Growth kinetics and phenol biodegradation of psychrotrophic Pseudomonas putida LY1

Hybrid peroxymonosulfate/activated carbon fiber-sequencing batch reactor system for efficient treatment of coking wastewater: Establishment and influential factors

Coking wastewater contains high concentrations of toxic and low biodegradable organics, causing long hydraulic retention times for its biological treatment process. This study developed a pretreatment method for coking wastewater by using activated carbon fiber (ACF) activated peroxymonosulfate (PMS) to improve the treatment performance of subsequent biological post-treatment process, sequencing batch reactor (SBR). The results showed that, after optimization of treatment processes, the removal efficiency of chemical oxygen demand (COD), phenol, and chroma in coking wastewater reached to 76, 98, and 98%, respectively, with a significantly improved biodegradability. Compared with the sole SBR system without any pretreatment that could remove 73% of COD, the ACF/PMS+SBR system removed over 97% of COD in coking wastewater. Moreover, this pretreatment method facilitated the growth of functional bacteria for organics biodegradation, indicating its high potential as a highly efficacious pretreatment strategy to improve the overall treatment efficiency of coking wastewater.

Phenolic compounds induce ferroptosis-like death by promoting hydroxyl radical generation in the Fenton reaction

Phenolic compounds are industrially versatile chemicals, also the most ubiquitous pollutants. Recently, biosynthesis and biodegradation of phenols has attracted increasing attention, while phenols' toxicity is a major issue. Here, we evolved phloroglucinol-tolerant Escherichia coli strains via adaptive evolution, and three mutations (ΔsodB, ΔclpX and fetAB overexpression) prove of great assistance in the tolerance improvement. We discover that phloroglucinol complexes with iron and promotes the generation of hydroxyl radicals in Fenton reaction, which leads to reducing power depletion, lipid peroxidation, and ferroptosis-like cell death of E. coli. Besides phloroglucinol, various phenols can trigger ferroptosis-like death in diverse organisms, from bacteria to mammalian cells. Furthermore, repressing this ferroptosis-like death improves phloroglucinol production and phenol degradation by corresponding strains respectively, showing great application potential in microbial degradation or production of desired phenolic compounds, and phloroglucinol-induced ferroptosis suppresses tumor growth in mice, indicating phloroglucinol as a promising drug for cancer treatment.

Biofilm formation in xenobiotic-degrading microorganisms

The increased presence of xenobiotics affects living organisms and the environment at large on a global scale. Microbial degradation is effective for the removal of xenobiotics from the ecosystem. In natural habitats, biofilms are formed by single or multiple populations attached to biotic/abiotic surfaces and interfaces. The attachment of microbial cells to these surfaces is possible via the matrix of extracellular polymeric substances (EPSs). However, the molecular machinery underlying the development of biofilms differs depending on the microbial species. Biofilms act as biocatalysts and degrade xenobiotic compounds, thereby removing them from the environment. Quorum sensing (QS) helps with biofilm formation and is linked to the development of biofilms in natural contaminated sites. To date, scant information is available about the biofilm-mediated degradation of toxic chemicals from the environment. Therefore, we review novel insights into the impact of microbial biofilms in xenobiotic contamination remediation, the regulation of biofilms in contaminated sites, and the implications for large-scale xenobiotic compound treatment.

Kinetic characterization of a new phenol degrading Acinetobacter towneri strain isolated from landfill leachate treating bioreactor

The objective of this study was to establish and to mathematically describe the phenol degrading properties of a new Acinetobacter towneri CFII-87 strain, isolated from a bioreactor treating landfill leachate. For this purpose, the biokinetic parameters of phenol biodegradation at various initial phenol concentrations of the A. towneri CFII-87 strain have been experimentally measured, and four different mathematical inhibition models (Haldane, Yano, Aiba and Edwards models) have been used to simulate the substrate-inhibited phenol degradation process. The results of the batch biodegradation experiments show that the new A. towneri CFII-87 strain grows on and metabolizes phenol up to 1000 mg/L concentration, manifests significant substrate inhibition and lag time only at concentrations above 800 mg/L phenol, and has a maximum growth rate at 300 mg/L initial phenol concentration. The comparison of the model predictions with the experimental phenol and biomass data revealed that the Haldane, Aiba and Edwards models can be used with success to describe the phenol biodegradation process by A. towneri CFII-87, while the Yano model, especially at higher initial phenol concentrations, fails to describe the process. The best performing inhibition model was the Edwards model, presenting correlation coefficients of R² > 0.98 and modelling efficiency of ME > 0.94 for the prediction of biomass and phenol concentrations on the validation datasets. The calculated biokinetic model parameters place this new strain among the bacteria with the highest tolerance towards phenol. The results suggest that the A. towneri CFII-87 strain can potentially be used in the treatment of phenolic wastewaters.

Biodegradation of phenol by Candida tropicalis sp.: Kinetics, identification of putative genes and reconstruction of catabolic pathways by genomic and transcriptomic characteristics

Candida tropicalis sp. was isolated with predominant biodegradation capability to phenol compounds, even with high concentration or in acid environment. The biodegradation of phenol was evaluated at the following concentrations 10-1750 mg L^-1, the strain exhibited well biodegradation efficiency. The maximum specific growth rate was 0.660 h^-1 and the specific biodegradation rates was 0.47 mg (phenol) [(mg (VSS) h]^-1. Differentially expressed genes were screened out, and results revealed a complete process of energy and carbon metabolism. The genes' arrangements and phylogenetic information showed the unique genetic characteristics of the strain. Catabolic pathways were reconstructed and some key phenol-degrading genes were obviously upregulated, including pheA, catA, OXCT and fadA. A notable detail that CMBL encoding carboxymethylenebutenolidase was speculated to be involved in a shortened pathway of phenol biodegradation, thereby contributing to the reconstruction of the novel phenol catabolic pathway through the hydrolases of dienelactone. Finally, key enzymes were verified by the analysis of specific activity.

