Chiang Mai Journal of Science

      Corn straw is a type of high-yield agricultural waste in China, but it has not been fully utilized owing to the difficulty of degrading it and its low utilization rate. To improve the rate of degradation of corn straw and ensure that the straw resources are utilized more fully, we obtained an actinomycete that could simultaneously degrade cellulose and pectin from the cold region and black glebe of northeast China. The strain was named DPA-3-18, and its biological morphology and the sequence of its 16S rRNA were identified. These analyses determined that it is a species of Streptomyces. The strain was combined with the lab-stored GS-30 and Bacillus subtilis to construct composite flora and conduct a single factor experiment. Significantly higher factors were selected by Plackett Burman, and its fermentation conditions were optimized using response surface methodology. The optimal cultivation conditions were 4% of inoculum, a culture temperature of 28.51°C, an initial pH value of the medium of 7.43, and the oscillation during fermentation took place at 199.62 rpm. Under these conditions, 40.38% of the corn straw was degraded. From the results of SEM, we found that the structure of corn straw before degradation was complete, and the internal structure of corn straw after degradation with composite flora was destructed. The FT-IR spectra shown that the absorption peaks in all places of corn straw were reduced after degradation by the composite flora, the absorption peaks at 1640 cm^-1 of corn straw after degradation were lower than that of before degradation, which confirmed the decrease in cellulose. It indicated that the corn straw was significantly degraded by the composite flora. This study contributed to understanding the change in corn straw after fermentation by the composite flora, and providing a theoretical basis for comprehensive utilization of corn straw.