Microbiological degradation of pesticides in yard waste composting.

Changes in public opinion and legislation have led to the general recognition that solid waste treatment practices must be changed. Solid-waste disposal by landfill is becoming increasingly expensive and regulated and no longer represents a long-term option in view of limited land space and environmental problems. Yard waste, a significant component of municipal solid waste, has previously not been separated from the municipal solid-waste stream. The treatment of municipal solid waste including yard waste must urgently be addressed because disposal via landfill will be prohibited by legislation. Separation of yard waste from municipal solid waste will be mandated in many localities, thus stressing the importance of scrutinizing current composting practices in treating grass clippings, leaves, and other yard residues. Yard waste poses a potential environmental health problem as a result of the widespread use of pesticides in lawn and tree care and the persistence of the residues of these chemicals in plant tissue. Yard waste containing pesticides may present a problem due to the recalcitrant and toxic nature of the pesticide molecules. Current composting processes are based on various modifications of either window systems or in-vessel systems. Both types of processes are ultimately dependent on microbial bioconversions of organic material to innocuous end products. The critical stage of the composting process is the thermophilic phase. The fate and mechanism of removal of pesticides in composting processes is largely unknown and in need of comprehensive analysis.     

Microbiological degradation of the herbicide dicamba

Summary Pseudomonas paucimobilis was isolated from a consortium which was capable of degrading dicamba (3,6-dichloro-2-methoxybenzoic acid) as the sole source of carbon. The degradation of dicamba byP. paucimobilis and the consortium was examined over a range of substrate concentration, temperature, and pH. In the concentration range of 100–2000 mg dicamba L^–1 (0.5–9.0 mM), the degradation was accompanied by a stoichiometric release of 2 mol of Cl^– per mol of dicamba degraded. The cultures had an optimum pH 6.5–7.0 for dicamba degradation. Growth studies at 10°C, 20°C, and 30°C yielded activation energy values in the range of 19–36 kcal mol^–1 and an average Q₁₀ value of 4.0. Compared with the pure cultureP. paucimobilis, the consortium was more active at the lower temperature.     

Microbiological degradation of bile acids. The preparation of some hypothetical metabolites involved in cholic acid degradation.

1. To identify the intermediates involved in the degradation of cholic acid, the further degradation of (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1beta-yl]valeric acid (IVa) by Arthrobacter simplex was attempted. The organism could not utilize this acid but some hypothetical intermediate metabolities of compound (IVa) were prepared for later use as reference compounds. 2. The nor homologue (IIIa) and the dinor homologue (IIIb) of compound (IVa) were prepared by exposure of 3-oxo-24-nor-5beta-cholan-23-oic acid (I) and (20S)-3beta-hydroxy-5-pregnene-20-carboxylic acid (II) to A. simplex respectively. These compounds correspond to the respective metabolites produced by the shortening of the valeric acid side chain of compound (IVa) in a manner analogous to the conventional fatty acid alpha- and beta-oxidation mechanisms. Their structures were confirmed by partial synthesis. 3. The following authentic samples of reduction products of the oxodicarboxylic acids (IIIa), (IIIb) and (IVa) were also synthesized as hypothetical metabolities: (4R)-4-[3aalpha-hexahydro-5alpha-hydroxy-4alpha-(3-hydroxypropyl)-7abeta-methylindan-1beta-yl]valeric acid (Vb) and its nor homologue (VIIa) and dinor homologue (IXa);(4R)-4-[3Aaalpha-hexahydro-5alpha-hydroxy-4alpha-(3-hydroxypropyl)-7abeta-methylindan-1beta-yl]-pentan-1-ol (Vc); and their respective 5beta epimers (Ve), (VIIc), (IXc) and (Vf). 4. In connexion with the non-utilization of compound (IVa) by A. simplex, the possibility that not all the metabolites formed from cholic acid by a certain micro-organism can be utilized by the same organism is considered.     