Valorization of phenol contaminated wastewater for lipid production by Rhodosporidium toruloides 9564T

Phenol is one of the most common hazardous organic compound presents in several industrial effluents which directly affects the aquatic environment. The present study envisaged the phenol biodegradation and simultaneous lipid production along with its underlying mechanism by oleaginous yeast Rhodosporidium toruloides 9564^T. Experiments were designed using simulated wastewater by varying phenol concentration in the range of 0.25-1.5 g/L and inoculum size of 1, 5, and 10% with and without glucose. The oleaginous yeast was found to completely degrade up to 0.75 g/L phenol with lipid accumulation of 26.3%. Phenol at > 0.5 g/L severely inhibited the growth of R. toruloides 9564^T at 1% and 5% inoculum size. Phenol toxicity up to 0.75 g/L can be overcome by increasing inoculum size to 10%. The maximum specific growth rate (μ_max) and phenol degradation rate (q_max) were found to be 0.0717 h^-1 and 0.01523 h^-1, respectively. The enzymatic pathway study suggested that R. toruloides 9564^T follows an ortho cleavage pathway for phenol degradation and lipid accumulation. Phytotoxicty and cytotoxicity tests for treated and untreated samples clearly demonstrated a decline in toxicity of the treated wastewater. R. toruloides brought about an important paradigm shift toward a circular economy in which industrial wastewater is considered a valuable resource for bioenergy production.

A study of highly efficient phenol biodegradation by a versatile Bacillus cereus ZWB3 on aerobic condition

As one of the organic pollutants in industrial wastewater, phenol seriously threatens the environment and human health. Among various methods, microbial degradation of phenol possesses the advantages of nontoxicity and no secondary pollution. Therefore, search for microbial resources that can efficiently degrade phenol has become an important issue. In this study, a strain that could efficiently degrade phenol was isolated. The strain was identified as Bacillus cereus based on its morphology, physiological and biochemical features and 16S rRNA sequence analysis. The strain can completely degrade phenol up to 1,500 mg/L within 26 h (57.7 mg·L^-1·h^-1), under the optimum conditions, faster compared with the known degrading bacteria. The strain could efficiently remove phenol at a wide range of temperatures (22-37 °C) and pH (7-9), and Mn²⁺ and Zn²⁺ stress. Interestingly, this strain displayed the potential on microthermal environment, which could degrade 1,200 mg/L phenol within 36 h at 22 °C. Further, the strain had capacity that used a variety of aromatic compounds as the sole carbon source for growth. This study shows a useful biodegradation route on the wastewater treatment under high phenol concentration conditions, providing alternatives for environmental remediation.

Adaptation of Pseudomonas helmanticensis to fat hydrolysates and SDS: fatty acid response and aggregate formation

An essential part of designing any biotechnological process is examination of the physiological state of producer cells in different phases of cultivation. The main marker of a bacterial cell's state is its fatty acid (FA) profile, reflecting membrane lipid composition. Consideration of FA composition enables assessment of bacterial responses to cultivation conditions and helps biotechnologists understand the most significant factors impacting cellular metabolism. In this work, soil SDS-degrading Pseudomonas helmanticensis was studied at the fatty acid profile level, including analysis of rearrangement between planktonic and aggregated forms. The set of substrates included fat hydrolysates, SDS, and their mixtures with glucose. Such media are useful in bioplastic production since they can help incrementally lower overall costs. Conventional gas chromatography-mass spectrometry was used for FA analysis. Acridine orange-stained aggregates were observed by epifluorescence microscopy. The bacterium was shown to change fatty acid composition in the presence of hydrolyzed fats or SDS. These changes seem to be driven by the depletion of metabolizable substrates in the culture medium. Cell aggregation has also been found to be a defense strategy, particularly with anionic surfactant (SDS) exposure. It was shown that simple fluidity indices (such as saturated/unsaturated FA ratios) do not always sufficiently characterize a cell's physiological state, and morphological examination is essential in cases where complex carbon sources are used.

Kinetics of Cometabolic Transformation of 4-chlorophenol and Phenol Degradation by Pseudomonas putida Cells in Batch and Biofilm Reactors

The biodegradation kinetics of 4-chlorophenol (4-CP) and phenol and microbial growth of Pseudomonas putida (P. putida) cells were estimated in batch and biofilm reactors. The kinetic parameters of cells on phenol were determined using the Haldane formula. The maximum specific growth rate of P. putida on phenol, the half-saturation constant of phenol and the self-inhibition constant of phenol were 0.512 h−1, 78.38 mg/L and 228.5 mg/L, respectively. The yield growth of cells on phenol (YP) was 0.618 mg phenol/mg cell. The batch experimental results for the specific transformation rate of 4-CP by resting P. putida cells were fitted with Haldane kinetics to evaluate the maximum specific utilization rate of 4-CP, half-saturation constant of 4-CP, and self-inhibition constant of 4-CP, which were 0.246 h−1, 1.048 mg/L and 53.40 mg/L, respectively. The negative specific growth rates of cells on 4-CP obtained were fitted using a kinetic equation to investigate the true transformation capacity and first-order endogenous decay coefficient, which were 4.34 mg 4-CP/mg cell and 5.99 × 10−3 h−1, respectively. The competitive inhibition coefficients of phenol to 4-CP transformation and 4-CP to phenol degradation were 6.75 and 9.27 mg/L, respectively; therefore, phenol had a higher competitive inhibition of 4-CP transformation than the converse. The predicted model examining cometabolic transformation of 4-CP and phenol degradation showed good agreement with the experimental observations. The removal efficiencies for phenol and 4-CP were 94.56–98.45% and 96.09–98.85%, respectively, for steady-state performance.

Effect of Fe3O4 nanoparticles exposure on the treatment efficiency of phenol wastewater and community shifts in SBR system

Increasing magnetic Fe₃O₄ nanoparticles (Fe₃O₄ NPs) application has aroused concern about its potential environmental toxicity. During acute and chronic exposure, key enzymes involved in phenol biodegradation were promoted at 0-600 mg/L Fe₃O₄ NPs, while were inhibited at 800 mg/L Fe₃O₄ NPs, correspondingly affected phenol degradation efficiency. Lactic dehydrogenase (LDH) increased when Fe₃O₄ NPs exceeded 600 mg/L, indicated the more severe cell rupture at high Fe₃O₄ NPs concentration. At the same Fe₃O₄ NPs concentration, the removal of EPS further inhibited key enzymes, decreased phenol degradation, and increased LDH, indicating that the existence of EPS relieved the adverse effects on microorganisms. Spectroscopic analysis showed that protein and polysaccharide associated bonds in EPS decreased at 0-600 mg/L Fe₃O₄ NPs, while increased when Fe₃O₄ NPs exceeded 600 mg/L, which was in accordance with EPS content. Biopolymer-degrading and phenol-degrading genera increased at 0-600 mg/L Fe₃O₄ NPs, while decreased at Fe₃O₄ NPs exceeded 600 mg/L, which conformed to EPS content and phenol degradation efficiency.

