Decomposition of non-steroidal anti-inflammatory drugs by activated sludge supported by biopreparation in sequencing batch reactor

The presence of non-steroidal anti-inflammatory drugs in wastewater from sewage treatment plants indicates that they are not completely biodegradable. The designed biopreparation based on immobilized bacteria enables the degradation of paracetamol, ibuprofen, naproxen and diclofenac at a rate of 0.50 mg/L*day, 0.14 mg/L*day, 0.16 mg/L*day and 0.04 mg/L*day, respectively. Lower degradation of drugs in the mixture than in monosubstrate systems indicates their additive, antagonistic effect, limiting the degradative capacity of microorganisms. The biopreparation is stable for at least 6 weeks in bioreactor conditions. Biochemical parameters of activated sludge functioning showed increased oxygen demand, which was related to increased ammonia concentration caused by long-term exposure of activated sludge to drugs. Reduced metabolic activity was also observed. The preparation enables decomposing drugs and their metabolites, restoring the activated sludge's functionality. The tested biopreparation can support activated sludge in sewage treatment plants in degrading non-steroidal anti-inflammatory drugs and phenolic compounds.

Non-steroidal anti-inflammatory drugs in the era of the Covid-19 pandemic in the context of the human and the environment

From 2019, life in the world has mainly been determined by successive waves of the COVID-19 epidemic. During this time, the virus structure, action, short- and long-term effects of the infection were discovered, and treatments were developed. This epidemic undoubtedly affected people's lives, but increasing attention is also being paid to the effects of the epidemic on the environment. Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines, a global scoping review of peer-reviewed information has been conducted on the use of over-the-counter non-steroidal anti-inflammatory drugs in the treatment of symptoms of SARS-CoV-2 infections and their positive and negative effects on the human body, the effects of non-steroidal anti-inflammatory drugs (NSAIDs) on aquatic organisms, and their adverse effects on non-target organisms. The literature from 1998 to 2021 was analysed using the Scopus®, Web of Science™ (WoS) and Google Scholar databases. As non-steroidal anti-inflammatory drugs place a heavy burden on the environment, all reports of the presence of these drugs in the environment during the pandemic period have been thoroughly analysed. Of the 70 peer-reviewed records within the scope, only 14% (n = 10) focussed on the analysis of non-steroidal anti-inflammatory drugs concentrations in wastewater and surface waters during the pandemic period. The percentage of these works indicates that it is still an open topic, and this issue should be supplemented with further reports in which the results obtained during the pandemic, which has been going on for several years, will be published. The authors hope this review will inspire scientists to investigate the problem of non-steroidal anti-inflammatory drugs in the environment to protect them for the next generation.

Use of xanthan gum for whole cell immobilization and its impact in bioremediation - a review

Xanthan gum is one of the exo-polysaccharides produced by bacteria and is characterized by unique non-Newtonian properties. Its structure and conformation strongly depend on the fermentation conditions and such factors as temperature and ions concentration. The properties of the xanthan gum were appreciated in the controlled drug delivery but in the crosslinked form. Due to its ability to enhance the survival rate of immobilized bacteria, the potential of a crosslinked form is promising. Unfortunately, xanthan gum crosslinking procedures often require toxic substances or harsh environmental conditions, which cannot be used in the entrapment of living cells. In this study, we summarised a crosslinking method that could potentially be modified to reduce its toxicity to living cells. Moreover, this review also includes using xanthan gum in bioremediation studies and possible utilization methods to avoid carrier accumulation in the environment.

Degradation of diclofenac by new bacterial strains and its influence on the physiological status of cells

Diclofenac (DCF) is one of the most commonly utilized non-steroidal anti-inflammatory drugs (NSAIDs), which is known to pose an ecotoxicological threat. In this study, from activated sludge and contaminated soil, we isolated four new bacterial strains able to degrade DCF under mono-substrate and co-metabolic conditions with glucose supplementation. We found that the effectiveness of DCF removal is strictly strain-specific and the addition of the primary substrate is not always beneficial. To assess the multidirectional influence of DCF on bacterial cells we evaluated the alterations of increasing concentrations of this drug on membrane structure. A significant increase was observed in the content of 17:0 cyclo fatty acid, which is responsible for reduced fluidity and profound changes in membrane rigidity. The cell injury and oxidative stress were assessed with biomarkers used as endpoints of toxicity, i.e. catalase (CAT), superoxide dismutase (SOD), lipids peroxidation (LPX), and both intra- and extracellular alkaline and acid phosphatase activity. Results indicated that DCF induced oxidative stress, frequently intensified by the addition of glucose. However, the response of the microbial cells to the presence of DCF should not be generalized, since the overall picture of the particular alterations greatly varied for each of the examined strains.

