柑橘废弃物堆肥中高效木质素降解菌的筛选及其降解效果

Screening of efficient lignin-degrading bacteria in citrus waste compost

摘要:

【背景】柑橘修剪枝是一种丰富可再生的生物质资源，但枝条中木质纤维素结构稳定且复杂，限制了其资源化利用。【目的】从柑橘废弃物堆肥中筛选和鉴定高效木质素降解菌，优化菌株降解木质素的条件，为柑橘枝类废弃物的资源化利用提供菌种资源。【方法】以苯胺蓝褪色法筛选菌株，对比不同菌株的漆酶、锰过氧化物酶和木质素过氧化物酶酶活，通过单因素试验、正交试验和响应面试验优化目的菌株LDB1的木质素降解条件，利用室内试验验证菌株LDB1对3种植物源木质素的降解效果。【结果】从柑橘枝废弃物堆肥中筛选出8株木质素降解细菌，其中菌株LDB1产酶能力最强，该菌被鉴定为解淀粉芽孢杆菌(Bacillus amyloliquefaciens)。pH、接种量和C/N是影响菌株LDB1降解木质素的显著影响因子，当三者分别为6.9、2.9%和29.0时，木质素降解率最大，4 d后达到(14.9±0.9)%，较正交试验结果提升2.0%。经菌株LDB1降解30 d后，柑橘枝、玉米秸秆和水稻秸秆的木质素降解率分别为12.0%、36.8%和30.6%。【结论】本研究筛选的解淀粉芽孢杆菌LDB1能同时分泌3种木质素降解酶，能够有效破坏木质纤维素结构，具备较强的木质纤维素降解能力。

Abstract:

[Background] Pruned branches of citrus are rich and renewable biomass resources, in which the stable and complex lignocellulose structure limits the utilization of the resources. [Objective] To screening and identify efficient lignin-degrading bacteria from citrus waste compost and optimize the lignin-degrading conditions of strains, thus providing strain resources for the utilization of citrus waste. [Methods] We isolated lignin-degrading strains from citrus waste compost by the aniline blue method and compared the laccase, manganese peroxidase, and lignin peroxidase activities between different strains. Then, we optimized the lignin degradation conditions of the target strain (LDB1) by single factor tests, orthogonal test, and response surface methodology. Finally, we verified the degradation effect of LDB1 on the lignin derived from three plant species by laboratory experiments. [Results] We isolated eight lignin-degrading bacterial strains from the citrus waste compost. Among them, strain LDB1 had the strongest enzyme activity and was identified as Bacillus amyloliquefaciens (GenBank No. OR244332). The lignin degradation by LDB1 was affected by pH, inoculum amount, and C/N ratio. The fermentation with LDB1 at pH 6.9, inoculum amount of 2.9%, and C/N ratio of 29.0 achieved the lignin degradation rate of (14.9±0.9)% after 4 days, which increased by 2.0% compared with the orthogonal test result. After 30 days, the lignin degradation rates of LDB1 for citrus branches, maize straw, and rice straw were 12.0%, 36.8%, and 30.6%, respectively. [Conclusion] B. amyloliquefaciens LDB1 can simultaneously secrete three lignin-degrading enzymes to destroy the lignocellulose structure, demonstrating strong lignocellulose-degrading ability.