Anaerobic biodegradation of phenol in wastewater treatment: achievements and limits

Anaerobic biodegradation of toxic compounds found in industrial wastewater is an attractive solution allowing the recovery of energy and resources but it is still challenging due to the low kinetics making the anaerobic process not competitive against the aerobic one. In this review, we summarise the present state of knowledge on the anaerobic biodegradation process for phenol, a typical target compound employed in toxicity studies on industrial wastewater treatment. The objective of this article is to provide an overview on the microbiological and technological aspects of anaerobic phenol degradation and on the research needs to fill the gaps still hindering the diffusion of the anaerobic process. The first part is focused on the microbiology and extensively presents and characterises phenol-degrading bacteria and biodegradation pathways. In the second part, dedicated to process feasibility, anaerobic and aerobic biodegradation kinetics are analysed and compared, and strategies to enhance process performance, i.e. advanced technologies, bioaugmentation, and biostimulation, are critically analysed and discussed. The final section provides a summary of the research needs. Literature data analysis shows the feasibility of anaerobic phenol biodegradation at laboratory and pilot scale, but there is still a consistent gap between achieved aerobic and anaerobic performance. This is why current research demand is mainly related to the development and optimisation of powerful technologies and effective operation strategies able to enhance the competitiveness of the anaerobic process. Research efforts are strongly justified because the anaerobic process is a step forward to a more sustainable approach in wastewater treatment.Key points• Review of phenol-degraders bacteria and biodegradation pathways.• Anaerobic phenol biodegradation kinetics for metabolic and co-metabolic processes.• Microbial and technological strategies to enhance process performance.

Biodegradation of Phenol by Rhodococcus sp. Strain SKC: Characterization and Kinetics Study

This study focuses on the kinetics of a pure strain of bacterium Rhodococcus sp. SKC, isolated from phenol-contaminated soil, for the biodegradation of phenol as its sole carbon and energy source in aqueous medium. The kinetics of phenol biodegradation including the lag phase, the maximum phenol degradation rate, maximum growth rate (R_m) and maximum yield coefficient (Y) for each S_i (initial phenol concentration, mg/L) were fitted using the Gompertz and Haldane models of substrate inhibition (R² > 0.9904, RMSE < 0.00925). The values of these parameters at optimum conditions were μ_max = 0.30 h⁻¹, K_s = 36.40 mg/L, and K_i = 418.79 mg/L, and that means the inhibition concentration of phenol was 418.79 mg/L. By comparing with other strains of bacteria, Rhodococcus sp. SKC exhibited a high yield factor and tolerance towards phenol. This study demonstrates the potential application of Rhodococcus sp. SKC for the bioremediation of phenol contaminate.

Kinetics of Phenol Biodegradation by Heavy Metal Tolerant Rhizobacteria Glutamicibacter nicotianae MSSRFPD35 From Distillery Effluent Contaminated Soils

Biodegradation of phenol using bacteria is recognized as an efficient, environmentally friendly and cost-effective approach for reducing phenol pollutants compared to the current conventional physicochemical processes adopted. A potential phenol degrading bacterial strain Glutamicibacter nicotianae MSSRFPD35 was isolated and identified from Canna indica rhizosphere grown in distillery effluent contaminated sites. It showed high phenol degrading efficiency up to 1117 mg L^–1 within 60 h by the secretion of catechol 1,2-dioxygenase via ortho intradial pathway. The strain MSSRFPD35 possess both the catechol 1,2 dioxygenase and catechol 2,3 dioxygenase coding genes that drive the ortho and meta pathways, but the enzymatic assay revealed that the strain cleaves catechol via ortho pathway. Haldane’s kinetic method was well fit to exponential growth data and the following kinetic parameter was obtained: μ^∗ = 0.574 h^–1, K_i = 268.1, K_s = 20.29 mg L^–1. The true μ_max and S_m were calculated as 0.37 h^–1 and 73.76 mg L^–1, respectively. The Haldane’s constant values were similar to earlier studies and healthy fitness depicted in correlation coefficient value R² of 0.98. Phenol degrading kinetic’s was predicted using Haldane’s model as q_max 0.983, K_i′ 517.5 and K_s′ 9.152. Further, MSSRFPD35 was capable of utilizing different monocyclic and polycyclic aromatic hydrocarbons and to degrade phenol in the presence of different heavy metals. This study for the first time reports high phenol degrading efficiency of G. nicotianae MSSRFPD35 in the presence of toxic heavy metals. Thus, the strain G. nicotianae MSSRFPD35 can be exploited for the bioremediation of phenol and its derivatives polluted environments, co-contaminated with heavy metals.

Biokinetic aspects for biocatalytic remediation of xenobiotics polluted seawater

AIMS

This research was conducted to investigate the biocatalytic remediation of xenobiotics polluted seawater using two biocatalysts; whole bacterial cells of facultative aerobic halotolerant Corynebacterium variabilis Sh42 and its extracted crude enzymes.