Suitability of Immobilized Systems for Microbiological Degradation of Endocrine Disrupting Compounds

The rising pollution of the environment with endocrine disrupting compounds has increased interest in searching for new, effective bioremediation methods. Particular attention is paid to the search for microorganisms with high degradation potential and the possibility of their use in the degradation of endocrine disrupting compounds. Increasingly, immobilized microorganisms or enzymes are used in biodegradation systems. This review presents the main sources of endocrine disrupting compounds and identifies the risks associated with their presence in the environment. The main pathways of degradation of these compounds by microorganisms are also presented. The last part is devoted to an overview of the immobilization methods used for the purposes of enabling the use of biocatalysts in environmental bioremediation.

Diclofenac Degradation-Enzymes, Genetic Background and Cellular Alterations Triggered in Diclofenac-Metabolizing Strain Pseudomonas moorei KB4

Diclofenac (DCF) constitutes one of the most significant ecopollutants detected in various environmental matrices. Biological clean-up technologies that rely on xenobiotics-degrading microorganisms are considered as a valuable alternative for chemical oxidation methods. Up to now, the knowledge about DCF multi-level influence on bacterial cells is fragmentary. In this study, we evaluate the degradation potential and impact of DCF on Pseudomonas moorei KB4 strain. In mono-substrate culture KB4 metabolized 0.5 mg L⁻¹ of DCF, but supplementation with glucose (Glc) and sodium acetate (SA) increased degraded doses up to 1 mg L⁻¹ within 12 days. For all established conditions, 4′-OH-DCF and DCF-lactam were identified. Gene expression analysis revealed the up-regulation of selected genes encoding biotransformation enzymes in the presence of DCF, in both mono-substrate and co-metabolic conditions. The multifactorial analysis of KB4 cell exposure to DCF showed a decrease in the zeta-potential with a simultaneous increase in the cell wall hydrophobicity. Magnified membrane permeability was coupled with the significant increase in the branched (19:0 anteiso) and cyclopropane (17:0 cyclo) fatty acid accompanied with reduced amounts of unsaturated ones. DCF injures the cells which is expressed by raised activities of acid and alkaline phosphatases as well as formation of lipids peroxidation products (LPX). The elevated activity of superoxide dismutase (SOD) and catalase (CAT) testified that DCF induced oxidative stress.

Xanthan gum as a carrier for bacterial cell entrapment: Developing a novel immobilised biocatalyst

Xanthan gum (XAN) is a widely used polysaccharide in various industries. Because of its unique properties, in this study, an attempt was made to adopt the procedure of xanthan gum cross-linking for the entrapment of bacterial cells that are able to biodegrade naproxen. The developed procedure proved to be completely neutral for Bacillus thuringiensis B1(2015b) cells, which demonstrated a survival rate of 99%. A negative impact of entrapment was noted for strain Planococcus sp. S5, which showed a survival rate in the 93-51% range. To achieve good mechanical properties of the composites, they were additionally hardened using polydopamine (PDA). XAN/PDA composites revealed a high stability in a wide range of pH, and their sorption capacity included both cationic and anionic molecules. Analysis of the survival rate during storage at 4 °C in 0.9% NaCl showed that, after 35 days, 98-99% of B1(2015b) and 47% of S5 cells entrapped in XAN/PDA remained alive. This study also presents the results of naproxen biodegradation conducted using XAN/PDA/B1(2015b) in a trickling filter with autochthonous microflora. Hence, owing to the significant acceleration of drug biodegradation (1 mg/L in 14 days) and the chemical oxygen demand removal, the entrapped B1(2015b) cells in XAN/PDA composites showed a promising potential in bioremediation studies and industrial applications.

Naproxen in the environment: its occurrence, toxicity to nontarget organisms and biodegradation

This article summarizes the current knowledge about the presence of naproxen in the environment, its toxicity to nontarget organisms and the microbial degradation of this drug. Currently, naproxen has been detected in all types of water, including drinking water and groundwater. The concentrations that have been observed ranged from ng/L to μg/L. These concentrations, although low, may have a negative effect of long-term exposure on nontarget organisms, especially when naproxen is mixed with other drugs. The biological decomposition of naproxen is performed by fungi, algae and bacteria, but the only well-described pathway for its complete degradation is the degradation of naproxen by Bacillus thuringiensis B1(2015b). The key intermediates that appear during the degradation of naproxen by this strain are O-desmethylnaproxen and salicylate. This latter is then cleaved by 1,2-salicylate dioxygenase or is hydroxylated to gentisate or catechol. These intermediates can be cleaved by the appropriate dioxygenases, and the resulting products are incorporated into the central metabolism. KEY POINTS: •High consumption of naproxen is reflected in its presence in the environment. •Prolonged exposure of nontargeted organisms to naproxen can cause adverse effects. •Naproxen biodegradation occurs mainly through desmethylnaproxen as a key intermediate.

