Multiple epidemic waves as the outcome of stochastic SIR epidemics with behavioral responses: a hybrid modeling approach.

In the behavioral epidemiology (BE) of infectious diseases, little theoretical effort seems to have been devoted to understand the possible effects of individuals' behavioral responses during an epidemic outbreak in small populations. To fill this gap, here we first build general, behavior implicit, SIR epidemic models including behavioral responses and set them within the framework of nonlinear feedback control theory. Second, we provide a thorough investigation of the effects of different types of agents' behavioral responses for the dynamics of hybrid stochastic SIR outbreak models. In the proposed model, the stochastic discrete dynamics of infection spread is combined with a continuous model describing the agents' delayed behavioral response. The delay reflects the memory mechanisms with which individuals enact protective behavior based on past data on the epidemic course. This results in a stochastic hybrid system with time-varying transition probabilities. To simulate such system, we extend Gillespie's classic stochastic simulation algorithm by developing analytical formulas valid for our classes of models. The algorithm is used to simulate a number of stochastic behavioral models and to classify the effects of different types of agents' behavioral responses. In particular this work focuses on the effects of the structure of the response function and of the form of the temporal distribution of such response. Among the various results, we stress the appearance of multiple, stochastic epidemic waves triggered by the delayed behavioral response of individuals.

Versatile Applications of Cyanobacteria in Biotechnology.

Cyanobacteria are blue-green Gram-negative and photosynthetic bacteria which are seen as one of the most morphologically numerous groups of prokaryotes. Because of their ability to fix gaseous nitrogen and carbon dioxide to organic materials, they are known to play important roles in the universal nutrient cycle. Cyanobacteria has emerged as one of the promising resources to combat the issues of global warming, disease outbreaks, nutrition insecurity, energy crises as well as persistent daily human population increases. Cyanobacteria possess significant levels of macro and micronutrient substances which facilitate the versatile popularity to be utilized as human food and protein supplements in many countries such as Asia. Cyanobacteria has been employed as a complementary dietary constituent of feed for poultry and as vitamin and protein supplement in aquatic lives. They are effectively used to deal with numerous tasks in various fields of biotechnology, such as agricultural (including aquaculture), industrial (food and dairy products), environmental (pollution control), biofuel (bioenergy) and pharmaceutical biotechnology (such as antimicrobial, anti-inflammatory, immunosuppressant, anticoagulant and antitumor); recently, the growing interest of applying them as biocatalysts has been observed as well. Cyanobacteria are known to generate a numerous variety of bioactive compounds. However, the versatile potential applications of cyanobacteria in biotechnology could be their significant growth rate and survival in severe environmental conditions due to their distinct and unique metabolic pathways as well as active defensive mechanisms. In this review, we elaborated on the versatile cyanobacteria applications in different areas of biotechnology. We also emphasized the factors that could impede the implementation to cyanobacteria applications in biotechnology and the execution of strategies to enhance their effective applications.

Phosphonates enantiomers receiving with fungal enzymatic systems.

BACKGROUND: Phosphonates derivatives are in the area of interests because of their unique chemical-physical features. These compounds manifest variety of biological interactions within the sensitive living cells, including impact on particular enzymes activities. Biological "cause and effect" interactions are based upon the specific matching between the structures and/or compounds and this is usually the result of proper optical configurations of particular chiral moieties. Presented research is targeted to the phosphonates with the heteroatom incorporated in their side functionalities. Such molecules are described as possible substrates of bioconversion for the first time lately and this field is not fully explored. RESULTS: Presented research is targeted to the synthesis of pure hetero-phosphonates enantiomers. The catalytic activity of yeasts and moulds were tested towards two substrates: the thienyl and imidazole phosphonates to resolve their racemic mixtures. Biotransformations conditions differed depending on the outcome, what included changing of following parameters: type of cultivation media, bioprocess duration (24-72 h), additional biocatalyst pre-treatment (24-48 h starvation step triggering the secondary metabolism). (S)-1-amino-1-(3-thienyl)methylphosphonate was produced with the assistance of R. mucilaginosa or A. niger (e.e. up to 98% and yield up to 100%), starting from the 3 mM of substrate racemic mixture. Bioconversion of racemic mixture of 3 mM of (1-amino-1-(4-imidazole)methylphosphonic acid) resulted in the synthesis of S-isomer (up to 95% of e.e.; 100% of yield) with assistance of R. mucilaginosa. 24 h biotransformation was conducted with biomass preincubated under 48-hour starvation conditions. Such stereoselective resolution of the racemic mixtures of substrates undergoes under kinetic control with the conversion of one from the enantiomers. CONCLUSIONS: Composition of the culturing media and pre-incubation in conditions of nutrient deficiency were significant factors influencing the results of kinetic resolution of racemic mixtures of phosphonic substrates and influencing the economic side of the biocatalysis e.g. by determining the duration of whole biocatalytic process.