METHODS AND RESULTS

One-Factor-at-A-Time technique and statistical analysis were applied to study the effect of initial substrate concentrations, pH, temperature, and initial biocatalyst concentrations on the batch biocatalytic degradation of three xenobiotic pollutants (2-hydroxybiphenyl (2-HBP), catechol and benzoic acid) in artificial seawater (salinity 3·1%). HPLC and gas-chromatography mass spectroscopy analyses were utilized to illustrate the quantitative removal of the studied aromatic xenobiotic pollutants and their catabolic pathway. The results revealed that the microbial and enzymatic cultures followed substrate inhibition kinetics. Yano and Koga's equation showed the best fit for the biokinetic degradation rates of 2-HBP and benzoic acid, whereas Haldane biokinetic model adequately expressed the specific biodegradation rate of catechol. The biokinetic results indicated the good efficiency and tolerance of crude enzyme for biocatalytic degradation of extremely high concentrations of aromatic pollutants than whole C. variabilis Sh42 cells. The monitored by-products indicated that the catabolic degradation pathway followed an oxidation mechanism via a site-specific monooxygenase enzyme. Benzoic acid and catechol were identified as major intermediates in the biodegradation pathway of 2-HBP, which were then biodegraded through meta-cleavage to 2-hydroxymuconic semialdehyde. With time elapsed, the semialdehyde product was further biodegraded to acetaldehyde and pyruvic acid, which would be further metabolized via the bacterial TCA cycle.

CONCLUSION

The batch enzymatic bioreactors performed superior-specific biocatalytic degradation rates for all the studied xenobiotic pollutants.

SIGNIFICANCE AND IMPACT OF THE STUDY

The enzymatic system of C. variabilis Sh42 is tolerable for toxic xenobiotics and different physicochemical environmental parameters. Thus, it can be recommended as an effective biocatalyst for biocatalytic remediation of xenobiotics polluted seawater.

Investigation on phenol degradation capability of Scenedesmus regularis: influence of process parameters

Phenol removal from environmental solutions has attracted much attention due to phenol's high toxicity, even at low concentrations. This study aims to reveal the phenol biodegradation capacity of Scenedesmus regularis. Batch system parameters (pH, amount of algal cell, phenol concentration) on biodegradation were examined. After 24 h of treatment, 92.16, 94.50, 96.20, 80.53, 65.32, 52 and 40% of phenol were removed by Scenedesmus regularis in aqueous solutions containing 5, 10, 15, 20, 30, 40 and 50 mg/L of phenol, respectively. To describe the correlation between degradation rate and phenol concentration, the Michaelis-Menten kinetic equation was used where V_max and K_m are 0.82 mg phenol g algea^-1 h^-1 and 24.97 ppm, respectively. Phenol remediation ability of S.regularis can enable the usage of the spent biomass as biofuel feedstock and animal feed makes it a 'green' environmental sustainable process.

Biodegradation of phenol in saline or hypersaline environments by bacteria: A review

With the continuous demand from industry for chemical raw materials, a large amount of high-salinity wastewater containing phenol is discharged into the aquatic environment, and the leakage of dangerous chemicals into the sea may lead to phenol pollution of the ocean. Phenol is a common chemical posing serious environmental hazard. Biodegradation is an effective, low-cost, environment-friendly method of removing phenol from water, but in hypersaline environments, traditional freshwater organisms are less efficacious. Here, at least 17 genera of bacteria from three phyla are found that can degrade phenol in different saline environments. The sources and taxonomy of halotolerant and halophilic bacteria are reviewed. Moreover, the pathway of phenol removal, kinetics of biodegradation, influencing factors, and recent treatment processes of wastewater are discussed.

Whole-genome sequencing of an acidophilic Rhodotorula sp. ZM1 and its phenol-degrading capability under acidic conditions

The goal of this work was to investigate the genetics of an acidophilic phenol-degrading yeast strain using whole-genome sequencing (WGS), characterize the growth of the strain and phenol degradation capability as well as degradation pathway under extremely acidic conditions. The result showed that the strain ZM1 isolated from an acid mine drainage (AMD) belongs to basidiomycetous yeast Rhodotorula sp., which possesses some unique genes compared to other four closely related Rhodotorula species. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that ZM1 possessed the degradation potentials for aromatic compounds. ZM1 was acidophilic with the optimum growth at the initial pH of 3.0. It could adjust pH to desired levels probably by acid production during the cultivation. Notably, at pH 3.0, the strain ZM1 showed a high phenol-degrading capability that almost completely degraded 1100 mg/L of phenol in 120 h with the highest degradation rate of 0.074 g/(g cell dry weight h). Under the same pH, the strain could completely degrade 500 mg/L phenol within 48 h at NaCl concentration up to 10 g/L. The identification of the gene catA by the KEGG analysis, together with the presence of metabolic intermediate of cis, cis-muconic acid detected by gas chromatography-mass spectrometry, confirmed that the strain ZM1 degraded phenol via ortho-cleavage pathway. These findings suggest that the indigenous yeasts strain ZM1 could be exploited as an important member for in-situ biodegradation of aromatic compounds in the extremely acidic environments.

Modelling of growth kinetics of isolated Pseudomonas sp. and optimisation of parameters for enhancement of xanthine oxidoreductase production by statistical design of experiments

This report presents the substrate inhibitory effect of xanthine (XN) on microbial growth and optimisation of effective parameters to achieve high enzyme activity of xanthine oxidoreductase (XOR) through statistical design. Three efficient isolated strains (Pseudomonas aeruginosa CEBP1 and CEBP2, Pseudomonas sp. CEB1G) were screened for growth kinetic studies. Substrate inhibitory models (eg. Aiba, Edward) could explain the growth kinetics of CEBP1, CEBP2 and CEB1G very well with various initial [XN] (S₀), e.g., 0.1-35 g L^-1. Highest XOR activity was obtained at stationary phase when biomass yield was high. Highest catalytic efficiency (k_cat/K_M) of XOR was obtained by CEBP1 at optimum specific growth rate of 0.082 h^-1 and biomass yield of 0.196 g g^-1 at S₀ = 5 g L^-1. The effects of S₀, pH and temperature were studied by Box-Behnken experimental design to evaluate the interactive effects of the significant variables influencing XOR production by CEBP1. ANOVA with high correlation coefficient (R² > 0.99) and lower 'Prob > F'value (< 0.05) validated the second order polynomial model for the enzyme production. The highest XOR activity of 31.2 KU min^-1mg^-1 was achieved by CEBP1 under optimised conditions (35 °C; S₀=5 g L^-1; pH = 7.0) as compared to any report in literature. A sevenfold substrate affinity of the enzyme was observed after purification.