A new pathway for naproxen utilisation by Bacillus thuringiensis B1(2015b) and its decomposition in the presence of organic and inorganic contaminants

Bacillus thuringiensis B1 (2015b) is a bacterial strain that is able to degrade naproxen. However, the potential effect of water co-contaminations on the degradation process and its pathway have not yet been evaluated. The results of our study show that in the presence of aromatic compounds, the B1 (2015b) strain utilised naproxen with an efficiency that was similar to what it was with no aromatic co-contaminations. In the presence of methanol, biodegradation of naproxen was inhibited, while the addition of ethanol increased the decomposition of naproxen. Among the metal ions that were tested, only cobalt (II) and cadmium (II) negatively affected the degradation of the drug. An analysis of the intermediates and enzymes that are engaged in degrading naproxen revealed that the key metabolites are O-desmethylnaproxen, which is the product of tetrahydrofolate-dependent O-demethylase activity, and salicylic acid. Salicylic acid can then be hydroxylated to catechol or gentisic acid or can be cleaved to 2-oxo-3,5-heptadienedioic acid. The high activity level of catechol 1,2-dioxygenase indicated that the main degradative pathway of naproxen in the B1 (2015b) strain is via catechol cleavage.

Naproxen ecotoxicity and biodegradation by Bacillus thuringiensis B1(2015b) strain

High level of naproxen consumption leads to the appearance of this drug in the environment but its possible effects on non-target organisms together with its biodegradation are not well studied. The aim of this work was to evaluate naproxen ecotoxicity by using the Microbial Assay for Risk Assessment. Moreover, Bacillus thuringiensis B1(2015b) was tested for both ecotoxicity and the ability of this strain to degrade naproxen in cometabolic conditions. The results indicate that the mean value of microbial toxic concentration estimated by MARA test amounts to 1.66 g/L whereas EC₅₀ of naproxen for B1(2015b) strain was 4.69 g/L. At toxic concentration, Bacillus thuringiensis B1(2015b) showed 16:0 iso 3OH fatty acid presence and an increase in the ratio of total saturated to unsaturated fatty acids. High resistance of the examined strain to naproxen correlated with its ability to degrade this drug in cometabolic conditions. The results of bacterial reverse mutation assay (Ames test) revealed that naproxen at concentrations above 1 g/L showed genotoxic effect but the response was not dose-dependent. Maximal specific naproxen removal rate was observed at pH 6.5 and 30 °C, and in the presence of 0.5 g/L glucose as a growth substrate. Kinetic analysis allowed estimation of the half saturation constant (K_s) and the maximum specific naproxen removal rate (q_max) as 6.86 mg/L and 1.26 mg/L day, respectively. These results indicate that Bacillus thuringiensis B1(2015b) has a high ability to degrade naproxen and is a potential tool for bioremediation.

Paracetamol - toxicity and microbial utilization. Pseudomonas moorei KB4 as a case study for exploring degradation pathway

Paracetamol, a widely used analgesic and antipyretic drug, is currently one of the most emerging pollutants worldwide. Besides its wide prevalence in the literature only several bacterial strains able to degrade this compound have been described. In this study, we isolated six new bacterial strains able to remove paracetamol. The isolated strains were identified as the members of Pseudomonas, Bacillus, Acinetobacter and Sphingomonas genera and characterized phenotypically and biochemically using standard methods. From the isolated strains, Pseudomonas moorei KB4 was able to utilize 50 mg L^-1 of paracetamol. As the main degradation products, p-aminophenol and hydroquinone were identified. Based on the measurements of specific activity of acyl amidohydrolase, deaminase and hydroquinone 1,2-dioxygenase and the results of liquid chromatography analyses, we proposed a mechanism of paracetamol degradation by KB4 strain under co-metabolic conditions with glucose. Additionally, toxicity bioassays and the influence of various environmental factors, including pH, temperature, heavy metals at no-observed-effective-concentrations, and the presence of aromatic compounds on the efficiency and mechanism of paracetamol degradation by KB4 strain were determined. This comprehensive study about paracetamol biodegradation will be helpful in designing a treatment systems of wastewaters contaminated with paracetamol.

