Cell immobilization using PVA crosslinked with boric acid

The optimization of poly(vinyl)-alcohol-alginate beads with a slow-release compound for the aerobic cometabolism of chlorinated aliphatic hydrocarbons

Chlorinated aliphatic hydrocarbons (CAHs), such as cis-1,2-dichloroethylene (cDCE), are prevalent in groundwater at many locations throughout the United States. When immobilized in hydrogel beads with slow-release compounds, the bacteria strain Rhodococcus rhodochrous ATCC 21198 can be used for the in situ bioremediation of cDCE. These hydrogel beads must exhibit high mechanical strength and resist degradation to extend the lifetime of slow-release compounds and bioremediation. We engineered poly(vinyl)-alcohol - alginate (PVA-AG) beads to immobilize ATCC 21198 with the slow-release compound, tetrabutoxysilane (TBOS) that produces 1-butanol as a growth substrate, for high mechanical strength. We optimized three inputs (concentration of PVA, concentration of AG, and the crosslinking time) on two responses (compressive modulus and rate of oxygen utilization) for batch incubation experiments between 1 and 30 days using a design of experiments approach. The predictive models generated from design of experiments were then tested by measuring the compressive strength, oxygen utilization, and abiotic rates of hydrolysis for a predicted optimal bead formulation. The result of this study generated a hydrogel bead with immobilized R. rhodochrous ATCC 21198 and TBOS that exhibited a high compressive modulus on day 1 and day 30, which was accurately predicted by models. These hydrogel beads exhibited low metabolic activity based on oxygen rates on day 1 and day 30 but were not accurately predicted by the models. In addition, the ratio between oxygen utilization and abiotic rates of hydrolysis were observed to be roughly half of what was expected stoichiometrically. Lastly, we demonstrated the capability to use these beads as a bioremediation technology for cDCE as we found that, for all bead formulations, cDCE was significantly reduced after 30 days. Altogether, this work demonstrates the capability to capture and enhance the material properties of the complex hydrogel beads with predictive models yet signals the need for more robust methods to understand the metabolic activity that occurs in the hydrogel beads.

Optimum quorum quenching bacteria concentration in the better-quality cell entrapping beads to control biofouling in membrane bioreactor

Quorum quenching (QQ) by cell entrapping beads (CEBs) is known to inhibit biofouling by its biological and physical cleaning effect. Although there are better QQ media reported, due to the ease of fabrication of QQ-CEBs, this study focused on improving the quality of CEBs by comparing two distinct bead-making methods - polyvinyl alcohol-alginate (PVA-alginate) and phase inversion - and on finding the optimum concentration of QQ bacteria in the CEBs. The evaluation of PVA-alginate bead showed better uniformity, and higher mechanical and chemical strength in comparison with the phase inversion bead. Through the operations of two control membrane bioreactors (MBRs) (no bead, vacant bead) and four QQ-MBRs with different Rhodococcus sp. BH4 concentrations (2.5-15 mg cell ml-1) in PVA-alginate CEBs, the maximum QQ effect was observed by 5 mg ml-1 BH4 concentration beads. This implies that an optimum cell concentration of QQ-CEBs is crucial to economically improve MBR performance using QQ.

Isolation of antibody by polymer microspheres embedded with E. coli displaying IgG-binding domain

Antibody purification is an important aspect of quality and cost control in the production process of antibody drugs. In this study, modified E. coli was embedded into polymer microspheres (polyvinyl alcohol/alginate) for antibody separation and the IgG binding domain was displayed on the surface of E. coli. The results showed that ZZ protein (Fc binding domain of the antibody) was successfully displayed on the surface of E. coli and was embedded in polyvinyl alcohol/alginate microspheres. In addition, it has excellent specific adsorption capacity for antibodies, with a maximum adsorption capacity of 35.74 mg/g (wet microspheres). Through the adsorption isotherm and adsorption kinetics simulation, the adsorption of IgG on the microsphere matrix conforms to the Langmuir model and follows the pseudo-first-order kinetic equation. The microsphere matrix can undergo saturation adsorption at pH 7.2 and desorption at around pH 3.0. Desorption characteristics are consistent with those of rProtein A Sepharose FF®. After five cycles of the adsorption-desorption processes, the IgG adsorption capacity remains above 80%. Using polymer microspheres to separate antibodies from mouse ascites, the antibody purity reached 86.7% and the yield was 83.5%. These results provide an alternative to protein A matrix with low-cost, fast preparation and moderate efficiency.