Biodegradation of phenol by cold-tolerant bacteria isolated from alpine soils of Binaloud Mountains in Iran

Degradation of phenol is considered to be a challenge because of harsh environments in cold regions and ground waters. Molecular characterization of phenol degrading bacteria was investigated to gain an insight into the biodegradation in cold areas. The psychrotolerant and psychrophiles bacteria were isolated from alpine soils in the northeast of Iran. These strains belonged to Pseudomonas sp., Stenotrophomonas spp. and Shinella spp. based on analysis of the 16S rRNA gene. These strains were capable of the complete phenol degradation at a concentration of 200 mg L^-1 at 20 °C. Moreover, the strains could degrade phenol at a concentration of 400 and 600 mg L^-1 at a higher time. Effects of environmental factors were studied using one factor at a time (OFAT) approach for Pseudomonas sp.ATR208. When the bacterium was grown in a liquid medium with 600 mg L^-1 of concentration supplemented with optimum carbon and nitrogen sources, more than 99% of phenol removal was obtained at 20 °C and 24 h. Therefore, the present study indicated the potential of the local cold tolerant bacteria in the phenol bioremediation.

Differential desulfurization of dibenzothiophene by newly identified MTCC strains: Influence of Operon Array

Since the sulfur specific cleavage is vital for the organic sulfur removal from fossil fuel, we explored potential bacterial strains of MTCC (Microbial Type Culture Collection) to desulfurize the Dibenzothiophene (DBT) through C-S bond cleavage (4-S pathway). MTCC strains Rhodococcus rhodochrous (3552), Arthrobacter sulfureus (3332), Gordonia rubropertincta (289), and Rhodococcus erythropolis (3951) capable of growing in 0.5 mM DBT were examined for their desulfurization ability. The presence of dsz genes as well as the metabolites was screened by polymerase chain reaction (PCR) and HPLC, respectively. All these strains showed > 99% DBT desulfurization with 10 days of incubation in minimal salt medium. From the HPLC analysis it was further revealed that these MTCC strains show differences in the end metabolites and desulfurize DBT differently following a variation in the regular 4-S pathway. These findings are also well corroborating with their respective organization of dszABC operons and their relative abundance. The above MTCC strains are capable of desulfurizing DBT efficiently and hence can be explored for biodesulfurization of petrochemicals and coal with an eco-friendly and energy economical process.

Performance and microbial community dynamics of electricity-assisted sequencing batch reactor (SBR) for treatment of saline petrochemical wastewater

High-salinity wastewater is often difficult to treat by common biological technologies due to salinity stress on the bacterial community. Electricity-assisted anaerobic technologies have significantly enhanced the treatment performance by alleviating the impact of salinity stress on the bacterial community, but electricity-assisted aerobic technologies have less been reported. Herein, a novel bio-electrochemistry system has been designed and operated in which a pair of stainless iron mesh-graphite plate electrodes were installed into a sequencing batch reactor (SBR, designated as S1) to strengthen the performance of saline petrochemical wastewater under aerobic conditions. The removal efficiency of phenol and chemical oxygen demand (COD) in S1 were 94.1 and 91.2%, respectively, on day 45, which was clearly higher than the removal efficiency of a single SBR (S2) and an electrochemical reactor (S3), indicating that a coupling effect existed between the electrochemical process and biodegradation. A certain amount of salinity (≤8000 mg/L) could enhance the treatment performance in S1 but weaken that in S2. Illumina sequencing revealed that microbial communities in S1 on days 45 and 91 were richer and more diverse than in S2, which suggests that electrical stimulation could enhance the diversity and richness of the microbial community, and reduce the negative effect of salinity on the microorganisms and enrich some salt-adapted microorganisms, thus improve the ability of S1 to respond to salinity stress. This novel bio-electrochemistry system was shown to be an alternative technology for the high saline petrochemical wastewater.

Effect of nutrients on Chlorella pyrenoidosa for treatment of phenolic effluent of coal gasification plant

The ability of Chlorella pyrenoidosa, a freshwater microalga, to degrade phenolic effluent of coal-based producer gas plant under ambient conditions was investigated. C. pyrenoidosa was able to grow in high-strength phenolic effluent. Major contaminant present in the effluent was phenol (C₆H₅OH). The effluent has 1475.3 ± 68 mg/L of initial total phenolic concentration. The effect of nutrients used for algal cultivation in phenol degradation was analyzed by inoculating four different concentrations, viz.,1, 2, 3, and 4 g of wet biomass/L of raw effluent of C. pyrenoidosa mixed with effluent into two batches (with and without nutrients). C. pyrenoidosa was able to degrade more than 95% of the phenol (C₆H₅OH) concentration with the algal concentrations of 3 and 4 g/L when supplemented with nutrients. With effluent devoid of nutrients, the average percent reduction in total phenolic compounds was observed to a maximum of 46%. No physical changes in the C. pyrenoidosa were observed during degradation. C. pyrenoidosa was able to consume the organic carbon present in the phenolic compounds as carbon source for its growth despite the inorganic carbon supplemented externally.

An adsorption-release-biodegradation system for simultaneous biodegradation of phenol and ammonium in phenol-rich wastewater

The feasibility of simultaneous biodegradation of phenol and ammonium in phenol-rich wastewater was evaluated in a reusable system, which contained macroporous adsorption resin and Alcaligenes faecalis strain WY-01. In the system, up to 6000mg/L phenol could be completely degraded by WY-01; meanwhile, 99.03±3.95% of ammonium was removed from the initial concentration of 384mg/L. This is the first study to show the capability of single strain in simultaneous removal of ammonium and phenol in wastewater containing such high concentrations of phenol. Moreover, the resin was regenerated during the biodegradation process without any additional manipulations, indicating the system was reusable. Furthermore, enzyme assay, gene expression patterns, HPLC-MS and gas chromatography analysis confirmed that phenol biodegradation accompanied with aerobic nitrifier denitrification process. Results imply that the reusable system provides a novel strategy for more efficient biodegradation of phenol and ammonium contained in some particular industrial wastewater.

