Biodegradation of crystal violet using Burkholderia vietnamiensis C09V immobilized on PVA-sodium alginate-kaolin gel beads

Enhanced removal of 2,4-dichlorophenol by a novel biotic-abiotic hybrid system based on zeolitic imidazolate framework-8

Biotic-abiotic hybrid systems have recently emerged as a potential technique for stable and efficient removal of persistent contaminants due to coupling of microbial catabolic with abiotic adsorption/redox processes. In this study, Burkholderia vietnamensis C09V (B.V.C09V) was successfully integrated with a Zeolitic Imidazolate Framework-8 (ZIF-8) to construct a state-of-art biotic-abiotic system using polyvinyl alcohol/ sodium alginate (PVA/SA) as media. The biotic-abiotic system (PVA/SA-ZIF-8 @B.V.C09V) was able to remove 99.0 % of 2,4-DCP within 168 h, which was much higher than either PVA/SA, PVA/SA-ZIF-8 or PVA/SA@B.V.C09V (53.8 %, 72.6 % and 67.2 %, respectively). Electrochemical techniques demonstrated that the carrier effect of PVA/SA and the driving effect of ZIF-8 collectively accelerated electron transfer processes associated with enzymatic reactions. In addition, quantitative-PCR (Q-PCR) revealed that ZIF-8 stimulated B.V.C09V to up-regulate expression of tfdB, tfdC, catA, and catC genes (2.40-, 1.68-, 1.58-, and 1.23-fold, respectively), which encoded the metabolism of related enzymes. Furthermore, the effect of key physical, chemical, and biological properties of PVA/SA-ZIF-8 @B.V.C09V on 2,4-DCP removal were statistically investigated by Spearman correlation analysis to identify the key factors that promoted synergistic removal of 2,4-DCP. Overall, this study has created an innovative new strategy for the sustainable remediation of 2,4-DCP in aquatic environments.

Adsorption and biodegradation of the azo dye methyl orange using Ralstonia pickettii immobilized in polyvinyl alcohol (PVA)-alginate-hectorite beads (BHec-RP)

Biological methods are widely used to treat dye waste, particularly methyl orange (MO) dye. The importance of MO degradation stems from its classification as a toxic dye. Within the scope of this research, successful bio-decolorization of MO was achieved through the use of Ralstonia pickettii bacteria immobilized in a PVA-alginate-hectorite matrix (BHec-RP). The optimum conditions for the degradation were observed at a composition of PVA (10%), hectorite (1%), static incubation, 40 °C, and pH 7. Subsequently, the adsorption kinetics of BHec-RP (dead cells) as well as the degradation kinetics of BHec-RP (live cells) and MO using free R. pickettii cells were evaluated. The decolorization of MO using BHec-RP (dead cells) is an adsorption process following pseudo-first-order kinetics (0.6918 mg g-1 beads) and occurs in a monolayer or physical process. Meanwhile, the adoption of BHec-RP (live cells) and free R. pickettii cells shows a degradation process under pseudo-first-order kinetics, with the highest rates at an initial MO concentration of 50 mg L-1 being 0.025 mg L-1 h-1 and 0.015 mg L-1 h-1, respectively. These results show that the immobilization system is superior compared to free R. pickettii cells. Furthermore, the degradation process shows the inclusion of several enzymes, such as azoreductase, NADH-DCIP reductase, and laccase, presumed to be included in the fragmentation of molecules. This results in five fragments based on LC-QTOF/MS analysis, with m/z values of 267.12; 189.09; 179.07; 169.09; and 165.05.

Anionic dye removal by immobilized bacteria into alginate-polyvinyl alcohol-bentonite matrix

Methyl orange (MO) is commonly used in the textile dyeing industry, posing serious health and environmental hazards due to its carcinogenic, mutagenic properties, and potential for bioaccumulation. Appropriate handling is needed to solve these problems by harnessing the capacity of living microorganisms and the adsorption properties of bentonite clay minerals. Although the conventional approach predominantly depends on free cells, recent study has developed other methods such as immobilization techniques. Therefore, this study aimed to investigate the efficiency of the immobilization matrix comprising sodium alginate (SA), polyvinyl alcohol (PVA), and bentonite by modifying Pseudomonas aeruginosa, Bacillus subtilis, and Ralstonia pickettii for MO removal of 50 mg/L. In the free cell technique, the results showed that the MO decreased to 43.13, 36.61, and 27.45% for each of the bacteria within 10 days at 35 °C. The bacterial immobilization technique, including live immobilized P. aeruginosa (LIPa), live immobilized B. subtilis (LIBs), and live immobilized R. pickettii (LIRp) beads also demonstrated significant efficiency, achieving MO removal rates up to 97.15, 95.65, and 66.63% within 10 days. These synthesized beads showed reusability, with LIPa, LIBs, and LIRp being used up to 4, 4, and 2 cycles, respectively. The external and internal surface conditions were observed using SEM instrument and the results showed that all components were agglomerated. Comparisons using dead bacterial biomass indicated that treatment with live bacteria consistently yielded significantly higher removal rates. These results showed the effectiveness of immobilized bacteria in MO removal, offering a promising potential in reducing pollutants.