Microbiological degradation of bile acids. The preparation of hexahydroindane derivatives as substrates for studying cholic acid degradation.

Relatively large amounts of 3-(3aalpha-hexahydro-7abeta-methyl-1,5-dioxoindan-4alpha-yl)propionic acid (IIb), which is believed to be one of the intermediates involved in the degradation of cholic acid (I), were needed to identify is further degradation products. A simple method for the preparation of this compound was then investigated. Arthrobacter simplex could degrade-3-oxoandrost-4-ene-17beta-carboxylic acid (IIIa) to 3-(1beta-carboxy-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-4alpha-yl)propionic acid (IVa) in good yield, the structure of which was established by partial synthesis. It was therefore expected that, if a similar degradation by this organism occurred with 17alpha-hydroxy-3-oxoandrost-4-ene-17beta-carboxylic acid (IIIb), which is easily obtained by chemical oxidation of commercially availabe 17alpha-hydroxydeoxycorticosterone, the resulting product, 3-(1beta-carboxy-3aalpha-hexahydro-1alpha-hydroxy-7abeta-methyl-5-oxoindan-4alpha-yl)propionic acid (IVb), could be readily converted chemically into the required dioxocarboxylic acid, (IIb). Exposure of compound (IIIb) to A. simplex produced, as expected, compound (IVb) which was then oxidized with NaBiO3 to give a reasonable yield of compound (IIb).     

Microbiological degradation of asymmetrical dimethylhydrazine--a toxic component of rocket fuel

A possibility of microbiological cleaning of water and soil polluted with asymmetric dimethylhydrazine (ADMH), a highly toxic rocket fuel ingredient (RFI), was studied. Several isolates (bacteria, yeast, and micromycetes) capable of utilizing ADMH as the only source of nitrogen, carbon, and energy were isolated from RFI-polluted tundra soil. Acceleration of RFI biodegradation was achieved using a biosorbent that involved cells of the degrader strain immobilized on granulated activated carbon. Biological testing in Escherichia coli and cereals (wheat and barley) demonstrated that biodegradation significantly decreased the integral toxicity of solutions containing ADMH, suggesting its utility for microbiological cleaning of polluted territories.     

Microbiological degradation of bile acids. Nitrogenous hexahydroindane derivatives formed from cholic acid by Streptomyces rubescens.

The metabolism of cholic acid (I) by Streptomyces rubescens was investigated. This organism effected ring A cleavage, side-chain shortening and amide bond formation and gave the following metabolites: (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1 beta-yl]valeric acid (IIa) and its mono-amide (valeramide) (IIb); and 2,3,4,6, 6abeta,7,8,9,9aalpha,9bbeta-decahydro-6abeta-methyl-1H-cyclopenta[f]quinoline-3,7-dione(IIIe)and its homologues with the beta-oriented side chains, valeric acid, valeramide, butanone and propionic acid, in the place of the oxo group at C-7, i.e.compounds (IIIa), (IIIb), (IIIc) and (IIId) respectively. All the nitrogenous metabolites were new compounds, and their structures were established by partial synthesis except for the metabolite (IIIc). The mechanism of formation of these metabolites is considered. A degradative pathway of cholic acid (I) into the metabolites is also tentatively proposed.     

Microbiological degradation of bile acids, further degradation of a cholic acid metabolite containing the hexahydroindane nucleus by Corynebacterium equi.