Isolation and growth kinetics of a novel phenol-degrading bacterium Microbacterium oxydans from the sediment of Taihu Lake (China)

Seven phylogenetically diverse phenol-degrading bacterial strains designated as P1 to P7 were isolated from the industry-effluent dump sites of an industrial area near Taihu Lake, China. Through the 16S rDNA sequence analysis, these strains were widely distributed among five different genera: Rhodococcus (P1), Pseudomonas (P2-P4), Acinetobacter (P5), Alcaligenes (P6), and Microbacterium (P7). All seven isolates were capable of growing with phenol as the sole carbon source. Strain P7 was found to be a novel phenol-degrading strain by detailed morphological, physiological and biochemical characteristic analysis as well as the 16S rDNA sequence analyses, and was named Microbacterium oxydans LY1 (M. oxydans LY1 in its short form). Degradation experiments of phenol at various initial concentrations (20-1,000 mg/L) revealed that phenol is an inhibitory substrate to M. oxydans LY1. In a batch culture experiment, more than 95% of the phenol (500 mg/L) was degraded by M. oxydans LY1 at 30°C, pH 7.0 and 120 rpm within 88 h. Phenol concentration higher than 200 mg/L was found to inhibit the bacterial growth. The growth kinetics correlated well with the Haldane model with μmax (maximum specific cell growth rate) = 0.243 h(-1), Ks (saturation constant) = 25.7 mg/L, and Ki (self-inhibition constant) = 156.3 mg/L. This is the first report of the ability of M. oxydans to degrade phenol, and the results could provide important information for bioremediation of phenol-contaminated environments.

Waste lubricating oil removal in a batch reactor by mixed bacterial consortium: a kinetic study

The growth kinetics and biodegradation of two waste lubricating oil samples including waste engine oil (WEO) and waste transformer oil (WTO) were studied using pure isolates and mixed culture of Ochrobactrum sp. C1 and Bacillus sp. K1. The mixed culture significantly influenced degradation efficiency of the pure isolates through bioaugmentation process. In particular, the mixed culture was capable of growing on various n-alkanes and polycyclic aromatic hydrocarbons and was able to tolerate unusually high concentrations of waste lubricants (WEO-86.0 g/L and WTO-81.5 g/L). The initial concentration of waste lubricating oils has been varied in the range of 1-10 % (v/v). Under this experimental range, the bacterial growth has been observed to follow Haldane-type kinetics characterizing the presence of substrate inhibition. Haldane model was used to fit the exponential growth data and the following kinetic parameters were obtained: μ max = 0.078 h(-1), K S = 23.101 g/L, K i = 43.844 g/L for WEO; and μ max = 0.044 h(-1), K S = 10.662 g/L, K i = 58.310 g/L for WTO. The values of intrinsic kinetic parameters, like specific growth rate μ max, half saturation constant, K S, inhibition constant, K i and the maximum substrate concentration, S max and growth yield coefficient Y x/s , have been determined using each model hydrocarbon and their mixture as limiting substrate. Relative changes in the values of the kinetic parameters have been correlated to the number of carbon atoms present in n-alkanes. The metabolites from degradation of model hydrocarbon compounds have been identified by GC-MS to elucidate the possible pathway of waste lubricating oil degradation process.

Intimately coupling of photolysis accelerates nitrobenzene biodegradation, but sequential coupling slows biodegradation

Photo(cata)lysis coupled with biodegradation is superior to photo(cata)lysis or biodegradation alone for removal of recalcitrant organic compounds. The two steps can be carried out sequentially or simultaneously via intimate coupling. We studied nitrobenzene (NB) removal and mineralization to evaluate why intimate coupling of photolysis with biodegradation was superior to sequential coupling. Employing an internal circulation baffled biofilm reactor, we compared direct biodegradation (B), biodegradation after photolysis (P+B), simultaneous photolysis and biodegradation (P&B), and biodegradation with nitrophenol (NP) and oxalic acid (OA) added individually and simultaneously (B+NP, B+OA, and B+NP+OA); NP and OA were NB's main UV-photolysis products. Compared with B, the biodegradation rate P+B was lower by 13-29%, but intimately coupling (P&B) had a removal rate that was 10-13% higher; mineralization showed similar trends. B+OA gave results similar to P&B, B+NP gave results similar to P+B, and B+OA+NP gave results between P+B and P&B, depending on the amount of OA and NP added. The photolysis product OA accelerated NB biodegradation through a co-substrate effect, but NP was inhibitory. Although decreasing the UV photolysis time could minimize the inhibition impact of NP in P+B, P&B gave the fastest removal of NB by accentuating the co-substrate effect of OA.

Enhancement of phenol biodegradation by Pseudochrobactrum sp. through ultraviolet-induced mutation

The phenol-degrading efficiency of Pseudochrobactrum sp. was enhanced by ultraviolet (UV) irradiation. First, a bacterial strain, Pseudochrobactrum sp. XF1, was isolated from the activated sludge in a coking plant. It was subjected to mutation by UV radiation for 120 s and a mutant strain with higher phenol-degrading efficiency, Pseudochrobactrum sp. XF1-UV, was selected. The mutant strain XF1-UV was capable of degrading 1800 mg/L phenol completely within 48 h and had higher tolerance to hydrogen ion concentration and temperature variation than the wild type. Haldane’s kinetic model was used to fit the exponential growth data and the following kinetic parameters were obtained: μ_max = 0.092 h⁻¹, Ks = 22.517 mg/L, and Ki = 1126.725 mg/L for XF1, whereas μ_max = 0.110 h⁻¹, Ks = 23.934 mg/L, and Ki = 1579.134 mg/L for XF1-UV. Both XF1 and XF1-UV degraded phenol through the ortho-pathway; but the phenol hydroxylase activity of XF1-UV1 was higher than that of XF1, therefore, the mutant strain biodegraded phenol faster. Taken together, our results suggest that Pseudochrobactrum sp. XF1-UV could be a promising candidate for bioremediation of phenol-containing wastewaters.

