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.