Organic micropollutants paracetamol and ibuprofen-toxicity, biodegradation, and genetic background of their utilization by bacteria

Currently, analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs) are classified as one of the most emerging group of xenobiotics and have been detected in various natural matrices. Among them, monocyclic paracetamol and ibuprofen, widely used to treat mild and moderate pain are the most popular. Since long-term adverse effects of these xenobiotics and their biological and pharmacokinetic activity especially at environmentally relevant concentrations are better understood, degradation of such contaminants has become a major concern. Moreover, to date, conventional wastewater treatment plants (WWTPs) are not fully adapted to remove that kind of micropollutants. Bioremediation processes, which utilize bacterial strains with increased degradation abilities, seem to be a promising alternative to the chemical methods used so far. Nevertheless, despite the wide prevalence of paracetamol and ibuprofen in the environment, toxicity and mechanism of their microbial degradation as well as genetic background of these processes remain not fully characterized. In this review, we described the current state of knowledge about toxicity and biodegradation mechanisms of paracetamol and ibuprofen and provided bioinformatics analysis concerning the genetic bases of these xenobiotics decomposition.

Stenotrophomonas maltophilia: A Gram-Negative Bacterium Useful for Transformations of Flavanone and Chalcone

A group of flavones, isoflavones, flavanones, and chalcones was subjected to small-scale biotransformation studies with the Gram-negative Stenotrophomonas maltophilia KB2 strain in order to evaluate the capability of this strain to transform flavonoid compounds and to investigate the relationship between compound structure and transformation type. The tested strain transformed flavanones and chalcones. The main type of transformation of compounds with a flavanone moiety was central heterocyclic C ring cleavage, leading to chalcone and dihydrochalcone structures, whereas chalcones underwent reduction to dihydrochalcones and cyclisation to a benzo-γ-pyrone moiety. Substrates with a C-2–C-3 double bond (flavones and isoflavones) were not transformed by Stenotrophomonas maltophilia KB2.

Exploring the Degradation of Ibuprofen by Bacillus thuringiensis B1(2015b): The New Pathway and Factors Affecting Degradation

Ibuprofen is one of the most often detected pollutants in the environment, particularly at landfill sites and in wastewaters. Contamination with pharmaceuticals is often accompanied by the presence of other compounds which may influence their degradation. This work describes the new degradation pathway of ibuprofen by Bacillus thuringiensis B1(2015b), focusing on enzymes engaged in this process. It is known that the key intermediate which transformation limits the velocity of the degradation process is hydroxyibuprofen. As the degradation rate also depends on various factors, the influence of selected heavy metals and aromatic compounds on ibuprofen degradation by the B1(2015b) strain was examined. Based on the values of non-observed effect concentration (NOEC) it was found that the toxicity of tested metals increases from Hg(II) < Cu(II) < Cd(II) < Co(II) < Cr(VI). Despite the toxic effect of metals, the biodegradation of ibuprofen was observed. The addition of Co²⁺ ions into the medium significantly extended the time necessary for the complete removal of ibuprofen. It was shown that Bacillus thuringiensis B1(2015b) was able to degrade ibuprofen in the presence of phenol, benzoate, and 2-chlorophenol. Moreover, along with the removal of ibuprofen, degradation of phenol and benzoate was observed. Introduction of 4-chlorophenol into the culture completely inhibits degradation of ibuprofen.

Toxicity and biodegradation of ibuprofen by Bacillus thuringiensis B1(2015b)

In recent years, the increased intake of ibuprofen has resulted in the presence of the drug in the environment. This work presents results of a study on degradation of ibuprofen at 25 mg L^-1 in the presence of glucose, as an additional carbon source by Bacillus thuringiensis B1(2015b). In the cometabolic system, the maximum specific growth rate of the bacterial strain was 0.07 ± 0.01 mg mL^-1 h^-1 and K _sμ 0.27 ± 0.15 mg L^-1. The maximum specific ibuprofen removal rate and the value of the half-saturation constant were q _max = 0.24 ± 0.02 mg mL^-1 h^-1 and K _s = 2.12 ± 0.56 mg L^-1, respectively. It has been suggested that monooxygenase and catechol 1,2-dioxygenase are involved in ibuprofen degradation by B. thuringiensis B1(2015b). Toxicity studies showed that B. thuringiensis B1(2015b) is more resistant to ibuprofen than other tested organisms. The EC50 of ibuprofen on the B1 strain is 809.3 mg L^-1, and it is 1.5 times higher than the value of the microbial toxic concentration (MTC_avg). The obtained results indicate that B. thuringiensis B1(2015b) could be a useful tool in biodegradation/bioremediation processes.

