Degradation of nitroesters by plant tissue cultures

Biodegradation of 2,4-dinitrotoluene by different plant species

Over the past century, rapid growth of population, mining and industrialization significantly contributed to extensive soil, air and water contamination. The 2,4-dinitrotoluene (2,4-DNT), used mostly as explosive, belongs to the hazardous xenobiotics. Soils and waters contaminated with 2,4-DNT may be cleaned by phytoremediation using suitable plant species. The ability of crop plants (hemp, flax, sunflower and mustard) to germinate and grow on soils contaminated with 2,4-DNT was compared. Stimulation of their growth was found at 0.252 mg/g 2,4-DNT. The lethal concentration for the growth for these species was around 1 mg/g. In hydropony, the above mentioned species were able to survive 200 mg/l 2,4-DNT, the concentration close to maximal solubility of 2,4-DNT in water. Metabolism of 2,4-DNT was tested using suspension culture of soapwort and reed. The degradation products 2-aminonitrotoluene and 4-aminonitrotoluene were found both in the medium and in the acetone extract of plant cells. The test showed that the toxicity of these metabolites was higher than the toxicity of the parent compound, but 2,4-diaminotoluene, the product of next reduction step, was less toxic in the concentration range tested (0-200 mg/l).

Denitrification of industrial wastewater: Influence of glycerol addition on metabolic activity and community shifts in a microbial consortium

The wastewater originating from explosives manufacturing plants are characterized by a high concentration of nitrates (3200mgNL(-1)), sulfates (1470mgL(-1)) and low pH (1.5) as well as the presence of organic compounds, such as nitroglycerin (1.9mgL(-1)) and nitroglycol (4.8mgL(-1)). The application of glycerol (C/N=3) at such a high concentration enabled complete removal of nitrates and did not cause the anaerobic glycerol metabolic pathway of the DNC4 consortium to activate, as confirmed by the low concentrations of 1,3-propanediol (0.16gL(-1)) and acetic acid (0.11gL(-1)) in the wastewater. Increasing the glycerol content (C/N=5) contributed to a notable increase in the concentration of both compounds: 1.12gL(-1) for acetic acid and 1.82 for 1,3-PD (1,3-propanediol). The nitrate reduction rate was at 44mgNg(-1) biomass d(-1). In order to assess the metabolic activity of the microorganisms, a method to determine the redox potential was employed. It was established, that the microorganisms can be divided into four groups, based on the determined denitrification efficiency and zero-order nitrate removal constants. The first group, involving Pseudomonas putida and Pseudomonas stutzeri, accounts for microorganisms capable of the most rapid denitrification, the second involves rapid denitrifying microbes (Citrobacter freundi and Pseudomonas alcaligenes), the third group are microorganisms exhibiting moderate denitrification ability: Achrobactrum xylosoxidans, Ochrobactrum intermedium and Stenotrophomonas maltophila, while the last group consists of slow denitrifying bacteria: Rodococcus rubber and Sphignobacterium multivorum.