一株低温木质素降解菌的筛选、产酶优化及酶学性质

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

摘要:

[背景] 我国北方地区秋冬两季平均气温较低，低温环境使得秸秆更难自然降解。[目的] 筛选高效低温木质素降解菌，探索其酶学特性并提高其产酶性能和秸秆降解效率。[方法] 通过苯胺蓝法和酶活测定对菌株进行筛选，以Lip、Lac、Mnp酶活力为评价指标，采用单因素和响应面法进行产酶条件优化及酶学性质研究，通过固态发酵试验研究其对秸秆的降解效率。[结果] 筛选到一株高效菌LS-1，经形态学和分子生物学鉴定其为嗜麦芽窄食单胞菌。菌株LS-1在木质素为碳源、蛋白胨为氮源、pH 8.0、培养温度15℃、培养时间3 d时产酶效果最佳，其中Lip酶活力为23.34 U/mL、Lac酶活力为9.37 U/mL、Mnp酶活力为50.89 U/mL。Lip和Lac最适作用温度为30℃且热稳定性良好，Mnp最适作用温度为50℃但热稳定性较差。Lac最适作用pH 4.0且耐酸性较好，Lip和Mnp最适作用pH 5.0；0.75 mmol/L Mg²⁺和0.5%吐温-20对Lip有促进作用，1 mmol/L Cu²⁺和丁香酸对Lac有促进作用，0.1%—0.5%吐温-20均对Mnp有促进作用。15℃固态发酵后，秸秆失重率达18.85%，木质素降解率达36.14%，比对照组提高约6倍以上。[结论] 本研究为低温木质素高效降解提供了优质菌种资源，在秸秆降解方面具有良好的应用前景。

关键词:低温木质素降解菌;产酶优化;酶学性质;秸秆降解

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.

Key words:low-temperature lignin-degrading bacteria;enzyme production optimization;enzymology properties;straw degradation