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5-Hydroxy-2-pyridone (2,5-DHP) is a central metabolic intermediate in catabolism of many pyridine derivatives, and has been suggested as a potential carcinogen. 2,5-DHP is frequently transformed to N-formylmaleamic acid (NFM) by a 2,5-DHP dioxygenase. Three hypotheses were formerly discussed for conversion of 2,5-DHP to maleamate. Based on enzymatic reactions of dioxygenase (Hpo) and N-formylamide deformylase (Nfo), we demonstrated that the dioxygenase does not catalyze the hydrolysis of NFM but rather that this activity is brought about by a separate deformylase. We report that the deformylase acts both on NFM and its trans-isomer, N-formylfumaramic acid (NFF), but the catalytic efficiency of Nfo for NFM is about 1,400 times greater than that for NFF. In addition, we uncover catalytic and structural characteristics of the new family that the Hpo belongs to, and support a potential 2-His-1-carboxylate motif (HX52HXD) by three-dimensional modeling and site-directed mutagenesis. This study provides a better understanding of 2,5-DHP catabolism.

Agricultural wastes, such as wheat bran and swine wastewater, were used for bioremediation of oil-contaminated soil. Two optimised strains that could degrade oil efficiently were selected. The result showed that the best ratio of strain A to strain B was 7:3. Swine wastewater could be a replacement for nitrogen source and process water for bioremediation. Next, the Box-Behnken design was used to optimise the culture medium, and the optimal medium was as follows: microbial dosage of 97 mL/kg, wheat bran of 158 g/kg and swine wastewater of 232 mL/kg. Under the optimal medium, the oil degradation rate reached 68.27 ± 0.71% after 40 d. The urease, catalase, and dehydrogenase activities in oil-contaminated soil all increased, and the microbe quantity increased significantly with manual composting. These investigations might lay a foundation for reducing the pollution of agricultural wastes, exploring a late model for bioremediation of oil-contaminated soil.

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