Polyacrylamide Biodegradation Research Articles

Construction of a mycelium sphere using a Fusarium strain isolate and Chlorella sp. for polyacrylamide biodegradation and inorganic carbon fixation.

In the context of global demand for carbon reduction, the formation of inorganic carbon (IC) in the wastewater from oil flooding becomes a potential threat. In this study, Chlorella sp. and Fusarium sp. were used to assemble a fungal-algal pellet to degrade polyacrylamide (PAM) and fix IC in synthetic oil-flooding wastewater. The results showed that the combination of Chlorella sp. and Fusarium sp. was more effective at degrading PAM and removing carbon than a monoculture. With PAM as the sole nitrogen source, the degradation of PAM by the consortium was enhanced up to 35.17 ± 0.86% and 21.63 ± 2.23% compared with the monocultures of fungi or microalgae, respectively. The degradation of the consortium was significantly enhanced by the addition of an external nitrogen source by up to 27.17 ± 2.27% and 22.86 ± 2.4% compared with the monoculture of fungi or microalgae, respectively. This may depend on the effect of synergy between the two species. For the removal of IC from the water, the removal efficiency of the consortium was higher than that of the microalgae by 38.5 ± 0.08%, which may be attributed to the ability of the fungi to aid in the adsorption of nutrients and its assimilation by the microalgae. Therefore, the Fusarium-Chlorella consortium can effectively degrade PAM, while simultaneously fixing carbon, which provides a feasible scheme for the treatment and carbon neutralization of the wastewater that contains PAM.

Two strains of bacteria from oilfield slickwater and their performance in partially hydrolyzed polyacrylamide biodegradation

Partially hydrolyzed polyacrylamide (HPAM) is widely used in oil recovery, but the HPAM residues also induce environmental pollution. In this study, two strains of bacteria, SCE2 and NMYGYB4, have been isolated from oilfield slickwater and identified as Tistrella bauzanensis (SCE2) and Brucella sp. (NMYGYB4). The optimal biodegradation conditions of Tistrella bauzanensis SCE2 were inoculation time 36 h, shaking speed 175 rpm, inoculum amount 3% (v/v), pH 3.0, and incubation temperature 37 °C with urea and glucose as the nitrogen and carbon sources. And the optimal biodegradation conditions of Brucella sp. NMYGYB4 were 12 h, 185 rpm, 2% (v/v), pH 7.0 and 37 °C with yeast powder and sucrose as the nitrogen carbon sources. HPAM removal rate of Tistrella bauzanensis SCE2 and Brucella sp. NMYGYB4 reached 75.3% and 63.59% at optimal conditions. The degraded samples were analyzed with GPC, FTIR, 1H NMR and HPLC. The results showed that HPAM was broken into small fragments, and amide group has been converted into carboxyl group, and no toxic acrylamide monomer was produced. The specific activities of extracellular amidases of Tistrella bauzanensis SCE2 and Brucella sp. NMYGYB4 were 5.31 U/mg and 4.79 U/mg, respectively. This work will provide novel bacteria strains for HPAM-containing wastewater treatment.

First insight into indigenous microorganisms in coal slurry involved in polyacrylamide biodegradation

Indigenous microorganisms can affect coal slurry settling by polyacrylamide biodegradation; however, they have rarely been examined in detail. In this study, the microbial community composition in coal slurry was explored using 16S rDNA, and the microorganisms are assigned to 34 phyla and 98 genera. The predicted function results show that microorganisms in coal slurry are closely related to the organic matter biodegradation. To prove it, the Sphingomonas was isolated from the coal slurry, which was used to biodegrade polyacrylamide in coal slurry, and the biodegradation rate reached 66.4 % within 76 h. The results of SEM, AFM, UV spectrometry, FTIR, and HPLC explain that the high molecular weight polyacrylamide is degraded into the smaller molecular weight organic products in the biodegradation process, and the coal slurry settling tests reflect that the settling rate and settling layer height are obviously inhibited by polyacrylamide biodegradation.