D-dimer concentrations in acute urticaria in children.

INTRODUCTION: Urticaria is a clinical entity presenting as wheals, angioedema, or both simultaneously. Elevated D-dimer levels were reported in the course of chronic spontaneous urticaria. Data regarding D-dimer levels in acute urticaria in children are limited. OBJECTIVES: To assess potential associations between duration of glucocorticosteroid (GCS) therapy and D-dimer concentrations in children with acute urticaria. PATIENTS, MATERIALS, AND METHODS: Hospital records of 106 children (59 females), aged 5.57 ± 4.91 years, hospitalized in 2014-2018 were analyzed retrospectively. The study group consisted of pediatric patients admitted to the hospital due to severe acute urticaria resistant to antihistaminic treatment that was ordered in the ambulatory care (out-patient clinic). Patients were divided into subgroups: no GCS treatment, short-duration treatment (up to 5 days) and long-duration treatment (6 and more days) GCS treatment. Simultaneously, patients received antihistaminic drugs. D-dimer level and other inflammatory factors such as white blood cell (WBC) count, platelet (PLT) count, and C-reactive protein (CRP) in each group were analyzed. RESULTS: The D-dimer level was elevated in 51% of cases. In the subgroup with longer GCS treatment, D-dimer concentration was significantly higher in comparison to patients with a shorter GCS course. There were no differences in the distribution of CRP, PLT, and WBC concentrations between these subgroups. CONCLUSIONS: In the studied group of children, there was a tendency for higher D-dimer levels in patients, who required a longer GCS treatment. This finding is hypothesis-generating and requires further investigation to confirm if D-dimers can be used as a prognostic factor in acute urticaria in children.

D-dimer concentrations in acute urticaria in children

INTRODUCTION: Urticaria is a clinical entity presenting as wheals, angioedema, or both simultaneously. Elevated D-dimer levels were reported in the course of chronic spontaneous urti-caria. Data regarding D-dimer levels in acute urticaria in children are limited. OBJECTIVES: To assess potential associations between duration of glucocorticosteroid (GCS) therapy and D-dimer concentrations in children with acute urticaria. Patients, materials, and methods: Hospital records of 106 children (59 females), aged 5.57 ± 4.91 years, hospitalized in 2014-2018 were analyzed retrospectively. The study group consisted of pediatric patients admitted to the hospital due to severe acute urticaria resistant to anti-histaminic treatment that was ordered in the ambulatory care (out-patient clinic). Patients were divided into subgroups: no GCS treatment, short-duration treatment (up to 5 days) and long-duration treatment (6 and more days) GCS treatment. Simultaneously, patients received antihistaminic drugs. D-dimer level and other inflammatory factors such as white blood cell (WBC) count, platelet (PLT) count, and C-reactive protein (CRP) in each group were analyzed. RESULTS: The D-dimer level was elevated in 51% of cases. In the subgroup with longer GCS treatment, D-dimer concentration was significantly higher in comparison to patients with a shorter GCS course. There were no differences in the distribution of CRP, PLT, and WBC concentrations between these subgroups. CONCLUSIONS: In the studied group of children, there was a tendency for higher D-dimer levels in patients, who required a longer GCS treatment. This finding is hypothesis-generating and requires further investigation to confirm if D-dimers can be used as a prognostic factor in acute urticaria in children

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Piece-wise linear models of biological systems-Application, analysis, and comparison with nonlinear models using the example of the p53 regulatory module.

