Cellulose degradation results from the synergistic effect of different enzymes,but which enzyme is involved in the initial stage of cellulose degradation is still not well understood.Cellobiohydrolase 2(CBH2)attached ...Cellulose degradation results from the synergistic effect of different enzymes,but which enzyme is involved in the initial stage of cellulose degradation is still not well understood.Cellobiohydrolase 2(CBH2)attached to the conidial surface is possibly associated with the initial stage.However,its specific mechanism is still incompletely known.This study explored the potential role of CBH2 in initiating cellulose degradation using a constitutive overexpression strategy.First,the CBH2-overexpression Trichoderma reesei strains Qgc2-5 and Qrc2-40 were constructed using the constitutive promoters P gpd1 and P rpS30,respectively.It was found that cbh2 was ex-pressed at a high level under the glucose conditions and was significantly higher than that of the parental strain QM9414 at the early stage of 29 h when cellulose was used as the carbon source.Particularly,the constitutive overexpression of cbh2 caused the strong expression of major cellulase-encoding genes(cbh1,eg1,and eg2)and the rapid decomposition of cellulosic material.Meanwhile,the scanning electron microscope showed that the groove-like structure of the cellulose surface was eroded seriously owing to CBH2 overexpression,which caused the cellulose surface to be smooth.These results showed that the overexpression of CHB2 caused the major cel-lulase enzymes to be expressed and contributed to cellulose degradation,showing the potential role of CBH2 in the initial stage of the cellulose hydrolytic process.展开更多
To accelerate the decomposition of wheat straw directly returned to soil, we constructed a microbial system （ADS-3） from agricultural soil containing rotting straw residues using a 40-wk limited cultivation. To asse...To accelerate the decomposition of wheat straw directly returned to soil, we constructed a microbial system （ADS-3） from agricultural soil containing rotting straw residues using a 40-wk limited cultivation. To assess its potential use for accelerating straw decomposing, the decomposing characteristics and the microbial composition of ADS-3 were analyzed. The results indicated that it could degrade wheat straw and filter paper by 63.8 and 80%, respectively, during 15 d of incubation. Straw hemicellulose degraded dramatically 51.2% during the first 3 d, decreasing up to 73.7% by the end of incubation. Cellulose showed sustained degradation reaching 53.3% in 15 d. Peak values of xylanase and cellulase activities appeared at 3 and 11 d, with 1.32 and 0.15 U mL-1, respectively. Estimated pH averaged 6.4-7.6 during the degradation process, which approximated acidity and alkalinity of normal soils. The microbial composition of ADS-3 was stable based on denaturing gradient gel electrophoresis （DGGE） analysis. By using bacterial 16S rRNA and fungal 26S rRNA gene clone library analysis, 20 bacterial clones and 7 fungal clones were detected. Closest identified relatives of bacteria represented by Bacillus fusiformis, Cytophaga sp., uncultured Clostridiales bacterium, Ruminobacillus xylanolyticum, Clostridium hydroxybenzoicum, and uncultured proteobacterium and the fungi were mainly identified as related to Pichia sp. and uncultured fungus.展开更多
基金supported by grants from the National Key R&D Program of China(2021YFC2101300,2018YFA0900503)the National Natural Science Foundation of China(31970070)the Youth Interdisciplinary Science and Innovative Research Groups of Shandong University(2020QNQT006).
文摘Cellulose degradation results from the synergistic effect of different enzymes,but which enzyme is involved in the initial stage of cellulose degradation is still not well understood.Cellobiohydrolase 2(CBH2)attached to the conidial surface is possibly associated with the initial stage.However,its specific mechanism is still incompletely known.This study explored the potential role of CBH2 in initiating cellulose degradation using a constitutive overexpression strategy.First,the CBH2-overexpression Trichoderma reesei strains Qgc2-5 and Qrc2-40 were constructed using the constitutive promoters P gpd1 and P rpS30,respectively.It was found that cbh2 was ex-pressed at a high level under the glucose conditions and was significantly higher than that of the parental strain QM9414 at the early stage of 29 h when cellulose was used as the carbon source.Particularly,the constitutive overexpression of cbh2 caused the strong expression of major cellulase-encoding genes(cbh1,eg1,and eg2)and the rapid decomposition of cellulosic material.Meanwhile,the scanning electron microscope showed that the groove-like structure of the cellulose surface was eroded seriously owing to CBH2 overexpression,which caused the cellulose surface to be smooth.These results showed that the overexpression of CHB2 caused the major cel-lulase enzymes to be expressed and contributed to cellulose degradation,showing the potential role of CBH2 in the initial stage of the cellulose hydrolytic process.
基金supported by the National Key Technology R&D Program of China (2008BADC4B01 and 2008BADC4B17)the National Special Research Fund for Non-Profit Sector, China (200803033)
文摘To accelerate the decomposition of wheat straw directly returned to soil, we constructed a microbial system （ADS-3） from agricultural soil containing rotting straw residues using a 40-wk limited cultivation. To assess its potential use for accelerating straw decomposing, the decomposing characteristics and the microbial composition of ADS-3 were analyzed. The results indicated that it could degrade wheat straw and filter paper by 63.8 and 80%, respectively, during 15 d of incubation. Straw hemicellulose degraded dramatically 51.2% during the first 3 d, decreasing up to 73.7% by the end of incubation. Cellulose showed sustained degradation reaching 53.3% in 15 d. Peak values of xylanase and cellulase activities appeared at 3 and 11 d, with 1.32 and 0.15 U mL-1, respectively. Estimated pH averaged 6.4-7.6 during the degradation process, which approximated acidity and alkalinity of normal soils. The microbial composition of ADS-3 was stable based on denaturing gradient gel electrophoresis （DGGE） analysis. By using bacterial 16S rRNA and fungal 26S rRNA gene clone library analysis, 20 bacterial clones and 7 fungal clones were detected. Closest identified relatives of bacteria represented by Bacillus fusiformis, Cytophaga sp., uncultured Clostridiales bacterium, Ruminobacillus xylanolyticum, Clostridium hydroxybenzoicum, and uncultured proteobacterium and the fungi were mainly identified as related to Pichia sp. and uncultured fungus.