Enzymes Involved in Naproxen Degradation by Planococcus sp. S5

Naproxen is a one of the most popular non-steroidal anti-inflammatory drugs (NSAIDs) entering the environment as a result of high consumption. For this reason, there is an emerging need to recognize mechanisms of its degradation and enzymes engaged in this process. Planococcus sp. S5 is a gram positive strain able to degrade naproxen in monosubstrate culture (27%). However, naproxen is not a suf-ficient growth substrate for this strain. In the presence of benzoate, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid or vanillic acid as growth substrates, the degradation of 21.5%, 71.71%, 14.75% and 8.16% of naproxen was observed respectively. It was shown that the activity of monooxygenase, hydroxyquinol 1,2-dioxygenase, protocatechuate 3,4-dioxygenase and protocatechuate 4,5-dioxyegnase in strain S5 was induced after growth of the strain with naproxen and 4-hydroxybenzoate. Moreover, in the presence of naproxen activity of gentisate 1,2-dioxygenase, enzyme engaged in 4-hydroxybenzoate metabolism, was completely inhibited. The obtained results suggest that monooxygenase and hydroxyquinol 1,2-dioxygenase are the main enzymes in naproxen degradation by Planococcus sp. S5.

Bacillus thuringiensis B1(2015b) is a Gram-Positive Bacteria Able to Degrade Naproxen and Ibuprofen

A Gram-positive bacterium, designated as strain B1(2015b), was isolated from the soil of the chemical factory "Organika-Azot" in Jaworzno, Poland. On the basis of 16S rRNA gene sequence analysis, the isolated strain was classified as a Bacillus thuringiensis species. Strain B1(2015b) is able to degrade ibuprofen and naproxen, however, these compounds are not sufficient carbon sources for this strain. In the presence of glucose, Bacillus thuringiensis B1(2015b) degrades ibuprofen and naproxen with higher efficiency. Twenty milligrams per liter of ibuprofen was degraded within 6 days and 6 mg l^-1 of naproxen was removed within 35 days. Simultaneously, the growth of the bacterial culture was observed. The obtained results suggest that Bacillus thuringiensis B1(2015b) appears to be a powerful and useful tool in the bioremediation of non-steroidal anti-inflammatory drugs-contaminated environment.

Enzymes Involved in Naproxen Degradation by Planococcus sp. S5

Naproxen is a one of the most popular non-steroidal anti-inflammatory drugs (NSAIDs) entering the environment as a result of high consumption. For this reason, there is an emerging need to recognize mechanisms of its degradation and enzymes engaged in this process. Planococcus sp. S5 is a gram positive strain able to degrade naproxen in monosubstrate culture (27%). However, naproxen is not a sufficient growth substrate for this strain. In the presence of benzoate, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid or vanillic acid as growth substrates, the degradation of 21.5%, 71.71%, 14.75% and 8.16% of naproxen was observed respectively. It was shown that the activity of monooxygenase, hydroxyquinol 1,2-dioxygenase, protocatechuate 3,4-dioxygenase and protocatechuate 4,5-dioxyegnase in strain S5 was induced after growth of the strain with naproxen and 4-hydroxybenzoate. Moreover, in the presence of naproxen activity of gentisate 1,2-dioxygenase, enzyme engaged in 4-hydroxybenzoate metabolism, was completely inhibited. The obtained results suggest that monooxygenase and hydroxyquinol 1,2-dioxygenase are the main enzymes in naproxen degradation by Planococcus sp. S5.

Over-the-Counter Monocyclic Non-Steroidal Anti-Inflammatory Drugs in Environment-Sources, Risks, Biodegradation

Recently, the increased use of monocyclic non-steroidal anti-inflammatory drugs has resulted in their presence in the environment. This may have potential negative effects on living organisms. The biotransformation mechanisms of monocyclic non-steroidal anti-inflammatory drugs in the human body and in other mammals occur by hydroxylation and conjugation with glycine or glucuronic acid. Biotransformation/biodegradation of monocyclic non-steroidal anti-inflammatory drugs in the environment may be caused by fungal or bacterial microorganisms. Salicylic acid derivatives are degraded by catechol or gentisate as intermediates which are cleaved by dioxygenases. The key intermediate of the paracetamol degradation pathways is hydroquinone. Sometimes, after hydrolysis of this drug, 4-aminophenol is formed, which is a dead-end metabolite. Ibuprofen is metabolized by hydroxylation or activation with CoA, resulting in the formation of isobutylocatechol. The aim of this work is to attempt to summarize the knowledge about environmental risk connected with the presence of over-the-counter anti-inflammatory drugs, their sources and the biotransformation and/or biodegradation pathways of these drugs.

Cometabolic Degradation of Naproxen by Planococcus sp. Strain S5

Naproxen is a non-steroidal anti-inflammatory drug frequently detected in the influent and effluent of sewage treatment plants. The Gram-positive strain Planococcus sp. S5 was able to remove approximately 30 % of naproxen after 35 days of incubation in monosubstrate culture. Under cometabolic conditions, with glucose or phenol as a growth substrate, the degradation efficiency of S5 increased. During 35 days of incubation, 75.14 ± 1.71 % and 86.27 ± 2.09 % of naproxen was degraded in the presence of glucose and phenol, respectively. The highest rate of naproxen degradation observed in the presence of phenol may be connected with the fact that phenol is known to induce enzymes responsible for aromatic ring cleavage. The activity of phenol monooxygenase, naphthalene monooxygenase, and hydroxyquinol 1,2-dioxygenase was indicated in Planococcus sp. S5 culture with glucose or phenol as a growth substrate. It is suggested that these enzymes may be engaged in naproxen degradation.