In this paper, we propose to use a linear system with switching methodology for description and analysis of complex biological systems. We show advantages of the proposed approach over the one usually used, which is based on ODE. We propose the detailed methodology of a full analysis of developed models, including analytical determination of the location and type of equilibrium points, finding an analytical solution, stability and bifurcation analysis. We illustrate the above with the example of the well-known p53 signalling pathway comparing the results with the results of a nonlinear, ODE-based version of the proposed model. The complex methodology proposed by us, especially due to the definition of model structure, which is easy to understand for biologists and medics, may be a bridge for closer cooperation between them and engineers in the future.

(S)-Thienyl and (R)-Pirydyl phosphonate Derivatives Synthesized by Stereoselective Resolution of Their Racemic Mixtures With Rhodotorula mucilaginosa (DSM 70403) - Scaling Approaches.

Rhodotorula mucilaginosa was successfully applied as a biocatalyst for the enantioselective resolution of the racemic mixtures of heteroatom phosphonates derivatives, resulting in receiving the following enantiomers: (S)-1-amino-1(2-thienyl)methylphosphonic acid (Product 1) and (R)-1-amino-1-(3'pirydyl) methylphosphonic acid (Product 2). Biological synthesis of both products is reported for the first time. Pure (S)-1-amino-1-(2-thienyl)methylphosphonic acid (Product 1) was isolated with a conversion degree of 50% after 24 h of biotransformation was conducted on a laboratory scale under moderate conditions (1.55 mM of substrate 1, 100 mL of distilled water, 135 rpm, 25°C; Method A). The scale was enlarged to semi-preparative one, using a simplified flow-reactor (Method C; 3.10 mM of substrate 1) and immobilized biocatalyst. The product was isolated with a conversion degree of 50% just after 4 h of biotransformation. Amino-1-(3'pirydyl)methylphosphonic acid (Substrate 2) was converted according to novel procedure, by the immobilized biocatalyst - Rhodotorula mucilaginosa. The process was carried out under moderate conditions (3.19 mM - substrate 2 solution; Method C1) with the application of a simplified flow reactor system, packed with the yeasts biomass entrapped in 4% agar-agar solution. Pure (R)-amino-1-(3'pirydyl)methylphosphonic (50% of conversion degree) was received within only 48 h.

Biogenic synthesis of silica nanoparticles from corn cobs husks. Dependence of the productivity on the method of raw material processing.

Corn processing generates thousands of tons of cob husks, which still contains many valuable elements. To make the most of these wastes, they are applied as substrates for biotransformation's procedures. This approach allowed converting or releasing, the elements deposited in the plant material and obtaining valuable products. Thus bioconversion of corn cob husks (CCH) using a fungus of the Fusarium culmorum genus resulted in obtaining silica nanoparticles of defined size and morphology. SEM analysis excluded their presence on the surface of the substrate. FTIR confirmed the presence of siloxane bonds and O-Si-O bonds in post-biotransformation fluid. Using the Heteropoly Blue Method, it was checked that the highest concentration of silica during 16-day biotransformation falls on the 7th day of the process, in which both the substrate sterilization and the process of the biocatalyst starvation were of key importance. Using the STEM and EDX analysis, it was proved that the obtained nanoparticles with a spherical form are structured and their dimensions are ~40 and ~70 nm. ICP-OES proved that the overall process efficiency was 47%. Such nanoparticles can be successfully used in the medical industry.

Carbon-Phosphorus Lyase-the State of the Art.

Organophosphonates are molecules that contain a very chemically stable carbon-phosphorus (C-P) bond. Microorganisms can utilize phosphonates as potential source of crucial elements for their growth, as developed several pathways to metabolize these compounds. One among these pathways is catalyzed by C-P lyase complex, which has a broad substrate specifity; therefore, it has a wide application in degradation of herbicides deposited in the environment, such as glyphosate. This multi-enzyme system accurately recognized in Escherichia coli and genetic studies have demonstrated that it is encoded by phn operon containing 14 genes (phnC-phnP). The phn operon is a member of the Pho regulon induced by phosphate starvation. Ability to degradation of phosphonates is also found in other microorganisms, especially soil and marine bacteria, that have homologous genes to those in E. coli. Despite the existence of differences in structure and composition of phn gene cluster, each of these strains contains phnGHIJKLM genes necessary in the C-P bond cleavage mechanism. The review provides a detailed description and summary of achievements on the C-P lyase enzymatic pathway over the last 50 years.

N-phosphonomethylglycine utilization by the psychrotolerant yeast Solicoccozyma terricola M 3.1.4.