Polyvinyl alcohol coating releasing fungal blastospores improves kill effect of attract-and-kill beads

Polyvinyl alcohol (PVA) is a biodegradable, water-soluble polymer with excellent film forming properties, commonly studied or used as tablet coating, food packaging or controlled release fertilizers. Attract-and-kill (AK) beads are sustainable, microbial alternatives to synthetic soil insecticides, whose onset of lethal effect largely depend on how fast the encapsulated entomopathogenic fungus forms virulent conidia. Therefore, the objective of this study was to develop a water-soluble coating accelerating the kill effect of AK beads by immediately releasing virulent Metarhizium brunneum CB15-III blastospores. We assessed three PVA types (PVA 4-88, 8-88, 10-98) which differed in their degree of hydrolysis or molecular weight for their ability to release viable blastospores from thin films after drying at 60-40 °C, and examined how polyethylene glycol and soy-lecithin impact the blastospore survival. Finally, we evaluated the effectiveness of coated AK beads in a bioassay against Tenebrio molitor larvae. The blastospore release rate quadrupled within the first 5 min with decreasing molecular weight and degree of hydrolysis, with PVA 4-88 releasing 79 ± 19% blastospores. Polyethylene glycol and soy-lecithin significantly increased the blastospore survival to 18-28% for all three PVA types. Coated beads exhibited a uniform, 22.4 ± 7.3 µm thin coating layer, with embedded blastospores, as confirmed by scanning electron microscopy. The blastospore coating increased the mortality rate of T. molitor larvae over uncoated AK beads, decreasing the median lethal time from 10 to 6 days. Consequently, the blastospore coating accelerated the kill effect of regular AK beads. These findings pave the way to enhanced pest control efficacy from coated systems such as beads or seeds.

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.

Preparation, optimization and reusability of immobilized petroleum-degrading bacteria

In the remediation of marine pollution, it is important to effectively degrade pollutants and reuse petroleum-degrading bacteria. In order to obtain more effective biodegradability and reusability, an immobilized bacteria combination with petroleum-degrading bacteria, sodium alginate (SA) and biochar by adsorption-embedding method was systematically analysed. The results indicated that the immobilized bacteria had good mechanical properties and the degradation rate was 51% when the straw (CS) was 3%, the SA and CaCl₂ were 4.5% and 6%, respectively. Besides, SA-CS-DM-PVA has the highest degradation rate and the lowest broken rate, above 51% and below 6.1% respectively. The optimum dosage of the modified immobilized bacteria was 132, degradation time was 5d, and reuse frequency was 4 times. Moreover, immobilized bacteria characterized by scanning electron microscopy (SEM), results showed that there were more pores on the surface after degradation, and the carrier was exposed. Therefore, the modified immobilized bacteria with good degradability and reusability, have good application prospects in the treatment of marine oil pollution.

Synthesis and Swelling Behavior of Sodium Alginate/Poly(vinyl alcohol) Hydrogels

Objectives

Hydrogels are macromolecular networks able to absorb and release water/biological fluids in a reverse-phase manner, in response to specific environmental stimuli. Such stimuli-sensitive behavior makes hydrogels interesting for the design of smart devices applicable to a variety of technological fields. They are able to absorb and retain 10-20% and up to 1000 times the water or biological fluids than their dry weight can. The aim of this study was to extend the work on drug delivery in the stomach at pH 2-2.2.

Materials and Methods

The authors synthesized sodium alginate (SA)/poly(vinyl alcohol) (PVA) hydrogels. These hydrogels were characterized by fourier transform infrared spectroscopy and scanning electron microscopy, and the swelling properties of the hydrogels were examined at different pH values, in different salts, at different temperatures, and in different acids and bases.

Results

The authors studied and reported the swelling effects or variations such as the effects of salts, acids, bases, temperature, and pH. The results for the crosslinking agent glutaraldehyde showed that 8 mL of glutaraldehyde had a higher swelling rate compared to that of 10 mL and 12 mL.

Conclusion

In this work the authors studied the swelling degree in different acids and bases. It is concluded that the degree of swelling decreases with increases in the concentration of glutaraldehyde and also depending on the concentrations of the acids. The swelling degrees of PVA/SA hydrogels gradually increase with increases in the concentrations of acids (low pH). The swelling of hydrogels decreases with increases in pH (>7) or at high alkaline. Based on the results for salt solutions the swelling behavior was found to be in the order: K⁺>Na⁺>Ca²⁺>Mg²⁺.