Bacterial cellulose as a reinforcement material of alginate beads improves effectiveness and recycling potential of immobilized photosynthetic bacteria for cooking oil waste removal

The rapid degradation of alginate beads limits the lifespan of immobilized cells. In this study, bacterial cellulose (BC) incorporated in alginate was used to improve the mechanical properties, swelling ratio, and recycling time of the immobilized photosynthetic bacterium Rhodopseudomonas faecalis PA2 for the removal of cooking oil residues. Beads reinforced with 25 and 50% BC showed a higher Young's modulus and compressive strength and a lower swelling ratio than the control treatment (0% BC). The incorporation of 50% BC increased biomass production and oil removal. Field-emission scanning electron microscopy revealed several bacteria-infested internal pores in the reinforced beads, indicating bacterial growth in the presence of BC. Bacterial viability was verified by BC immersion in the bacterial culture broth and by injecting bacteria into the BC matrix. Without BC reinforcement, beads collapsed after reuse in two batches, whereas reinforced beads could be reused for five batches, resulting in an oil removal rate of up to 76.3 %. Our results show that BC can be used as an alginate reinforcing material to improve bead stability and prolong the effective recycling period of immobilized bacteria without negatively affecting bacterial growth or waste oil removal.

Biodegradation Capabilities of Paraquat-Degrading Bacteria Immobilized on Nanoceramics

The biodegradation of paraquat was investigated using immobilized microbial cells on nanoceramics fabricated from nanoscale kaolinite. Pseudomonas putida and Bacillus subtilis, which degrade paraquat, were immobilized separately on nanoceramics (respectively called IC_nc-P and IC_nc-B). The attachment of bacteria to nanoceramics resulted from electrostatic force interactions, hydrogen bonding, and covalent bonding (between the cells and the support materials). The initial 10 mg L^-1 concentration of paraquat in water was removed by the adsorption process using nanoceramics at 68% and ceramics at 52%, respectively. The immobilized cells on the nanoceramics were able to remove approximately 92% of the paraquat within 10 h, whereas the free cells could only remove 4%. When the paraquat was removed, the cell-immobilized nanoceramics exhibited a significant decrease in dissolved organic nitrogen (DON). IC_nc-B was responsible for 34% of DON biodegradation, while IC_nc-P was responsible for 22%. Ammonia was identified as the end product of ammonification resulting from paraquat mineralization.

Isolation and identification of 17β-estradiol degrading bacteria and its degradation pathway

The widespread presence of 17β-estradiol (E2) in the environment is an emerging problem because it poses a potential threat to human health and aquatic organisms. In this study, a strain of E2 degrading bacteria was isolated from activated sludge. 16s rRNA analysis combined with physiological and biochemical detection confirmed that the bacterium was Ochrobactrum sp. strain FJ1. At an initial E2 concentration of 15 mg L^-1, strain FJ1 degraded 98 ± 1% of E2 after 10 days. Furthermore, when methanol was added as an additional carbon source, the biomass of strain FJ1 increased by 35 ± 1%, and E2 degradation efficiency was slightly inhibited. Compared with E2 alone when glucose, sodium acetate, and methanol were added as additional carbon sources, biomass decreased by 20 ± 1, 13 ± 1 and 35 ± 1%, respectively. Analysis of the degradation products of E2 by LC/Q-TOF-MS confirmed that the major degradation products of E2 were estrone (E1) and 4,16-OH-E1, which was further degraded by strain FJ1 to several other unknown compounds. Based on SEM and FTIR analysis, the morphology of the bacteria became thicker and the thickness of the cell walls decreased under initial E2 stress, and thereafter E2 was transported into the bacteria primarily via several proteins on the cell surface. Considering the ability and efficiency of Ochrobactrum sp. strain FJ1 to degrade high E2 content, the strain could provide a new bioremediation technology for the effective biodegradation of E2. Finally, a potential bioremediation pathway of E2 by Ochrobactrum sp. strain FJ1 was proposed.

Poly (vinyl alcohol)-alginate as potential matrix for various applications: A focused review

Advances in polymers have made significant contribution in diverse application oriented fields. Multidisciplinary applicability of polymers generates a range of strategies, which is pertinent in a wide range of fields. Blends of natural and synthetic polymers have spawned a different class of materials with synergistic effects. Specifically, poly (vinyl alcohol) (PVA) and alginate (AG) blends (PVAG) have demonstrated some promising results in almost every segment, ranging from biomedical to industrial sector. Combination of PVAG with other materials, immobilization with specific moieties and physical and chemical crosslinking could result in amendments in the structure and properties of the PVAG matrices. Here, we provide an overview of the recent developments in designing PVAG based matrix and complexes with their structural and functional properties. The article also provides a comprehensive outline on the applicability of PVAG matrix in wastewater treatment, biomedical, photocatalysis, food packaging, and fuel cells and sheds light on the challenges that need to be addressed. Finally, the review elaborates the future prospective of PVAG matrices in other unexplored fields like aircraft industry, nuclear science and space exploration.