Combination of biochar and immobilized bacteria accelerates polyacrylamide biodegradation in soil by both bio-augmentation and bio-stimulation strategies

Polyacrylamide (PAM) has been used extensively due to its well-known stable chemical properties, but limited information is available on the biodegradation of soil-containing PAM. In this work, sufficient degradation of PAM was achieved via the addition of the Klebsiella sp. PCX-biochar composite to PAM-containing soil, due to the synergic effect of bio-augmentation and bio-stimulation. The optimal degradation rate of 69.1% over 30-day period was observed under the following conditions: the addition of immobilized bacteria at 0.07 g/g, pH 6.6, and temperature at 38.0 °C. In this study, we showed that PAM was successfully hydrolyzed by amidase, and ammonia in the hydrolysis product was then oxidized by the nitrifying bacteria. The decrease of water-extractable organic carbon (WEOC) also demonstrated the chain cleavage in PAM. PAM was utilized as a carbon source not only by Klebsiella sp. PCX but also by some taxa from indigenous bacteria. Last but not least, it was shown in this study that biochar, even though immobilized with exogenous microorganisms, actually enhanced bacterial diversity and stimulated the growth of some indigenous PAM-degrading taxa. Based on the above observations, we concluded that PAM biodegradation via the addition of bacteria-immobilized biochar was a synergy of both bio-augmentation and bio-stimulation strategies.

Biodegradation of low molecular weight polyacrylamide under aerobic and anaerobic conditions: effect of the molecular weight.

The biodegradation of polyacrylamide (PAM) includes the hydrolysis of amino groups and cleavage of the carbon chain; however, the effect of molecular weight on the biodegradation needs further investigations. In this study, biodegradation of low molecular weight PAM (1.6 × 106 Da) was evaluated in two aerobic (25 °C and 40 °C) and two anaerobic (35 °C and 55 °C) reactors over 100 days. The removal of the low molecular weight PAM (52.0-52.6%) through the hydrolysis of amino groups by anaerobic treatment (35 °C and 55 °C) was much higher than that of the high molecular weight (2.2 × 107 Da, 11.2-17.0%) observed under the same conditions. The molecular weight was reduced from 1.6 × 106 to 6.45-7.42 × 105 Da for the low molecular weight PAM, while the high molecular weight PAM declined from 2.2 × 107 to 3.76-5.87 × 106 Da. The results showed that the amino hydrolysis of low molecular weight PAM is easier than that of the high molecular weight one, while the cleavage of its carbon chain is still difficult. The molecular weights of PAM in the effluents from the two aerobic reactors (25 °C and 40 °C) were further reduced to 4.31 × 105 and 5.68 × 105 Da by the biofilm treatment, respectively. The results would be useful for the management of wastewater containing PAM.

Potential of hydrolyzed polyacrylamide biodegradation to final products through regulating its own nitrogen transformation in different dissolved oxygen systems

Potential of hydrolyzed polyacrylamide (HPAM) biodegradation to final products was studied through regulating its own nitrogen transformation. Under the conditions of 2, 3 and 4 mg/L of DO, HPAM removal ratio reached 16.92%, 24.51% and 30.78% and the corresponding removal ratio reached 49.15%, 60.25% and 76.44% after anaerobic biodegradation. NO3−-N concentration was 9.43, 14.10 and 17.99 mg/L in aerobic stages and the corresponding concentration was 0.17, 0.07 and 0.008 mg/L after anaerobic biodegradation. Oxygen as electron acceptors stimulated the activities of nitrification bacteria and other functional bacteria, thus further enhanced nitrification and HPAM biodegradation. NO3− (from HPAM oxidation) as electron acceptors stimulated the activities of nitrate-reducing, acetate-producing and methanogenic microorganisms and they could form a synergistic effect on denitrification and methanogenesis. Thermodynamic opportunity window revealed that NOx− could accelerate anaerobic HPAM bioconversion to methane. Aerobic and anaerobic growth-process equations of cells verified that the metabolism on HPAM was feasible.