Shape stable poly(vinyl alcohol) hydrogels with immobilized activated sludge at repeated dry-rewet cycles

The poly(vinyl alcohol) (PVA) hydrogels can be used as a non-toxic and inexpensive immobilization matrix for microbial cells with capability of degrading organic or inorganic pollutants in wastewaters. This study for the first time produced the PVA hydrogels with immobilized cells by two-stage crosslinking which have high shape stability at dry-rewet cycles and, when recovered after sequentially three 24-hr cultivations, reveal high bioactivity in wastewater treatment. The [B(OH)₃][SO₄^2-] cores inside the PVA-boric acid-sulfate hydrogels are proposed to support the immobilized cells with sufficient structure flexibility and strength to maintain hydrogel structural integrity and of sufficient recalcitrance to biological attack. Conversely, neither the PVA-boric acid hydrogels nor the PVA-borate hydrogels can be applied as organic pollutant degraders with dry storage capability. The PVA-boric acid-sulfate hydrogels are proposed as ideal matrix that can be produced and stored in dry, massive quantity and then applied latter at the same or different sites.

Reduction of silver nanoparticle toxicity affecting ammonia oxidation using cell entrapment technique

Occurrence of silver nanoparticles (AgNPs) in wastewater treatment systems could impact the ammonia oxidation (AO). This study investigated the reduction of AgNPs and dissociated silver ion (Ag⁺) toxicity on nitrifying sludge using cell entrapment technique. Three entrapment materials, including barium alginate (BA), polyvinyl alcohol (PVA), and a mixture of polyvinyl alcohol and barium alginate (PVA-BA), were applied. The BA beads provided the highest reduction of silver toxicity (up to 90%) and durability. Live/dead assays showed fatality of entrapped cells after exposure to AgNPs and Ag⁺. The maximum AO rate of the BA-entrapped cells was 5.6 mg-N/g-MLSS/h. The AO kinetics under the presence of silver followed an uncompetitive inhibition kinetic model. The experiments with AgNPs and Ag⁺ gave the apparent maximum AO rates of 4.2 and 4.8 mg-N/g-MLSS/h, respectively. The apparent half-saturation constants of the BA-entrapped cells under the presence of silver were 10.5 to 13.4 mg/L. Scanning electron microscopic observation coupled with energy-dispersive X-ray spectroscopy indicated no silver inside the beads. This elucidates that the silver toxicity can be reduced by preventing silver penetration through the porous material, leading to less microbial cell damage. This study revealed the potential of the entrapment technology for mitigating the effect of silver species on nitrification.

Effects of Polymer Matrices and Carbon Nanotubes on the Generation of Electric Energy in a Microbial Fuel Cell

The anode of a microbial fuel cell (MFC) was formed on a graphite electrode and immobilized Gluconobacter oxydans VKM-1280 bacterial cells. Immobilization was performed in chitosan, poly(vinyl alcohol) or N-vinylpyrrolidone-modified poly(vinyl alcohol). Ethanol was used as substrate. The anode was modified using multiwalled carbon nanotubes. The aim of the modification was to create a conductive network between cell lipid membranes, containing exposed pyrroloquinoline quinone (PQQ)-dependent alcoholdehydrogenases, and the electrode to facilitate electron transfer in the system. The bioelectrochemical characteristics of modified anodes at various cell/polymer ratios were assessed via current density, power density, polarization curves and impedance spectres. Microbial fuel cells based on chitosan at a matrix/cell volume ratio of 5:1 produced maximal power characteristics of the system (8.3 μW/cm²) at a minimal resistance (1111 Ohm cm²). Modification of the anode by multiwalled carbon nanotubes (MWCNT) led to a slight decrease of internal resistance (down to 1078 Ohm cm²) and to an increase of generated power density up to 10.6 μW/cm². We explored the possibility of accumulating electric energy from an MFC on a 6800-μF capacitor via a boost converter. Generated voltage was increased from 0.3 V up to 3.2 V. Accumulated energy was used to power a Clark-type biosensor and a Bluetooth transmitter with three sensors, a miniature electric motor and a light-emitting diode.

