular polymeric substance in Pseudomonas fluorescens for efficient chromium (VI) absorption

A novel extracellular polymeric substance (EPS) with flocculating activity produced by Pseudomonas fluorescein isolated from soil was studied in this paper. Firstly, atmospheric and room temperature plasma (ARTP) was applied to get a mutant of P. fluorescein with higher EPS production. A mutant T4-2 exhibited a 106.48% increase in flocculating activity compared to the original strain. The maximum EPS yield from T4-2 was enhanced up to 6.42 g/L, nearly 10 times higher than the original strain on a 3.6-L bioreactor with optimized fermentation conditions. Moreover, the flocculating activity of the mutant reached 3023.4 U/mL, 10.96-fold higher than that of T4. Further identification showed that EPS from mutant T4-2 was mainly composed of polysaccharide (76.67%) and protein (15.8%) with a molecular weight of 1.17 × 105 Da. The EPS showed excellent adsorption capacities of 80.13 mg/g for chromium (VI), which was much higher than many reported adsorbents such as chitosan and cellulose. The adsorption results were described by Langmuir isotherm and pseudo-second-order kinetic model. The thermodynamic parameters (ΔG0, ΔH0 and ΔS0) revealed that the adsorption process was spontaneous and exothermic. Adsorption mechanisms were speculated to be electrostatic interaction, reduction, and chelation.

Sustainable and efficient technologies for removal and recovery of toxic and valuable metals from wastewater: Recent progress, challenges, and future perspectives

Due to their numerous effects on human health and the natural environment, water contamination with heavy metals and metalloids, caused by their extensive use in various technologies and industrial applications, continues to be a huge ecological issue that needs to be urgently tackled. Additionally, within the circular economy management framework, the recovery and recycling of metals-based waste as high value-added products (VAPs) is of great interest, owing to their high cost and the continuous depletion of their reserves and natural sources. This paper reviews the state-of-the-art technologies developed for the removal and recovery of metal pollutants from wastewater by providing an in-depth understanding of their remediation mechanisms, while analyzing and critically discussing the recent key advances regarding these treatment methods, their practical implementation and integration, as well as evaluating their advantages and remaining limitations. Herein, various treatment techniques are covered, including adsorption, reduction/oxidation, ion exchange, membrane separation technologies, solvents extraction, chemical precipitation/co-precipitation, coagulation-flocculation, flotation, and bioremediation. A particular emphasis is placed on full recovery of the captured metal pollutants in various reusable forms as metal-based VAPs, mainly as solid precipitates, which is a powerful tool that offers substantial enhancement of the remediation processes' sustainability and cost-effectiveness. At the end, we have identified some prospective research directions for future work on this topic, while presenting some recommendations that can promote sustainability and economic feasibility of the existing treatment technologies.

Production and Characterization of a Bioflocculant from Pichia kudriavzevii MH545928.1 and Its Application in Wastewater Treatment

A variety of flocculants have been used to aggregate colloidal substances. However, recently, owing to the adverse effects and high costs of conventional flocculants, natural flocculants such as microbial flocculants are gaining attention. The aim of the study was to produce and characterize a bioflocculant from Pichia kudriavzevii MH545928.1 and apply it in wastewater treatment. A mixture of butanol and chloroform (5:2 v/v) was used to extract the bioflocculant. Phenol–sulphuric acid, Bradford and Carbazole assays were utilized for the identification of carbohydrates, proteins and uronic acid, respectively. Scanning electron microscopy (SEM) and elemental detector were employed to determine the surface morphology and elemental compositions. The removal efficiencies were 73%, 49% and 47% for BOD, COD and P, respectively. The bioflocculant (2.836 g/L) obtained showed the presence of carbohydrates (69%), protein (11%) and uronic acid (16%). The bioflocculant displayed a cumulus-like structure and the elemental composition of C (16.92%), N (1.03%), O (43:76%), Na (0.18%), Mg (0.40%), Al (0.80%), P (14.44%), S (1.48%), Cl (0.31%), K (0.34%) and Ca (20.35). It showed the removal efficiencies of 43% (COD), 64% (BOD), 73% (P) and 50% (N) in coal mine wastewater. This bioflocculant is potentially viable to be used in wastewater treatment.

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.