Biodegradation of paraquat by Pseudomonas putida and Bacillus subtilis immobilized on ceramic with supplemented wastewater sludge

This work aimed to study the performance of paraquat removal by cell-immobilized ceramics. Two strains of paraquat degrading bacteria, Pseudomonas putida and Bacillus subtilis, were separately immobilized on the ceramic with and without wastewater sludge addition. Results showed that the ceramic surface with sludge has more functional groups and a more highly negative charge on the surface than the original ceramic. The ceramic with sludge had 2-3-fold of the immobilized cells higher than that of the control (without sludge) and less leaching of the immobilized cells. The sludge addition at 20% (w/w) to the ceramic provided the highest cell adhesion for both P. putida and B. subtilis. The paraquat removal efficiencies were higher than 98%, while the control ceramic could remove only 77 ± 1.2%. The immobilized cells on ceramic with sludge provided a significant degree of dissolved organic nitrogen reduction (82%) during the paraquat removal. Most organic nitrogen in paraquat was biologically mineralized (ammonified). Findings from this work suggest the superiority of ceramic with sludge in mineralizing organic nitrogen associated with paraquat.

Biodegradation of reactive yellow dye using mixed cells immobilized in different biocarriers by sequential anaerobic/aerobic biotreatment: experimental and modelling study

In this study, the application of immobilized mixed cells for decolourization, biodegradation, and detoxification of reactive yellow dye (RY15) in textile wastewater was investigated via a sequential anaerobic-aerobic process in bench-scale bioreactors and lab-scale bioreactors as well. The mixed cultures were immobilized using three different biocarriers which were sodium alginate (SA), starch (St), and Gelatin (Ge), by the cross-linking with polyvinyl alcohol (PVA). Results revealed that the immobilized cultures had a potential degrading efficiency in the anaerobic and aerobic environment, targeting the initial structure and the formed compounds, respectively. Complete decolourization (100%) of RY15 was observed with a significant chemical oxygen demand (COD) removal, which enhanced the subsequent aerobic phase. Results demonstrated that COD removals were 92% ± 6.8, 96% ± 3.5, and 100%, using PVA-SA, PVA-St, and PVA-Ge at RY15 initial concentrations of 10 mg/L, respectively. The experimental work was extended to investigate the dye biodegradation in real textile wastewater using mixed cells in immobilized in PVA-SA. The Overloading rate (OLR) and Hydraulic retention time (HRT) of the aerobic bioreactor are 24.5 mg/L h and 41.37 h, respectively. The experimental profiles of RY concentration, COD reduction along with biomass growth, were in good agreement with the model predicted profiles. The effectiveness factors were 0.96 and 0.99 for the anaerobic and aerobic phases, respectively.

Intelligent modeling and experimental study on methylene blue adsorption by sodium alginate-kaolin beads

As tighter regulations on color in discharges to water bodies are more widely implemented worldwide, the demand for reliable inexpensive technologies for dye removal grows. In this study, the removal of the basic dye, methylene blue, by adsorption onto low-cost sodium alginate-kaolin beads was investigated to determine the effect of operating parameters (initial dye concentration, contact time, pH, adsorbent dosage, temperature, agitation speed) on dye removal efficiency. The composite beads and individual components were characterized by a number of analytical techniques. Three models were developed to describe the adsorption as a function of the operating parameters using regression analysis, and two powerful intelligent modeling techniques, genetic programming and artificial neural network (ANN). The ANN model is best in predicting dye removal efficiency with R² = 0.97 and RMSE = 3.59. The developed model can be used as a useful tool to optimize treatment processes using the promising adsorbent, to eliminate basic dyes from aqueous solutions. Adsorption followed a pseudo-second order kinetics and was best described by the Freundlich isotherm. Encapsulating the kaolin powder in sodium alginate resulted in removal efficiency of 99.56% and a maximum adsorption capacity of 188.7 mg.g^-1, a more than fourfold increase over kaolin alone.

Effect of Pseudomonas moorei KB4 Cells' Immobilisation on Their Degradation Potential and Tolerance towards Paracetamol

Pseudomonas moorei KB4 is capable of degrading paracetamol, but high concentrations of this drug may cause an accumulation of toxic metabolites. It is known that immobilisation can have a protective effect on bacterial cells; therefore, the toxicity and degradation rate of paracetamol by the immobilised strain KB4 were assessed. Strain KB4 was immobilised on a plant sponge. A toxicity assessment was performed by measuring the concentration of ATP using the colony-forming unit (CFU) method. The kinetic parameters of paracetamol degradation were estimated using the Hill equation. Toxicity analysis showed a protective effect of the carrier at low concentrations of paracetamol. Moreover, a pronounced phenomenon of hormesis was observed in the immobilised systems. The obtained kinetic parameters and the course of the kinetic curves clearly indicate a decrease in the degradation activity of cells after their immobilisation. There was a delay in degradation in the systems with free cells without glucose and immobilised cells with glucose. However, it was demonstrated that the immobilised systems can degrade at least ten succeeding cycles of 20 mg/L paracetamol degradation. The obtained results indicate that the immobilised strain may become a useful tool in the process of paracetamol degradation.