Effects of different electron acceptors on the methanogenesis of hydrolyzed polyacrylamide biodegradation in anaerobic activated sludge systems

The type of electron acceptor was a crucial factor in regulating the methanogenic process of anaerobic hydrolyzed polyacrylamide (HPAM) degradation. The combined methods of biodegradation experiments and thermodynamic calculations were applied to explore the effects of different electron acceptors on methanogenic HPAM degradation. Under the conditions of without electron acceptor, SO42−, Fe3+, SO42− and Fe3+ as electron acceptors, HPAM biodegradation ratio reached 31.56%, 41.48%, 49.4% and 61.1%, acetate production reached 0.0532, 28.28, 112.7 and 141.95mg·L−1, CH4 production reached 0.024, 0.3015, 9.446 and 11.78mg·L−1, respectively. The synergistic effect of SO42− and Fe3+ further promoted methanogenic HPAM biotransformation. Archaeal community analysis revealed that Methanobacteriales, Methanomicrobiales and Methanosarcinales were dominant. Thermodynamic opportunity windows of methanogenesis with Fe3+ as electron acceptor are 35 times larger than that with SO42− as electron acceptor. It indicated that acetoclastic methanogenesis was dominant and hydrogenotrophic methanogenesis was inhibited in the methane-producing process of anaerobic HPAM degradation.

The Research of HPAM Degradation Efficiency of an Anaerobic Strain SN10 with Simultaneous Capabilities of Denitrification and Sulfate Reduction

Anaerobic bacterium (strain SN10) with simultaneous capabilities of denitrification and sulfate reduction was enriched and isolated by anaerobic Hungate technology. The characterisation of SN10 was conducted from the morphologial, physiological, phylogenetic aspects and HPAM degradation efficiency. It was a rod-shaped, gram-negative, 0.40~1.0μm in width and 1.5~2.5 μm in length. Most of the fatty acids of SN10 was distributed among C12:0~C19-CYC-FAME and the main of them was consisted of C14:0 FAME, C16:0-FAME, C18:1c-FAME, C18:0-FAME and C19-CYC-FAME. Based on the morphologial, physiological characteristics and the phylogenetic analysis, SN10 was identified as Paenibacillus sp. (EU124565), Because its 16S rDNA can reach 97% of the similarity to that of Paenibacillus lautus SN10 (Accession No.DQ450463). The removal efficiencies of NO3 - and SO4 2- were up to 98.52% and 96.49 % when the initial concentrations of NO3 - and SO4 2- were 5830.92 mg/L and 682.83 mg/L, HPAM solution density was 2400mg/L, three days strain biodegradation rate was 68.27%, which can result in obviously decreased viscosity. The SN10 strain isolated would have provided the new microorganism resources for the polyacrylamide biodegradation.

Biodegradation of Polyacrylamide and Its Derivatives

Although polyacrylamide (PAM) and its derivatives have many useful applications, their release in nature can have impacts on the environment and human health, thus bioremediation approaches for residual PAM are urgently needed. Biodegradation of PAM and its derivatives has been studied only in the last two decades, with most emphasis on acrylamide biodegradation. Microorganisms have been shown to utilize, not only acrylamide, but also PAM and its derivatives as the sole source of nitrogen and/or carbon under aerobic as well as anaerobic conditions. Microbial degradation lowered the molecular weight of the polymer, the viscosity, and the amide nitrogen was degraded to ammonia. Few species belonging to the bacterial genera Enterobacter sp., Azomonas sp., Bacillus sp., Acinetobacter sp., Pseudomonas sp., and Clostridium sp., were able to degrade 16–91% of PAM/HPAM under aerobic or anaerobic conditions. The monomer acrylamide is toxic to most microorganisms, however, some bacteria and fungi could degrade it using amidases that deaminate acrylamide to acrylic acid and ammonium, and further utilize acrylic acid to produce CO2 and water. Some fungi and yeasts could degrade 60–80% of acrylamide. The biodegradation of PAM and its derivatives are initiated by the enzyme amidase, either under aerobic or anaerobic conditions, and are further degraded partially or completely by an array of different enzymes. Future research should focus on elucidating the exact pathways and the enzymes involved in the biodegradation process, especially by fungi and anaerobic bacteria, as well as utilizing PAM-degrading microbes for bioremediation purposes.