Energy-saving preparation of a bioflocculant under high-salt condition by using strain Bacillus sp. and the interaction mechanism towards heavy metals

A highly efficient bioflocculant, i.e., Na-Bsp was successfully prepared by using a tolerant strain-Bacillus sp. under high-salt condition without sterilization. Salt-containing medium was not infected by other strains throughout the whole incubation period in 168 h. The as-prepared Na-Bsp was found to be cation-dependent, exhibiting high flocculant efficiency (FE) i.e., 97.69 ± 0.61%, towards kaolin particles by aid of Fe³⁺. High FE values were well maintained under a wide pH range and/or boiled water treatment, likely because of the main constituent of polysaccharide. The presence of hydroxyl, carboxyl, and amine groups on the bioflocculant surface were possibly responsible for strong interactions with heavy metals. The adsorption capacities of Pb²⁺, Cu²⁺ and Cr⁶⁺ were 1000.0, 434.8 and 384.6 mg g^-1, respectively. The changing of structure and configuration of bioflocculant during the metal adsorption were explored by the scanning electron microscope with electron energy loss spectroscopy and three-dimensional excitation-emission fluorescence spectrometry. This study provided a novel production method, whereby the conventional sterilization could be avoided, which is of great environmental significance for steam-saving. Furthermore, the as-prepared Na-Bsp exhibited high adsorption capacities toward heavy metals, which sheds lights on its potential usage as an alternative adsorbent.

Marine Actinobacteria Bioflocculant: A Storehouse of Unique Biotechnological Resources for Wastewater Treatment and Other Applications

The bioactive compounds produced by actinobacteria have played a major role in antimicrobials, bioremediation, biofuels, enzymes, and anti-cancer activities. Biodegradable microbial flocculants have been produced by bacteria, algae, and fungi. Microbial bioflocculants have also attracted biotechnology importance over chemical flocculants as a result of degradability and environmentally friendly attributes they possess. Though, freshwater actinobacteria flocculants have been explored in bioflocculation. Yet, there is a paucity of information on the application of actinobacteria flocculants isolated from the marine environment. Similarly, marine habitats that supported the biodiversity of actinobacteria strains in the field of biotechnology have been underexplored in bioflocculation. Hence, this review reiterates the need to optimize culture conditions and other parameters that affect bioflocculant production by using a response surface model or artificial neural network.

Effect of biosurfactant on ammonia removal from anaerobically digested swine wastewater by multi soil layering treatment bioreactors

A biosurfactant was harvested from anaerobically digested swine wastewater (ADSW) and employed to enhance ammonia removal in a comparative study using two multiple soil layer bioreactors (MSLs). Results showed that toxicity of the biosurfactant to microorganisms was negligible within the experimental concentration range. Optimal dose of the biosurfactant in MSLs to remove ammonia from ADSW was 0.1 CMC (Critical Micelle Concentration) under different hydraulic loading rate (HLR). For instance, when the HLR was adjusted as 80, 120, 160, and 200 L/(m²·d), the average ammonia removal efficiency in MSL without biosurfactant addition was appeared as 85.6%, 89.2%, 85.2% and 84.1%, respectively, after enhanced by 0.1 CMC of the biosurfactant under the same condition, the average ammonia removal efficiency was improved to 90.1%, 92.6%, 90.3%, and 87.4%, respectively. Inlet ammonia concentration obviously affected ammonia removal, the average ammonia removal efficiency increased rapidly to 93.0% and 89.1% in MSLs (with and without biosurfactant) along with the increasing inlet ammonia concentration from 800 mg/L to 1000 mg/L, and subsequently dropped to 78.9% and 79.7% with a further increase in the inlet ammonia concentration to 1400 mg/L. These results showed that the biosurfactant effectively enhanced ammonia removal by using MSL. Thus, the construction of MSL represented an effective means of reducing ammonia pollution caused by swine wastewater, and the use of biosurfactant was assuredly a promising and feasible option for enhancing the biological activity in MSL bioreactor.

Bioflocculant production using palm oil mill and sago mill effluent as a fermentation feedstock: Characterization and mechanism of flocculation

This study was conducted to examine the production of bioflocculants using agricultural wastewater as a fermentation feedstock under different temperatures and incubation times. The mechanism of flocculation was studied to gain a detailed understanding of the flocculation activity. The highest bioflocculant yield (2.03 g/L) at a temperature of 40 °C was produced in a palm oil mill effluent medium (BioF-POME). Bioflocculant produced from a fermented SME medium (BioF-SME) showed the highest activity. The flocculation tests for colour and turbidity removal from lake water indicated that BioF-SME and BioF-POME performed comparably to commercial alum. Analyses of the bioflocculants using liquid chromatography-mass spectrometry (LC-MS) found that the bioflocculants contained xylose and glucose. The mechanism study showed that flocculation occurred through charge neutralization and interparticle bridging between the bioflocculant polymer and the particles in the lake water. Thus, agricultural wastewater can be used as a fermentation feedstock for high-quality bioflocculants.

