Nitrogen Incorporation into Lignite Humic Acids during Microbial Degradation
Abstract:Previous study showed that nitrogen content in lignite humic acids (HA) increased significantly during lignite biodegradation. In this paper we evaluated the factors responsible for the increased level of N in HA and the formation of new nitrogen compound following microbial degradation. When the ammonium sulfate concentration in lignite medium was < 0.5%, the N-content in HA was higher than that in the crude lignite humic acid (cHA); when the ammonium sulfate concentration was ≥ 0.5%, both the biodegraded humic acid (bHA) N-content and the content of bHA in lignite increased significantly, but at 2.0% no increase was observed. This indicated that HA incorporated N existing in the lignite medium, and more HA can incorporate more N with the increase of bHA amount in lignite during microbial degradation. CP/MAS 15N NMR analysis showed that the N incorporated into HA during biotransformation was in the form of free or ionized NH2-groups in amino acids and sugars, as well as NH4+. We propose nitrogen can be incorporated into HA biotically and abiotically. The high N content bHA has a potential application in agriculture since N is essential for plant growth.
Document Type: Research Article
Affiliations: State Key Lab for Agrobiotechnology, College of Biological Sciences and Center of Biomass Engineering, China Agricultural University, Beijing, PR, China
Publication date: October 1, 2009