Hydrolyzed polyacrylamide biodegradation and mechanism in sequencing batch biofilm reactor

An investigation was performed to study the performance of a sequencing batch biofilm reactor (SBBR) to treat hydrolyzed polyacrylamides (HPAMs) and to determine the mechanisms of HPAM biodegradation. The mechanisms for the optimized parameters that significantly improved the degradation efficiency of the HPAMs were investigated by a synergistic effect of the co-metabolism in the sludge and the enzyme activities. The HPAM and TOC removal ratio reached 54.69% and 70.14%. A significant decrease in the total nitrogen concentration was measured. The carbon backbone of the HPAMs could be degraded after the separation of the amide group according to the data analysis. The HPLC results indicated that the HPAMs could be converted to polymer fragments without the generation of the acrylamide monomer intermediate. The results from high-throughput sequencing analysis revealed proteobacterias, bacteroidetes and planctomycetes were the key microorganisms involved in the degradation.

Waste-Activated Sludge Fermentation for Polyacrylamide Biodegradation Improved by Anaerobic Hydrolysis and Key Microorganisms Involved in Biological Polyacrylamide Removal.

During the anaerobic digestion of dewatered sludge, polyacrylamide (PAM), a chemical conditioner, can usually be consumed as a carbon and nitrogen source along with other organic matter (e.g., proteins and carbohydrates in the sludge). However, a significant accumulation of acrylamide monomers (AMs) was observed during the PAM biodegradation process. To improve the anaerobic hydrolysis of PAM, especially the amide hydrolysis process, and to avoid the generation of the intermediate product AM, a new strategy is reported herein that uses an initial pH of 9, 200 mg COD/L of PAM and a fermentation time of 17 d. First, response surface methodology (RSM) was applied to optimize PAM removal in the anaerobic digestion of the sludge. The biological hydrolysis of PAM reached 86.64% under the optimal conditions obtained from the RSM. Then, the mechanisms for the optimized parameters that significantly improved the biological hydrolysis of PAM were investigated by the synergistic effect of the main organic compounds in the sludge, the floc size distribution, and the enzymatic activities. Finally, semi-continuous-flow experiments for a microbial community study were investigated based on the determination of key microorganisms involved in the biological hydrolysis of PAM.

Biodegradation of polyacrylamide by anaerobic digestion under mesophilic condition and its performance in actual dewatered sludge system

Polyacrylamide (PAM) used in sludge dewatering widely exists in high-solid anaerobic digestion. Degradation of polyacrylamide accompanied with accumulation of its toxic monomer is important to disposition of biogas residues. The potential of anaerobic digestion activity in microbial utilization of PAM was investigated in this study. The results indicated that the utilization rate of PAM (as nitrogen source) was influenced by accumulation of ammonia, while cumulative removal of amide group was accorded with zeroth order reaction in actual dewatered system. The adjoining amide group can combined into ether group after biodegradation. PAM can be broken down in different position of its carbon chain backbone. In actual sludge system, the hydrolytic PAM was liable to combined tyrosine-rich protein to form colloid complex, and then consumed as carbon source to form monomer when easily degradable organics were exhausted. The accumulation of acrylamide was leveled off ultimately, accompanied with the yield of methane.

Biodegradation of polyacrylamide by bacteria isolated from activated sludge and oil-contaminated soil

Polyacrylamide (PAM), a linear water soluble polymeric compound with high molecular weight, is extensively used for oil production in China. Compared with the physico-chemical degradation of PAM, there is no acrylamide monomer, which causes peripheral neuropathy, released in the process of biodegradation. Unfortunately, few microorganisms have been isolated which can degrade PAM. In this study, two PAM-degrading bacterial strains, named HWBI and HWBII, were isolated from the activated sludge and soil in an oil field that had been contaminated by PAM for an extended period. These were subsequently identified as Bacillus cereus and Bacillus flexu, respectively. Both strains grew on a medium composed of 60 mg L −1 PAM as the sole source of carbon. Although both strains degraded PAM in different rates, after 72 h cultivation more than 70% of the PAM was consumed. This degradation efficiency was much higher than previous studies. Both strains degraded a determinate proportion of PAM when 50–1000 mg L −1 of the initial PAM was supplied. Glucose with a concentration lower than 200 mg L −1 can be used as co-metabolism substrate with PAM. The Fourier Transform Infrared (FT-IR) spectrograms of the cultures before and after PAM degradation were also recorded. The result showed that amido groups of the PAM were picked off by the microorganisms from the main chain of the PAM, and metabolism products other than acrylamide were formed in the degradation.