Co-immobilized spore laccase/TiO2 nanoparticles in the alginate beads enhance dye removal by two-step decolorization

Combinatorial application of different dye removal methods with specific features can lead to a novel and robust decolorizing system. In this study the bacterial spore laccase and TiO₂ nanoparticles were co-entrapped to enhance dye degradation. The optimum entrapment conditions were achieved in the presence of alginate 2% (w/v) and Ca²⁺ (0.2M), Cu²⁺ (0.05M) and Zn²⁺ (0.25M) as matric polymer and counterions, respectively. Immobilized laccase showed a wide range of pH and temperature stability in comparison to the free spores. The entrapped degradation systems include single laccase, single TiO₂, laccase + TiO₂ (one-step remediation), TiO₂/laccase (two-step remediation), and laccase/TiO₂ (two-step remediation) that result to the 22%, 26% 45.6%, 47.6%, and 69.3% indigo carmine decolorization in 60 min. In the kinetic studies, the half-life of indigo carmine (25 mg/l) in the remediation processes containing laccase, TiO₂, laccase + TiO₂, TiO₂/laccase, and laccase/TiO₂ was calculated as 173, 138, 161, 115, and 57 min, respectively. The degradation products by co-entrapped system were not toxic against Sorghum vulgare. The results showed two-step decolorization by co-entrapped spore laccase and TiO₂ nanoparticles, including the pretreatment of dye by laccase, and then, treatment by TiO₂ has potential for degradation of indigo carmine.

New application of Orchis mascula as a biocarrier for immobilization of mixed cells for biodegradation and detoxification of reactive azo dyes

In this study, the application of novel biocarrier Orchis mascula plant for immobilization of non-adapted mixed cells biodegrade reactive azo dyes in aqueous solution was investigated via a sequential anaerobic-aerobic process. Three reactive azo dyes including red (RR2), blue (RB4), and yellow (RY15) were individually used as the target pollutants. Results revealed that the immobilized biocatalysts had a potential degrading efficiency, targeting the initial structure and the formed aromatic/aliphatic compounds, respectively. Complete decolorization (100%) of RR2, RB4, and RY15 was observed in the anaerobic phase with significant COD removal which has been enhanced during the subsequent aerobic phase. Results demonstrated that COD removals at 10, 20, and 40 mg/L were 100 ± 0.13%, 95 ± 0.05%, and 90 ± 0.03% for RR2; 90 ± 0.11%, 85 ± 0.9%, and 81 ± 0.18% for RB4; and 100 ± 0.08%, 92 ± 0.16%, and 86 ± 0.06% for RY15, respectively. Immobilized cells exhibited better performance compared with free cells, particularly for high dye concentration up to 100 mg/L.

A novel approach to production of Chlorella protothecoides oil-loaded nanoparticles via electrospraying method: Modeling of critical parameters for particle sizing

Bioactive compounds in algae have chain rings that protect the tissue from chemical damage and disease symptoms. In addition, algal bioactive agents have the ability to stimulate the immune system, protective and therapeutic effects against many diseases, including various types of cancers, coronary heart disease, premature aging, and arthritis. These bioactive compounds also have antioxidant, anticoagulant, antiviral, and anti-inflammatory properties. It is very important to encapsulate these algal compounds for preserving bioactive properties. Two of the most efficient methods used for encapsulation are electrospraying and microemulsion techniques. Although electrospraying is a novel technique to produce nanoparticles in recent years, microemulsion is more conventional method compared with electrospraying. In this study, Chlorella protothecoides oil was encapsulated by using sodium alginate and chitosan biopolymers, and the effects of production parameters of electrospraying and microemulsion methods on the particle size and loading efficiency were investigated. Statistical modeling of critical parameters for particle sizing in microemulsion method and electrospraying technique, which is a novel approach to obtain microalgal oil-loaded nanoparticles, was also presented. It was seen that electrospraying is suitable for obtaining smaller nanoparticles (123.9-610 nm), homogeneous distribution, and higher oil loading efficiency (60%-77%) compared with microemulsion method (756.9-1128.2 nm and 57%-73%).

Immobilized-microbial bioaugmentation protects aerobic denitrification from heavy metal shock in an activated-sludge reactor

The inhibition of denitrification by heavy metals is a problem in nitrogen wastewater treatment, but the solutions are rarely studied. In this study, Pseudomonas brassicacearum LZ-4, immobilized in sodium alginate-kaolin, was applied in an activated-sludge reactor to protect denitrifiers from hexavalent chromium (Cr(VI)). Q-PCR result showed that the strain LZ-4 was incorporated into activated sludge under the help of immobilization. In the non-bioaugmentation system, the removal efficiency of nitrate was decreased by 86.07% by 30 mg/L Cr(VI). Whereas, denitrification was protected and 95% of nitrate was removed continuously in immobilized-cell bioaugmentation system. Miseq sequencing data showed that bioaugmentation decreased the impact of Cr(VI) on microbial communities and increased the abundance of denitrifiers. Based on the results of biomass and extracellular polymers, activated sludge was protected from Cr(VI) toxicity. This discovery will provide a feasible technique for nitrogen wastewater treatment in the presence of distressing heavy metals.

