Biodegradation of lignin and the associated degradation pathway by psychrotrophic Arthrobacter sp. C2 from the cold region of China

Degradation of most of the lignocellulose-rich agricultural residue in the cold regions of China is limited due to the cold climate. Lignin is the main component of lignocellulose, and the effective degradation of lignin is one of the most crucial processes in degrading lignocellulose. Psychrotrophic lignin-degrading bacteria and cold adapted ligninolytic enzymes have promising potential for the degradation and transformation of lignin, which are conducive to the resource utilization of lignocelluloses and energy-saving production under cold conditions. In this study, a newly psychrotrophic bacterial strain, Arthrobacter sp. C2, was isolated. The optimal enzyme activity conditions and lignin degradation pathways of C2 were investigated using sodium lignin sulfonate as substrate. The optimal conditions for enzyme activity included an initial pH of 6.74, a temperature of 14.9 degrees C, an incubation time of 6.87 days, and an inoculum size of 2.24%. Under the optimal conditions, the lignin peroxidase and manganese peroxidase activities and the degradation rate reached 29.8 U/L, 56.4 U/L and 40.1%, respectively. The biodegradation products including acids, phenols, aldehydes and alcohols were analyzed by gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy. Further, the potential degradation pathways were proposed according to the results obtained in this study and those presented in the relevant literature. This study not only provides valuable psychrotrophic strain resources for the sustainable utilization of lignocellulose in cold regions, but also supplies potential application options for energy-saving production of useful chemicals using cold adapted enzymes. Graphic abstract