Isopropanol biodegradation by immobilized Paracoccus denitrificans in a three-phase fluidized bed reactor

A three-phase bed bioreactor including a mix of immobilized microbes was used to degrade isopropanol (IPA). The immobilization method was studied and cells immobilized with calcium alginate, polyvinyl alcohol, activated carbon, and SiO₂ were demonstrated to be the best immobilization method for the degradation of 90% of 2 g/L IPA in just 4 days, 1 day earlier than with free cells. Acetone was monitored as an indicator of microbial IPA utilization as the major intermediate of aerobic IPA biodegradation. The bioreactor was operated at hydraulic retention time (HRT) values of 32, 24, 16, 12, and 10 hr, which correspond to membrane fluxes of 0.03, 0.04, 0.06, 0.08, and 0.10 L/m²/hr, respectively. The chemical oxygen demand (COD) removal efficiencies were maintained at 98.0, 97.8, 89.1, 80.6, and 71.1% at a HRT of 32, 24, 16, 12, and 10 hr, respectively, while the IPA degradations were 98.6, 98.3, 90.3, 81.6, and 73.3%, respectively. With a comprehensive consideration of COD removal and economy, the optimal HRT was 24 hr. The results demonstrate the potential of immobilized mixed bacterial consortium in a three-phase fluidized bed reactor system for the aerobic treatment of wastewater containing IPA.

Novel characteristics of horseradish peroxidase immobilized onto the polyvinyl alcohol-alginate beads and its methyl orange degradation potential

Herein, we report the immobilization of in-house isolated horseradish peroxidase (HRP) from Armoracia rusticana with novel characteristics. The HRP was immobilized onto the self-fabricated polyvinyl alcohol-alginate (PVA-alginate) beads using sodium nitrate as a cross-linker. The PVA-alginate beads (2.0mm size) developed using 10% PVA and 1.5% sodium alginate showed maximal immobilization yield. The surface morphologies of the PVA-alginate (control) and immobilized-HRP were characterized by scanning electron microscopy (SEM). The immobilized-HRP retained 64.14% of its initial activity after 10 consecutive substrate-oxidation cycles as compared to the free counterpart. Simultaneously, the thermal stability of the immobilized-HRP was significantly enhanced as compared to the free HRP. The enzyme leakage (E_L) assay was performed by storing the immobilized-HRP in phosphate buffer solution for 30days. Evidently, the leakage of immobilized-HRP was recorded to be 6.98% and 14.82% after 15 and 30days of incubation, respectively. Finally, the immobilized-HRP was used for methyl orange (MO) dye degradation in a batch mode. A noticeable decline in spectral shift accompanied by no appearance of a new peak demonstrated the complete degradation of MO. The degraded fragments of MO were scrutinized by ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). A plausible degradation pathway for MO was proposed based on the identified intermediates. In conclusion, the study portrays the PVA-alginate-immobilized-HRP as a cost-effective and industrially desirable green catalyst, for biotechnological at large and industrial in particular, especially for the treatment of textile dyes or dye-containing industrial waste effluents.

Biodegradation of real petroleum wastewater by immobilized hyper phenol-tolerant strains of Bacillus cereus in a fluidized bed bioreactor

Microbial bioremediation of petroleum wastewater by phenol-degrading-bacteria holds promise in circumventing the issue of petroleum-spill related pollution. Herein, biodegradation of petroleum wastewater samples collected from oil refinery site was carried out in a fluidized bed bioreactor by Ca-alginate immobilized biomass of phenol-degrading strains of Bacillus cereus (AKG1 MTCC9817 and AKG2 MTCC9818). Degradation performance of the system was evaluated by measuring the changes in chemical oxygen demand (COD) and level of phenolic compounds in the wastewater samples during the microbial treatment. The microbial treatment reduced initial COD level and concentration of phenolic compounds by 95 % or more, demonstrating the excellent efficacy of immobilized AKG1 and AKG2 strains in treating petroleum wastewater in continuous mode of operation. The present study demonstrates the potential of immobilized AKG1 and AKG2 in treating petroleum wastewater in fluidized bed bioreactors.

Poly(vinyl alcohol) and alginate cross-linked matrix with immobilized Prussian blue and ion exchange resin for cesium removal from waters

Cesium (Cs) removal from contaminated water bodies is an emerging issue after the disaster at the Fukushima Daiichi Nuclear Power Plant. The Prussian blue (PB) is an effective Cs adsorbent but will release hexacyanoferrate fragments from the adsorbent matrix during adsorption. Alginate is an affordable biopolymer for PB particles immobilization. This study synthesized poly(vinyl alcohol) (PVA) and alginate cross-linked matrix for immobilization of PB nano-sized particles and a surface-modified styrene-ethyl styrene divinyl benzene resin and tested their swelling stability and Cs adsorption performance in fresh water and in seawater. The PVA-alginate granules have high structural stability in both fresh water and seawater, with the Cs adsorption capability higher for the former than the latter. The adopted resin effectively remove released PB fragments from the tested granules. The transport and reaction parameters for the granules and for the sand filter bed were estimated.