A reusable immobilization matrix for the biodegradation of phenol at 5000 mg/L

Bacteria-mediated degradation of toxins has been reported as a practical technique for the innocuous removal of toxic organic compounds from water. Specifically, immobilized and pre-acclimatized Pseudomonas putida has been shown to clear low levels of contaminants (less than 2000 mg/L) from wastewater, wherein the bacteria consumes toxic aromatic compounds as the only source of carbon and energy. Here we report the preparation of a high-capacity composite adsorbent as an immobilization matrix for pre-acclimatized P. putida that is capable of complete degradation of 5000 mg/L of phenol within 80 hours. The composite adsorbent, a n-Butyl acrylate (BA)-resin evenly coated on polyester fiber (PF), can quickly reduce the phenol concentration to a level that is suitable for the immobilized bacteria to start the biodegradation process. Furthermore, the composite adsorbent (PF-BA) is regenerated during the biodegradation process without any additional manipulations, therefore it is reusable. As a whole, we provide a general strategy for more efficient biodegradation for phenol, which can be generalized to other water-soluble toxic organics removal for waste water treatment.

Experimental and kinetic study on the cometabolic biodegradation of phenol and 4-chlorophenol by psychrotrophic Pseudomonas putida LY1

This study investigated the kinetics of phenol and 4-chlorophenol (4-CP) biodegradation by a cold-adapted bacteria, Pseudomonas putida LY1, isolated from Songhua River sediment. The results showed that P. putida LY1 cannot grow on 4-CP as a sole carbon source. P. putida LY1 had the potential to cometabolic biodegrade phenol and 4-CP in a wide range of temperature (varying from 5 to 35 °C) with the optimal temperature around 25 °C. Mixture of phenol and 4-CP were completely removed at two 4-CP concentrations (15 and 40 mg/L) over a wide range of phenol (20-400 mg/L) concentrations, whereby the ratio of 4-CP/biomass (S 2/X) was lower than 0.03. The kinetic models of cometabolic biodegradation of phenol and 4-CP were proposed, considering the growth and nongrowth substrate inhibition. These models successfully simulate the processes of cometabolic degradation of phenol and 4-CP.

A novel Bacillus pumilus-related strain from tropical landfarm soil is capable of rapid dibenzothiophene degradation and biodesulfurization

BACKGROUND

The presence of organic sulfur-containing compounds in the environment is harmful to animals and human health. The combustion of these compounds in fossil fuels tends to release sulfur dioxide in the atmosphere, which leads to acid rain, corrosion, damage to crops, and an array of other problems. The process of biodesulfurization rationally exploits the ability of certain microorganisms in the removal of sulfur prior to fuel burning, without loss of calorific value. In this sense, we hypothesized that bacterial isolates from tropical landfarm soils can demonstrate the ability to degrade dibenzothiophene (DBT), the major sulfur-containing compound present in fuels.

RESULTS

Nine bacterial isolates previously obtained from a tropical landfarm soil were tested for their ability to degrade dibenzothiophene (DBT). An isolate labeled as RR-3 has shown the best performance and was further characterized in the present study. Based on physiological aspects and 16 s rDNA sequencing, this isolate was found to be very closely related to the Bacillus pumillus species. During its growth, high levels of DBT were removed in the first 24 hours, and a rapid DBT degradation within the first hour of incubation was observed when resting cells were used. Detection of 2-hydroxybiphenyl (HBP), a marker for the 4S pathway, suggests this strain has metabolical capability for DBT desulfurization. The presence of MgSO4 in growth medium as an additional sulfur source has interfered with DBT degradation.

CONCLUSIONS

To our knowledge, this is the first study showing that a Bacillus strain can metabolize DBT via the 4S pathway. However, further evidences suggest RR-3 can also use DBT (and/or its derivative metabolites) as carbon/sulfur source through another type of metabolism. Compared to other reported DBT-degrading strains, the RR-3 isolate showed the highest capacity for DBT degradation ever described in quantitative terms. The potential application of this isolate for the biodesulfurization of this sulfur-containing compound in fuels prior to combustion was discussed.

Degradation of polyurethane by bacterium isolated from soil and assessment of polyurethanolytic activity of a Pseudomonas putida strain

The increasing usage and the persistence of polyester polyurethane (PU) generate significant sources of environmental pollution. The effective and environmental friendly bioremediation techniques for this refractory waste are in high demand. In this study, three novel PU degrading bacteria were isolated from farm soils and activated sludge. Based upon 16S ribosomal RNA gene sequence blast, their identities were determined. Particularly robust activity was observed in Pseudomonas putida; it spent 4 days to degrade 92% of Impranil DLN(TM) for supporting its growth. The optimum temperature and pH for DLN removal by P. putida were 25 °C and 8.4, respectively. The degradation and transformation of DLN investigated by Fourier transformed infrared spectroscopy show the decrease in ester functional group and the emergence of amide group. The polyurethanolytic activities were both presented in the extracellular fraction and in the cytosol. Esterase activity was detected in the cell lysate. A 45-kDa protein bearing polyurethanolytic activity was also detected in the extracellular medium. This study presented high PU degrading activity of P. putida and demonstrated its responsible enzymes during the PU degradation process, which could be applied in the bioremediation and management of plastic wastes.

Pseudomonas putida response in membrane bioreactors under salicylic acid-induced stress conditions

Starvation and changing feeding conditions are frequently characteristics of wastewater treatment plants. They are typical causes of unsteady-state operation of biological systems and provoke cellular stress. The response of a membrane bioreactor functioning under feed-induced stress conditions is studied here. In order to simplify and considerably amplify the response to stress and to obtain a reference model, a pure culture of Pseudomonas putida was selected instead of an activated sludge and a sole substrate (salicylic acid) was employed. The system degraded salicylic acid at 100-1100mg/L with a high level of efficiency, showed rapid acclimation without substrate or product inhibition phenomena and good stability in response to unsteady states caused by feed variations. Under starvation conditions, specific degradation rates of around 15mg/gh were achieved during the adaptation of the biomass to the new conditions and no biofilm formation was observed during the first days of experimentation using an initial substrate to microorganisms ratio lower than 0.1. When substrate was added to the reactor as pulses resulting in rapidly changing concentrations, P. putida growth was observed only for substrate to microorganism ratios higher than 0.6, with a maximum YX/S of 0.5g/g. Biofilm development under changing feeding conditions was fast, biomass detachment only being significant for biomass concentrations on the membrane surface that were higher than 16g/m(2).

