Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2001-05-23
2002-11-05
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S612000, C210S615000, C210S903000, C210S909000, C435S254500, C435S262500, C435S933000, C405S128150
Reexamination Certificate
active
06475387
ABSTRACT:
DISCLOSURE
1. Field of the Invention
The present invention relates to a microbiological process for eliminating a nitroaromatic compound present in a solution or in a soil, and to a microorganism strain capable of mineralising said nitroaromatic compound.
The method according to the invention is for example very useful for treating a solution, such as an industrial effluent, or a soil, polluted with a nitroaromatic compound, for example with dinitrotoluene (DNT) or trinitrotoluene (TNT).
2. State of the Related Art
Different nitroaromatic compound degradation processes have been studied in the prior art. These processes are essentially either biological or chemical.
For example, in 1998, KALAFUT et al. studied the transformation of TNT by three aerobic bacteria:
Pseudomonas aeruginosa
, Bacillus sp. and Staphylococcus sp. It demonstrated that these three strains transformed TNT but could not use it as the only source of carbon or nitrogen. The study is reported in the document KALAFUT, T et al., “Biotransformation patterns of 2,4,6-trinitrotoluene by aerobic bacteria”, Cur. Microbiol., 1998, 36, 45-54.
In 1998, BOOPATHY et al. developed a laboratory-scale aerobic/anoxic bioreactor to decontaminate a soil contaminated with TNT. This method may be carried out in a batch or semi-continuous system. Batch treatment enables TNT transformation, but some metabolites accumulate. However, in semi-continuous mode (regular change of 10% of soil), TNT (8 g/kg of soil) is completely broken down. The balance, after a 14-day incubation period, indicates that only 23% of the TNT was mineralised, 27% assimilated and 8% was adsorbed on the soil. The remaining percentage corresponds to the formation of metabolites such as amino-dinitrotoluenes (4%), 2,4-diamino-6-nitrotoluene (3%) and 2,3-butanediol produced by the splitting of the cycle (30%). Successive additions of soil once, twice or three times a week do not affect the TNT degradation rate. In addition, this reactor makes it possible to maintain the bacterial population, with 0.3% molasses being the only co-substrate required. Using the same method, it is possible to eliminate other soil contaminants, such as hexahydro-1,3,5-trinitro-1,3,4-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), trinitrotoluene and 2,4-dinitrotoluene. These results are reported in BOOPATHY, R. et al. “A laboratory study of the bioremediation of 2,4,6-trinitrotoluene-contaminated soil using aerobic/anoxic soil slurry reactor”, Water Environment Research, 1998.
In 1998, VORBECK et al. studied the microbiological reduction of TNT nitro groups and the microbiological hydrogenation of the aromatic cycle. Due to electron deficiency caused by the presence of electron-attracting nitro groups, the first microbial transformation of TNT is a nitro-reduction. The hydrogenation of the aromatic cycle described for picric acid remains a minority. Two bacteria were isolated from an aerobic medium, enriched with TNT as the only source of nitrogen: the strain TNT-8 (gram−) and the strain TNT-32 (gram+). They catalyse the nitro-reduction of TNT. However, the strains
Rhodoccus
erythropolis HL PM-1 (growing on picric acid) and Mycobacterium sp. HL 4-NT-1 (growing on 4-nitrotoluene) with enzyme systems which catalyse the hydrogenation of TNT and, consequently, the addition of a hydride ion on the aromatic cycle. The TNT Meisenheimer hydride complex (H-TNT) formed is then converted into a yellow non-degradable metabolite, identified by NMR. In this case, no reductive denitration of the TNT was observed. The mineralisation of TNT was not studied. These results are reported in VORBECK, C. et al., “Initial Reductive reactions in aerobic microbial metabolism of 2,4,6-trinitrotoluene”, Appl. Environ. Microbiol., 1998, 64(1), 246-252.
However, none of the micro-organisms described in these documents enable the total or almost total mineralisation of TNT.
Chemical degradation processes, for their part, involve numerous disadvantages related to the use of chemical reagents. These disadvantages particularly include the cost of the chemical reagents and the pollution generated by these reagents in treated solutions and soils.
DESCRIPTION OF THE INVENTION
The specific aim of the present invention is to provide a method enabling the total or almost total elimination of a nitroaromatic compound in a solution or in a soil, by means of the mineralisation of said compound.
In this way, the method according to the present invention is a method which may be used to treat a solution or a soil containing one or more undesirable (due to pollution) nitroaromatic compounds.
The method according to the invention is a microbiological method for eliminating at least one nitroaromatic compound present in a solution or in a soil, said method being characterised in that it comprises contact of said solution or said soil with a biomass of a Penicillium strain under suitable conditions for mineralisation of the nitroaromatic compound by the Penicillium strain.
The terms “nitroaromatic compound” or “nitroaromatic compound solution” below refer to “the nitroaromatic compound(s)” and “solution of the nitroaromatic compound(s)”, respectively.
According to the invention, the nitroaromatic compound solution may be, for example, a laboratory solution, an industrial effluent or surface water containing one or more nitroaromatic compound(s) and wherein, preferentially, the Penicillium strain can metabolise the nitroaromatic compound. Advantageously, according to the method of the invention, this solution is an aqueous solution.
According to the invention, the, at least one, nitroaromatic compound may be a compound comprising at least one aromatic cycle comprising at least one nitro group and, if applicable, at least one function selected in the group comprising —OH, —COOH, a halogen, —NH
2
, a cyclic or linear ose, a linear or ramified alkyl comprising 1 to 12 carbon atoms or an aryl, not substituted or substituted, by at least one function selected in the group comprising —OH, —COOH, a halogen, —NH
2
, —OH.
For example, the, at least one, nitroaromatic compound may be a compound selected from nitrotoluene, dinitrotoluene, trinitrotoluene and their derivatives or a mixture of these compounds.
According to the invention, the method of the present invention may also comprise, before the contact step, a step consisting of neutralising the pH of the nitroaromatic compound solution or the soil such that the contact with the biomass, for example a Penicillium strain, can be performed at a pH of 4.5 to 6.5.
According to the invention, the contact may for example be performed in the presence of glucose at a concentration of 0.5 to 50 g of glucose/l of said solution.
According to the invention, the Penicillium strain may be a common Penicillium strain. For example, the Penicillium sp. LCM strain registered under the number I-2081 at Collection Nationale de Cultures de Microorganismes (CNCM) kept by Institut Pasteur in France may be used in the method according to the present invention. The invention also relates to the Penicillium sp. LCM strain registered under number I-2081 at the CNCM kept by Institut Pasteur in France.
According to the invention, the biomass of the Penicillium strain may be obtained using conventional microbiological methods to form a biomass, for example using Penicillium culture in a culture medium that is preferentially rich, solid or liquid, preferentially liquid, at a suitable temperature and pH to enable an optimal metabolism for the Penicillium strain.
A culture medium that can be used to develop the biomass is given in the examples below.
When a sufficient quantity of biomass is obtained, and when the culture medium is liquid, the biomass may for example be recovered by filtration or by centrifugation, advantageously by filtration.
Preferentially, in the method according to the present invention, the biomass is used fresh, which does not exclude any other use.
The biomass placed in contact with the solution or soil must be sufficient in quantity to enable the mineralisat
Le Campion Laurence
Ouazzani Jamal
Commissariat a l'Energie Atomique
Prince Fred
Simmons David A.
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