Continuous l-lactic acid production from defatted rice bran hydrolysate using corn stover bagasse immobilized carrier

In this paper, l-lactic acid (LLA) was produced using defatted rice bran hydrolysate.

Co-immobilization of Pseudomonas stutzeri YHA-13 and Alcaligenes sp. ZGED-12 with polyvinyl alcohol-alginate for removal of nitrogen and phosphorus from synthetic wastewater

Nitrogen (N) and phosphorus (P) are the two main factors causing water eutrophication. Immobilized micro-organisms have been widely studied in N and P removal. However, the effects of various immobilizing conditions on the removal efficiency of N and P using immobilized micro-organism beads (IMOBs) remain unclear. Polyvinyl alcohol (PVA) and alginate, as the two frequently immobilizing-used matrixes, were used for co-immobilizing Pseudomonas stutzeri YHA-13 and Alcaligenes sp. ZGED-12. PVA, alginate and CaCl₂contents, immobilization time and different wet biomass ratios of P. stutzeri to Alcaligenes sp. were conducted to elucidate their roles in and influences on the removal efficiency of N and P from synthetic wastewater. The application potential of IMOBs was estimated as well. Results showed that IMOBs prepared by cross-link of 4% PVA and 2-3% alginate with 5% CaCl₂and saturated boric acid solution for 10-15 min are the best ones in removal of N and P. Though IMOBs containing P. stutzeri and/or Alcaligenes sp. were capable of removal of the two nutrients, the highest removal efficiency was observed when the wet biomass ratio of P. stutzeri to Alcaligenes sp. was adjusted to 2:2. In addition, the IMOBs were of good ability to remove chemical oxygen demand (COD), NO(3)(-), NO(2)(-), NH(4)(+)- N, total nitrogen (TN) and total phosphorus (TP) from artificial wastewater. Of which, micro-organisms immobilized in matrixes were mainly responsible for NO(3)(-) and TP removal. Therefore, P. stutzeri YHA-13 and Alcaligenes sp. ZGED-12 are reliable bioresources to remove N and P from wastewater.

Fabrication and properties of irradiation-cross-linked poly(vinyl alcohol)/clay aerogel composites

Poly(vinyl alcohol) (PVOH)/clay aerogel composites were fabricated by an environmentally friendly freeze-drying of the aqueous precursor suspensions, followed by cross-linking induced by gamma irradiation without chemical additives. The influences of cross-linking conditions, i.e., absorbed dose and polymer loading as well as density on the aerogel structure and properties, were investigated. The absorbed dose of 30 kGy was found to be the optimum dose for fabricating strong PVOH composites; the compressive modulus of an aerogel prepared from an aqueous suspension containing 2 wt % PVOH/8 wt % clay increased 10-fold, and that containing 1 wt % PVOH/9 wt % clay increased 12 times upon cross-linking with a dose of 30 kGy. Increasing the solids concentration led to an increase in the mechanical strength, in accordance with the changes in microstructure from layered structure to network structure. The increase of absorbed dose also led to decreased porous size of the network structure. Cross-linking and the increase of the PVOH lead to decreased thermal stability. The strengthened PVOH/clay aerogels possess very low flammability, as measured by cone calorimetry, with heat, smoke, and volatile products release value decreasing as increasing clay content. The mechanism of flame retardation in these materials was investigated with weight loss, FTIR, WAXD, and SEM of the burned residues. The proposed mechanism is that with decreasing fuel content (increasing clay content), increased heat and mass transport barriers are developed; simultaneously low levels of thermal conductivity are maintained during the burning.

Modified PVA-alginate encapsulated photocatalyst ferro photo gels for Cr(VI) reduction

In this study magnetic separable photocatalyst beads containing maghemite nanoparticles (γ-Fe(2)O(3)) in polyvinyl alcohol (PVA) polymer were prepared and used in the reduction of Cr(VI) to Cr(III) in an aqueous solution under sunlight. The unique superparamagnetic property of the photocatalyst contributed by the γ-Fe(2)O(3) and robust property of PVA polymer allow the magnetic beads to be recovered easily and reused for at least 7 times without washing. The concentration of γ-Fe(2)O(3) was varied from 8% (v/v) to 27% (v/v) and the results revealed that the beads with 8% (v/v) γ-Fe(2)O(3) exhibited the best performance where Cr(VI) was reduced to Cr(III) in only 30 min under sunlight. The use of the PVA has improved the bead properties and life cycle of beads which is in line with sustainable practices.