Bacterial degradation of naproxen--undisclosed pollutant in the environment

The presence of non-steroidal anti-inflammatory drugs (NSAIDs) in the environment is an emerging problem due to their potential influence on human health and biocenosis. This is the first report on the biotransformation of naproxen, a polycyclic NSAID, by a bacterial strain. Stenotrophomonas maltophilia KB2 transformed naproxen within 35 days with about 28% degradation efficiency. Under cometabolic conditions with glucose or phenol as a carbon source degradation efficiency was 78% and 40%, respectively. Moreover, in the presence of naproxen phenol monooxygenase, naphthalene dioxygenase, hydroxyquinol 1,2-dioxygenase and gentisate 1,2-dioxygenase were induced. This suggests that degradation of naproxen occurs by its hydroxylation to 5,7,8-trihydroxynaproxen, an intermediate that can be cleaved by hydroxyquinol 1,2-dioxygenase. The cleavage product is probably further oxidatively cleaved by gentisate 1,2-dioxygenase. The obtained results provide the basis for the use of cometabolic systems in the bioremediation of polycyclic NSAID-contaminated environments.

Altering substrate specificity of catechol 2,3-dioxygenase from Planococcus sp. strain S5 by random mutagenesis

c23o gene, encoding catechol 2,3-dioxygenase from Planococcus sp. strain S5 was randomly mutagenized to generate variant forms of the enzyme with higher degradation activity. Additionally, the effect of introduced mutations on the enzyme structure was analyzed based on the putative 3D models the wild-type and mutant enzymes. C23OB58 and C23OB81 mutant proteins with amino acid substitutions in close proximity to the enzyme surface or at the interface and in the vicinity of the enzyme active site respectively showed the lowest activity towards all catecholic substrates. The relative activity of C23OC61 mutant towards para-substituted catechols was 20-30% lower of the wild-type enzyme. In this mutant all changes: F191I, C268R, Y272H, V280A and Y293D were located within the conserved regions of C-terminal domain. From these F191I seems to have significant implications for enzyme activity. The highest activity towards different catechols was found for mutant C23OB65. R296Q mutation improved the activity of C23O especially against 4-chlorocatechol. The relative activity of above-mentioned mutant detected against this substrate was almost 6-fold higher than the wild-type enzyme. These results should facilitate future engineering of the enzyme for bioremediation.

Immobilization as a strategy for improving enzyme properties-application to oxidoreductases

The main objective of the immobilization of enzymes is to enhance the economics of biocatalytic processes. Immobilization allows one to re-use the enzyme for an extended period of time and enables easier separation of the catalyst from the product. Additionally, immobilization improves many properties of enzymes such as performance in organic solvents, pH tolerance, heat stability or the functional stability. Increasing the structural rigidity of the protein and stabilization of multimeric enzymes which prevents dissociation-related inactivation. In the last decade, several papers about immobilization methods have been published. In our work, we present a relation between the influence of immobilization on the improvement of the properties of selected oxidoreductases and their commercial value. We also present our view on the role that different immobilization methods play in the reduction of enzyme inhibition during biotechnological processes.

Protocatechuate 3,4-dioxygenase: a wide substrate specificity enzyme isolated from Stenotrophomonas maltophilia KB2 as a useful tool in aromatic acid biodegradation

Protocatechuate 3,4-dioxygenases (P34Os) catalyze the reaction of the ring cleavage of aromatic acid derivatives. It is a key reaction in many xenobiotic metabolic pathways. P34Os characterize narrow substrate specificity. This property is an unfavorable feature in the biodegradation process because one type of pollution is rarely present in the environment. Thus, the following study aimed at the characterization of a P34O from Stenotrophomonas maltophilia KB2, being able to utilize a wide spectrum of aromatic carboxylic acids. A total of 3 mM vanillic acid and 4-hydroxybenzoate were completely degraded during 8 and 4.5 h, respectively. When cells of strain KB2 were grown on 9 mM 4-hydroxybenzoate, P34O was induced. Biochemical analysis revealed that the examined enzyme was similar to other known P34Os, but showed untypical wide substrate specificity. A high activity of P34O against 2,4- and 3,5-dihydroxybenzoate was observed. As these substrates do not possess ortho configuration hydroxyl groups, it is postulated that their cleavage could be connected with their monodentate binding of substrate to the active site. Since this enzyme characterizes untypical wide substrate specificity it makes it a useful tool in applications for environmental clean-up purposes.