Effective decolorization of anthraquinone dye reactive blue 19 using immobilized Bacillus sp. JF4 isolated by resuscitation-promoting factor strategy

Given the highly complex recalcitrant nature of synthetic dyes, biological treatment of textile wastewater using efficient bacterial species is still considered as an environmentally friendly manner. In this study, a reactive blue 19 (RB19)-degrading strain, Bacillus sp. JF4, which was isolated by resuscitation-promoting factor (Rpf) strategy, was immobilized into polyvinyl alcohol-calcium alginate-activated carbon beads (JF4-immobilized beads) for RB19 decolorization. Results suggest that the JF4-immobilized beads, which were capable of simultaneous adsorption and biodegradation, showed a high decolorization activity, while they exhibited better tolerability towards high RB19 concentrations. The JF4-immobilized beads could almost completely decolorize 100 mg/L RB19 within 10 d, while only 92.1% was decolorized by free bacteria within 12 d. Further investigation on the equilibrium and kinetics of the adsorption process suggests that the pseudo-second-order model best fit the adsorption kinetics data, and the Freundlich isotherm was the most suitable for the description of the equilibrium data. Notably, the repeated batch cycles indicated that complete decolorization of 100 mg/L RB19 by JF4-immobilized beads can be maintained for at least three cycles without much reduction in efficiency. These findings suggest that immobilizing Rpf-resuscitated strain into beads was an effective strategy for textile wastewater treatment.

Study on the degradation performance and kinetics of immobilized cells in straw-alginate beads in marine environment

In this study, two strains Halomonas and Aneurinibacillus were mixed in equal proportions as free cells that could degrade diesel and produce biosurfactant. A new type of immobilized cells, free cells immobilized in beads combined with sodium alginate and straw, was studied. The components of straw-alginate beads were optimized by Response Surface Method, and the degradation performance of immobilized cells was determined. The result indicated that the density, strength and broken rate of straw-alginate beads were 1.04 g/cm³, 216 g and 4%, respectively. The best degradation rate of immobilized cells in straw-alginate beads could be 68.68%. Lately, by analyzing the Monod model, v_max (maximum specific degradation rate of diesel) and K_S (half saturation rate constant) of immobilized cells in straw-alginate beads were 1.84 d^-1 and 3.23 g/L, respectively, which explained the higher degradation performance.

New nano-biomaterials for the removal of malachite green from aqueous solution via a response surface methodology

The development of new biomaterials for the remove of organic contaminants from wastewater has attracted much attention over the few past years. One of the most cost-effective approaches is to produce new high value biomaterials from low value solid agricultural biowastes. In this work, sugarcane bagasse and agricultural waste rich in reducing sugars, acted as both a green bioreductant for graphene oxide (GO) and a sustainable supporter for the immobilization of Burkholderia cepacia. Therefore, this new biomaterial which contained both reduced graphene oxide (RGO) and Burkholderia cepacia, was cable of initial adsorption of malachite green (MG) and its subsequent biodegradation. After 60 h, immobilized Burkholderia cepacia degraded more MG (98.5%) than a cell cultured Burkholderia cepacia (87.7%) alone. Raman spectroscopy confirmed that GO was successfully reduced by bagasse and that consequently a composite (B-RGO) was prepared. SEM indicated that Burkholderia cepacia was well immobilized and kinetics studies showed that the adsorption of MG onto the developed composite fitted a pseudo-second order kinetics model (R² > 0.99). Biodegradation of MG, was confirmed by the detection of appropriate degradation products such as N, N-dimethylaniline and 4-(Dimethylamino) benzophenone using GC-MS, UV and FT-IR, and via best fit first-order biodegration kinetics. Furthermore, a response surface methodology (RSM) was applied to the removal process by varying four independent parameters using a Box-Behnken design (BBD). Optimum MG removal (99.3%) was achieved at 31.5 °C, with an initial MG concentration of 114.5 mg L^-1, initial pH of 5.85, and an adsorbent dosage of 0.11 g L ^-1. The excellent removal efficiency indicated that agricultural waste derived reduced graphene oxide bio-adsorbents have significant potential for the removal of dyes such as MG from industrial wastewaters.

Immobilization of Sphingomonas sp. GY2B in polyvinyl alcohol-alginate-kaolin beads for efficient degradation of phenol against unfavorable environmental factors

In this study, batch experiments were carried out to evaluate the biodegradation of phenol by Sphingomonas sp. GY2B, which were immobilized in polyvinyl alcohol (PVA)-sodium alginate-kaolin beads under different conditions. The optimal degradation performance was achieved by GY2B immobilized in beads containing 1.0% (w/v) of kaolin, 10% (w/v) of PVA, 0.3% (w/v) of sodium alginate, 10% (v/v) of biomass dosage, and exposed to an initial phenol concentration of 100 mg/L. The experimental results indicated that PVA-sodium alginate-kaolin beads can accelerate the degradation rate of phenol by reducing the degradation time and also improve degradation rate. The biodegradation rate of phenol by immobilized cells (16.79 ± 0.81 mg/(L·h)) was significantly higher than that of free cells (11.49 ± 1.29 mg/(L·h)) under the above optimal conditions. GY2B immobilized on beads was more competent than free GY2B in degradation under conditions with high phenol concentrations (up to 300 mg/L) and in strong acidic (pH = 1) and alkaline (pH = 12) environments. Higher phenol concentrations inhibit the biomass and reduce the biodegradation rate, while the lower biodegradation rate at low initial phenol concentrations is attributed to mass transfer limitations. The Haldane inhibitory model was in agreement with the experimental data well, revealing that phenol showed a considerable inhibitory effect on the biodegradation by Sphingomonas sp. GY2B, especially at concentrations higher than 90 mg/L. Intra-particle diffusion model analysis suggests that adsorption of phenol by immobilized beads was controlled by both rapid surface adsorption as well as pore diffusion mechanism. It's worth noting that the presence of 1 mg/L Cr(VI) enhanced the biodegradation of phenol by free cells, while Cr(VI) showed no obvious impact on the removal of phenol by immobilized cells. In addition, immobilized cells were reused 16 times and removed 99.5% phenol, and when stored at 4 °C for 90 days, more than 99% phenol was removed. These results showed that immobilized cells can significantly improve the microbial degradation performance, and protect microorganisms against unfavorable environment. It is implied that PVA -sodium alginate-kaolin beads have great potential to be applied in a practical and economical phenolic wastewater treatment system.