Solicoccozyma terricola M 3.1.4., the yeast strain isolated from soil sample from blueberry cultivation in Miedzyrzec Podlaski in Poland, is capable to split of phosphorus to nitrogen and nitrogen to carbon bonds in N-phosphonomethylglycine (PMG, glyphosate). The biodegradation process proceeds in the phosphate-independent manner. It is the first example of a psychrotolerant yeast strain able to degrade PMG via CN bond cleavage accompanied by AMPA formation and not like in most microorganisms via CP bond disruption followed by the sarcosine pathway. Glyphosate oxidoreductase (GOX) type activity was detected in cell-free extracts prepared from S. terricola M 3.1.4. pregrown on 4 mM PMG as a sole phosphorus and nitrogen source in cultivation medium.

Reductive capabilities of different cyanobacterial strains towards acetophenone as a model substrate - Prospect of applications for chiral building blocks synthesis.

Bioreductive capabilities of four morphologically different strains of cyanobacteria have been assessed in this work. Arthrospira maxima, Leptolyngbya foveolarum, Nodularia sphaerocarpa and Synechococcus bigranulatus were applied as catalysts for the reduction of acetophenone to the corresponding chiral phenylethyl alcohol. The process was modified regarding substrate concentration, duration of pre-cultivation period, duration of biotransformation, light regime and glucose addition to the culture media. Obtained results clearly showed that cyanobacteria were active towards acetophenone what resulted in the substrate reduction to (S)-1-phenylethanol with high enantiomeric excess. The reaction efficiency increased with the biotransformation time, but the higher concentration of substrate limited the process yield. Also, all tested strains performed reaction with the highest efficacy under continuous light regime. The most active strains - N. sphaerocarpa and S. bigranulatus carried out the conversion of 1 mM acetophenone with high efficiency of respectively 97.6% and 96.2% after 13 days of biotransformation. A. maxima reached 45.8% of conversion after 13 days of biotransformation whereas L. foveolarum did not exceed 20%. The enantiomeric excesses were respectively 98.8%- A. maxima, 91.7%- L. foveolarum, 72.6%- S. bigranulatus and N. sphaerocarpa 16.2%.

First biological conversion of chiral heterophosphonate derivative - Scaling and paths of conversion discussion.

Presented work describes the first approach for the biocatalytic resolution of racemic mixtures of heterophosphonate derivative. Penicillium funiculosum and Rhodotorula mucilaginosa were successfully applied for the biological conversion of racemic mixture of 1-amino-1-(3'-pyridyl)methylphosphonic acid 3. Both microorganisms carried out the kinetically driven process leading to conversion of one from the substrate enantiomers, leaving the second one unreacted. Application of R. mucilaginosa allowed obtaining pure enantiomer of the substrate (yield 100%, e.e 100% - unreacted isomer) after 24 h of biotransformation of 3 in the laboratory scale process (Method E), applying biocatalyst pre-treatment step - 24 h of starvation. In case of other biocatalyst, application of whole cells of P. funiculosum in laboratory scale process, also resulted in conversion of the racemic mixture of substrate 3via oxidative deamination into ketone derivative, which was then bioreduced (second step of the process) into 1-hydroxy-1-(3'-pyridyl)methylphosphonic acid 4. This time two products were isolated: unreacted substrate and hydroxy compound 4. Conversion degree ranged from 30% (standard procedure, method A) to even 70% (with extra addition of sodium pyruvate - method B2). However, in this case, bioconversion was not enantioselective - products: amino- and hydroxyderivative were obtained as racemic mixtures. Both biocatalysts were also tested towards the scaling so other biocatalytic procedures were introduced - with immobilized fungal mycelium. In case of Rhodotorula mucilaginosa this approach failed (data not shown) but Penicillium funiculosum turned out to be active and also selective. Thus, application of this biocatalyst in the half-preparative scale, continuous-flow bioprocess (Method C2) resulted in the obtaining of pure S-3 (100% e.e.) isomer with the 100% of conversion degree, without any side products. Recorded NMR spectra allowed confirming the reaction progress and its selectivity and also postulating possible mechanism of conversion.

Nanosilica synthesis mediated by Aspergillus parasiticus strain.

