Screening, enzyme-production optimization and enzymatic properties of a low-temperature lignin-degrading bacteria

Abstract:

[Background] In northern China, the average temperature in autumn and winter is low, which makes straw more difficult to degrade naturally.[Objective] Screening high efficiency lignin-degrading bacteria of low-temperature, explore enzymatic properties and improve enzyme-producing performance and straw degradation efficiency.[Methods] High efficiency lignin degradation strains were screened by aniline blue method and enzyme activity determination, and the enzymatic production conditions were optimized by single-factor screening and response surface experiment, and the degradation efficiency of straw was determined through solid-state fermentation experiments.[Results] An efficient lignin-degradation strain LS-1 was screened and identified as Stenotrophomonas maltophilia. When the carbon and nitrogen sources of LS-1 were lignin and pepone, pH 8.0, temperature 15℃, time 3 days, the activities of Lip, Lac and Mnp were 23.34 U/mL, 9.37 U/mL and 50.89 U/mL, respectively. The optimal temperature of Lip and Lac was 30℃ and the thermal stability was well, while the optimal temperature of Mnp was 50℃ and the thermal stability was poor, the optimum action environment of the three enzymes was acidic. 0.75 mmol/L Mg²⁺ and 0.5% Tween-20 can promote Lip activity, 1 mmol/L Cu²⁺ and syringic acid can promote Lac activity, and 0.1%—0.5% Tween-20 can promote Mnp activity. After low-temperature solid-state fermentation, the weight loss rate of straw was 18.85%, and the lignin degradation rate was 36.14%, which was about 6 times higher than that of the control group.[Conclusion] This experimental provides high-quality bacterial resources for the efficient degradation of low-temperature lignin and has a well application prospect in straw degradation.