[The controversial Burkholderia cepacia complex, a group of plant growth promoting species and plant, animals and human pathogens]

The Burkholderia cepacia complex is a group of 22 species, which are known as opportunistic pathogens in immunocompromised people, especially those suffering from cystic fibrosis. It is also found in nosocomial infections and is difficult to eradicate due to intrinsic resistance to several antibiotics. The species have large genomes (up to 9 Mbp), distributed into 2-5 replicons. These features significantly contribute to genome plasticity, which makes them thrive in different environments like soil, water, plants or even producing nodules in legume plants. Some B. cepacia complex species are beneficial in bioremediation, biocontrol and plant-growth promotion. However, because the B. cepacia complex is involved in human infection, its use in agriculture is restricted. B. cepacia complex is being constantly studied due to the health problems that it causes and because of its agricultural potential. In this review, the history of B. cepacia complex and the most recently published information related to this complex are revised.

Two contrary roles of Fe3O4 nanoparticles on kinetic and thermodynamic of Paclitaxel degradation by Citrobacter amalonaticus Rashtia immobilized on sodium alginate gel beads

Roles of Fe₃O₄ nanoparticles (NPs) on biodegradation of Paclitaxel by Citrobacter amalonaticus immobilized on alginate gel beads were investigated. Limitation in substrate diffusion is the major drawback of the cell immobilization method. To overcome this problem, bacterial cells were immobilized on the gel beads containing different concentrations (5-20mg/mL) of Fe₃O₄ NPs and their Paclitaxel degrading potential at different temperatures was investigated using kinetic and thermodynamic modeling. Co-immobilization of bacterial cells with 5, 10 and 20mg/mL Fe₃O₄ NPs enhanced biodegradation efficiencies to 66%, 80% and 78%, respectively, compared to the NPs free immobilized cells (41.9%). The optimum concentration of Fe₃O₄ NPs (10mg/mL) had both inhibitory and accelerating effects on paclitaxel degradation depending on the incubation time and temperature. Increasing dose of Fe₃O₄ NPs could increase paclitaxel degradation, despite increasing of thermodynamic inhibitory factors, only when longer time and higher temperature were used. ΔG values increased about 11.2 KJ/mol at all temperatures of 285, 295 and 305K, and ΔH increased 54.4%, in comparison with the treatment without NPs. This indicates that, inclusion of Fe₃O₄ NPs into the immobilization gels can increase the local concentration of Paclitaxel (with OH₂⁺ groups) and bacterial accessibility to the substrate and thus enhance biodegradation efficiency.

Comparison of inoculum sources for long-term process performance and fate of ANAMMOX bacteria niche in poly(vinyl alcohol)/sodium alginate gel beads

The process performance and microbial niche of anaerobic ammonia oxidation (ANAMMOX) bacteria were compared in two identical bioreactors inoculated with different inoculum sources (i.e., pre-cultured ANAMMOX bacteria: PAB and activated sludge: AS) entrapped in poly(vinyl alcohol)/sodium alginate (PVA/SA) gel beads for a long-term period (i.e., 1.5 years). The start-up period with AS was longer than that with PAB; however, both bioreactors were successfully operated over the long-term with stable ANAMMOX activity. After long-term operation, the 16S rRNA gene concentration of ANAMMOX bacteria in both bioreactors was significantly increased, and thereby became comparable. In addition, Candidatus Jettenia sp. became the dominant ANAMMOX species in both bioreactors. Our results suggested that the ANAMMOX performance and microbial niche of ANAMMOX bacteria became nearly identical during long-term operation despite the use of different inoculum sources. Therefore, the use of PVA/SA gel beads entrapping AS appears to be a relevant option for constructing an ANAMMOX process in places where a full-scale ANAMMOX process has never been done previously.

Adsorption of Crystal Violet oNto Nitrogen-Doped Mesoporous Carbon

A series of nitrogen-doped mesoporous carbons (NDMCs) was prepared using p-phenylenediamine and glyoxal as a carbon source and mesoporous silica as a hard template. N2 adsorption–desorption isotherms indicated that mesopores with a wider distribution exist in NDMCs. Elemental analysis showed that the N content on the surface of NDMC-800 was 9.9at.%, with a result close to 8.4at.% from X-ray photoelectron spectroscopy. The adsorption capacity of NDMCs for crystal violet (CV) in aqueous solution was investigated. Static equilibrium data were well described by the Langmuir isotherm model, with a maximum adsorption capacity of 243.9 mg g−1. Adsorption kinetics data suggested that the adsorption control process follows the pseudo first-order kinetics model. The results showed that this carbon material has the potential for application in adsorption of CV.