Rice husks (RHs) are plant waste materials abundant in phytoliths silica bodies. These were used as starting material for fungal-mediated biotransformation leading to the synthesis of a high-value added product. A strain of Aspergillus parasiticus was capable of transforming the amorphous silica conglomerates into structured nanoparticles (NPs) in the process of RHs biotransformation. Silica NPs were produced extracellularly and their size ranged from 3 to 400 nm depending on the biotransformation conditions and the post-biotransformation supernatant processing. To characterize the NP's structure and dimension, SEM, STEM, EDX and FTIR technics were applied. These demonstrated and confirmed that pyramid (400 nm), cubical (85 nm) and spherical (3 nm and 24 ± 8 nm) forms of silica NPs were obtained.

Fungal synthesis of chiral phosphonic synthetic platform - Scope and limitations of the method.

Chiral hydroxyphosphonates due to their wide range of biological properties are industrially important chemicals. Chemical synthesis of their optical isomers is expensive, time consuming and not friendly to the environment, so biotransformations are under consideration. Among others, these compounds act as enzymes inhibitors. This makes the bioconversions of phosphonates, especially scaling experiments, hard to perform. Biocatalysis is one of the methods that can be applied in synthesis of optically pure compounds. To increase the efficiency of the process with whole cell biocatalysts, it is essential to ensure optimal reaction conditions that minimize cellular stress and can enhance the metabolic activity of cells. The present investigation focuses on the scaling up of the kinetic resolution of racemic mixture of 2-butyryloxy-2-(ethoxy-P-phenylphosphinyl)acetic acid, applying free and immobilized form of the fungal biocatalysts and two operation systems: shake flask and recirculated fixed-bed batch reactor. Protocols of effective mycelium immobilization on polyurethane foams were set for T. purpurogenus IAFB 2512, F. oxysporum, P. commune. The best results of biotransformation were obtained with the immobilized P. commune in the column recirculated fixed-bed batch reactor. The conversion reaches 56% (maximal for the kinetic process) and the enantiomeric enrichment of the isomers mixture ranges between 82 and 93% (93% for ester of RP,R conformation). All biocatalysts exhibit SP-preference toward tested compound, what is essential because of importance of the phosphorus atom chirality for its biological activity.

Influence of parameter perturbations on the reachability of therapeutic target in systems with switchings.

BACKGROUND: Examination of physiological processes and the influences of the drugs on them can be efficiently supported by mathematical modeling. One of the biggest problems is related to the exact fitting of the parameters of a model. Conditions inside the organism change dynamically, so the rates of processes are very difficult to estimate. Perturbations in the model parameters influence the steady state so a desired therapeutic goal may not be reached. Here we investigate the effect of parameter deviation on the steady state in three simple models of the influence of a therapeutic drug on its target protein. Two types of changes in the model parameters are taken into account: small perturbations in the system parameter values, and changes in the switching time of a specific parameter. Additionally, we examine the systems response in case of a drug concentration decreasing with time. RESULTS: The models which we analyze are simplified, because we want to avoid influences of complex dynamics on the results. A system with a negative feedback loop is the most robust and the most rapid, so it requires the largest drug dose but the effects are observed very quickly. On the other hand a system with positive feedback is very sensitive to changes, so small drug doses are sufficient to reach a therapeutic target. In systems without feedback or with positive feedback, perturbations in the model parameters have a bigger influence on the reachability of the therapeutic target than in systems with negative feedback. Drug degradation or inactivation in biological systems enforces multiple drug applications to maintain the level of a drug's target under the desired threshold. The frequency of drug application should be fitted to the system dynamics, because the response velocity is tightly related to the therapeutic effectiveness and the time for achieving the goal. CONCLUSIONS: Systems with different types of regulation vary in their dynamics and characteristic features. Depending on the feedback loop, different types of therapy may be the most appropriate, and deviations in the model parameters have different influences on the reachability of the therapeutic target.

Biodiversity in targeted metabolomics analysis of filamentous fungal pathogens by 1H NMR-based studies.

