A lignin-degrading strain with nicotine tolerance: screening and the degradation effect on tobacco stems

Abstract:

[Background] The lignin in tobacco waste acts as a primary obstacle for environmental microorganisms to degrade lignocellulose in tobacco stems or other straw. Additionally, the nicotine in tobacco stem threatens the survival of most reported lignin-degrading microorganisms. [Objective] To screening the strains with strong degrading effects on tobacco stems, so as to solve the problem of long-term accumulation of tobacco stems which are difficult to degrade and enhance the industrial availability of tobacco stems. [Methods] The aniline blue fading method and the guaiacol assay were employed to screen out the dominant strains capable of degrading lignin from cattle manure. The nicotine tolerance of the strains was tested, and the degradation effects of the strains on tobacco stems were verified. [Results] The lignin-degrading strain YP-2023-9 screened belonged to Enterobacter and showed tolerance to nicotine with the concentration≤0.60%. The strain produced lignin peroxidase and manganese peroxidase, thereby promoting lignin degradation in tobacco stems. The maximum levels of the two enzymes reached 309.68 U/mL on day 5 and 21.76 U/mL on day 1, respectively. Scanning electron microscopy demonstrated that the strain primarily facilitated the degradation of lignin and hemicellulose on the tobacco stem surface, causing evident damage to the cell wall structure of tobacco stems. After incubation at 30 ℃ for 15 days, YP-2023-9 showed a degradation rate of 42.42% against tobacco stems, with the relative degradation rates of 13.17% and 33.12% against hemicellulose and lignin, respectively. [Conclusion] This strain exhibits promising potential for application in the degradation of both tobacco stems and associated waste.