1株高产纤维素酶菌株的筛选鉴定及对稻秆降解的研究

Screening and identification of a cellulase-producing strain and its degradation of rice straw

【目的】筛选高效纤维素降解菌,用于稻秆原位还田菌剂的开发。【方法】通过稻秆粉培养基和刚果红-纤维素选择性培养基,从芜湖地区腐殖土中筛选分离出高效纤维素降解菌CX1,测定不同底物条件和不同反应温度下的纤维素酶活性。通过滤纸条崩解试验、土培降解试验、菌株与化学物质协同降解稻秆试验、发酵液对小麦幼苗生长的影响试验,探究菌株CX1腐解稻秆的特性。【结果】通过菌株形态学特征及16S rDNA序列相似性(99%)比对,确定CX1为高温嗜热芽孢杆菌Thermophilic Bacillus sp.。以稻秆粉为底物,50℃条件下菌株CX1纤维素酶活力达13.87 U·mL^(–1),65℃时酶活力仍能达到9.73 U·mL^(–1)。添加菌株CX1培养4 d后滤纸条完全崩解,到15 d时,稻秆纤维素降解率达到52.55%,土培40 d时稻秆相对降解率达到25.38%。预先用质量浓度为0.05 g·mL^(–1)的NaOH溶液浸泡处理的稻秆更利于菌株CX1对稻秆的降解,腐解14 d时稻秆失重率比对照组增加了6.69%。添加经菌株CX1降解稻秆后的发酵液可使小麦的各项生长指标有明显提高,小麦的出苗率、苗高、根鲜质量和苗鲜质量分别提高了9.66%、55.55%、59.71%和118.84%。【结论】菌株CX1对高温具有耐受性,能高效降解纤维素,可在农业生产中促进稻秆原位还田方面发挥积极的作用。

【Objective】To screen efficient cellulose degrading bacteria,and develop a bacterial agent for rice straw degradation and in situ returning to field.【Method】The efficient cellulolytic bacterium CX1 was screened from soil in Wuhu area by using rice straw powder medium and Congo red-cellulose selective medium.The cellulase activity under different substrate conditions and different reaction temperatures were determined.We performed the filter paper disintegration test,soil degradation test,experiment on synergistic degradation of rice straw by bacterium and chemical substances,and tested the effect of fermentation broth on growth of wheat seedlings.The decomposition characteristics of strain CX1 were analyzed.【Result】Strain CX1 was identified as Thermophilic Bacillus sp.based on morphology and 16S rDNA sequence similarity(99%).Using rice straw powder as the substrate,the activity of cellulase from CX1 reached 13.87 U·mL^–1 at 50℃and 9.73 U·mL^–1 at 65℃.The filter paper completely disintegrated after 4 days of culture with CX1.The degradation rate of rice straw cellulose reached 52.55%after 15 days of culture with CX1.The relative degradation rate of rice straw reached 25.38%after 40 days of degradation in soil.The rice straw immersed with 0.05 g·mL^–1 NaOH solution in advance was more easily to be degraded by strain CX1,and its weight loss rate increased by 6.69%compared with the control group.The addition of fermentation broth from rice straw degradation with strain CX1 obviously promoted the growth of wheat seedlings,and the germination rate,seedling height,root fresh weight and seedling fresh weight increased by 9.66%,55.55%,59.71%and 118.84%,respectively.【Conclusion】Strain CX1 has high temperature resistance and can efficiently degrade cellulose.It can be used for promoting rice straw returning to field in agricultural production.