The taxonomical classification among fungi kingdom in the last decades was evolved. In this work the targeted metabolomics study based on 1H NMR spectroscopy combined with chemometrics tools was reported to be useful for differentiation of three model of fungal strains, which represent various genus of Ascomycota (Aspergillus pallidofulvus, Fusarium oxysporum, Geotrichum candidum) were selected in order to perform metabolomics studies. Each tested species, revealed specific metabolic profile of primary endo-metabolites. The species of A. pallidofulvus is represented by the highest concentration of glycerol, glucitol and Unk5. While, F. oxysporum species is characterised by increased level of propylene glycol, ethanol, 4-aminobutyrate, succinate, xylose, Unk1 and Unk4. In G. candidum, 3-methyl-2-oxovalerate, glutamate, pyruvate, glutamine and citrate were elevated. Additionally, a detailed analysis of metabolic changes among A. pallidofulvus, F. oxysporum and G. candidum showed that A. pallidofulvus seems to be the most pathogenic fungi. The obtained results demonstrated that targeted metabolomics analysis could be utilized in the future as a supporting taxonomical tool for currently methods.

Metabolomics analysis of fungal biofilm development and of arachidonic acid-based quorum sensing mechanism.

The infections caused by filamentous fungi are becoming worldwide problem of healthcare systems due to increasing drug-resistance of this microorganism and increasing number of immunocompromised nosocomial patients. These infections are related with Aspergillus ability to form sessile communities referred to as the biofilms. The small compounds known as quorum sensing (QS) molecules allow this microorganism to coordinate all processes taking place during biofilm formation and maturation. In the study presented, the HRMAS 1 H NMR metabolomic approach was applied to define composition of extra and intracellular metabolites produced by biofilmic and planktonic (aka free-swimming) cultures of this microorganism and to evaluate impact of quorum sensing molecule, arachidonic acid (AA) on biofilm formation. The Scanning Electron Microscopy was used to confirm Aspergillus ability to form biofilm in vitro, while multivariate and univariate data analysis was applied to analyze data obtained. The Aspergillus strain was able to form strong biofilm structures in vitro. The statistical analysis revealed significant changes of metabolite production depending on Aspergillus culture type (biofilm vs. plankton), time and presence of QS molecules. The data obtained, if developed, might be used in future NMR diagnostics as markers of Aspergillus biofilm-related infections and lead to shorten time between pathogen identification and introduction of treatment.

Lipases and whole cell biotransformations of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid and its ester.

A wide spectrum of commercially available lipases and microbial whole cells catalysts were tested for biotransformations of 2-hydroxy-2-(ethoxyphenylphosphinyl)acetic acid 1 and its butyryl ester. The best results were achieved for biocatalytic hydrolysis of ester: 2-butyryloxy-2-(ethoxyphenylphosphinyl)acetic acid 2 performed by lipase from Candida cylindracea, what gave optically active products with 85% enantiomeric excess, 50% conversion degree and enantioselectivity 32.9 for one pair of enantiomers. Also enzymatic systems of Penicillium minioluteum and Fusarium oxysporum were able to hydrolyze tested compound with high enantiomeric excess (68-93% ee), enantioselectivity (44 for one pair of enantiomers) and conversion degree about 50-55%. Enzymatic acylation of hydroxyphosphinate was successful in case when porcine pancreas lipase was used. After 4days of biotransformation the conversion reaches 45% but the enantiomeric enrichment of the isomers mixture do not exceed 43%. Obtained chiral compounds are valuable derivatizing agents for spectroscopic (NMR) evaluation of enantiomeric excess for particular compounds (e.g. amino acids).

Fungal platform for direct chiral phosphonic building blocks production. Closer look on conversion pathway.

The application of Rhodospirillum toruloides strain allowed resolving the chemically synthesized racemic mixtures of following chiral aminophosphonic acids: 1-aminoethylphosphonic acid (1), 1-amino-1-iso-propyl-1-phosphonic acid (2), 1-amino-1-phenylmethylphosphonic acid (4) and 1-amino-2-phenylethylphosphonic acid (3). The applied protocols resulted in obtaining pure (R)-1-aminoethylphosphonic acid (100 % of e.e.) and enantiomerically enriched mixtures of other phosphonates (73 % e.e. of (S)-1-amino-1-phenylmethylphosphonic acid, 51 % e.e. of (R)-1-amino-2-phenylethylphosphonic acid and 40 % e.e. of (S)-1-amino-2-methylpropylphosphonic acid). Products are valuable chiral building blocks and serve as aminophosphonic acids platform for further applications. Performed experiments allowed to define the path of xenobiotics bioconversion.