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.

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.

Bioflocculant production and heavy metal sorption by metal resistant bacterial isolates from gold mining soil

Two bioflocculant producing bacterial isolates from mining soil samples were investigated for their application in heavy metal removal. The bacterial isolates were identified as Pseudomonas koreensis and Pantoea sp. using 16S rRNA gene. Cadmium resistant genes cadA and CzcD were detected in Pantoea sp. while P. koreensis harbor CzcD and chrA responsible for Cd and Cr resistance respectively. The isolates showed maximum flocculating activity of 71.3% and 51.7% with glucose and yield of 2.98 g L^-1 and 3.26 g L^-1 for Pantoea sp. and P. koreensis respectively. The optimum flocculating activity was achieved at pH 7.5 and temperature of 30 °C. Fourier transform infrared analysis of the bioflocculants produced by the two isolates showed the presence of carboxyl, hydroxyl and amino groups characteristic of polysaccharide and protein. Heavy metal sorption by bioflocculant of Pantoea sp. removed 51.2% Cd, 52.5% Cr and 80.5% Pb while that of P. koreensis removed 48.5% Cd, 42.5% Cr and 73.7% Pb. The bioflocculants produced have potential in metal removal from industrial wastes.

The adsorptive removal of As (III) using biomass of arsenic resistant Bacillus thuringiensis strain WS3: Characteristics and modelling studies

Globally, the contamination of water with arsenic is a serious health issue. Recently, several researches have endorsed the efficiency of biomass to remove As (III) via adsorption process, which is distinguished by its low cost and easy technique in comparison with conventional solutions. In the present work, biomass was prepared from indigenous Bacillus thuringiensis strain WS3 and was evaluated to remove As (III) from aqueous solution under different contact time, temperature, pH, As (III) concentrations and adsorbent dosages, both experimentally and theoretically. Subsequently, optimal conditions for As (III) removal were found; 6 (ppm) As (III) concentration at 37 °C, pH 7, six hours of contact time and 0.50 mg/ml of biomass dosage. The maximal As (III) loading capacity was determined as 10.94 mg/g. The equilibrium adsorption was simulated via the Langmuir isotherm model, which provided a better fitting than the Freundlich model. In addition, FESEM-EDX showed a significant change in the morphological characteristic of the biomass following As (III) adsorption. 128 batch experimental data were taken into account to create an artificial neural network (ANN) model that mimicked the human brain function. 5-7-1 neurons were in the input, hidden and output layers respectively. The batch data was reserved for training (75%), testing (10%) and validation process (15%). The relationship between the predicted output vector and experimental data offered a high degree of correlation (R² = 0.9959) and mean squared error (MSE; 0.3462). The predicted output of the proposed model showed a good agreement with the batch work with reasonable accuracy.

Characterization of a novel bioflocculant from a marine bacterium and its application in dye wastewater treatment

Background

The identification of microorganisms with excellent flocculant-producing capability and optimization of the fermentation process are necessary for the wide-scale application of bioflocculants. Thus, we evaluated the flocculant-producing ability of a novel strain identified by the screening of marine bacteria, and we report for the first time the properties of the bioflocculant produced by Alteromonas sp. in the treatment of dye wastewater.

Results

A bioflocculant-producing bacterium was isolated from seawater and identified as Alteromonas sp. CGMCC 10612. The optimal carbon and nitrogen sources for the strain were 30 g/L glucose and 1.5 g/L wheat flour. In a 2-L fermenter, the flocculating activity and bioflocculant yield reached maximum values of 2575.4 U/mL and 11.18 g/L, respectively. The bioflocculant was separated and showed good heat and pH stability. The purified bioflocculant was a proteoglycan consisting of 69.61% carbohydrate and 21.56% protein (wt/wt). Infrared spectrometry further indicated the presence of hydroxyl, carboxyl and amino groups preferred for flocculation. The bioflocculant was a nanoparticle polymer with an average mass of 394,000 Da. The purified bioflocculant was able to remove Congo Red, Direct Black and Methylene Blue at efficiencies of 98.5%, 97.9% and 72.3% respectively.

Conclusions

The results of this study indicated that the marine strain Alteromonas sp. is a good candidate for the production of a novel bioflocculant and suggested its potential industrial utility for biotechnological processes.

Electronic supplementary material

The online version of this article (10.1186/s12896-017-0404-z) contains supplementary material, which is available to authorized users.