Influence of phenolic substrates utilised by yeast Trichosporon cutaneum on the degradation kinetics

The degradation kinetics of different phenolic substrates utilised by Trichosporon cutaneum R57 was studied. The following compounds were used as substrates: phenol, resorcinol, hydroquinone, 3-nitrophenol, 2,6-dinitrophenol, 3-chloro phenol and p-cresol. The specific degradation rates (Q_s) were described by a Haldane kinetic model. The unknown model parameters were estimated using the mathematical optimisation procedure for direct search. The results obtained demonstrated that Q_s varied greatly in the experiments carried out. The level of biodegradability depended on the different structure and toxicity of compounds used as carbon substrates. The highest Q_s values were observed for less toxic hydroxylated phenols (0.77–0.85 h⁻¹), while the most toxic chlorinated phenols were characterised with the lowest Q_s values (0.224 h⁻¹). The results obtained with different concentrations of resorcinol (from 0.2 to 0.8 g L⁻¹) and 2,6-dinitrophenol (from 0.2 to 0.7 g L⁻¹) demonstrated a growing inhibitory effect directly correlating with the extended time necessary for complete degradation of both compounds.

Kinetics of phenol biodegradation at high concentration by a metabolically versatile isolated yeast Candida tropicalis PHB5

A highly tolerant phenol-degrading yeast strain PHB5 was isolated from wastewater effluent of a coke oven plant and identified as Candida tropicalis based on phylogenetic analysis. Biodegradation experiments with C. tropicalis PHB5 showed that the strain was able to utilize 99.4% of 2,400 mg l(-1) phenol as sole source of carbon and energy within 48 h. Strain PHB5 was also observed to grow on 18 various aromatic hydrocarbons. Haldane model was used to fit the exponential growth data and the following kinetic parameters were obtained: μ max = 0.3407 h(-1), K S = 15.81 mg l(-1), K i = 169.0 mg l(-1) (R (2) = 0.9886). The true specific growth rate, calculated from μ max, was 0.2113. A volumetric phenol degradation rate (V max) was calculated by fitting the phenol consumption data with Gompertz model and specific degradation rate (q) was calculated from V max. The q values were fitted with Haldane model, yielding following parameters: q max = 0.2766 g g(-1) h(-1), K S ' = 2.819 mg l(-1), K i ' = 2,093 (R (2) = 0.8176). The yield factor (Y X/S ) varied between 0.185 to 0.96 g g(-1) for different initial phenol concentrations. Phenol degradation by the strain proceeded through a pathway involving production of intermediates such as catechol and cis,cis-muconic acid which were identified by enzymatic assays and HPLC analysis.

Yeast performance in wastewater treatment: case study of Rhodotorula mucilaginosa

The ability of Rhodotorula mucilaginosa to degrade some phenolic compounds and to grow on olive mill wastewater (OMW) is investigated. R. mucilaginosa isolated from OMW was molecularly identified using 18S RNA sequencing. The biodegradation of six phenolic compounds was studied at an initial concentration of 1 g l(-1). The isolated yeast exhibited a complete degradation of protocatechuic, vanillic and p-coumaric acids and tyrosol. In addition, it reduced 56% and 44% of gallic acid and catechol, respectively. Protocatechuic acid, vanillic acid and p-coumaric acid kinetic degradation showed a simple order equation and the growth rate varied from 0.05 h(-1) to 0.08 h(-1), while tyrosol and catechol degradation fitted a second-degree equation. With OMW as culture medium, R. mucilaginosa was able to reduce 38.38%, 47.69% and 56.91% of chemical oxygen demand (COD) and 5.84%, 27.89% and 34.81% of phenols, respectively, at initial COD concentrations 26,700, 14,400 and 6500 mg l(-1). The use of such red pigmented yeast would present a double interest: first it would purify OMW and, second, an antioxidant would be produced at the same time, having antioxidant properties.

A novel 2,3-xylenol-utilizing Pseudomonas isolate capable of degrading multiple phenolic compounds

This work characterized a novel 2,3-xylenol-utilizing Pseudomonas isolate XQ23. From 16S rRNA phylogenetic analysis, XQ23 was found to be a member of the Pseudomonas putida group. Most of its physiological characteristics also shared similarities to P. putida. Phenols were catabolized by the meta-cleavage pathway. The dependence of the specific growth rate on 2,3-xylenol concentration could be well fitted by the Haldane model, with the maximum occurring at the concentration around 180 mg l(-1). Kinetic parameters indicated that XQ23 was sensitive to 2,3-xylenol and had low affinity. Three patterns, i.e. constant, linear decline, and allometric decline, were proposed to describe the biomass yields of phenols during bacterial degradation and XQ23 under 2,3-xylenol culturing conditions followed the allometric pattern. In a mineral-salts medium supplemented with 180 mg l(-1) of 2,3-xylenol as the sole carbon and energy source, over 40% of 2,3-xylenol was turned into CO(2) to provide energy by complete oxidization.

Growth kinetic models for phenol biodegradation in a batch culture of Pseudomonas putida

Biodegradation of phenol with pure culture of Pseudomonas putida was investigated. P. putida (PTCC 1694) was grown in facultative anaerobic condition at 27 degrees C and media pH value of 7. The effect of initial phenol concentration on the biodegradation rate was studied. The initial concentrations of phenol varied from 300 to 1000 mg/l. Experiments were performed for the duration of seven days while daily samples were withdrawn. The initial rate of biodegradation of phenol increased with initial concentration of 300-500 mg/l. Further increase in phenol concentration resulted in a slight decrease in the rate of biodegradation due to phenol inhibition. It was observed that by increasing the concentration of phenol, the lag phase was prolonged. Phenol is known to be an inhibitory substrate, thus Monod, Haldane and logistic kinetic models were applied to evaluate the growth kinetic parameters. The Monod model was unable to present the growth parameters over the defined concentration range. However, Haldane and logistic models perfectly fitted with the experimental data. The yield coefficients for the growth on phenol at concentrations of 300, 500, 700 and 1000 mg/l were 0.177, 0.062, 0.035 and 0.012 mg/mg, respectively.