Cloning and mutagenesis of catechol 2,3-dioxygenase gene from the gram-positive Planococcus sp. strain S5

In this study, the catechol 2,3-dioxygenase gene that encodes a 307- amino-acid protein was cloned from Planococcus sp. S5. The protein was identified to be a member of the superfamily I, subfamily 2A of extradiol dioxygenases. In order to study residues and regions affecting the enzyme's catalytic parameters, the c23o gene was randomly mutated by error-prone PCR. The wild-type enzyme and mutants containing substitutions within either the C-terminal or both domains were functionally produced in Escherichia coli and their activity towards catechol was characterized. The C23OB65 mutant with R296Q substitution showed significant tolerance to acidic pH with an optimum at pH 5.0. In addition, it showed activity more than 1.5 as high as that of the wild type enzyme and its Km was 2.5 times lower. It also showed altered sensitivity to substrate inhibition. The results indicate that residue at position 296 plays a role in determining pH dependence of the enzyme and its activity. Lower activity toward catechol was shown for mutants C23OB58 and C23OB81. Despite lower activity, these mutants showed higher affinity to catechol and were more sensitive to substrate concentration than nonmutated enzyme.

High activity catechol 1,2-dioxygenase from Stenotrophomonas maltophilia strain KB2 as a useful tool in cis,cis-muconic acid production

This is the first report of a catechol 1,2-dioxygenase from Stenotrophomonas maltophilia strain KB2 with high activity against catechol and its methyl derivatives. This enzyme was maximally active at pH 8.0 and 40 °C and the half-life of the enzyme at this temperature was 3 h. Kinetic studies showed that the value of K m and V max was 12.8 μM and 1,218.8 U/mg of protein, respectively. During our studies on kinetic properties of the catechol 1,2-dioxygenase we observed substrate inhibition at >80 μM. The nucleotide sequence of the gene encoding the S. maltophilia strain KB2 catechol 1,2-dioxygenase has high identity with other catA genes from members of the genus Pseudomonas. The deduced 314-residue sequence of the enzyme corresponds to a protein of molecular mass 34.5 kDa. This enzyme was inhibited by competitive inhibitors (phenol derivatives) only by ca. 30 %. High tolerance against condition changes is desirable in industrial processes. Our data suggest that this enzyme could be of use as a tool in production of cis,cis-muconic acid and its derivatives.

Influence of metal ions on bioremediation activity of protocatechuate 3,4-dioxygenase from Stenotrophomonas maltophilia KB2

The aim of this paper was to describe the effect of various metal ions on the activity of protocatechuate 3,4-dioxygenase from Stenotrophomonas maltophilia KB2. We also compared activity of different dioxygenases isolated from this strain, in the presence of metal ions, after induction by various aromatic compounds. S. maltophilia KB2 degraded 13 mM 3,4-dihydroxybenzoate, 10 mM benzoic acid and 12 mM phenol within 24 h of incubation. In the presence of dihydroxybenzoate and benzoate, the activity of protocatechuate 3,4-dioxygenase and catechol 1,2-dioxygenase was observed. Although Fe(3+), Cu(2+), Zn(2+), Co(2+), Al(3+), Cd(2+), Ni(2+) and Mn(2+) ions caused 20-80 % inhibition of protocatechuate 3,4-dioxygenase activity, the above-mentioned metal ions (with the exception of Ni(2+)) inhibited catechol 1,2-dioxygenase to a lesser extent or even activate the enzyme. Retaining activity of at least one of three dioxygenases from strain KB2 in the presence of metal ions makes it an ideal bacterium for bioremediation of contaminated areas.

Characterization of catechol 2,3-dioxygenase from Planococcus sp. strain S5 induced by high phenol concentration

This study aimed at characterization of a new catechol 2,3-dioxygenase isolated from a Gram-positive bacterium able to utilize phenol as the sole carbon and energy source. Planococcus sp. strain S5 grown on 1 or 2 mM phenol showed activity of both a catechol 1,2- and catechol 2,3-dioxygenase while at a higher concentrations of phenol only catechol 2,3-dioxygenase activity was observed. The enzyme was optimally active at 60°C and pH 8.0. Kinetic studies showed that the K(m) and V(max) of the enzyme were 42.70 µM and 329.96 mU, respectively. The catechol 2,3-dioxygenase showed the following relative meta-cleavage activities for various catechols tested: catechol (100%), 3-methylcatechol (13.67%), 4-methylcatechol (106.33%) and 4-chlorocatechol (203.80%). The high reactivity of this enzyme towards 4-chlorocatechol is different from that observed for other catechol 2,3-dioxygenases. Nucleotide sequencing and homology search revealed that the gene encoding the S5 catechol 2,3-dioxygenase shared the greatest homology with the known genes encoding isoenzymes from Gram-negative Pseudomonas strains.