Simultaneous aerobic denitrification and Cr(VI) reduction by Pseudomonas brassicacearum LZ-4 in wastewater

Inorganic nitrogen and heavy metals pervasively co-exist in industrial and domestic wastewaters. In this work, Pseudomonas brassicacearum LZ-4 was tested for the simultaneous reduction of Cr(VI) and nitrate. Nitrate was found to be the best inorganic nitrogen source for strain LZ-4, and could promote Cr(VI) reduction. Cr(VI) had a low degree of inhibition on denitrification, and even 50mgL^-1 Cr(VI) did not inhibit reduction of 100mgL^-1 NO₃^--N. The capability of simultaneous reduction of Cr(VI) and nitrate was illustrated by the reductase genes contained in the LZ-4 genome. Application in a batch membrane bioreactor showed that the immobilized strain LZ-4 could remove over 95% of 500mgL^-1 NO₃^--N, 80% of 10mgL^-1 Cr(VI), and 96% of 5000mgL^-1 COD in each batch of 46days. In summary, the strain LZ-4 is an ideal candidate for remediation of co-contaminants.

Enrichment and immobilization of sulfide removal microbiota applied for environmental biological remediation of aquaculture area

To remove sulfide in the deteriorating aquaculture sediment and water, sulfide-oxidizing microbiota was enriched from Jiaozhou Bay, China, by using sulfide-rich medium. Composition and structure of microbial communities in the enrichments were investigated by 16S rDNA molecular biotechniques. Results showed that microbial community structure continuously shifted and the abundance of sulfate reducing bacteria, i.e., Desulfobacterium, Desulfococcus and Desulfobacca apparently declined. Several halophile genera, Vibrio, Marinobacter, Pseudomonas, Prochlorococcus, Pediococcus and Thiobacillus predominated finally in the microbiota. The enriched microbiota was capable of removing a maximum of 1000 mg/L sulfide within 12 h with 10% inoculum at pH 7.0, 20-30 °C. After immobilized, the microbiota presented excellent resistance to impact and could completely remove 600 mg/L sulfide in 12 h. Moreover, the immobilized microbiota recovered well even recycled for five times. In conclusion, the immobilized sulfide-removing microbiota showed a quite promising application for biological restoring of sulfide-rich aquaculture environment.

Removal of environmental estrogens by bacterial cell immobilization technique

Contamination of steroidal estrogens in the environment has raised a great public concern, and therefore, developing an effective method for removal of trace amount of environmental estrogens is necessary. In this study, two estrogen-degrading bacteria were isolated from activated sludge and were identified as strain Sphingomonas sp. AHC-F and strain Sphingobium sp. AX-B. They were capable of utilizing estrone (E1) and 17ß-estradiol (E2) as sole carbon and energy source. Cell immobilization technique was applied to these two estrogen-degrading bacteria. Confocal laser-scanning microscopy images with live and dead staining of entrapped bacterial cells showed that most bacteria were present inside the porous structure and were mostly viable after immobilization procedures. Batch estrogen degradation study showed that immobilized strains AHC-F and AX-B could effectively degrade 2 mg/L of E2 and its metabolite E1. Immobilized bacteria column reactors using pure culture of strain AHC-F were set up for continuous-flow removal of 850 ng/L of E2 in the influent. The removal efficiency of E2 and equivalent estrogenic quantity of E2 (EEQ) could achieve 94 and 87% under 12 h hydraulic retention time (HRT), respectively. Increasing HRT could further improve the removal efficiency of EEQ. When the HRT increased to 72 h, the effluent concentrations of E2 and E1 were not detectable by gas chromatography-mass spectrometry. Our results also proved that most of the estrogen removal was due to biodegradation. This study has demonstrated the potential use of immobilized bacteria technique for the removal of environmental estrogens.

Removal of Cd (II) from synthetic wastewater by alginate-Ayous wood sawdust (Triplochiton scleroxylon) composite material

The biosorption characteristics of Cd (II) ions from synthetic wastewater using raw Ayous wood sawdust (Triplochiton scleroxylon), r-AS, immobilized by sodium alginate were investigated with respect to pH, biomass quantity, contact time, initial concentration of heavy metal, temperature and stirring rate. The experimental data fitted well with the Langmuir isotherm, suggesting that monolayer adsorption of the cadmium ions onto alginate-Ayous sawdust composite (a-ASC). The obtained monolayer adsorption capacity of a-ASC for Cd (II) was 6.21 mg/g. From the Dubinin-Radushkevich isotherm model, a 5.39 kJ/mol value for the mean free energy was calculated, indicating that Cd (II) biosorption could include an important physisorption stage. Thermodynamic calculations showed that the Cd (II) biosorption process was feasible, endothermic and spontaneous in nature under examined conditions. The results indicated that a-ASC could be an alternative material replacing more costly adsorbents used for the removal of heavy metals.

Removal of mixed contaminants, crystal violet, and heavy metal ions by using immobilized stains as the functional biomaterial

A new functional biomaterial based on Burkholderia vietnamiensis C09V (C09V) was immobilized on beads and used for simultaneous removal of both heavy metals and crystal violet (CV).

