Effect of temperature on reaction rate and microbial community in composting of cattle manure with rice straw

The effects of temperature on microbial communities and mass reduction in composting were studied by comparing the mesophilic process with the thermophilic process of cattle manure-rice straw composting for 21 d. The respiratory quinone content (indicator of microbial biomass) continuously increased in the mesophilic process, but in the thermophilic process, it was much higher after 3 d and then decreased to the same level as that in the mesophilic process after 21 d. The diversity of quinones increased continuously in both the mesophilic and thermophilic processes with a higher value in the thermophilic process. The mesophilic microbial community was characterized by the predominance of ubiquinones and menaquinone (MK-8), which correspond to Proteobacteria and fungi. The thermophilic microbial community was characterized by the dominance of MK-7 in the initial period, and increases in the amounts of menaquinones with long and partially-saturated side chains in the later period, corresponding to Firmicutes and Actinobacteria, respectively. DNA fingerprinting by denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal RNA genes also confirmed that diversity of microbial communities increased but differently in the two processes. Our results suggest that mesophilic composting is more effective for mass reduction in cattle manure composting than thermophilic composting because of the higher decomposition activity of the microbial community characterized by the predominance of Proteobacteria and fungi.