Characterization of catechol 2,3-dioxygenase from Planococcus sp. strain S5 induced by high phenol concentration

This study aimed at characterization of a new catechol 2,3-dioxygenase isolated from a Gram-positive bacterium able to utilize phenol as the sole carbon and energy source. Planococcus sp. strain S5 grown on 1 or 2 mM phenol showed activity of both a catechol 1,2- and catechol 2,3-dioxygenase while at a higher concentrations of phenol only catechol 2,3-dioxygenase activity was observed. The enzyme was optimally active at 60°C and pH 8.0. Kinetic studies showed that the K(m) and V(max) of the enzyme were 42.70 µM and 329.96 mU, respectively. The catechol 2,3-dioxygenase showed the following relative meta-cleavage activities for various catechols tested: catechol (100%), 3-methylcatechol (13.67%), 4-methylcatechol (106.33%) and 4-chlorocatechol (203.80%). The high reactivity of this enzyme towards 4-chlorocatechol is different from that observed for other catechol 2,3-dioxygenases. Nucleotide sequencing and homology search revealed that the gene encoding the S5 catechol 2,3-dioxygenase shared the greatest homology with the known genes encoding isoenzymes from Gram-negative Pseudomonas strains.

Modulation of FAD-dependent monooxygenase activity from aromatic compounds-degrading Stenotrophomonas maltophilia strain KB2

The purpose of this study was purification and characterization of phenol monooxygenase from Stenotrophomonas maltophilia strain KB2, enzyme that catabolises phenol and its derivatives through the initial hydroxylation to catechols. The enzyme requires NADH and FAD as a cofactors for activity, catalyses hydroxylation of a wide range of monocyclic phenols, aromatic acids and dihydroxylated derivatives of benzene except for catechol. High activity of this monooxygenase was observed in cell extract of strain KB2 grown on phenol, 2-methylphenol, 3-metylphenol or 4-methylphenol. Ionic surfactants as well as cytochrome P450 inhibitors or 1,4-dioxane, acetone and n-butyl acetate inhibited the enzyme activity, while non-ionic surfactants, chloroethane, ethylbenzene, ethyl acetate, cyclohexane, and benzene enhanced it. These results indicate that the phenol monooxygenase from Stenotrophomonas maltophilia strain KB2 holds great potential for bioremediation.

Modulation of FAD-dependent monooxygenase activity from aromatic compounds-degrading Stenotrophomonas maltophilia strain KB2

The purpose of this study was purification and characterization of phenol monooxygenase from Stenotrophomonas maltophilia strain KB2, enzyme that catabolises phenol and its derivatives through the initial hydroxylation to catechols. The enzyme requires NADH and FAD as a cofactors for activity, catalyses hydroxylation of a wide range of monocyclic phenols, aromatic acids and dihydroxylated derivatives of benzene except for catechol. High activity of this monooxygenase was observed in cell extract of strain KB2 grown on phenol, 2-methylphenol, 3-metylphenol or 4-methylphenol. Ionic surfactants as well as cytochrome P450 inhibitors or 1,4-dioxane, acetone and n-butyl acetate inhibited the enzyme activity, while non-ionic surfactants, chloroethane, ethylbenzene, ethyl acetate, cyclohexane, and benzene enhanced it. These results indicate that the phenol monooxygenase from Stenotrophomonas maltophilia strain KB2 holds great potential for bioremediation.

Induction of aromatic ring: cleavage dioxygenases in Stenotrophomonas maltophilia strain KB2 in cometabolic systems

Stenotrophomonas maltophilia KB2 is known to produce different enzymes of dioxygenase family. The aim of our studies was to determine activity of these enzymes after induction by benzoic acids in cometabolic systems with nitrophenols. We have shown that under cometabolic conditions KB2 strain degraded 0.25-0.4 mM of nitrophenols after 14 days of incubation. Simultaneously degradation of 3 mM of growth substrate during 1-3 days was observed depending on substrate as well as cometabolite used. From cometabolic systems with nitrophenols as cometabolites and 3,4-dihydroxybenzoate as a growth substrate, dioxygenases with the highest activity of protocatechuate 3,4-dioxygenase were isolated. Activity of catechol 1,2- dioxygenase and protocatechuate 4,5-dioxygenase was not observed. Catechol 2,3-dioxygenase was active only in cultures with 4-nitrophenol. Ability of KB2 strain to induce and synthesize various dioxygenases depending on substrate present in medium makes this strain useful in bioremediation of sites contaminated with different aromatic compounds.