低温降解玉米秸秆的木霉菌株筛选

Screening of Trichoderma strains for maize straw degradation at low temperature

【背景】木霉是自然界中常见的纤维素和半纤维素降解菌,在农业废弃物降解中具有重要应用潜力。【目的】筛选可在低温环境降解玉米秸秆的木霉菌株。【方法】测定31种木霉111个菌株在低温下的生长状况、水解纤维素和木聚糖产生的透明圈直径及部分菌株对玉米秸秆的相对降解率(relative degradation rate,RDR);利用DNS法测定不同RDR代表菌株的纤维素滤纸酶(filter paper cellulase,FPase)、羧甲基纤维素酶(carboxymethyl cellulase,CMCase)和木聚糖酶(xylanase)活性,并分析它们在不同发酵阶段的酶活与秸秆降解率的关系。【结果】在10℃和5℃培养分别有100株和42株供试菌株能够生长,在15℃均能生长,其中19个菌株培养6 d产生的水解纤维素和木聚糖产生的透明圈直径大于60 mm、培养10 d对玉米秸秆的RDR为0.45%−8.09%;菌株9145、TC425、TC505和8987的FPase、CMCase和xylanase活性随着培养时间呈现动态变化,其中前两者的活性变化趋势基本一致,与RDR的关系密切。【结论】钩状木霉、西蒙斯木霉、深绿木霉和深褐木霉菌株在低温条件下对玉米秸秆具有较高的降解能力,将为后续玉米秸秆腐熟剂开发、降解机理研究及秸秆资源化利用提供种质资源。

[Background]Species of Trichoderma are common cellulose and hemicellulosedegrading fungi in nature and play an important role in the degradation of agricultural wastes.[Objective]To screen out Trichoderma strains that can degrade maize straw under low temperature.[Methods]This study determined the growth rates and the diameter of hydrolytic transparent circle produced by cellulase and xylanase of 111 strains belonging to 31 Trichoderma species under low temperature,as well as the relative degradation rate(RDR)of the representative strains on maize straw.The cellulose filter paper enzyme(FPase),carboxymethyl cellulase(CMCase),and xylanase activities of the representative strains with different RDR values were determined by the DNS method,and the relationship between their enzyme activities and RDR in different fermentation stages were further analyzed.[Results]All the tested strains were able to grow at 15℃,whereas,100 and 42 out of them could grow at 10℃and 5℃,respectively.Among them,19 strains produced hydrolytic both cellulose and xylan transparent circles with diameters more than 60 mm after 6 days,and their RDRs on maize straw after 10 days were 0.45%−8.09%.The activities of FPase,CMCase,and xylanase of the strains 9145,TC425,TC505,and 8987 showed a dynamic change with the cultivation time,of which the tendency of FPase and CMCase was basically identical and closely related to the RDR.[Conclusion]The strains of T.atrobrunneum,T.atroviride,T.hamatum,and T.simmonsii show high degradation rates of maize straw at low temperatures,which will provide germplasm resources for subsequent development of ripening agent,degradation mechanism research,and resource utilization of maize straw.