一株芽孢杆菌的筛选及其降解木质纤维素性能

A Bacillus strain capable of degrading lignocellulose

摘要:

目的 为了更好地利用因气候、机械配套等原因导致苜蓿延迟收割而沉积的木质纤维素，筛选可以降解木质纤维素的菌株，为苜蓿的高效利用提供菌种资源。 方法 采用碱性木质素、羧甲基纤维素钠培养法初筛菌株；结合颜色变化和褪色圈复筛能够分泌木质素酶和纤维素酶的菌株；通过16S rRNA基因和全基因组测序进行分类鉴定；将全基因组测序结果与京都基因与基因组百科全书(Kyoto encyclopedia of genes and genomes, KEGG)和碳水化合物活性酶(carbohydrate-active enzymes, CAZy)数据库比对，注释基因功能；利用扫描电镜法评价菌株对苜蓿茎微观结构的降解效果；采用菌株添加法评价其对苜蓿干草养分和微生物群落变化的影响。 结果 获得1株能够分泌木质素酶和纤维素酶的菌株S1，经全基因组测序鉴定为蜡样芽孢杆菌( Bacillus cereus)。其基因组中有305个基因被注释为参与碳水化合物代谢，其中包含139个编码碳水化合物活性酶的基因。在苜蓿干草中添加该菌株后，茎中维管束的微观结构发生显著变化，粗蛋白(crude protein, CP)含量随储存时间增加而升高，木质素、中性洗涤纤维(neutral detergent fiber, NDF)和酸性洗涤纤维(acid detergent fiber, ADF)含量降低，同时微生物α多样性也有所下降。 结论 筛选鉴定的菌株为蜡样芽孢杆菌，其具有较强的木质纤维素降解能力。

Abstract:

Objective To screen out a strain that can degrade lignocellulose for the application of lignocellulose deposited by delayed harvest of alfalfa under inappropriate climate and mechanical matching and provide strain resources for the efficient use of alfalfa. Methods The primary screening was carried out by culture with alkali lignin and sodium carboxymethyl cellulose. Based on color changes and fading circles, the strain with the ability to secrete ligninase and cellulase was screened out. The target strain was identified by 16S rRNA gene sequencing and whole genome sequencing, and then Kyoto encyclopedia of genes and genomes (KEGG) and carbohydrate-active enzymes (CAZy) were employed to annotate gene functions based on the whole genome sequence. The microstructure of the alfalfa stems degraded by the strain was observed by scanning electron microscopy. The nutrient and microbial community changes in alfalfa hay treated with the strain were evaluated. Results A strain S1 producing ligninase and cellulase was identified as Bacillus cereus by whole genome sequencing. A total of 305 genes involved in carbohydrate metabolism were annotated, including 139 genes encoding CAZy. After treatment with this strain, the microstructure of vascular bundles in alfalfa stems changed significantly. The crude protein content in alfalfa hay increased, while the lignin, neutral detergent fiber, and acid detergent fiber content and the alpha-diversity of microorganisms decreased over time. Conclusion The screened strain identified as B. cereus demonstrates a robust ability to degrade lignocellulose.