Scientists have found a bacterium of the genus Pseudomonas, which can use a polyurethane oligomer and monomer toluidine as the sole source of carbon, nitrogen and energy. The authors proposed metabolic pathway of cleavage of these substances and found genes of enzymes that can catalyze the described reaction. Article published in the journal Frontiers in Microbiology.
Polyurethane is one of the most common types of plastic. For example, in Europe in 2015, he was fifth on the demand of synthetic polymer, it is used mainly in insulating materials. These compounds are referred to hetero-polymers in their structure can include essential or polyester group, aliphatic, polycyclic, and aromatic structures and functional groups of different nature. Because of this heterogeneity, polyurethanes are difficult to decompose both chemical and biological means.
Known methods for decomposition of polyurethanes, which are based on simple essential communications, bacteria, fungi or selected enzymes. Biological degradation of ester polyurethanes studied worse and mainly in fungi. Among the products of hydrolysis of the polyurethane diamines have methylendianiline and toluidinesthat the European Agency for chemicals recognized as dangerous (toluidines is a carcinogen).
Maria Espinosa (Maria Espinosa) from the Center for environmental studies Helmholtz found in places where plastic waste bacteria that grow on the medium with tolualdehyde. The scientists grew these bacteria on the medium in which 2,4-toluidine was the only source of carbon and nitrogen, and then on Wednesdays with the other aromatics and oligomers of polyurethane. Also checked the toxicity of tolualdehyde to other bacteria, which were in exponential growth phase and developed on the medium with succinate.
To determine the taxonomic affiliation of bacteria was found, the authors conducted whole genome DNA sequencing. In addition, they found stretches of DNA that look like genes of other bacteria that encode enzymes of various pathways of degradation of aromatics.
According to the results of whole genome sequencing and analysis of the fatty acid profile of bacteria related to the genus Pseudomonas, they were the closest to the types of P. oryzihabitans and P. putida. The bacteria were fed 2,4-tolualdehyde, even if it was the only source of carbon and nitrogen in the environment. Optimal concentrations for bacterial growth to two moles per liter. Bacteria growing on the substrate with aliphatic polyurethane oligomer.
Add dvuhmillimetrovy solution of 2,4-tolualdehyde in the environment of the control bacteria which were in the exponential phase of growth and were fed with succinate, reduced the growth of colonies by 55 percent. A higher concentration of the diamine was significantly more toxic.
Scientists have proposed a possible path decompositions of tolualdehyde and genes, which may encode the corresponding enzymes. First, in their view, the oxidation of the methyl group and the amino group in the ortho-position, the result is a catecholamine. After that, probably, estradiol-dioxygenase cleaves the aromatic ring in meta-position, then there is a further degradation of the product.