Polyvinyl alcohol-immobilized Phanerochaete chrysosporium and its application in the bioremediation of composite-polluted wastewater

A novel biosorbent, polyvinyl alcohol (PVA)-immobilized Phanerochaete chrysosporium, was applied to the bioremediation of composite-polluted wastewater, containing both cadmium and 2,4-dichlorophenol (2,4-DCP). The optimum removal efficiency achieved was 78% for Cd(II) and 95.4% for 2,4-DCP at initial concentrations of 20 mg/L Cd(II) and 40 mg/L 2,4-DCP. PPBs had significantly enhanced the resistance of P. chrysosporium to 2,4-DCP, leading to the degradation rates of 2,4-DCP beyond 90% with varying initial 2,4-DCP concentrations. This research demonstrated that 2,4-DCP and secreted proteins might be used as carbon and nitrogen sources by PVA-immobilized P. chrysosporium beads (PPBs) for Cd(II) removal. Fourier transform infrared spectroscopy analysis showed that hydroxyl and carboxyl groups on the surface of PPBs were dominant in Cd(II) binding. The mechanism underlying the degradation of 2,4-DCP into fumaric acid and 1-hexanol was investigated. The adsorption-desorption studies indicated that PPBs kept up to 98.9% of desorption efficiency over three cycles.

Burkholderia vietnamiensis C09V as the functional biomaterial used to remove crystal violet and Cu(II)

Burkholderia vietnamiensis C09V (B.V. C09V) was used to remove both crystal violet (CV) and Cu(II) because dye effluents often contain dyes and metal ions. Inhibiting the strain׳s growth through the biosorption of Cu(II) on B.V. C09V and promoting its growth by using CV as a carbon source led to the degradation of CV (30mg/L). It fell to 36.9 percent and the amount of Cu(II) (50mg/L) removed rose to 34.9 percent in the presence of both CV and Cu(II). This outcome is comparable to the single presence of CV and Cu(II). EDS analysis showed that Cu(II) was adsorbed onto the strain (the atomic percentage of Cu(II) was 1.9 percent), while kinetic studies indicated that firstly, the decolorization of CV fitted well to the pseudo first-order degradation kinetic model and secondly, the biosorption of Cu(II) fitted well to the pseudo second-order kinetic model. The degradation rate constants of CV were stable in the 0.101-0.0068/h range and R(2) was both higher than 0.981 when Cu(II) concentrations were present. Furthermore, the biosorption capacity of Cu(II) ranged from 38.8 to 20.3mg/g at the CV concentration of 30mg/L (both R(2)>0.96). This suggests that the strain has the potential to degrade CV and facilitate the biosorption of Cu(II) in dye effluent.

A coupled biological and photocatalysis pretreatment system for the removal of crystal violet from wastewater

The efficiency of a coupled photocatalytic-biological system for removing crystal violet (CV) from an aqueous solution was assessed. Initial experiments demonstrated that the optimal operating parameters for the photoreactor were a 1.5-h reaction time, pH 7.0, and a 2.0-min retention time. Under these conditions, the photocatalytic reaction reduced the toxicity of the CV solution by 94%. Subsequent evaluation of the performance and characteristics of the coupled photocatalytic-biological system in terms of CV removal revealed that the coupled system successfully removed and efficiently mineralized CV in a semi-continuous mode when the CV concentration was <150mgL(-1). Based on our analysis of the degradation products, CV degradation in this coupled system involved stepwise demethylation and aromatic ring opening. Phylogenetic analysis of the bioreactor effluent showed that the predominant phyla were Proteobacteria, followed by Bacteroidetes and Actinobacteria, suggesting that this coupled system is conducive for such processes as demethylation, aromatic ring opening, carbon oxidation, and nitrification. These results were verified in a GC-MS analysis. To our knowledge, this is the first report on CV removal using a coupled system.

Biodegradation of high concentration of nitrobenzene by Pseudomonas corrugata embedded in peat-phosphate esterified polyvinyl alcohol

Efficiency on biodegradation of high concentration of nitrobenzene (NB) by peat-phosphate esterified polyvinyl alcohol-embedded NB-degrading bacteria Pseudomonas corrugata was conducted compared to free bacteria cells. Its biodegradation kinetics, reuse ability, degradation effect in the absence of the essential element needed for the growth of bacteria and degradation efficiency of the raw water from the contaminated site were also invested. Results show that the degradation rate when the concentration of NB was at 600, 750, and 900 mg/L reached 91.02, 83.23, and 55.9 %, which was higher than that observed in free bacteria at the same concentration levels. Biodegradation kinetics of the material could be well described by first- and zero-order kinetics when the concentration of NB was at 300, 450 mg/L and 600, 750, 900 mg/L, respectively. Stable degradation activity (stayed at a level of approximately 70 %) was displayed during the 11th repeat-batch experiment. The affect of absence of phosphorus in the medium can be abated ascribed to the addition of peat, which contributes with organic matter and other elements such as nitrogen and phosphorus necessary to maintain metabolically active the microorganisms. Effective biodegradation of the raw water from the experimental site revealed that the material can be a potential candidate for treating NB-contaminated wastewater in the practical setting.