Enhancement of biodegradation of tar-rich coal through sequential treatment by N. mangyaensis and Ochrobactrum sp.

Sequential degradation using two bacteria with complementary metabolic capabilities offers a promising strategy for enhancing coal biodegradation efficiency. In this work, the biodegradation processes of the Baode tar-rich coal in Ordos Basin by two sequential treatment modes of N. mangyaensis and Ochrobactrum sp. were investigated. In mode 1, the coal was degraded firstly by N. mangyaensis, and after the degradation process was completed, the separated residual coal was secondly degraded by Ochrobactrum sp.. In mode 2, the stages were the opposite of mode 1. The biodegradation rates of tar-rich coal for mode 1, mode 2, N. mangyaensis and Ochrobactrum sp. were 55.7, 50.1, 43.2, and 29.8%, respectively, indicating that sequential degradation significantly enhanced biodegradation efficiency. Analysis of the solid and liquid products revealed that this difference was due to the distinct degradation characteristics of the bacteria: N. mangyaensis preferentially degraded hydrogen-rich structures, while Ochrobactrum sp. targeted aromatic compounds. The superior performance of mode 1 was attributed to N. mangyaensis initially degrading the hydrogen-rich structures in coal, depolymerizing macromolecules into smaller aromatic compounds and creating more accessible substrates for Ochrobactrum sp., thereby improving the overall biodegradation process. Conversely, in mode 2, Ochrobactrum sp. primarily degraded polycyclic aromatic hydrocarbons in the tar-rich coal during the first stage, resulting in fewer degradable intermediates for the second stage and reducing the overall efficiency of the degradation process. The applicability of this sequential degradation strategy to other types of coal or organic pollutants also warrants exploration, potentially broadening its industrial and environmental relevance.