A bamboo lignin-degrading strain: screening and degradation performance

Abstract:

[Background] Bamboo is considered an excellent source for biorefining for its high cellulose content. However, the complex interactions between lignin and cellulose present an obstacle to the efficient utilization of bamboo. The process of lignin degradation is essential for the efficient utilization of bamboo. [Objective] To screen out the strains that specialize in degrading bamboo lignin and investigate their enzyme activities and effects of lignin degradation. [Methods] A culture medium with lignin as the solo carbon source was used for the primary screening, which was followed by the secondary screening with the media containing aniline blue and Congo red. The activities of enzymes were measured to assess the lignocellulose degradation performance. X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy were employed to study the changes of bamboo appearance and structure after degradation. [Results] A strain XKG6 capable of degrading lignin was isolated from the bamboo forest and identified as Pseudomonas oleovorans. The maximum activities of lactase, lignin peroxidase, manganese peroxidase, filter paper enzyme, and xylanase secreted by the strain reached 1 543.21, 6 229.32, 826.41, 2 602.1, and 1 889.25 U/L, respectively. The strain showed a degradation rate of 14.04% against alkaline lignin on day 7. Fourier transform infrared spectroscopy and scanning electron microscopy showed the significant structural changes in bamboo lignin after treatment with XKG6. [Conclusion] In this study, a bacterial strain with the ability to degrade lignin was screened out. This strain retained much cellulose while degrading bamboo lignin, serving as an alternative strain for the industrial production of lignocellulosic resources.