秸秆降解菌的筛选及对秸秆的降解效果

Screening of straw degrading microbial strains and their degradation effects

作物秸秆作处置不当可能严重影响农村生态环境。目前东北地区的秸秆处置方式主要为直接打碎还田,但秸秆在自然环境中不易腐化,影响春耕。从添加外源微生物促进秸秆原位腐化角度开发新型可培养秸秆降解菌,具有重要意义。本实验通过菌种富集培养、刚果红培养基初筛和滤纸条崩解试验复筛的方法,从腐烂的秸秆和牛肠道中分离筛选潜在的高效纤维素降解菌,测定其最适生长温度和pH,在液态发酵培养条件下考察菌株实际降解能力,共获得具有较高玉米秸秆降解能力的降解菌5株。5种菌株的生长峰值均出现在温度20~30℃,pH值7.5~8.5范围内。液态发酵培养15天后,秸秆失重率为菌株NX9(53.88%)>NF6(51.36%)>JF3(46.97%)>JZ8(45.2%)>JX4(35.79%)>CK(23.88%)。其中,菌株NX9(温度30℃、pH 7.5)对秸秆半纤维素和木质素的降解能力最强,15天降解率分别为48%和37.7%;筛选出的NF6和JF3属于耐冷微生物,特别是菌株NF6在4℃条件下也能生长繁殖,为北方开展"外源微生物促进秸秆原位腐化"技术提供了基础。

Improper disposal of crop straw might have negative effects on rural ecological environment.At present,the main way of straw disposal in Northeast China is to smash and return the straw to the field directly.However,the straw is not easily decomposed in natural environment,which affects the spring ploughing.Therefore,it is important to find new types of culturable straw-degradation bacteria from the perspective of adding exogenous microorganisms to promote straw in-situ decay.In this study,the potential high-efficiency cellulose degrading bacteria were isolated and screened from the rotten straw and cattle intestines by enrichment culture,primary screening of Congo red culture medium,and disintegration test of filter paper.The optimum growth temperature and pH were assessed.The actual degradation ability of the strains was investigated in liquid fermentation culture.Five strains with high degradation ability of corn straw were obtained.The growth peaks of the five strains occurred in the range of temperature 20-30℃,pH7.5-8.5.After 15 days of liquid fermentation,the weight loss rate of straw by the five strains was in the order of NX9(53.88%)>NF6(51.36%)>JF3(46.97%)>JZ8(45.2%)>JX4(35.79%)>CK(23.88%).Among them,strain NX9(temperature 30℃,p H 7.5)had the strongest degradation ability to straw hemicellulose and lignin,with the degradation rate of 48%and 37.7%in 15 days,respectively.Strain NF6 and JF3 belong to cold resistant bacteria.Especially,strain NF6 can grow and propagate at 4℃.Our results provide a basis for developing the technology of"exogenous microorganism promoting straw in situ decay"in northern China.