1. The further degradation of a cholic acid (I) metabolite, (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1beta-yl]valeric acid (IIa), by Corynebacterium equi was investigated. This organism effected ring-opening and gave (4R)-4-[2alpha-(2-carboxyethyl)-3beta-(3-carboxypropionyl)-2beta-methylcyclopent-1beta-yl]valeric acid (VI). The new metabolite was isolated as its trimethyl ester and identified by partical synthesis. It was not utilized by C. equi. 2. (4R)-4[4alpha-(2-Carboxyethyl)-3aalpha-decahydro-8abeta-methyl5-oxa-6-oxoazulen-1beta-yl]valeric acid (IVa), which is a hypothetical initial oxidation product in the above degradation, was not converted by C. equi into the expected metabolite (VI), but into 3 - [2beta - [(2S) - tetrahydro - 5 - oxofur - 2 - yl] - 1beta - methyl - 5 - oxocyclopent - 1alpha - yl]-propionic acid (VIII), the structure of which was established by partial synthesis. 3. Both the possible precursors of the metabolite (VI), an isomer of the epsilon-lactone (IVa), the gamma-lactone (XIa), and the open form of these lactones, the hydroxytricarboxylic acid (V), were also not utilized by C. equi. 4. Under some incubation conditions, C. equi also converted compound (IIa) and 3-(3aalpha-hexahydro-7abeta-methyl-1,5-dioxoindan-4alpha-yl)propionic acid (IIb) into 5-methyl-4-oxo-octane-1,8-dioic acid (III), (4R)-4-(2,3,4,6,6abeta,7,8,9,9aalpha,9bbeta-decahydro-6abeta-methyl-3-oxo-1H-cyclopenta[f]quinolin-7beta-yl)valeric acid (VII) and probably a monohydroxy derivative of compound (IIa) and compound (III), respectively. 5. The possibility that an initial step in the degradation of compound (IIa) by C. equi is oxygenation of the Baeyer-Villiger type, yielding compound (IVa), is discussed. Metabolic pathways of compound (IIa) to compounds (III), (VI), (VII) and (VIII) are also considered.     

Microbiological hydroxylation of norethisterone.

Hydroxylation of norethisterone by a large number of fungi has been investigated. 1alpha-Hydroxy-, 6beta-hydroxy-, 10beta-hydroxy-, 10beta,11beta-dihydroxy-15alpha-and 15beta-hydroxy-derivatives were formed from norethisterone. The microbiological dehydrogenation of 10beta-hydroxy-norethisterone resulting in 10beta,17beta-dihydroxy-17-ethynyl-1,4-estradien-3-one was also observed. The structure of transformation products was established by chemical and spectroscopical methods.     

Microbiological degradation of bile acids. The conjugation of a certain cholic acid metabolite with amino acids in Corynebacterium equi.

1. (4R)-4[4alpha-(2-Carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1beta-yl]valeric acid (II) could not be utilized by Arthrobacter simplex, even though the acid was one of the metabolites formed from cholic acid (I) by this organism. Therefore the further degradation of the acid (II) by Corynebacterium equi was investigated to identify the intermediates involved in the cholic acid degradation. 2. The organism, cultured in a medium containing the acid (II) as the sole source of carbon, produced unexpected metabolites, the conjugates of this original acid (II) with amino acids or their derivatives, although the yield was very low. These new metabolites were isolated and identified by chemical synthesis as the Na-((4R)-4-[4alpha-(2-carboxyethyl)-3a alpha-hexahydro-7a beta-methyl-5-oxoindan-1 beta-yl]-valeryl) derivatives of L-alanine, glutamic acid, O-acetylhomoserine and glutamine, i.e. compounds (IIIa), (IIIb), (IIId) respectively. 3. The possibility that the bacterial synthetic reaction observed in the acid (II) metabolism with C. equi is analogous to peptide conjugation known in both animals and higher plants is discussed. A possible mechanism for this bacterial conjugation is also considered.     

Microbiological Transformations 15. The Enantioselective Microbiological Baeyer-Villiger Oxidation of Alpha-Substituted Cyclopentanones

Two strains of Acinetobacteria have been studied in order to perform enantioselective Baeyer-Villiger-type oxidations of racemic alpha-substituted cyclopentanones. This allows a one-step synthesis of various delta-lactones showing optical purities up to 97%, using whole-cell procedures. Tetraethylpyrophosphate and 1,2-cyclohexanediol have been used in order to enhance the yields of the bioconversion. The obtained (S)-lactones are of high interest as readily accessible chirons as well as to the flavor industry.